NASA’s Lucy spacecraft skimming Earth’s atmosphere today!

Lucy’s second slingshot of Earth. The Lucy spacecraft will perform its second Earth gravity assist on December 12, 2024. Video via NASA Goddard.

• Our planet Earth will give NASA’s Lucy spacecraft its 2nd gravity assist today (December 12, 2024). This close flyby will give Lucy a boost, placing it on a new trajectory that’ll carry the spacecraft through the main asteroid belt and out to Jupiter’s Trojan asteroids.
• Observers in the Hawaiian Islands might be able to catch a glimpse of Lucy as the spacecraft approaches Earth, before it passes into Earth’s shadow. Lucy will then be visible to observers with a telescope in western regions of Africa and eastern regions of South America.
• Lucy’s next encounter will be with asteroid Donaldjohanson on April 20, 2025.

This article by Erin Morton was published originally at the NASA Lucy Mission blog. Edits by EarthSky.

NASA’s Lucy spacecraft prepares for 2nd Earth gravity assist

On Thursday, December 12, at 11:15 p.m. EST (04:15 UTC on Dec. 13), NASA’s Lucy spacecraft, currently in a two-year orbit around the sun, will skim Earth’s atmosphere. It will pass only about 220 miles (350 kilometers) above the surface. This close flyby will result in a gravity assist. This puts the spacecraft on a new trajectory that travels through the main asteroid belt and out to the never-before-explored Jupiter Trojan asteroids.

Trojans orbit the sun at the same distance as Jupiter.

This 2nd Earth gravity assist occurs three years into the Lucy spacecraft’s 12-year voyage. Its 1st gravity assist was on October 16, 2022, one year after launch. It boosted the spacecraft from an initial one-year orbit onto the present two-year orbit. That orbit reached into the inner limits of the main asteroid belt.

This enabled Lucy’s 1st asteroid encounter, with the small asteroid Dinkinesh and its satellite Selam.

Through the asteroid belt and on to the Trojans

Then, the upcoming gravity assist will boost the spacecraft into a six-year orbit. That one that will carry Lucy through the main asteroid belt (where it will fly past the asteroid Donaldjohanson). It will then go into the Trojan asteroid swarm that leads Jupiter in its orbit, for the 1st Trojan asteroid encounter in 2027.

Looking for a Christmas gift for someone who loves astronomy? The 2025 EarthSky lunar calendar is now available! A unique and beautiful poster-sized calendar. Makes a great gift!

NASA Lucy spacecraft’s 2nd Earth gravity assist (EGA) dramatically alters the spacecraft’s trajectory, enabling it to travel through the Jupiter Trojan asteroids. Lucy’s trajectory prior to the EGA is shown in solid red. The trajectory afterward is shown by a dashed red curve. The orbits of the nearby planets are shown for reference, and the grey regions indicate the approximate location of the main asteroid belt and the leading (L4) Jupiter trojan asteroids. In addition, the main belt asteroid, Donaldjohanson, and the Trojan asteroid, Eurybates, are shown at the time of Lucy’s encounters. Image via NASA/ SwRI

Lucy spacecraft’s approach invisible in the glare of the sun

During the gravity assist, the Lucy spacecraft, from Earth’s perspective, will approach from the direction of the sun. This means that observers on Earth will not be able to see Lucy approaching, as it will be lost in the sun’s glare. Lucy’s trajectory will bring the spacecraft very close to the Earth. In fact, it will be even lower in altitude than the International Space Station.

Also, to ensure the safety of the spacecraft as it passes through this region full of Earth-orbiting satellites and debris, NASA has procedures to anticipate and avoid potential collisions. If needed, the spacecraft will execute a small trajectory correction maneuver 12 hours before closest approach. This will alter the time of closest approach by one or two seconds, enough to avoid a potential collision.

The trajectory of NASA’s Lucy spacecraft during its 2nd Earth gravity assist on December 12, 2024, as seen looking down on the Earth. The dots along the trajectory mark the position of the spacecraft every 10 minutes. Image via NASA/ SwRI.

Probe might be visible in early evening for Hawaiians

Shortly after sunset, keen observers in the Hawaiian Islands may be able to catch a glimpse of Lucy as the spacecraft approaches Earth before it passes into Earth’s shadow at 6:14 p.m. HST (04:14 UTC on December 13). Lucy will speed over the continental U.S. in darkness, travelling over 33,000 miles per hour (14.8 kilometers per second). It will then emerge from Earth’s shadow 20 minutes later at 11:34 p.m. EST (04:34 UTC).

At that time, Lucy may be visible to observers with a telescope in the western regions of Africa and the eastern regions of South America. Sunlight reflects off the spacecraft’s large solar panels (observers in the eastern United States will be looking at the much dimmer “back” side of the solar panels, making Lucy harder to see. Go here for more information about observing Lucy during this gravity assist). Lucy will then rapidly recede from Earth and return to interplanetary space. The gravity assist increased the spacecraft’s speed with respect to the sun by over 16,000 miles per hour (7.2 kilometers per second).

During the 1st Earth gravity assist in 2022, the spacecraft imaged the Earth and the moon as part of an instrument calibration. As no further calibrations are needed at this time, the instruments will be off during this encounter. Lucy’s next asteroid encounter will be with the small main belt asteroid Donaldjohanson on April 20, 2025.

Bottom line: The Lucy spacecraft will make a close approach to Earth today. Its six-year mission will carry it through the main asteroid belt and into the orbit of Jupiter.

Read more: Lucy spacecraft update: And then there were 3!

The post NASA’s Lucy spacecraft skimming Earth’s atmosphere today! first appeared on EarthSky.

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Lucy’s second slingshot of Earth. The Lucy spacecraft will perform its second Earth gravity assist on December 12, 2024. Video via NASA Goddard.

• Our planet Earth will give NASA’s Lucy spacecraft its 2nd gravity assist today (December 12, 2024). This close flyby will give Lucy a boost, placing it on a new trajectory that’ll carry the spacecraft through the main asteroid belt and out to Jupiter’s Trojan asteroids.
• Observers in the Hawaiian Islands might be able to catch a glimpse of Lucy as the spacecraft approaches Earth, before it passes into Earth’s shadow. Lucy will then be visible to observers with a telescope in western regions of Africa and eastern regions of South America.
• Lucy’s next encounter will be with asteroid Donaldjohanson on April 20, 2025.

This article by Erin Morton was published originally at the NASA Lucy Mission blog. Edits by EarthSky.

NASA’s Lucy spacecraft prepares for 2nd Earth gravity assist

On Thursday, December 12, at 11:15 p.m. EST (04:15 UTC on Dec. 13), NASA’s Lucy spacecraft, currently in a two-year orbit around the sun, will skim Earth’s atmosphere. It will pass only about 220 miles (350 kilometers) above the surface. This close flyby will result in a gravity assist. This puts the spacecraft on a new trajectory that travels through the main asteroid belt and out to the never-before-explored Jupiter Trojan asteroids.

Trojans orbit the sun at the same distance as Jupiter.

This 2nd Earth gravity assist occurs three years into the Lucy spacecraft’s 12-year voyage. Its 1st gravity assist was on October 16, 2022, one year after launch. It boosted the spacecraft from an initial one-year orbit onto the present two-year orbit. That orbit reached into the inner limits of the main asteroid belt.

This enabled Lucy’s 1st asteroid encounter, with the small asteroid Dinkinesh and its satellite Selam.

Through the asteroid belt and on to the Trojans

Then, the upcoming gravity assist will boost the spacecraft into a six-year orbit. That one that will carry Lucy through the main asteroid belt (where it will fly past the asteroid Donaldjohanson). It will then go into the Trojan asteroid swarm that leads Jupiter in its orbit, for the 1st Trojan asteroid encounter in 2027.

Looking for a Christmas gift for someone who loves astronomy? The 2025 EarthSky lunar calendar is now available! A unique and beautiful poster-sized calendar. Makes a great gift!

NASA Lucy spacecraft’s 2nd Earth gravity assist (EGA) dramatically alters the spacecraft’s trajectory, enabling it to travel through the Jupiter Trojan asteroids. Lucy’s trajectory prior to the EGA is shown in solid red. The trajectory afterward is shown by a dashed red curve. The orbits of the nearby planets are shown for reference, and the grey regions indicate the approximate location of the main asteroid belt and the leading (L4) Jupiter trojan asteroids. In addition, the main belt asteroid, Donaldjohanson, and the Trojan asteroid, Eurybates, are shown at the time of Lucy’s encounters. Image via NASA/ SwRI

Lucy spacecraft’s approach invisible in the glare of the sun

During the gravity assist, the Lucy spacecraft, from Earth’s perspective, will approach from the direction of the sun. This means that observers on Earth will not be able to see Lucy approaching, as it will be lost in the sun’s glare. Lucy’s trajectory will bring the spacecraft very close to the Earth. In fact, it will be even lower in altitude than the International Space Station.

Also, to ensure the safety of the spacecraft as it passes through this region full of Earth-orbiting satellites and debris, NASA has procedures to anticipate and avoid potential collisions. If needed, the spacecraft will execute a small trajectory correction maneuver 12 hours before closest approach. This will alter the time of closest approach by one or two seconds, enough to avoid a potential collision.

The trajectory of NASA’s Lucy spacecraft during its 2nd Earth gravity assist on December 12, 2024, as seen looking down on the Earth. The dots along the trajectory mark the position of the spacecraft every 10 minutes. Image via NASA/ SwRI.

Probe might be visible in early evening for Hawaiians

Shortly after sunset, keen observers in the Hawaiian Islands may be able to catch a glimpse of Lucy as the spacecraft approaches Earth before it passes into Earth’s shadow at 6:14 p.m. HST (04:14 UTC on December 13). Lucy will speed over the continental U.S. in darkness, travelling over 33,000 miles per hour (14.8 kilometers per second). It will then emerge from Earth’s shadow 20 minutes later at 11:34 p.m. EST (04:34 UTC).

At that time, Lucy may be visible to observers with a telescope in the western regions of Africa and the eastern regions of South America. Sunlight reflects off the spacecraft’s large solar panels (observers in the eastern United States will be looking at the much dimmer “back” side of the solar panels, making Lucy harder to see. Go here for more information about observing Lucy during this gravity assist). Lucy will then rapidly recede from Earth and return to interplanetary space. The gravity assist increased the spacecraft’s speed with respect to the sun by over 16,000 miles per hour (7.2 kilometers per second).

During the 1st Earth gravity assist in 2022, the spacecraft imaged the Earth and the moon as part of an instrument calibration. As no further calibrations are needed at this time, the instruments will be off during this encounter. Lucy’s next asteroid encounter will be with the small main belt asteroid Donaldjohanson on April 20, 2025.

Bottom line: The Lucy spacecraft will make a close approach to Earth today. Its six-year mission will carry it through the main asteroid belt and into the orbit of Jupiter.

Read more: Lucy spacecraft update: And then there were 3!

