Is this an alien radio signal from a super-Earth exoplanet?

View larger. | Artist’s concept of the exoplanet called K2-155 d. China’s FAST radio telescope detected an intriguing radio signal coming from the direction of this super-Earth world. Is it an alien radio signal? Image via NASA.

• Did China’s FAST radio telescope detect an alien radio signal?
• The narrowband radio signal came from the direction of the super-Earth exoplanet K2-155 d, 238 light-years away.
• The signal fit several criteria for an extraterrestrial signal, but other details make the scientists think it is probably earthly radio interference.

Science news, night sky events and beautiful photos, all in one place. Click here to subscribe to our free daily newsletter.

An alien radio signal from K2-155 d?

Are there any alien civilizations out there? For several decades, scientists have been searching for evidence that they exist. That effort is collectively known as the Search for Extraterrestrial Intelligence (SETI). In recent years, China’s Five-hundred-meter Aperture Spherical Radio Telescope (FAST) has become involved. And in late August, scientists with FAST said in a new paper that they found something interesting while surveying 33 planetary systems.

They announced that FAST detected a narrowband radio signal coming from the direction of the planetary system K2-155, 238 light-years away.

The system contains a super-Earth type exoplanet, K2-155 d, that could be potentially habitable. It orbits a red dwarf star and is 1.6 times the radius of Earth. Of course, we don’t know enough about this world to have any serious confidence in it being a likely place for life to start.

FAST actually originally detected the signal in 2021, but it went unnoticed at the time. The research team was sifting through the data using new machine-learning search pipeline. This pipeline is designed to allow them to more easily separate genuine candidates from earthly radio interference.

The intriguing peer-reviewed results were published in The Astronomical Journal on August 27, 2026.

Whittling down the candidates

This survey produced 139,127 initial candidates. Those were eventually narrowed down to just the two most promising candidates. One of them, from the direction of the star Kepler-438, was then ultimately found to be earthly radio interference.

That left K2-155.

View larger. | Size comparison between K2-155 d and Earth (artist’s concept). Image via Martin Vargic/ Halcyon Maps/ Wikimedia Commons.

Ticking the boxes for an alien radio signal

The signal, at 1148.4167 megahertz, was coming from the direction of K2-155, a small red dwarf star 238 light-years away. And it seemed to pass the initial tests that astronomers have for determining whether it was a natural radio signal from the cosmos or an artificial signal created by us (earthly radio interference) or even some other intelligence out there.

The new machine-learning algorithm uses a mathematical technique called wavelet analysis to tease out faint signals from the other noisy radio data.

The researchers first noticed that the signal was very narrow. It is rare for natural sources to produce narrowband signals. Such signals are usually artificial in origin. The paper states:

Natural astrophysical processes rarely generate extremely narrow spectral features while engineered transmitters often do.

Another possible clue was that the signal drifted. That’s because the relative motion of a planet rotating on its axis and orbiting its host star can shift the frequency of a radio signal through the Doppler effect. This produces a telltale drift of the signal over time. The K2-155 signal drifted.

One problem, though, is that terrestrial interference can sometimes imitate that drift.

Another issue is where the signal is in the sky. Ideally, it should be in just one spot. If it’s in multiple locations, it’s probably terrestrial interference. The K2-155 signal was in just one spot. Another box ticked for it possibly being alien.

View larger. | The FAST radio telescope in China as seen on August 10, 2025. Image via SCJiang/ Wikimedia Commons.

I looked at the data, and it looks like terrestrial interference: Astronomers Searched 33 Planetary Systems For Alien Signals. One Caught Their Attention. https://ift.tt/BCRefEu… iopscience.iop.org/article/10.3…

— Prof. Abel Méndez (@profabelmendez.bsky.social) 2026-09-30T15:33:19.754Z

Earthly origin more likely

All of this looked promising for the K2-155 signal. But there was another problem. It was only strong in one polarization channel of the telescope. And there were similar signals at three other stars, close to the same frequency.

That would make terrestrial interference the more likely source. The researchers, however, don’t know what produced it.

So for now, the source of the signal remains unknown. Could it still be alien? Maybe. But unfortunately, the current evidence seems to suggest otherwise.

Bottom line: Did China’s FAST radio telescope detect an alien radio signal coming from the super-Earth exoplanet K2-155 d? Probably not.

Source: A Wavelet-integrated Search Pipeline for Narrowband Technosignatures in FAST Observations of 33 Exoplanet Systems

Via Science Alert

Read more: SETI@home takes a closer look at 100 notable signals

Read more: Strange double starlight pulses revealed in new SETI search

The post Is this an alien radio signal from a super-Earth exoplanet? first appeared on EarthSky.

from EarthSky https://ift.tt/rLObyR5

View larger. | Artist’s concept of the exoplanet called K2-155 d. China’s FAST radio telescope detected an intriguing radio signal coming from the direction of this super-Earth world. Is it an alien radio signal? Image via NASA.

• Did China’s FAST radio telescope detect an alien radio signal?
• The narrowband radio signal came from the direction of the super-Earth exoplanet K2-155 d, 238 light-years away.
• The signal fit several criteria for an extraterrestrial signal, but other details make the scientists think it is probably earthly radio interference.

Science news, night sky events and beautiful photos, all in one place. Click here to subscribe to our free daily newsletter.

An alien radio signal from K2-155 d?

Are there any alien civilizations out there? For several decades, scientists have been searching for evidence that they exist. That effort is collectively known as the Search for Extraterrestrial Intelligence (SETI). In recent years, China’s Five-hundred-meter Aperture Spherical Radio Telescope (FAST) has become involved. And in late August, scientists with FAST said in a new paper that they found something interesting while surveying 33 planetary systems.

They announced that FAST detected a narrowband radio signal coming from the direction of the planetary system K2-155, 238 light-years away.

The system contains a super-Earth type exoplanet, K2-155 d, that could be potentially habitable. It orbits a red dwarf star and is 1.6 times the radius of Earth. Of course, we don’t know enough about this world to have any serious confidence in it being a likely place for life to start.

FAST actually originally detected the signal in 2021, but it went unnoticed at the time. The research team was sifting through the data using new machine-learning search pipeline. This pipeline is designed to allow them to more easily separate genuine candidates from earthly radio interference.

The intriguing peer-reviewed results were published in The Astronomical Journal on August 27, 2026.

Whittling down the candidates

This survey produced 139,127 initial candidates. Those were eventually narrowed down to just the two most promising candidates. One of them, from the direction of the star Kepler-438, was then ultimately found to be earthly radio interference.

That left K2-155.

View larger. | Size comparison between K2-155 d and Earth (artist’s concept). Image via Martin Vargic/ Halcyon Maps/ Wikimedia Commons.

Ticking the boxes for an alien radio signal

The signal, at 1148.4167 megahertz, was coming from the direction of K2-155, a small red dwarf star 238 light-years away. And it seemed to pass the initial tests that astronomers have for determining whether it was a natural radio signal from the cosmos or an artificial signal created by us (earthly radio interference) or even some other intelligence out there.

The new machine-learning algorithm uses a mathematical technique called wavelet analysis to tease out faint signals from the other noisy radio data.

The researchers first noticed that the signal was very narrow. It is rare for natural sources to produce narrowband signals. Such signals are usually artificial in origin. The paper states:

Natural astrophysical processes rarely generate extremely narrow spectral features while engineered transmitters often do.

Another possible clue was that the signal drifted. That’s because the relative motion of a planet rotating on its axis and orbiting its host star can shift the frequency of a radio signal through the Doppler effect. This produces a telltale drift of the signal over time. The K2-155 signal drifted.

One problem, though, is that terrestrial interference can sometimes imitate that drift.

Another issue is where the signal is in the sky. Ideally, it should be in just one spot. If it’s in multiple locations, it’s probably terrestrial interference. The K2-155 signal was in just one spot. Another box ticked for it possibly being alien.