The post NASA’s Lucy spacecraft skimming Earth’s atmosphere today! first appeared on EarthSky.

from EarthSky https://ift.tt/fmHs4e8

Astronomers map giant starspots on distant XX Trianguli

A visualization of starspots on the red giant star XX Trianguli. The size of the sun is shown on the left for comparison. Image via HUN-REN RCAES/ Zs. Kovári, MOME/ Á. Radványi, AIP/ K. Strassmeier.

Astronomers mapped starspots on the red giant star XX Trianguli using Doppler imaging over 16 years.

Some of these distant starspots are big, bigger than our entire sun!

XX Trianguli’s starspot activity is chaotic and non-periodic, in contrast to our sun’s regular 11-year cycle of activity.

XX Trianguli as ‘the most spotted star in the sky’

If you follow EarthSky’s daily sun news, you know an active sun has many sunspots, or temporary dark spots on its surface. Our sun is a star, so it’s no surprise that distant stars have dark spots, too. Astronomers call them starspots. On December 4, 2024, astronomers at Konkoly Thege Miklós Astronomical Institute in Hungary said they’ve mapped starspots on a star called XX Trianguli. They found this star has enormous spots, bigger than our entire sun! But, unlike our sun – which waxes and wanes in activity over an 11-year cycle – XX Trianguli appears to lack a regular cycle of producing spots.

The researchers published their study in the peer-reviewed journal Nature Communications on December 4, 2024.

XX Trianguli is located in the direction of our northern constellation Triangulum. It’s about 642 light-years away. And this star is about the same mass as our sun. But the star is about 10 times bigger than our sun, because its outer layers have expanded outward.

In other words, XX Trianguli is a red giant, near the end of its evolutionary lifetime. Zsolt Kovári, at the Konkoly Observatory in Hungary, explained:

The large-amplitude variations in the brightness of the red giant XX Trianguli have been observed before, so it was also known that the variations were caused by dark spots, coming in and out view as the star rotates around its axis in 24 days. These spots are even larger than the entire surface of our sun, which is why XX Trianguli has been dubbed ‘the most spotted star in the sky.’

The sun’s a pretty stable star

The creation and maintenance of our sun’s magnetic field is thanks to what scientists call a solar dynamo. The movement of charged particles inside the sun, and the sun’s rotation, are the main drivers of this dynamo.

Characteristics of the sun’s magnetic field, in turn, drive the 11-year sun cycle of activity. Each cycle sees an increase, then a decrease, in sun surface phenomena such as solar flares and sunspots. Throughout 2024, our sun has been extremely active. Experts at NASA believe it reached the peak of the current sunspot cycle this fall.

XX Trianguli’s starspots show it’s a chaotic star

In contrast, the distant star XX Trianguli doesn’t have a regular sunspot cycle. In fact, the astronomers said its dynamo is

… Non-periodic, most likely chaotic in nature.

Kovári commented:

The solar dynamo shows a cyclic behavior in the number and distribution of sunspots that repeats every 11 years on average, known as the butterfly diagram. However, XX Trianguli is a red giant star about 10 times larger than the sun and its internal structure differs significantly from the sun’s, which is a main sequence dwarf. We found no evidence of similar cycles for XX Trianguli.

By studying stellar dynamos, we can also get closer to understanding the solar dynamo. Moreover, dynamo operation is not only responsible for the magnetic features on the sun or other spotted stars, but also the Earth’s magnetic field is created by a similar mechanism, which, on the other hand, happens to protect our technical civilization from harmful solar storms.

Our goal is to be able to observe the manifestations of the dynamo mechanism in as many stars with different characteristics as possible, since by knowing the similarities and differences, we will ultimately better understand the processes that shape our own environment.

This video about the starspots on XX Trianguli is from Konkoly Observatory in Hungary.

Mapping starspots on a distant star

From 2006 to 2022, scientists observed XX Trianguli using the STELLA robotic telescopes in Tenerife, Spain. This twin telescope system, operated remotely, is designed to monitor activity on the surface of stars.

Overall, the researchers collected over 2,000 XX Trianguli spectra (measurements of the star’s component colors) over 16 years. Then, they used the spectra to reconstruct 99 images of the star’s surface, using a technique called Doppler imaging.

The STELLA Robotic Observatory in Tenerife, Spain. Image via Michael Weber/ Wikimedia Commons (CC BY-SA 2.0 DE).

Doppler imaging

Doppler imaging is a method for visualizing the surface of bright stars. Basically, using specialized equipment, astronomers break up a star’s light into its component colors. This observing technique is spectroscopy. Within this rainbow – or the spectrum – are dark spectral lines. Elements on the star’s surface, like sodium and calcium, create these lines by absorbing light at specific wavelengths. As the star rotates, wavelengths of light from different surface regions shift slightly from their expected positions (a phenomenon called the Doppler effect). With this in mind, astronomers use advanced calculations to interpret those shifts to produce a surface map of the star.

Kovári said the observations of this spotted star will continue and might reveal future details about the star’s dynamo operation.

Mercator projections of the starspots on XX Trianguli, obtained using Doppler imaging. In all, scientists created 99 maps over 16 years. Image via Strassmeier, K. G., et al./ Nature Communications (CC BY-NC-ND 4.0).

Bottom line: Astronomers have mapped starspots over a 16-year period on a star named XX Trianguli using advanced Doppler imaging techniques.

Source: Long-term Doppler imaging of the star XX Trianguli indicates chaotic non-periodic dynamo

Via Konkoly Observatory

Read more: Polaris, the North Star, has spots on its surface

The post Astronomers map giant starspots on distant XX Trianguli first appeared on EarthSky.

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A visualization of starspots on the red giant star XX Trianguli. The size of the sun is shown on the left for comparison. Image via HUN-REN RCAES/ Zs. Kovári, MOME/ Á. Radványi, AIP/ K. Strassmeier.

Astronomers mapped starspots on the red giant star XX Trianguli using Doppler imaging over 16 years.

Some of these distant starspots are big, bigger than our entire sun!

XX Trianguli’s starspot activity is chaotic and non-periodic, in contrast to our sun’s regular 11-year cycle of activity.

XX Trianguli as ‘the most spotted star in the sky’

If you follow EarthSky’s daily sun news, you know an active sun has many sunspots, or temporary dark spots on its surface. Our sun is a star, so it’s no surprise that distant stars have dark spots, too. Astronomers call them starspots. On December 4, 2024, astronomers at Konkoly Thege Miklós Astronomical Institute in Hungary said they’ve mapped starspots on a star called XX Trianguli. They found this star has enormous spots, bigger than our entire sun! But, unlike our sun – which waxes and wanes in activity over an 11-year cycle – XX Trianguli appears to lack a regular cycle of producing spots.

The researchers published their study in the peer-reviewed journal Nature Communications on December 4, 2024.

XX Trianguli is located in the direction of our northern constellation Triangulum. It’s about 642 light-years away. And this star is about the same mass as our sun. But the star is about 10 times bigger than our sun, because its outer layers have expanded outward.

In other words, XX Trianguli is a red giant, near the end of its evolutionary lifetime. Zsolt Kovári, at the Konkoly Observatory in Hungary, explained:

The large-amplitude variations in the brightness of the red giant XX Trianguli have been observed before, so it was also known that the variations were caused by dark spots, coming in and out view as the star rotates around its axis in 24 days. These spots are even larger than the entire surface of our sun, which is why XX Trianguli has been dubbed ‘the most spotted star in the sky.’

The sun’s a pretty stable star

The creation and maintenance of our sun’s magnetic field is thanks to what scientists call a solar dynamo. The movement of charged particles inside the sun, and the sun’s rotation, are the main drivers of this dynamo.

Characteristics of the sun’s magnetic field, in turn, drive the 11-year sun cycle of activity. Each cycle sees an increase, then a decrease, in sun surface phenomena such as solar flares and sunspots. Throughout 2024, our sun has been extremely active. Experts at NASA believe it reached the peak of the current sunspot cycle this fall.

XX Trianguli’s starspots show it’s a chaotic star

In contrast, the distant star XX Trianguli doesn’t have a regular sunspot cycle. In fact, the astronomers said its dynamo is

… Non-periodic, most likely chaotic in nature.

Kovári commented:

The solar dynamo shows a cyclic behavior in the number and distribution of sunspots that repeats every 11 years on average, known as the butterfly diagram. However, XX Trianguli is a red giant star about 10 times larger than the sun and its internal structure differs significantly from the sun’s, which is a main sequence dwarf. We found no evidence of similar cycles for XX Trianguli.

By studying stellar dynamos, we can also get closer to understanding the solar dynamo. Moreover, dynamo operation is not only responsible for the magnetic features on the sun or other spotted stars, but also the Earth’s magnetic field is created by a similar mechanism, which, on the other hand, happens to protect our technical civilization from harmful solar storms.

Our goal is to be able to observe the manifestations of the dynamo mechanism in as many stars with different characteristics as possible, since by knowing the similarities and differences, we will ultimately better understand the processes that shape our own environment.

This video about the starspots on XX Trianguli is from Konkoly Observatory in Hungary.

Mapping starspots on a distant star

From 2006 to 2022, scientists observed XX Trianguli using the STELLA robotic telescopes in Tenerife, Spain. This twin telescope system, operated remotely, is designed to monitor activity on the surface of stars.

Overall, the researchers collected over 2,000 XX Trianguli spectra (measurements of the star’s component colors) over 16 years. Then, they used the spectra to reconstruct 99 images of the star’s surface, using a technique called Doppler imaging.

The STELLA Robotic Observatory in Tenerife, Spain. Image via Michael Weber/ Wikimedia Commons (CC BY-SA 2.0 DE).

Doppler imaging

Doppler imaging is a method for visualizing the surface of bright stars. Basically, using specialized equipment, astronomers break up a star’s light into its component colors. This observing technique is spectroscopy. Within this rainbow – or the spectrum – are dark spectral lines. Elements on the star’s surface, like sodium and calcium, create these lines by absorbing light at specific wavelengths. As the star rotates, wavelengths of light from different surface regions shift slightly from their expected positions (a phenomenon called the Doppler effect). With this in mind, astronomers use advanced calculations to interpret those shifts to produce a surface map of the star.

Kovári said the observations of this spotted star will continue and might reveal future details about the star’s dynamo operation.

Mercator projections of the starspots on XX Trianguli, obtained using Doppler imaging. In all, scientists created 99 maps over 16 years. Image via Strassmeier, K. G., et al./ Nature Communications (CC BY-NC-ND 4.0).

Bottom line: Astronomers have mapped starspots over a 16-year period on a star named XX Trianguli using advanced Doppler imaging techniques.

Source: Long-term Doppler imaging of the star XX Trianguli indicates chaotic non-periodic dynamo

Via Konkoly Observatory

Read more: Polaris, the North Star, has spots on its surface

The post Astronomers map giant starspots on distant XX Trianguli first appeared on EarthSky.

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Odd, slowly repeating radio bursts traced to red dwarf star

View larger. | Artist’s concept of AR Scorpii, a binary star system with a red dwarf and white dwarf. The new slowly repeating radio bursts source, GLEAM-X J0704-37, is thought to be similar to this. Image via M. Garlick/ University of Warwick/ ESO.

• Slowly repeating radio bursts are natural radio signals from space that are similar to signals from pulsars, but these repeat much more slowly. Astronomers discovered the first one in 2022, which repeated every 18 minutes. Their sources and causes have remained a mystery.
• Now, for the first time, astronomers have pinpointed the origin of a slowly repeating radio burst. It comes from a red dwarf star.
• A white dwarf star might be orbiting the red dwarf. A stream of charged particles from the red dwarf, like our sun’s solar wind, could hit the white dwarf, producing the radio waves.

Unusual, slowly repeating radio bursts

In 2022, astronomers discovered a signal of powerful radio bursts from space that repeated every 18 minutes. What were they and what was causing them? Unlike other similar natural radio pulses, these repeated more slowly and did not seem to be coming from pulsars. So, astronomers have been trying to determine their origin ever since. On December 1, 2024, a team of astronomers led by researchers at Curtin University in Perth, Australia, said the source of a newly discovered slow repeater is a red dwarf star about 5,000 light-years away. And it is likely in a binary orbit with a white dwarf star.

The researchers wrote about the new findings in The Conversation on December 1, 2024. And they published the peer-reviewed results in The Astrophysical Journal Letters on November 26.

Looking for a Christmas gift for someone who loves astronomy? The 2025 EarthSky lunar calendar is now available! A unique and beautiful poster-sized calendar. Keep up with all phases of the moon every night of the year. Get yours today!

Initial discoveries

Astronomers first detected similar repeating radio signals back in 2022, from a source dubbed GLEAM-X J162759.5-523504. They were intense in strength, but after three months, they vanished. What was causing them? Astronomers knew that some other similar repeating radio bursts came from radio pulsars, pulsars that emit radio waves. Pulsars are spinning neutron stars. But they tend to spin rapidly, about once per second or faster. On the other hand, these new signals were repeating much more slowly, only once every 18 minutes.

According to our current knowledge, pulsars that rotate as slow as that should not produce any radio waves. So it seemed less likely that a pulsar was the explanation.

So, was there something about pulsars that scientists didn’t understand yet, or was there another explanation?

The source of the radio waves from GLEAM-X J0704-37, as seen by the Murchison Widefield Array (MWA) at low resolution (magenta circle) and MeerKAT at high resolution (cyan circle). The white circles are stars in our own Milky Way galaxy. Image via Hurley-Walker et al. 2024/ The Astrophysical Journal Letters.

Additional slowly repeating radio bursts

Since the initial discovery in 2022, astronomers have found more of the slowly repeating signals, at least 10. Scientists call them “long-period radio transients.” They are similar, in that each radio pulse lasts about a minute. But there’s one problem. All of them are immensely far away, in the heart of our Milky Way galaxy. Natasha Hurley-Walker, a radio astronomer at Curtin University, said in The Conversation:

Until now, every one of these sources has been found deep in the heart of the Milky Way. This makes it very hard to figure out what kind of star or object produces the radio waves, because there are thousands of stars in a small area. Any one of them could be responsible for the signal, or none of them.

Hurley-Walker also said:

The long-period transients are very exciting, and for astronomers to understand what they are, we need an optical image. However, when you look toward them, there are so many stars lying in the way that it’s like 2001: A Space Odyssey. ‘My god, it’s full of stars!’

Slowest radio burst yet

But now, the researchers with the new study have discovered another slow repeater. And it’s the slowest one yet. They discovered it using the Murchison Widefield Array (MWA) radio telescope in Western Australia. Csanád Horváth, an undergraduate student at Curtin University, processed the data. Instead of the inner regions of the Milky Way, the researchers scanned areas farther on the outskirts, with less stars. And they found a new slowly repeating radio source, which they named GLEAM-X J0704-37. As Hurley-Walker explained:

In a stroke of good fortune, the newly discovered transient, named GLEAM-X J0704-37, was found on the outskirts of our galaxy, in a much emptier region of space in the Puppis constellation, around 5,000 light-years away. Our new discovery lies far off the Galactic Plane, so there are only a handful of stars nearby, and we’re now certain one star system, in particular, is generating the radio waves.

But this radio burst source was even slower than previous ones. Instead of 18 minutes, the pulses repeated every 2.9 hours. They are the slowest-repeating radio pulses that astronomers have found so far.

Artist’s impression video of the exotic binary star system AR Scorpii, thought to be similar to GLEAM-X J0704-37. Video via ESO/ L. Calçada/ University of Warwick.

A red dwarf star … and a white dwarf?

This time, the astronomers were able to pinpoint the source of the radio pulses: a red dwarf star. Red dwarfs are smaller and cooler than the sun. They are also the most common type of star in our galaxy.

The researchers used the MeerKAT telescope in South Africa. The radio signals didn’t seem to be coming from the star itself, however. The pulses repeated, like others, but they would vary in time. Sometimes they arrived a bit earlier, and sometimes a bit later. This meant that the actual source of the signals was probably in a binary orbit with the red dwarf.

The researchers said this source was most likely a white dwarf star. White dwarfs are the remaining burned-out cores of sun-like stars that have died. Hurley-Walker said:

Based on previous studies of the evolution of stars, we think this invisible radio emitter is most likely to be a white dwarf, which is the final endpoint of small to medium-sized stars like our own sun. If it were a neutron star or a black hole, the explosion that created it would have been so large it should have disrupted the orbit.

How do they produce the slowly repeating radio bursts?

So, how would a red dwarf and white dwarf produce the repeating radio pulses? The researchers said the red dwarf likely emits a stream of charged particles, like our sun’s solar wind. When those particles collide with the white dwarf’s magnetic field, that would create radio waves.

The red dwarf and white dwarf system AR Scorpii is likely similar to GLEAM-X J0704-37. Radio waves from the white dwarf are hitting the red dwarf, about every two minutes.

Bottom line: Astronomers have pinpointed the source of slowly repeating radio bursts in space for the first time: a red dwarf star with a possible white dwarf companion.

Source: A 2.9 hr Periodic Radio Transient with an Optical Counterpart

Via:

The Conversation

ICRAR

Curtin University

Read more: What’s a pulsar? Why does it pulse?

Read more: Slow-spinning neutron star: A new class of object?

The post Odd, slowly repeating radio bursts traced to red dwarf star first appeared on EarthSky.

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View larger. | Artist’s concept of AR Scorpii, a binary star system with a red dwarf and white dwarf. The new slowly repeating radio bursts source, GLEAM-X J0704-37, is thought to be similar to this. Image via M. Garlick/ University of Warwick/ ESO.

• Slowly repeating radio bursts are natural radio signals from space that are similar to signals from pulsars, but these repeat much more slowly. Astronomers discovered the first one in 2022, which repeated every 18 minutes. Their sources and causes have remained a mystery.
• Now, for the first time, astronomers have pinpointed the origin of a slowly repeating radio burst. It comes from a red dwarf star.
• A white dwarf star might be orbiting the red dwarf. A stream of charged particles from the red dwarf, like our sun’s solar wind, could hit the white dwarf, producing the radio waves.

Unusual, slowly repeating radio bursts

In 2022, astronomers discovered a signal of powerful radio bursts from space that repeated every 18 minutes. What were they and what was causing them? Unlike other similar natural radio pulses, these repeated more slowly and did not seem to be coming from pulsars. So, astronomers have been trying to determine their origin ever since. On December 1, 2024, a team of astronomers led by researchers at Curtin University in Perth, Australia, said the source of a newly discovered slow repeater is a red dwarf star about 5,000 light-years away. And it is likely in a binary orbit with a white dwarf star.

The researchers wrote about the new findings in The Conversation on December 1, 2024. And they published the peer-reviewed results in The Astrophysical Journal Letters on November 26.

Looking for a Christmas gift for someone who loves astronomy? The 2025 EarthSky lunar calendar is now available! A unique and beautiful poster-sized calendar. Keep up with all phases of the moon every night of the year. Get yours today!

Initial discoveries

Astronomers first detected similar repeating radio signals back in 2022, from a source dubbed GLEAM-X J162759.5-523504. They were intense in strength, but after three months, they vanished. What was causing them? Astronomers knew that some other similar repeating radio bursts came from radio pulsars, pulsars that emit radio waves. Pulsars are spinning neutron stars. But they tend to spin rapidly, about once per second or faster. On the other hand, these new signals were repeating much more slowly, only once every 18 minutes.

According to our current knowledge, pulsars that rotate as slow as that should not produce any radio waves. So it seemed less likely that a pulsar was the explanation.

So, was there something about pulsars that scientists didn’t understand yet, or was there another explanation?

The source of the radio waves from GLEAM-X J0704-37, as seen by the Murchison Widefield Array (MWA) at low resolution (magenta circle) and MeerKAT at high resolution (cyan circle). The white circles are stars in our own Milky Way galaxy. Image via Hurley-Walker et al. 2024/ The Astrophysical Journal Letters.

Additional slowly repeating radio bursts

Since the initial discovery in 2022, astronomers have found more of the slowly repeating signals, at least 10. Scientists call them “long-period radio transients.” They are similar, in that each radio pulse lasts about a minute. But there’s one problem. All of them are immensely far away, in the heart of our Milky Way galaxy. Natasha Hurley-Walker, a radio astronomer at Curtin University, said in The Conversation:

Until now, every one of these sources has been found deep in the heart of the Milky Way. This makes it very hard to figure out what kind of star or object produces the radio waves, because there are thousands of stars in a small area. Any one of them could be responsible for the signal, or none of them.

Hurley-Walker also said:

The long-period transients are very exciting, and for astronomers to understand what they are, we need an optical image. However, when you look toward them, there are so many stars lying in the way that it’s like 2001: A Space Odyssey. ‘My god, it’s full of stars!’

Slowest radio burst yet

But now, the researchers with the new study have discovered another slow repeater. And it’s the slowest one yet. They discovered it using the Murchison Widefield Array (MWA) radio telescope in Western Australia. Csanád Horváth, an undergraduate student at Curtin University, processed the data. Instead of the inner regions of the Milky Way, the researchers scanned areas farther on the outskirts, with less stars. And they found a new slowly repeating radio source, which they named GLEAM-X J0704-37. As Hurley-Walker explained:

In a stroke of good fortune, the newly discovered transient, named GLEAM-X J0704-37, was found on the outskirts of our galaxy, in a much emptier region of space in the Puppis constellation, around 5,000 light-years away. Our new discovery lies far off the Galactic Plane, so there are only a handful of stars nearby, and we’re now certain one star system, in particular, is generating the radio waves.

But this radio burst source was even slower than previous ones. Instead of 18 minutes, the pulses repeated every 2.9 hours. They are the slowest-repeating radio pulses that astronomers have found so far.