View larger. | The FAST radio telescope in China as seen on August 10, 2025. Image via SCJiang/ Wikimedia Commons.

I looked at the data, and it looks like terrestrial interference: Astronomers Searched 33 Planetary Systems For Alien Signals. One Caught Their Attention. https://ift.tt/BCRefEu… iopscience.iop.org/article/10.3…

— Prof. Abel Méndez (@profabelmendez.bsky.social) 2026-09-30T15:33:19.754Z

Earthly origin more likely

All of this looked promising for the K2-155 signal. But there was another problem. It was only strong in one polarization channel of the telescope. And there were similar signals at three other stars, close to the same frequency.

That would make terrestrial interference the more likely source. The researchers, however, don’t know what produced it.

So for now, the source of the signal remains unknown. Could it still be alien? Maybe. But unfortunately, the current evidence seems to suggest otherwise.

Bottom line: Did China’s FAST radio telescope detect an alien radio signal coming from the super-Earth exoplanet K2-155 d? Probably not.

Source: A Wavelet-integrated Search Pipeline for Narrowband Technosignatures in FAST Observations of 33 Exoplanet Systems

Via Science Alert

Read more: SETI@home takes a closer look at 100 notable signals

Read more: Strange double starlight pulses revealed in new SETI search

The post Is this an alien radio signal from a super-Earth exoplanet? first appeared on EarthSky.

from EarthSky https://ift.tt/rLObyR5

Could an Earthlike planet with 2 stars be nearby?

This artist’s concept shows a planet orbiting 2 stars, visible at upper left and upper right. The binary star system 70 Ophiuchi is about 16 light-years from Earth. A new study said this system could support an Earthlike planet. Image via NASA/ ESA/ CSA/ STScI/ Robert Hurt (Caltech/IPAC).

Fascinating science, night sky events and beautiful photos, all in one place. Click here to subscribe to our free daily newsletter.

Could an Earthlike planet with 2 stars be nearby?

People are fascinated by the idea of a planet orbiting more than one star, like Tatooine in “Star Wars” or Trisolaris in “The Three-Body Problem.” On September 29, 2026, researchers at the University of California, Riverside, said they have modeled a nearby binary star system and found that it could potentially support an Earth-sized planet in a habitable-zone orbit.

The researchers used 70 Ophiuchi as their model. This two-star system lies about 16 light-years away. Both of the stars in the 70 Ophiuchi system are a bit smaller and cooler than our sun. And while we’ve yet to find a planet orbiting either star, the UC Riverside astronomers said they’ve found that one could feasibly exist in a stable orbit around one of the two stars. And it could lie within the habitable zone of one of the stars, where liquid water would be stable on its surface.

The researchers published their peer-reviewed study on September 29, 2026, in The Astrophysical Journal.

Why look at 70 Ophiuchi?

The researchers targeted 70 Ophiuchi for their study. It’s a nearby star at around 16 light-years away, and people have been observing it for decades. From a dark-sky site, you can see it with the unaided eye as a single dim point of light at around magnitude 4 in the constellation Ophiuchus the Serpent Bearer.

With measurement data that goes back decades, the researchers were able to create a better model of what might happen there. Using their computer model, the researchers could then introduce an Earth-mass planet in different locations to see what happens to the system. Co-author Skylar D’Angiolillo of UC Riverside said:

We calculated the boundaries of the habitable zone around the primary star. Then I tested whether an Earth-mass planet could maintain a stable orbit at different distances within that zone.

What we found is that stable orbits are possible in the habitable zone of the primary star. You might expect the second star to disrupt those orbits, but that isn’t necessarily what happens.

D’Angiolillo added:

You can think of Earth’s orbit as being fairly circular. An unstable planet’s orbit can become increasingly elongated until eventually the planet is essentially flung away from the system. By repeating the simulation at different locations, we can identify regions where an Earth-sized planet could remain stable.

This is an early observation of the binary star system 70 Ophiuchi. This image is from the U.S. Naval Observatory from 1937. Image via UC Riverside.