Artist’s impression video of the exotic binary star system AR Scorpii, thought to be similar to GLEAM-X J0704-37. Video via ESO/ L. Calçada/ University of Warwick.

A red dwarf star … and a white dwarf?

This time, the astronomers were able to pinpoint the source of the radio pulses: a red dwarf star. Red dwarfs are smaller and cooler than the sun. They are also the most common type of star in our galaxy.

The researchers used the MeerKAT telescope in South Africa. The radio signals didn’t seem to be coming from the star itself, however. The pulses repeated, like others, but they would vary in time. Sometimes they arrived a bit earlier, and sometimes a bit later. This meant that the actual source of the signals was probably in a binary orbit with the red dwarf.

The researchers said this source was most likely a white dwarf star. White dwarfs are the remaining burned-out cores of sun-like stars that have died. Hurley-Walker said:

Based on previous studies of the evolution of stars, we think this invisible radio emitter is most likely to be a white dwarf, which is the final endpoint of small to medium-sized stars like our own sun. If it were a neutron star or a black hole, the explosion that created it would have been so large it should have disrupted the orbit.

How do they produce the slowly repeating radio bursts?

So, how would a red dwarf and white dwarf produce the repeating radio pulses? The researchers said the red dwarf likely emits a stream of charged particles, like our sun’s solar wind. When those particles collide with the white dwarf’s magnetic field, that would create radio waves.

The red dwarf and white dwarf system AR Scorpii is likely similar to GLEAM-X J0704-37. Radio waves from the white dwarf are hitting the red dwarf, about every two minutes.

Bottom line: Astronomers have pinpointed the source of slowly repeating radio bursts in space for the first time: a red dwarf star with a possible white dwarf companion.

Source: A 2.9 hr Periodic Radio Transient with an Optical Counterpart

Via:

The Conversation

ICRAR

Curtin University

Read more: What’s a pulsar? Why does it pulse?

Read more: Slow-spinning neutron star: A new class of object?

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Orange Aldebaran is Taurus the Bull’s fiery eye

Taurus the Bull contains 2 star clusters that are easy to spot, the Pleiades and the Hyades. Aldebaran appears as part of the Hyades cluster although it’s a foreground star, not actually a member of the star cluster. Chart via EarthSky.

The orange star Aldebaran – the fiery eye of the Bull in the constellation Taurus – is easy to find. It’s part of a V-shaped group of stars – the Hyades – that forms the Bull’s face. You can locate Aldebaran using the famous constellation Orion as a guide. Notice the three stars of Orion’s Belt. Then draw an imaginary line through the Belt to the right. The first bright star you come to will be Aldebaran with its distinctive reddish-orange glow.

If you can find the prominent constellation Orion, you can find the bright red-orange star Aldebaran. Orion’s Belt always points to Aldebaran. Look east in mid-evening in December. Check Stellarium for a precise view at your location.

The 2025 EarthSky lunar calendar makes a great gift. Get yours today!

When to spot Aldebaran

Aldebaran is the 14th brightest star, but five of those that outshine it are only barely visible or not visible at all from much of the Northern Hemisphere. Aldebaran is primarily a winter and spring star for us on the northern part of Earth. That’s when this orange star is most easily visible in the evening sky. By early December, it rises shortly after sunset and is visible all night. Then, three months later it is high to the south at sunset, and sets at around midnight. By early May, it hangs low about the western sunset glow, and before the end of the month, it’s lost altogether. It returns to the predawn sky around late June.

By the way, although it appears among them, Aldebaran is not actually a member of the V-shaped Hyades cluster. It is actually much closer to us in space than the other Hyades stars.

In December 2024, the bright planet Jupiter is near Aldebaran. You can’t miss them!

Bright Jupiter rises high in the east in the evening. It is surrounded by the Pleiades, the Hyades and Aldebarn, Betelgeuse and Capella. They’ll be visible all night. Chart via EarthSky.

History and mythology of Aldebaran

Artists often depict Aldebaran as the fiery eye of Taurus the Bull. Because it is bright and prominent, ancient Persians honored Aldebaran one of the Four Royal Stars, the other three being Regulus, Antares and Fomalhaut.

The name Aldebaran is from the Arabic for the follower, presumably as a hunter following prey, which was likely the star cluster we call the Pleiades. Some viewed the latter as a flock of birds, perhaps doves. According to Richard Hinckley Allen in his classic book Star Names: Their Lore and Meaning, people once applied the name Aldebaran to the entire Hyades star cluster, a large loose collection of faint stars.

More star lore

In Hindu myth, Aldebaran was a beautiful young woman named Rohini, disguised as an antelope and pursued by her lecherous father, disguised as a deer, Mriga. Several other ancient peoples associated the star with rain. In a Dakota Sioux myth, Aldebaran was a star which had fallen to the Earth and whose killing of a serpent led to the formation of the Mississippi River. Allen notes a number of other alternate names, but precious little mythology is known for Aldebaran separately.

Also, Aldebaran is the name of one of the chariot horses in the movie and book “Ben Hur.”

On a different note, astronomer Jack Eddy has suggested a connection with the Big Horn Medicine Wheel, an ancient circle of stones atop a mountain in Wyoming. Eddy wrote that the ancient Americans may have used this site as a sort of observatory to view the rising of Aldebaran just before the sun in June to predict the June solstice.

Interestingly, in about 2 million years, the NASA space probe Pioneer 10, now heading out into deep space, will pass Aldebaran.

The constellation Taurus. See Aldebaran marked as the Bull’s Eye? Image via Wikipedia (public domain).

Science of Aldebaran

Aldebaran is a huge aging star. The diameter is about 44 times the size of our sun. In fact, if Aldebaran replaced our sun, its surface would extend past the orbit of Mercury.

A comparison of the size of Aldebaran with our sun. Image via Wikipedia (public domain).

Aldebaran glows with the orangish color of a K5 giant star. In visible light, it is about 153 times brighter than the sun, although its surface temperature is lower, roughly 4,000 K (about 3,700 degrees C or 6,700 degrees F) compared to 5,800 K (about 5,500 C or 10,000 F) for the sun.

Although Aldebaran is associated with the stars of the Hyades, it’s much closer at 65 light-years distant. The Hyades are about 150 light-years away.

Aldebaran is an erratic variable with minor variations too small to see with the eye. Also, five faint stars are visible near Aldebaran, but so far none have been confirmed to be gravitationally bound to Aldebaran.

Aldebaran’s position is RA: 4h 35m 55s, dec: 16°30’35”

Bottom line: Aldebaran is an enormous, orange-colored star that marks one of the eyes of Taurus the Bull. It also marks one point of the V-shape of the Bull’s face.

The post Orange Aldebaran is Taurus the Bull’s fiery eye first appeared on EarthSky.

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Taurus the Bull contains 2 star clusters that are easy to spot, the Pleiades and the Hyades. Aldebaran appears as part of the Hyades cluster although it’s a foreground star, not actually a member of the star cluster. Chart via EarthSky.

The orange star Aldebaran – the fiery eye of the Bull in the constellation Taurus – is easy to find. It’s part of a V-shaped group of stars – the Hyades – that forms the Bull’s face. You can locate Aldebaran using the famous constellation Orion as a guide. Notice the three stars of Orion’s Belt. Then draw an imaginary line through the Belt to the right. The first bright star you come to will be Aldebaran with its distinctive reddish-orange glow.

If you can find the prominent constellation Orion, you can find the bright red-orange star Aldebaran. Orion’s Belt always points to Aldebaran. Look east in mid-evening in December. Check Stellarium for a precise view at your location.

The 2025 EarthSky lunar calendar makes a great gift. Get yours today!

When to spot Aldebaran

Aldebaran is the 14th brightest star, but five of those that outshine it are only barely visible or not visible at all from much of the Northern Hemisphere. Aldebaran is primarily a winter and spring star for us on the northern part of Earth. That’s when this orange star is most easily visible in the evening sky. By early December, it rises shortly after sunset and is visible all night. Then, three months later it is high to the south at sunset, and sets at around midnight. By early May, it hangs low about the western sunset glow, and before the end of the month, it’s lost altogether. It returns to the predawn sky around late June.

By the way, although it appears among them, Aldebaran is not actually a member of the V-shaped Hyades cluster. It is actually much closer to us in space than the other Hyades stars.

In December 2024, the bright planet Jupiter is near Aldebaran. You can’t miss them!

Bright Jupiter rises high in the east in the evening. It is surrounded by the Pleiades, the Hyades and Aldebarn, Betelgeuse and Capella. They’ll be visible all night. Chart via EarthSky.

History and mythology of Aldebaran

Artists often depict Aldebaran as the fiery eye of Taurus the Bull. Because it is bright and prominent, ancient Persians honored Aldebaran one of the Four Royal Stars, the other three being Regulus, Antares and Fomalhaut.

The name Aldebaran is from the Arabic for the follower, presumably as a hunter following prey, which was likely the star cluster we call the Pleiades. Some viewed the latter as a flock of birds, perhaps doves. According to Richard Hinckley Allen in his classic book Star Names: Their Lore and Meaning, people once applied the name Aldebaran to the entire Hyades star cluster, a large loose collection of faint stars.

More star lore

In Hindu myth, Aldebaran was a beautiful young woman named Rohini, disguised as an antelope and pursued by her lecherous father, disguised as a deer, Mriga. Several other ancient peoples associated the star with rain. In a Dakota Sioux myth, Aldebaran was a star which had fallen to the Earth and whose killing of a serpent led to the formation of the Mississippi River. Allen notes a number of other alternate names, but precious little mythology is known for Aldebaran separately.

Also, Aldebaran is the name of one of the chariot horses in the movie and book “Ben Hur.”

On a different note, astronomer Jack Eddy has suggested a connection with the Big Horn Medicine Wheel, an ancient circle of stones atop a mountain in Wyoming. Eddy wrote that the ancient Americans may have used this site as a sort of observatory to view the rising of Aldebaran just before the sun in June to predict the June solstice.

Interestingly, in about 2 million years, the NASA space probe Pioneer 10, now heading out into deep space, will pass Aldebaran.

The constellation Taurus. See Aldebaran marked as the Bull’s Eye? Image via Wikipedia (public domain).

Science of Aldebaran

Aldebaran is a huge aging star. The diameter is about 44 times the size of our sun. In fact, if Aldebaran replaced our sun, its surface would extend past the orbit of Mercury.

A comparison of the size of Aldebaran with our sun. Image via Wikipedia (public domain).

Aldebaran glows with the orangish color of a K5 giant star. In visible light, it is about 153 times brighter than the sun, although its surface temperature is lower, roughly 4,000 K (about 3,700 degrees C or 6,700 degrees F) compared to 5,800 K (about 5,500 C or 10,000 F) for the sun.

Although Aldebaran is associated with the stars of the Hyades, it’s much closer at 65 light-years distant. The Hyades are about 150 light-years away.

Aldebaran is an erratic variable with minor variations too small to see with the eye. Also, five faint stars are visible near Aldebaran, but so far none have been confirmed to be gravitationally bound to Aldebaran.

Aldebaran’s position is RA: 4h 35m 55s, dec: 16°30’35”

Bottom line: Aldebaran is an enormous, orange-colored star that marks one of the eyes of Taurus the Bull. It also marks one point of the V-shape of the Bull’s face.

The post Orange Aldebaran is Taurus the Bull’s fiery eye first appeared on EarthSky.

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Mysterious 3200 Phaethon: Parent to the Geminids

Artist’s concept of asteroid 3200 Phaethon. Most asteroids are rocky or metallic, and they don’t vent stuff into space. But 3200 Phaethon appears to be made of different materials from most asteroids. The sun might heat its surface so that gases inside it vaporize and vent into space. That might be how it sometimes brightens like a comet, and it might also dislodge small pieces of rocky debris … That is, potential Geminid meteors! Image via NASA/ JPL-Caltech/ IPAC.

The Geminid meteor shower is peaking on the overnight of December 13-14. Read more about 2024’s Geminid meteor shower.

Weirdly comet-like 3200 Phaethon

Most meteors in annual showers have comets as their sources. But not December’s Geminid meteors, whose source, known as 3200 Phaethon, is a strange hybrid of an asteroid and a comet. This “rock-comet” isn’t icy, like a comet is. But it brightens as it nears the sun, as comets do. And it’s been observed to have a tail when nearest the sun. Plus, it spawns the Geminid meteor shower. And so scientists have long puzzled over 3200 Phaethon. How can a rocky asteroid leave behind debris that sparks a meteor shower? Where does its tail come from?

In 2023, a couple of new studies provide insights on 3200 Phaethon, parent object of one of the year’s best meteor showers.

The 2025 EarthSky lunar calendar makes a great gift. Get yours today!

New research from Lowell Observatory

The Planetary Science Journal published a new study about 3200 Phaethon in April 2023.

On December 13, 2023, Spaceweather.com quoted astronomer Karl Battams of the U.S. Naval Observatory – a co-author of the April study – as saying:

Our work has upended years of belief about 3200 Phaethon, the source of the Geminids. It’s not what we thought it was.

In other words, since its discovery in 1983, 3200 Phaethon has appeared to be a rocky asteroid. NASA’s STEREO spacecraft first observed its tail – which appears when 3200 Phaethon passes near the sun in its 524-day orbit – in 2009 and 2012.

But, according to the story in Spaceweather.com today (December 13), Qicheng Zhang at Lowell Observatory in Flagstaff was “never convinced.” Spaceweather.com explained:

For one thing, the Geminid debris stream is massive (1,013 kg or 2,233 pounds), while the tail of 3200 Phaethon is puny, providing less than 1% of the mass required to explain the Geminids.

‘The tail we see today could never supply enough dust to supply the Geminid meteor shower,’ says Zhang.

Zhang, Battams, and colleagues decided to take a closer look. Using coronagraphs on the Solar and Heliospheric Observatory (SOHO), they monitored Phaethon as it passed by the sun in 2022. Color filters on the spacecraft revealed no dust or rock. Instead, Phaethon’s tail is made of sodium gas.

And therein lies the twist. Meteor showers are made of meteoroids, not gas. Suddenly, the Geminids are a mystery again.

‘We’re back to square one,’ says Zhang. ‘Where do the Geminids come from?’

Source: Sodium Brightening of (3200) Phaethon near Perihelion

More new research on 3200 Phaethon

Could the answer come from more new research, published on November 2, 2023, by a team at the University of Helsinki? This new study appears in the journal Nature Astronomy.

This team compared an infrared spectrum of 3200 Phaethon – from NASA’s Spitzer space telescope – to infrared spectra of known meteorites. They found Phaethon’s spectrum showed olivine, carbonates, iron sulfides and oxide minerals. Those substances are also found in the composition of CY carbonaceous chondrite meteorites (a rare type of meteorites with only six samples available for study).

When CY meteorites are exposed to high temperatures, the carbonates in the meteorites produce carbon dioxide. That releases water vapor, and the sulfides release sulfur gas. Could that be what’s happening in 3200 Phaethon also? Is that why this object has a tail when nearest the sun?

Source: Thermal decomposition as the activity driver of near-Earth asteroid (3200) Phaethon

NASA also found sodium coming off 3200 Phaethon’s surface

Scientists with NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, first announced sodium fizzing from the asteroid’s surface in 2021. Their statement explained that this asteroid:

… brightens as it gets close to the sun. Comets typically behave like this: When they heat up, their icy surfaces vaporize, causing them to become more active and brighten as the venting gases and dust scatter more sunlight. But what is causing Phaethon to brighten if not vaporizing ices?

So it’s been thought for a few years that sodium could play a role in the formation of 3200 Phaethon’s tail.

Read more: Fizzing Sodium Could Explain Asteroid Phaethon’s Cometlike Activity

View larger. | Look closely to see the faint dust trail between the white dots. Asteroid 3200 Phaethon, parent body for the Geminid meteor shower, left this trail. The WISPR camera aboard the Parker Solar Probe captured the trail for the 1st time in 2019. At that time, astronomers said that something “catastrophic” might have happened to Phaethon a couple of thousand years ago to create this trail of debris and the Geminid meteor shower. However, NASA astronomers wondered if sodium fizz is a better answer. Image via Brendan Gallagher/ Guillermo Stenborg/ US Naval Research Lab.

All that, and blue, too

By the way, the comet-like behavior of this asteroid isn’t the only unusual thing about it. For one thing, 3200 Phaethon has an odd color for an asteroid. Most asteroids are dull grey to red, depending on the type of material on their surface. 3200 Phaethon is blue. It’s not the only blue asteroid, but blue asteroids make up only a fraction of all known asteroids. And Phaethon isn’t just blue. It’s one of the bluest of similarly colored asteroids (or comets) in the solar system.

Here’s another odd feature of 3200 Phaethon. While comets tend to have more elliptical orbits, asteroid orbits are more circular. 3200 Phaethon’s orbit – which is now exceedingly well known – is highly elongated, reminiscent of some comets. Its orbit crosses the orbits of Mars, Earth, Venus and Mercury.

Plus, its orbit brings 3200 Phaethon closer to the sun than any other named asteroid (though some smaller, unnamed asteroids come even closer). At its closest point, Phaethon is only 13 million miles (20.9 million km) from the sun. That’s less than half of Mercury’s closest distance.

The name of this object – 3200 Phaethon – honors its relationship to the sun. In Greek mythology, Phaethon was the son of the sun god Helios.

A potentially hazardous asteroid

3200 Phaethon is classified as a potentially hazardous asteroid. But that doesn’t mean it’s a threat to Earth. It just means two things. First, 3200 Phaethon is big. The latest estimates (2021) suggest it’s 3.6 miles (5.8 km) wide. It’s big enough to cause significant regional damage if it were to strike Earth. Second, it makes periodic close approaches to Earth. But astronomers know of no upcoming strike by this object in the foreseeable future.

In 2017, 3200 Phaethon came closer to Earth than it will again until 2093. At its closest in 2017, it was still about 26 times the moon’s distance away.

Videos of 3200 Phaethon

Both amateur and professional astronomers watched 3200 Phaethon as carefully as they could in 2017. For example, Northolt Branch Observatories in London, England, created the animation below from images it captured in 2017.

Steven Bellavia also produced a video (below) of 3200 Phaethon in 2017. He commented then that he’d endured cloudy weather and subfreezing temperatures in order to capture the images.

Astronomers at the Arecibo Observatory generated these radar images of 3200 Phaethon on December 17, 2017. Image via Arecibo Observatory/ NASA/ NSF/ Wikimedia Commons (public domain).

The history of 3200 Phaethon

3200 Phaethon was the first asteroid discovered via spacecraft, on October 11, 1983. Astronomers Simon F. Green and John K. Davies noticed it while searching Infrared Astronomical Satellite data for moving objects. Charles T. Kowal confirmed it optically and said it was asteroid-like in appearance. The object received the provisional designation 1983 TB. Two years later, in 1985, using the convention for naming asteroids, astronomers assigned it its asteroid number and name: 3200 Phaethon.

Before 3200 Phaethon, scientists linked all known meteor showers to comets and not asteroids.

Thus, 3200 Phaethon surprised them from the beginning, because – while it looked like an asteroid – it appeared to be the source of the annual Geminid meteor shower. Astronomers began calling 3200 Phaethon a comet-asteroid hybrid, an asteroid that behaves like a comet. Later, they began using the term rock-comet.

What else will we learn about this object, as the years pass?

Bottom line: The Geminid meteor shower has a unique source – 3200 Phaethon – sometimes called a comet-asteroid hybrid, or a rock-comet. In November 2023, scientists found the composition of 3200 Phaethon matches a rare type of meteorite that releases gas when heated to temperatures like 3200 Phaethon experiences when it nears the sun. And in 2021, scientists suggested that some of this object’s comet-like behavior might stem from sodium fizzing from its surface.

Source: Thermal decomposition as the activity driver of near-Earth asteroid (3200) Phaethon

Via University of Helsinki, JPL and U.S. Naval Research Lab

The post Mysterious 3200 Phaethon: Parent to the Geminids first appeared on EarthSky.

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Artist’s concept of asteroid 3200 Phaethon. Most asteroids are rocky or metallic, and they don’t vent stuff into space. But 3200 Phaethon appears to be made of different materials from most asteroids. The sun might heat its surface so that gases inside it vaporize and vent into space. That might be how it sometimes brightens like a comet, and it might also dislodge small pieces of rocky debris … That is, potential Geminid meteors! Image via NASA/ JPL-Caltech/ IPAC.

The Geminid meteor shower is peaking on the overnight of December 13-14. Read more about 2024’s Geminid meteor shower.

Weirdly comet-like 3200 Phaethon

Most meteors in annual showers have comets as their sources. But not December’s Geminid meteors, whose source, known as 3200 Phaethon, is a strange hybrid of an asteroid and a comet. This “rock-comet” isn’t icy, like a comet is. But it brightens as it nears the sun, as comets do. And it’s been observed to have a tail when nearest the sun. Plus, it spawns the Geminid meteor shower. And so scientists have long puzzled over 3200 Phaethon. How can a rocky asteroid leave behind debris that sparks a meteor shower? Where does its tail come from?

In 2023, a couple of new studies provide insights on 3200 Phaethon, parent object of one of the year’s best meteor showers.

The 2025 EarthSky lunar calendar makes a great gift. Get yours today!

New research from Lowell Observatory

The Planetary Science Journal published a new study about 3200 Phaethon in April 2023.

On December 13, 2023, Spaceweather.com quoted astronomer Karl Battams of the U.S. Naval Observatory – a co-author of the April study – as saying:

Our work has upended years of belief about 3200 Phaethon, the source of the Geminids. It’s not what we thought it was.