Our sun is the oddball

The sun does not have a stellar companion. And that makes it a bit of an oddball. The majority of stars that astronomers have studied come in pairs. In fact, some 85% of all sun-like stars in the Milky Way have either one or more companions. So finding that an Earthlike planet in a habitable orbit can exist in a binary system would be an important step toward understanding whether potentially habitable worlds can exist around the most common types of stars in our galaxy. Co-author Stephen Kane of UC Riverside said:

Having a 2nd sun may sound exotic, but we need to consider worlds that could be habitable without necessarily looking like Earth’s neighborhood.

D’Angiolillo added:

One reason this kind of work is important is that there are a lot of steps we can take before trying to directly observe a planet. We can ask first: Is this system even capable of hosting a potentially habitable planet?

That kind of dynamical vetting could be useful for the Habitable Worlds Observatory, a NASA mission planned for the 2040s that is intended to help search for potentially habitable worlds. There are many other binary systems that could benefit from this type of analysis as scientists begin considering possible targets.

But Kane said they will keep investigating 70 Ophiuchi in the meantime. Kane commented:

Who knows? We might actually discover an Earth-size planet in the habitable zone that Skylar has predicted could be there even before the Habitable Worlds Observatory launches.

Artist’s concept of a planet with 2 suns. Image via NASA/ JPL-Caltech/ T. Pyle.

Bottom line: Astronomers found that an Earthlike planet could have a stable and potentially habitable orbit around one of two nearby suns.

Source: A Century of Radial-velocity and Astrometric Monitoring of 70 Oph AB: New PFS Data and Constraints on Possible Planetary Companions

Via UC Riverside

The post Could an Earthlike planet with 2 stars be nearby? first appeared on EarthSky.

from EarthSky https://ift.tt/fW68gDy

This artist’s concept shows a planet orbiting 2 stars, visible at upper left and upper right. The binary star system 70 Ophiuchi is about 16 light-years from Earth. A new study said this system could support an Earthlike planet. Image via NASA/ ESA/ CSA/ STScI/ Robert Hurt (Caltech/IPAC).

Fascinating science, night sky events and beautiful photos, all in one place. Click here to subscribe to our free daily newsletter.

Could an Earthlike planet with 2 stars be nearby?

People are fascinated by the idea of a planet orbiting more than one star, like Tatooine in “Star Wars” or Trisolaris in “The Three-Body Problem.” On September 29, 2026, researchers at the University of California, Riverside, said they have modeled a nearby binary star system and found that it could potentially support an Earth-sized planet in a habitable-zone orbit.

The researchers used 70 Ophiuchi as their model. This two-star system lies about 16 light-years away. Both of the stars in the 70 Ophiuchi system are a bit smaller and cooler than our sun. And while we’ve yet to find a planet orbiting either star, the UC Riverside astronomers said they’ve found that one could feasibly exist in a stable orbit around one of the two stars. And it could lie within the habitable zone of one of the stars, where liquid water would be stable on its surface.

The researchers published their peer-reviewed study on September 29, 2026, in The Astrophysical Journal.

Why look at 70 Ophiuchi?

The researchers targeted 70 Ophiuchi for their study. It’s a nearby star at around 16 light-years away, and people have been observing it for decades. From a dark-sky site, you can see it with the unaided eye as a single dim point of light at around magnitude 4 in the constellation Ophiuchus the Serpent Bearer.

With measurement data that goes back decades, the researchers were able to create a better model of what might happen there. Using their computer model, the researchers could then introduce an Earth-mass planet in different locations to see what happens to the system. Co-author Skylar D’Angiolillo of UC Riverside said:

We calculated the boundaries of the habitable zone around the primary star. Then I tested whether an Earth-mass planet could maintain a stable orbit at different distances within that zone.

What we found is that stable orbits are possible in the habitable zone of the primary star. You might expect the second star to disrupt those orbits, but that isn’t necessarily what happens.

D’Angiolillo added:

You can think of Earth’s orbit as being fairly circular. An unstable planet’s orbit can become increasingly elongated until eventually the planet is essentially flung away from the system. By repeating the simulation at different locations, we can identify regions where an Earth-sized planet could remain stable.

This is an early observation of the binary star system 70 Ophiuchi. This image is from the U.S. Naval Observatory from 1937. Image via UC Riverside.

Our sun is the oddball

The sun does not have a stellar companion. And that makes it a bit of an oddball. The majority of stars that astronomers have studied come in pairs. In fact, some 85% of all sun-like stars in the Milky Way have either one or more companions. So finding that an Earthlike planet in a habitable orbit can exist in a binary system would be an important step toward understanding whether potentially habitable worlds can exist around the most common types of stars in our galaxy. Co-author Stephen Kane of UC Riverside said:

Having a 2nd sun may sound exotic, but we need to consider worlds that could be habitable without necessarily looking like Earth’s neighborhood.

D’Angiolillo added:

One reason this kind of work is important is that there are a lot of steps we can take before trying to directly observe a planet. We can ask first: Is this system even capable of hosting a potentially habitable planet?

That kind of dynamical vetting could be useful for the Habitable Worlds Observatory, a NASA mission planned for the 2040s that is intended to help search for potentially habitable worlds. There are many other binary systems that could benefit from this type of analysis as scientists begin considering possible targets.

But Kane said they will keep investigating 70 Ophiuchi in the meantime. Kane commented:

Who knows? We might actually discover an Earth-size planet in the habitable zone that Skylar has predicted could be there even before the Habitable Worlds Observatory launches.

Artist’s concept of a planet with 2 suns. Image via NASA/ JPL-Caltech/ T. Pyle.

Bottom line: Astronomers found that an Earthlike planet could have a stable and potentially habitable orbit around one of two nearby suns.

Source: A Century of Radial-velocity and Astrometric Monitoring of 70 Oph AB: New PFS Data and Constraints on Possible Planetary Companions

Via UC Riverside

The post Could an Earthlike planet with 2 stars be nearby? first appeared on EarthSky.

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October birthstone: Colorful opal and tourmaline

Polished opals from Australia. The opal is an October birthstone. Image via Sevenopal/ Wikimedia Commons.

October babies have two birthstones to choose from: opal or tourmaline.

Opal, the primary October birthstone

The best known October birthstone is the opal. Opals are amazingly diverse rocks, taking on different appearances depending on how they formed. Precious opals, known for their flashy iridescent colors, are popular in some jewelry. But even the less dazzling common opals possess a quiet beauty that makes them popular in specimen collections.

Unlike most other gemstones, opals don’t qualify as minerals in the usual sense. They contain myriads of tiny silica spheres in a tightly-packed lattice. Because of their structure, these stones, although at 5-6.5 on the Mohs scale, are prone to fractures. These gemstones are famous for their play of colors. They flash rainbow hues when moved. The colors come from the interference of light with their internal structure.

Opals form in near-surface volcanic rocks within cavities and cracks. In sedimentary volcanic ash rock, percolating water in the ground dissolves silica that eventually precipitates to form the opal. On rare occasions, it becomes the replacement material for fossils – shells, bones, wood – whose original material had dissolved away.

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Characteristics of opals

An opal is a soft stone, easily altered in appearance by changes in heat and pressure. Varying amounts of water within it determine the appearance of the gemstone. When water evaporates out of an opal, the stone appears slightly smaller and the stress of the evaporation creates cracks on it.

Australia mines most of the world’s opals. That’s especially the case for magnificent black opals. Ethiopia is another emerging source of opals. At a smaller scale, a wide variety of opals are found in northern Nevada; some of those opals are in the form of fossilized wood. Other commercial sources of opal are Mexico, Canada, Brazil, Honduras, Nicaragua, Guatemala, Turkey and the Czech Republic.

Impurities within the stones create the characteristic colors of opals. Milky or pearly opals indicate tiny gas bubble inclusions. Yellows and reds indicate iron oxide inclusions. The spectacular black opals that sometimes flash green, blue and red get their color from magnesium oxides and organic carbon within the stone. Perhaps the most valuable opal pattern is the harlequin. It has large angular patches of red, yellow and green resembling the checks on a clown’s costume.