In other words, since its discovery in 1983, 3200 Phaethon has appeared to be a rocky asteroid. NASA’s STEREO spacecraft first observed its tail – which appears when 3200 Phaethon passes near the sun in its 524-day orbit – in 2009 and 2012.

But, according to the story in Spaceweather.com today (December 13), Qicheng Zhang at Lowell Observatory in Flagstaff was “never convinced.” Spaceweather.com explained:

For one thing, the Geminid debris stream is massive (1,013 kg or 2,233 pounds), while the tail of 3200 Phaethon is puny, providing less than 1% of the mass required to explain the Geminids.

‘The tail we see today could never supply enough dust to supply the Geminid meteor shower,’ says Zhang.

Zhang, Battams, and colleagues decided to take a closer look. Using coronagraphs on the Solar and Heliospheric Observatory (SOHO), they monitored Phaethon as it passed by the sun in 2022. Color filters on the spacecraft revealed no dust or rock. Instead, Phaethon’s tail is made of sodium gas.

And therein lies the twist. Meteor showers are made of meteoroids, not gas. Suddenly, the Geminids are a mystery again.

‘We’re back to square one,’ says Zhang. ‘Where do the Geminids come from?’

Source: Sodium Brightening of (3200) Phaethon near Perihelion

More new research on 3200 Phaethon

Could the answer come from more new research, published on November 2, 2023, by a team at the University of Helsinki? This new study appears in the journal Nature Astronomy.

This team compared an infrared spectrum of 3200 Phaethon – from NASA’s Spitzer space telescope – to infrared spectra of known meteorites. They found Phaethon’s spectrum showed olivine, carbonates, iron sulfides and oxide minerals. Those substances are also found in the composition of CY carbonaceous chondrite meteorites (a rare type of meteorites with only six samples available for study).

When CY meteorites are exposed to high temperatures, the carbonates in the meteorites produce carbon dioxide. That releases water vapor, and the sulfides release sulfur gas. Could that be what’s happening in 3200 Phaethon also? Is that why this object has a tail when nearest the sun?

Source: Thermal decomposition as the activity driver of near-Earth asteroid (3200) Phaethon

NASA also found sodium coming off 3200 Phaethon’s surface

Scientists with NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, first announced sodium fizzing from the asteroid’s surface in 2021. Their statement explained that this asteroid:

… brightens as it gets close to the sun. Comets typically behave like this: When they heat up, their icy surfaces vaporize, causing them to become more active and brighten as the venting gases and dust scatter more sunlight. But what is causing Phaethon to brighten if not vaporizing ices?

So it’s been thought for a few years that sodium could play a role in the formation of 3200 Phaethon’s tail.

Read more: Fizzing Sodium Could Explain Asteroid Phaethon’s Cometlike Activity

View larger. | Look closely to see the faint dust trail between the white dots. Asteroid 3200 Phaethon, parent body for the Geminid meteor shower, left this trail. The WISPR camera aboard the Parker Solar Probe captured the trail for the 1st time in 2019. At that time, astronomers said that something “catastrophic” might have happened to Phaethon a couple of thousand years ago to create this trail of debris and the Geminid meteor shower. However, NASA astronomers wondered if sodium fizz is a better answer. Image via Brendan Gallagher/ Guillermo Stenborg/ US Naval Research Lab.

All that, and blue, too

By the way, the comet-like behavior of this asteroid isn’t the only unusual thing about it. For one thing, 3200 Phaethon has an odd color for an asteroid. Most asteroids are dull grey to red, depending on the type of material on their surface. 3200 Phaethon is blue. It’s not the only blue asteroid, but blue asteroids make up only a fraction of all known asteroids. And Phaethon isn’t just blue. It’s one of the bluest of similarly colored asteroids (or comets) in the solar system.

Here’s another odd feature of 3200 Phaethon. While comets tend to have more elliptical orbits, asteroid orbits are more circular. 3200 Phaethon’s orbit – which is now exceedingly well known – is highly elongated, reminiscent of some comets. Its orbit crosses the orbits of Mars, Earth, Venus and Mercury.

Plus, its orbit brings 3200 Phaethon closer to the sun than any other named asteroid (though some smaller, unnamed asteroids come even closer). At its closest point, Phaethon is only 13 million miles (20.9 million km) from the sun. That’s less than half of Mercury’s closest distance.

The name of this object – 3200 Phaethon – honors its relationship to the sun. In Greek mythology, Phaethon was the son of the sun god Helios.

A potentially hazardous asteroid

3200 Phaethon is classified as a potentially hazardous asteroid. But that doesn’t mean it’s a threat to Earth. It just means two things. First, 3200 Phaethon is big. The latest estimates (2021) suggest it’s 3.6 miles (5.8 km) wide. It’s big enough to cause significant regional damage if it were to strike Earth. Second, it makes periodic close approaches to Earth. But astronomers know of no upcoming strike by this object in the foreseeable future.

In 2017, 3200 Phaethon came closer to Earth than it will again until 2093. At its closest in 2017, it was still about 26 times the moon’s distance away.

Videos of 3200 Phaethon

Both amateur and professional astronomers watched 3200 Phaethon as carefully as they could in 2017. For example, Northolt Branch Observatories in London, England, created the animation below from images it captured in 2017.

Steven Bellavia also produced a video (below) of 3200 Phaethon in 2017. He commented then that he’d endured cloudy weather and subfreezing temperatures in order to capture the images.

Astronomers at the Arecibo Observatory generated these radar images of 3200 Phaethon on December 17, 2017. Image via Arecibo Observatory/ NASA/ NSF/ Wikimedia Commons (public domain).

The history of 3200 Phaethon

3200 Phaethon was the first asteroid discovered via spacecraft, on October 11, 1983. Astronomers Simon F. Green and John K. Davies noticed it while searching Infrared Astronomical Satellite data for moving objects. Charles T. Kowal confirmed it optically and said it was asteroid-like in appearance. The object received the provisional designation 1983 TB. Two years later, in 1985, using the convention for naming asteroids, astronomers assigned it its asteroid number and name: 3200 Phaethon.

Before 3200 Phaethon, scientists linked all known meteor showers to comets and not asteroids.

Thus, 3200 Phaethon surprised them from the beginning, because – while it looked like an asteroid – it appeared to be the source of the annual Geminid meteor shower. Astronomers began calling 3200 Phaethon a comet-asteroid hybrid, an asteroid that behaves like a comet. Later, they began using the term rock-comet.

What else will we learn about this object, as the years pass?

Bottom line: The Geminid meteor shower has a unique source – 3200 Phaethon – sometimes called a comet-asteroid hybrid, or a rock-comet. In November 2023, scientists found the composition of 3200 Phaethon matches a rare type of meteorite that releases gas when heated to temperatures like 3200 Phaethon experiences when it nears the sun. And in 2021, scientists suggested that some of this object’s comet-like behavior might stem from sodium fizzing from its surface.

Source: Thermal decomposition as the activity driver of near-Earth asteroid (3200) Phaethon

Via University of Helsinki, JPL and U.S. Naval Research Lab

The post Mysterious 3200 Phaethon: Parent to the Geminids first appeared on EarthSky.

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What if we find alien life and don’t recognize it?

This artist’s image depicts part of a model of Earth’s tree of life. When humans finally discover alien life, will they be able to recognize it? Astrobiologists are developing a universal theory of life to provide a framework for the search for extraterrestrial life. Image via Zosia Rostomian/ Lawrence Berkeley National Laboratory.

• Astrobiologists are developing a theory of life to provide a framework for identifying extraterrestrial biology.
• The task includes considering alternatives to Earth’s chemistry in light of the diverse environments on worlds where life might form.
• Detecting alien life may involve studying exoplanets for biosignatures, technosignatures or signs of mineral evolution that hint at the presence of life.

By Chris Impey, University of Arizona

The 2025 EarthSky Lunar Calendar is now available! A unique and beautiful poster-sized calendar. Makes a great gift. Get yours today!

Extraterrestrial life may look nothing like life on Earth

We have only one example of biology forming in the universe: life on Earth. But what if life can form in other ways? How do you look for alien life when you don’t know what alien life might look like?

These questions are preoccupying astrobiologists, who are scientists who look for life beyond Earth. Astrobiologists have attempted to come up with universal rules that govern the emergence of complex physical and biological systems both on Earth and beyond.

I’m an astronomer who has written extensively about astrobiology. Through my research, I’ve learned that the most abundant form of extraterrestrial life is likely to be microbial, since single cells can form more readily than large organisms. But just in case there’s advanced alien life out there, I’m on the international advisory council for the group designing messages to send to those civilizations.

Universe is teeming with alien worlds

Since the first discovery of an exoplanet in 1995, more than 5,000 exoplanets, or planets orbiting other stars, have been found.

Many of these exoplanets are small and rocky, like Earth, and in the habitable zones of their stars. The habitable zone is the range of distances between the surface of a planet and the star it orbits that would allow the planet to have liquid water, and thus support life as we on Earth know it.

The sample of exoplanets detected so far projects 300 million potential biological experiments in our galaxy – or 300 million places, including exoplanets and other bodies such as moons, with suitable conditions for biology to arise.

Detecting alien life beyond Earth

The uncertainty for researchers starts with the definition of life. It feels like defining life should be easy, since we know life when we see it, whether it’s a flying bird or a microbe moving in a drop of water. But scientists don’t agree on a definition, and some think a comprehensive definition might not be possible.

NASA defines life as a “self-sustaining chemical reaction capable of Darwinian evolution.” That means organisms with a complex chemical system that evolve by adapting to their environment. Darwinian evolution says that the survival of an organism depends on its fitness in its environment.

Evolution is the process of change in systems. It can describe how a group of something becomes more complex – or even just different – over time.

Exoplanets are remote and hundreds of millions of times fainter than their parent stars, so studying them is challenging. Astronomers can inspect the atmospheres and surfaces of Earth-like exoplanets using a method called spectroscopy to look for chemical signatures of life.

Spectroscopy might detect signatures of oxygen in a planet’s atmosphere. On Earth, microbes called blue-green algae released oxygen into the atmosphere via photosynthesis several billion years ago. Or it might detect chlorophyll signatures, which on Earth indicate plant life.

NASA’s definition of life leads to some important but unanswered questions. Is Darwinian evolution universal? What chemical reactions can lead to biology off Earth?

How does order arise in a chaotic universe?

All life on Earth, from a fungal spore to a blue whale, evolved from a microbial last common ancestor about 4 billion years ago.

The same chemical processes are seen in all living organisms on Earth, and those processes might be universal. They also may be radically different elsewhere.

In October 2024, a diverse group of scientists gathered to think outside the box on evolution. They wanted to step back and explore what sort of processes created order in the universe – biological or not – to figure out how to study the emergence of life totally unlike life on Earth.

Two researchers present argued that complex systems of chemicals or minerals, when in environments that allow some configurations to persist better than others, evolve to store larger amounts of information. As time goes by, the system will grow more diverse and complex, gaining the functions needed for survival, through a kind of natural selection.

They speculated that there might be a law to describe the evolution of a wide variety of physical systems. Biological evolution through natural selection would be just one example of this broader law.

Finding the boundary between life and nonlife

In biology, information refers to the instructions stored in the sequence of nucleotides on a DNA molecule, which collectively make up an organism’s genome and dictate what the organism looks like and how it functions.

If you define complexity in terms of information theory, natural selection will cause a genome to grow more complex as it stores more information about its environment.

Complexity might be useful in measuring the boundary between life and nonlife.

However, it’s wrong to conclude that animals are more complex than microbes. Biological information increases with genome size, but evolutionary information density drops. Evolutionary information density is the fraction of functional genes within the genome, or the fraction of the total genetic material that expresses fitness for the environment.

Organisms that people think of as primitive, such as bacteria, have genomes with high information density and so appear better designed than the genomes of plants or animals.

A universal theory of life is still elusive. Such a theory would include the concepts of complexity and information storage, but it would not be tied to DNA or the particular kinds of cells we find in terrestrial biology.

Implications for the search for alien life

Researchers have explored alternatives to terrestrial biochemistry. All known living organisms, from bacteria to humans, contain water, and it is a solvent that is essential for life on Earth. A solvent is a liquid medium that facilitates chemical reactions from which life could emerge. But life could potentially emerge from other solvents, too.

Astrobiologists William Bains and Sara Seager have explored thousands of molecules that might be associated with life. Plausible solvents include sulfuric acid, ammonia, liquid carbon dioxide and even liquid sulfur.

Alien life might not be based on carbon, which forms the backbone of all life’s essential molecules – at least here on Earth. It might not even need a planet to survive.

Advanced forms of life on alien planets could be so strange that they’re unrecognizable. As astrobiologists try to detect life off Earth, they’ll need to be creative.

One strategy is to measure mineral signatures on the rocky surfaces of exoplanets, since mineral diversity tracks terrestrial biological evolution. As life evolved on Earth, it used and created minerals for exoskeletons and habitats. The hundred minerals present when life first formed have grown to about 5,000 today.

For example, zircons are simple silicate crystals that date back to the time before life started. A zircon found in Australia is the oldest known piece of Earth’s crust. But other minerals, such as apatite, a complex calcium phosphate mineral, are created by biology. Apatite is a primary ingredient in bones, teeth and fish scales.

Another strategy to finding life unlike that on Earth is to detect evidence of a civilization, such as artificial lights, or the industrial pollutant nitrogen dioxide in the atmosphere. These are examples of tracers of intelligent life called technosignatures.

It’s unclear how and when a first detection of life beyond Earth will happen. It might be within the solar system, or by sniffing exoplanet atmospheres, or by detecting artificial radio signals from a distant civilization.

The search is a twisting road, not a straightforward path. And that’s for life as we know it. For life as we don’t know it, all bets are off.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: Astrobiologists are exploring how complexity arises in the universe to build frameworks for recognizing alien life when we finally find it.

Read more: Is alien life purple? Researchers look beyond Earth’s green

The post What if we find alien life and don’t recognize it? first appeared on EarthSky.

from EarthSky https://ift.tt/N5WROPk

This artist’s image depicts part of a model of Earth’s tree of life. When humans finally discover alien life, will they be able to recognize it? Astrobiologists are developing a universal theory of life to provide a framework for the search for extraterrestrial life. Image via Zosia Rostomian/ Lawrence Berkeley National Laboratory.

• Astrobiologists are developing a theory of life to provide a framework for identifying extraterrestrial biology.
• The task includes considering alternatives to Earth’s chemistry in light of the diverse environments on worlds where life might form.
• Detecting alien life may involve studying exoplanets for biosignatures, technosignatures or signs of mineral evolution that hint at the presence of life.

By Chris Impey, University of Arizona

The 2025 EarthSky Lunar Calendar is now available! A unique and beautiful poster-sized calendar. Makes a great gift. Get yours today!

Extraterrestrial life may look nothing like life on Earth

We have only one example of biology forming in the universe: life on Earth. But what if life can form in other ways? How do you look for alien life when you don’t know what alien life might look like?

These questions are preoccupying astrobiologists, who are scientists who look for life beyond Earth. Astrobiologists have attempted to come up with universal rules that govern the emergence of complex physical and biological systems both on Earth and beyond.

I’m an astronomer who has written extensively about astrobiology. Through my research, I’ve learned that the most abundant form of extraterrestrial life is likely to be microbial, since single cells can form more readily than large organisms. But just in case there’s advanced alien life out there, I’m on the international advisory council for the group designing messages to send to those civilizations.

Universe is teeming with alien worlds

Since the first discovery of an exoplanet in 1995, more than 5,000 exoplanets, or planets orbiting other stars, have been found.

Many of these exoplanets are small and rocky, like Earth, and in the habitable zones of their stars. The habitable zone is the range of distances between the surface of a planet and the star it orbits that would allow the planet to have liquid water, and thus support life as we on Earth know it.

The sample of exoplanets detected so far projects 300 million potential biological experiments in our galaxy – or 300 million places, including exoplanets and other bodies such as moons, with suitable conditions for biology to arise.

Detecting alien life beyond Earth

The uncertainty for researchers starts with the definition of life. It feels like defining life should be easy, since we know life when we see it, whether it’s a flying bird or a microbe moving in a drop of water. But scientists don’t agree on a definition, and some think a comprehensive definition might not be possible.

NASA defines life as a “self-sustaining chemical reaction capable of Darwinian evolution.” That means organisms with a complex chemical system that evolve by adapting to their environment. Darwinian evolution says that the survival of an organism depends on its fitness in its environment.

Evolution is the process of change in systems. It can describe how a group of something becomes more complex – or even just different – over time.

Exoplanets are remote and hundreds of millions of times fainter than their parent stars, so studying them is challenging. Astronomers can inspect the atmospheres and surfaces of Earth-like exoplanets using a method called spectroscopy to look for chemical signatures of life.

Spectroscopy might detect signatures of oxygen in a planet’s atmosphere. On Earth, microbes called blue-green algae released oxygen into the atmosphere via photosynthesis several billion years ago. Or it might detect chlorophyll signatures, which on Earth indicate plant life.

NASA’s definition of life leads to some important but unanswered questions. Is Darwinian evolution universal? What chemical reactions can lead to biology off Earth?

How does order arise in a chaotic universe?

All life on Earth, from a fungal spore to a blue whale, evolved from a microbial last common ancestor about 4 billion years ago.

The same chemical processes are seen in all living organisms on Earth, and those processes might be universal. They also may be radically different elsewhere.

In October 2024, a diverse group of scientists gathered to think outside the box on evolution. They wanted to step back and explore what sort of processes created order in the universe – biological or not – to figure out how to study the emergence of life totally unlike life on Earth.

Two researchers present argued that complex systems of chemicals or minerals, when in environments that allow some configurations to persist better than others, evolve to store larger amounts of information. As time goes by, the system will grow more diverse and complex, gaining the functions needed for survival, through a kind of natural selection.

They speculated that there might be a law to describe the evolution of a wide variety of physical systems. Biological evolution through natural selection would be just one example of this broader law.

Finding the boundary between life and nonlife

In biology, information refers to the instructions stored in the sequence of nucleotides on a DNA molecule, which collectively make up an organism’s genome and dictate what the organism looks like and how it functions.

If you define complexity in terms of information theory, natural selection will cause a genome to grow more complex as it stores more information about its environment.

Complexity might be useful in measuring the boundary between life and nonlife.

However, it’s wrong to conclude that animals are more complex than microbes. Biological information increases with genome size, but evolutionary information density drops. Evolutionary information density is the fraction of functional genes within the genome, or the fraction of the total genetic material that expresses fitness for the environment.

Organisms that people think of as primitive, such as bacteria, have genomes with high information density and so appear better designed than the genomes of plants or animals.

A universal theory of life is still elusive. Such a theory would include the concepts of complexity and information storage, but it would not be tied to DNA or the particular kinds of cells we find in terrestrial biology.

Implications for the search for alien life

Researchers have explored alternatives to terrestrial biochemistry. All known living organisms, from bacteria to humans, contain water, and it is a solvent that is essential for life on Earth. A solvent is a liquid medium that facilitates chemical reactions from which life could emerge. But life could potentially emerge from other solvents, too.

Astrobiologists William Bains and Sara Seager have explored thousands of molecules that might be associated with life. Plausible solvents include sulfuric acid, ammonia, liquid carbon dioxide and even liquid sulfur.

Alien life might not be based on carbon, which forms the backbone of all life’s essential molecules – at least here on Earth. It might not even need a planet to survive.

Advanced forms of life on alien planets could be so strange that they’re unrecognizable. As astrobiologists try to detect life off Earth, they’ll need to be creative.

One strategy is to measure mineral signatures on the rocky surfaces of exoplanets, since mineral diversity tracks terrestrial biological evolution. As life evolved on Earth, it used and created minerals for exoskeletons and habitats. The hundred minerals present when life first formed have grown to about 5,000 today.

For example, zircons are simple silicate crystals that date back to the time before life started. A zircon found in Australia is the oldest known piece of Earth’s crust. But other minerals, such as apatite, a complex calcium phosphate mineral, are created by biology. Apatite is a primary ingredient in bones, teeth and fish scales.

Another strategy to finding life unlike that on Earth is to detect evidence of a civilization, such as artificial lights, or the industrial pollutant nitrogen dioxide in the atmosphere. These are examples of tracers of intelligent life called technosignatures.

It’s unclear how and when a first detection of life beyond Earth will happen. It might be within the solar system, or by sniffing exoplanet atmospheres, or by detecting artificial radio signals from a distant civilization.

The search is a twisting road, not a straightforward path. And that’s for life as we know it. For life as we don’t know it, all bets are off.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: Astrobiologists are exploring how complexity arises in the universe to build frameworks for recognizing alien life when we finally find it.

Read more: Is alien life purple? Researchers look beyond Earth’s green

The post What if we find alien life and don’t recognize it? first appeared on EarthSky.

from EarthSky https://ift.tt/N5WROPk

Meet Pisces the Fish, 1st constellation of the zodiac

Pisces the Fish is a constellation of the zodiac that lies near the Great Square of Pegasus. Pisces contains an asterism, or informal but noticeable grouping of stars, known as the Circlet. Chart via EarthSky.

Pisces the Fish is one of the constellations of the zodiac, which means that it lies on the ecliptic, or path of the sun and planets through our sky.

Pisces has the nickname of first constellation of the zodiac, because the sun appears in front of this constellation during the March equinox. With this in mind, one tropical year is usually defined as the period of time between successive March equinoxes. So – in this sense – the March equinox marks the beginning of a new year. Also, that is why Pisces often appears as marking the starting point of the zodiac.

Generally, the best time to view constellations in the night sky is when they’re opposite the sun in the sky. They rise at sunset and are up all night. So, if the sun is in Pisces in March, then the opposite side of the calendar, October and the following months, is a good time for observing Pisces. Indeed, in December, by the time the sky is dark, Pisces is already high in the southern sky for us in the Northern Hemisphere. Pisces is at its highest for the evening at about 8 p.m. your local time in December.