A Harlequin opal. Image via Aisha Brown/ Wikimedia Commons.

Opal lore

The name opal is derived from the Sanskrit word “upala,” as well as the Latin “opalus,” meaning “precious stone.”

The ancient Roman natural historian Pliny the Elder wrote about the captivating iridescence of the opal in his book, The Natural History of Precious Stones.

Of all precious stones, it is opal that presents the greatest difficulties of description, it displaying at once the piercing fire of carbunculus, the purple brilliancy of amethystos, and the sea-green of smaragdus, the whole blended together and refulgent with a brightness that is quite incredible.

There is an Indian legend about the origin of the opal. As Willard Heaps wrote in Gemstones:

… the gods Brahma, Vishnu and Shiva once vied in jealous love for a beautiful woman. This angered the Eternal, who changed the fair mortal into a creature made of mist. Thereupon each of the three gods endowed her with his own color so as to be able to recognize her. Brahma gave her the glorious blue of the heavens, Vishnu enriched her with the splendor of gold and Shiva lent her his flaming red. But all this was in vain, since the lovely phantom was whisked away by the winds. Finally, the Eternal took pity on her and transformed her into a stone, the opal, that sparkles in all the colors of the rainbow.

Heaps also wrote that ancient cultures attached meaning to opals. Romans called opals the Cupid stone. Asians called it the anchor of hope. Arabs believed they fell from the sky. In Poland, people thought that opals made their wearer invisible; hence, the opal was the talisman of thieves and spies.

October birthstone: evil superstitions

During the medieval period, a change in color intensity of an opal was believed to indicate if its wearer was ill or in good health. Supposedly the opal maintained a strong heart, prevented fainting, protected against infection and cleansed foul-smelling air. The stone, as in ancient times, still represented a symbol of hope.

But the opal’s reputation changed in the mid-14th century. The Black Death swept across Europe, killing 1/4 of its population. People thought the gem was the cause of death. When worn by someone struck with the deadly plague, it would appear brilliant only until the person died. Then it would change in appearance, losing its luster. In reality, it was the sensitivity of this stone to changes in temperature that altered its appearance, as the heat from a burning fever gave way to the cold of death.

In Elizabethan England, people treasured the opal for its beauty. Shakespeare wrote of it in his play Twelfth Night as the queen of gems. Queen Victoria is said to have loved opals and presented them to her children, thus making the stone popular. But the stone continued to have a mixed reputation, chiefly due to a novel, Anne of Geierstein, written by Sir Walter Scott in 1829 that depicted it as a stone of evil.

In Australia, opals have long been a part of Australian Aboriginal cultures. In one story, set during the Dreamtime, a pelican was resting in an area of beautiful colors. When he pecked at the colored stones, a spark flew out and lit the dry grass on fire. As the fire spread, it reached his people who, for the first time, were able to cook fish and meat.

Tourmaline, an alternate October birthstone

An alternate October birthstone is tourmaline, a gemstone that exhibits the broadest spectrum of gemstone colors. Gem-quality forms of this mineral have in the past been misidentified as rubies, emeralds and sapphires. In fact, a famous tourmaline – the size of a pigeon’s egg – belonging to the Russian empress Catherine the Great was long thought to be a ruby.

The name of this gemstone is believed to derive from the Singhalese (Sri Lankan) word toramalli, a term applied to colorful stones.

A green elbaite crystal, a type of tourmaline, from Brazil. (The white crystal is another mineral, albite.) Image via Ivar Leidus/ Wikimedia Commons.

Tourmaline characteristics

Tourmaline is a complex boron-bearing silicate mineral that can also contain other elements such as aluminum, magnesium, sodium, iron and lithium. They come in a myriad of colors: yellow, green, red, blue, pink, brown and black. Metals within the crystal structure are responsible for the gemstone colors. Pink, for example, comes from the presence of manganese. Iron produces black to deep brown colors, while magnesium creates browns and yellows. Tourmalines rich in lithium can produce several different colors such as blues, greens and reds. Some crystals even have bicolored properties. One variety, called the watermelon tourmaline, has green outer edges that transition to a transparent white zone that gives way to a pink or light red interior. Tourmaline has a hardness of 7-7.5 on the Mohs scale.