The 2025 EarthSky lunar calendar makes a great gift. Get yours today!

How to find Pisces

However, you need a dark country sky to see this fairly dim constellation swimming in what the early stargazers considered to be a watery region of the lore-laden heavens. Pisces is northeast of the constellation Aquarius the Water Bearer and to the northwest of the constellation Cetus the Whale.

Fortunately, you can find Pisces rather handily by referring to the signpost known as the Great Square of Pegasus. Look first for the Circlet of Pisces – otherwise known as the head of the Western Fish – to the south of the Square of Pegasus. Once you’ve found the Western Fish, go on from there to catch the Eastern Fish that’s jumping upward to the east of the Square of Pegasus. As seen from the northern tropics or the Southern Hemisphere, the Eastern Fish appears to be plunging downward. The entire constellation looks like the letter V, and a very graceful and lovely V at that.

The stars of the Fish

Pisces has few bright stars. The stars most people focus on are the ones that create the Circlet of Pisces. The brightest star here is the 3.7-magnitude Gamma Piscium. Moving counterclockwise around the circle, we next find Theta Piscium at magnitude 4.2. Then comes Iota Piscium at magnitude 4.1. Lastly is Lambda Piscium at magnitude 4.5. These stars are too dim to see from a light-polluted city.

Marking the bottom of the V-shape where the tails of the fish come together is a magnitude-3.8 star named Al Risha, or Alpha Piscium. Fourteen degrees northwest is magnitude 3.6 Eta Piscium, the constellation’s brightest star. (Halfway between is magnitude 4.2 Omicron Piscium.) Just over one degree east from Eta Piscium is the one Messier object in Pisces.

Star chart for Pisces the Fish. The two fish lie on either side of the Great Square of Pegasus. The ecliptic (the path of the planets, sun, and moon) cuts through Pisces, which makes it one of the constellations of the zodiac. Image via IAU.

The lone Messier object

Pisces can only claim one Messier object – that is, a fuzzy object resembling a comet but really a star cluster, nebula or galaxy – within its borders. It’s Messier 74 (M74), a face-on spiral galaxy looming at an estimated 35 million light-years distant.

In the month of March, when it’s technically possible to see all the Messier objects in the span of one night during a Messier marathon, this Messier object in the constellation Pisces is one that is commonly missed.

That’s because, at that time of year, M74 lurks rather low in the western sky at nightfall and quickly sinks out of view shortly thereafter. Plus, this distant galaxy has an extremely low surface brightness, so excellent seeing conditions are absolutely critical for catching it. You don’t need a large telescope as much as you need a dark, transparent sky.

Try spotting it this December using averted vision on a dark, clear moonless night.

A Hubble Space Telescope image of Messier 74. Image via NASA.

Pisces in mythology and star lore

Greek and Roman versions of Pisces’ sky lore seemed to have come from Syria, where fish were regarded as divine. There seems to be some confusion as to whether the ancient Syrians abstained from fish altogether or only fish from the Chalos River (presently called the Queiq or Aleppo River).

The Syrian goddess of love and fertility, Atagartis, is often portrayed as half woman and half fish. She is thought to be the origin of the Greek goddess Aphrodite and the Roman goddess Venus.

According to Greek mythology, the fire-breathing monster Typhon was about to devour Aphrodite (the Roman Venus) and her son Eros (the Roman Cupid), so they turned into fish and jumped into the Euphrates River to make a great escape. Mother and son tied themselves together with a cord to make sure they would not lose one another in the tumbling waters.

How long is the Age of Pisces?

By some definitions, we’ll continue to live within the Age of Pisces as long the sun shines in front of this constellation on the March equinox. By the way, although the sun hasn’t appeared in front of the constellation Aries on the equinox for over 2,000 years, we still refer to the March equinox point as the First Point in Aries.

If we accept the constellation boundaries as defined by the International Astronomical Union, the Age of Pisces started in 68 BCE and the Age of Aquarius will begin in 2597.

But there are many varied views on this, some of which you can read about in this post: When will the Age of Aquarius begin?

Bottom line: Pisces the Fish is a zodiac constellation that is high in the sky on December evenings. Look for it and its asterism, the Circlet of Pisces.

Meet Taurus the Bull in the evening sky
Meet Gemini the Twins, home to 2 bright stars
Leo the Lion and its backward question mark
Virgo the Maiden represents a harvest goddess
Meet Cancer the Crab and its Beehive Cluster
Meet Libra the Scales, a zodiacal constellation
Scorpius the Scorpion is a summertime delight
Sagittarius the Archer and its famous Teapot
Capricornus the Sea-goat has an arrowhead shape
Meet Aquarius the Water Bearer and its stars
Meet Pisces the Fish, 1st constellation of the zodiac
Say hello to Aries the Ram
Born under the sign of Ophiuchus?

The post Meet Pisces the Fish, 1st constellation of the zodiac first appeared on EarthSky.

from EarthSky https://ift.tt/n5J0BD1

Pisces the Fish is a constellation of the zodiac that lies near the Great Square of Pegasus. Pisces contains an asterism, or informal but noticeable grouping of stars, known as the Circlet. Chart via EarthSky.

Pisces the Fish is one of the constellations of the zodiac, which means that it lies on the ecliptic, or path of the sun and planets through our sky.

Pisces has the nickname of first constellation of the zodiac, because the sun appears in front of this constellation during the March equinox. With this in mind, one tropical year is usually defined as the period of time between successive March equinoxes. So – in this sense – the March equinox marks the beginning of a new year. Also, that is why Pisces often appears as marking the starting point of the zodiac.

Generally, the best time to view constellations in the night sky is when they’re opposite the sun in the sky. They rise at sunset and are up all night. So, if the sun is in Pisces in March, then the opposite side of the calendar, October and the following months, is a good time for observing Pisces. Indeed, in December, by the time the sky is dark, Pisces is already high in the southern sky for us in the Northern Hemisphere. Pisces is at its highest for the evening at about 8 p.m. your local time in December.

The 2025 EarthSky lunar calendar makes a great gift. Get yours today!

How to find Pisces

However, you need a dark country sky to see this fairly dim constellation swimming in what the early stargazers considered to be a watery region of the lore-laden heavens. Pisces is northeast of the constellation Aquarius the Water Bearer and to the northwest of the constellation Cetus the Whale.

Fortunately, you can find Pisces rather handily by referring to the signpost known as the Great Square of Pegasus. Look first for the Circlet of Pisces – otherwise known as the head of the Western Fish – to the south of the Square of Pegasus. Once you’ve found the Western Fish, go on from there to catch the Eastern Fish that’s jumping upward to the east of the Square of Pegasus. As seen from the northern tropics or the Southern Hemisphere, the Eastern Fish appears to be plunging downward. The entire constellation looks like the letter V, and a very graceful and lovely V at that.

The stars of the Fish

Pisces has few bright stars. The stars most people focus on are the ones that create the Circlet of Pisces. The brightest star here is the 3.7-magnitude Gamma Piscium. Moving counterclockwise around the circle, we next find Theta Piscium at magnitude 4.2. Then comes Iota Piscium at magnitude 4.1. Lastly is Lambda Piscium at magnitude 4.5. These stars are too dim to see from a light-polluted city.

Marking the bottom of the V-shape where the tails of the fish come together is a magnitude-3.8 star named Al Risha, or Alpha Piscium. Fourteen degrees northwest is magnitude 3.6 Eta Piscium, the constellation’s brightest star. (Halfway between is magnitude 4.2 Omicron Piscium.) Just over one degree east from Eta Piscium is the one Messier object in Pisces.

Star chart for Pisces the Fish. The two fish lie on either side of the Great Square of Pegasus. The ecliptic (the path of the planets, sun, and moon) cuts through Pisces, which makes it one of the constellations of the zodiac. Image via IAU.

The lone Messier object

Pisces can only claim one Messier object – that is, a fuzzy object resembling a comet but really a star cluster, nebula or galaxy – within its borders. It’s Messier 74 (M74), a face-on spiral galaxy looming at an estimated 35 million light-years distant.

In the month of March, when it’s technically possible to see all the Messier objects in the span of one night during a Messier marathon, this Messier object in the constellation Pisces is one that is commonly missed.

That’s because, at that time of year, M74 lurks rather low in the western sky at nightfall and quickly sinks out of view shortly thereafter. Plus, this distant galaxy has an extremely low surface brightness, so excellent seeing conditions are absolutely critical for catching it. You don’t need a large telescope as much as you need a dark, transparent sky.

Try spotting it this December using averted vision on a dark, clear moonless night.

A Hubble Space Telescope image of Messier 74. Image via NASA.

Pisces in mythology and star lore

Greek and Roman versions of Pisces’ sky lore seemed to have come from Syria, where fish were regarded as divine. There seems to be some confusion as to whether the ancient Syrians abstained from fish altogether or only fish from the Chalos River (presently called the Queiq or Aleppo River).

The Syrian goddess of love and fertility, Atagartis, is often portrayed as half woman and half fish. She is thought to be the origin of the Greek goddess Aphrodite and the Roman goddess Venus.

According to Greek mythology, the fire-breathing monster Typhon was about to devour Aphrodite (the Roman Venus) and her son Eros (the Roman Cupid), so they turned into fish and jumped into the Euphrates River to make a great escape. Mother and son tied themselves together with a cord to make sure they would not lose one another in the tumbling waters.

How long is the Age of Pisces?

By some definitions, we’ll continue to live within the Age of Pisces as long the sun shines in front of this constellation on the March equinox. By the way, although the sun hasn’t appeared in front of the constellation Aries on the equinox for over 2,000 years, we still refer to the March equinox point as the First Point in Aries.

If we accept the constellation boundaries as defined by the International Astronomical Union, the Age of Pisces started in 68 BCE and the Age of Aquarius will begin in 2597.

But there are many varied views on this, some of which you can read about in this post: When will the Age of Aquarius begin?

Bottom line: Pisces the Fish is a zodiac constellation that is high in the sky on December evenings. Look for it and its asterism, the Circlet of Pisces.

Meet Taurus the Bull in the evening sky
Meet Gemini the Twins, home to 2 bright stars
Leo the Lion and its backward question mark
Virgo the Maiden represents a harvest goddess
Meet Cancer the Crab and its Beehive Cluster
Meet Libra the Scales, a zodiacal constellation
Scorpius the Scorpion is a summertime delight
Sagittarius the Archer and its famous Teapot
Capricornus the Sea-goat has an arrowhead shape
Meet Aquarius the Water Bearer and its stars
Meet Pisces the Fish, 1st constellation of the zodiac
Say hello to Aries the Ram
Born under the sign of Ophiuchus?

The post Meet Pisces the Fish, 1st constellation of the zodiac first appeared on EarthSky.

from EarthSky https://ift.tt/n5J0BD1