When tourmalines are warmed or rubbed, they attract small bits of paper, lint and ash. This occurs because the gem becomes charged with static electricity. In fact, Benjamin Franklin used this gem in his studies of electricity. Maintaining a tourmaline exhibit at museums requires frequent cleaning of the gemstone because heat from lights of the display case create a charge in the stone that attracts dust.

Compared with other gemstones, tourmalines are a relatively recent discovery. Hence, it lacks the rich lore that accompanies many other precious gems. However, some people think of tourmaline as the peace stone, believed to dispel fear and make its wearer calm.

Schorl is the most commonly found form of tourmaline. In this specimen from Namibia, a small piece of green fluorite is perched atop the tourmaline crystals. Image via Robert M. Lavinsky/ Wikimedia Commons.

Find out about birthstones for the rest of the year

January birthstone
February birthstone
March birthstone
April birthstone
May birthstone
June birthstone
July birthstone
August birthstone
September birthstone
October birthstone
November birthstone
December birthstone

Bottom line: October has two birthstones, opal and tourmaline.

The post October birthstone: Colorful opal and tourmaline first appeared on EarthSky.

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Polished opals from Australia. The opal is an October birthstone. Image via Sevenopal/ Wikimedia Commons.

October babies have two birthstones to choose from: opal or tourmaline.

Opal, the primary October birthstone

The best known October birthstone is the opal. Opals are amazingly diverse rocks, taking on different appearances depending on how they formed. Precious opals, known for their flashy iridescent colors, are popular in some jewelry. But even the less dazzling common opals possess a quiet beauty that makes them popular in specimen collections.

Unlike most other gemstones, opals don’t qualify as minerals in the usual sense. They contain myriads of tiny silica spheres in a tightly-packed lattice. Because of their structure, these stones, although at 5-6.5 on the Mohs scale, are prone to fractures. These gemstones are famous for their play of colors. They flash rainbow hues when moved. The colors come from the interference of light with their internal structure.

Opals form in near-surface volcanic rocks within cavities and cracks. In sedimentary volcanic ash rock, percolating water in the ground dissolves silica that eventually precipitates to form the opal. On rare occasions, it becomes the replacement material for fossils – shells, bones, wood – whose original material had dissolved away.

You deserve a daily dose of good news. For the latest in science and the night sky, subscribe to EarthSky’s free daily newsletter.

Characteristics of opals

An opal is a soft stone, easily altered in appearance by changes in heat and pressure. Varying amounts of water within it determine the appearance of the gemstone. When water evaporates out of an opal, the stone appears slightly smaller and the stress of the evaporation creates cracks on it.

Australia mines most of the world’s opals. That’s especially the case for magnificent black opals. Ethiopia is another emerging source of opals. At a smaller scale, a wide variety of opals are found in northern Nevada; some of those opals are in the form of fossilized wood. Other commercial sources of opal are Mexico, Canada, Brazil, Honduras, Nicaragua, Guatemala, Turkey and the Czech Republic.

Impurities within the stones create the characteristic colors of opals. Milky or pearly opals indicate tiny gas bubble inclusions. Yellows and reds indicate iron oxide inclusions. The spectacular black opals that sometimes flash green, blue and red get their color from magnesium oxides and organic carbon within the stone. Perhaps the most valuable opal pattern is the harlequin. It has large angular patches of red, yellow and green resembling the checks on a clown’s costume.

A Harlequin opal. Image via Aisha Brown/ Wikimedia Commons.

Opal lore

The name opal is derived from the Sanskrit word “upala,” as well as the Latin “opalus,” meaning “precious stone.”

The ancient Roman natural historian Pliny the Elder wrote about the captivating iridescence of the opal in his book, The Natural History of Precious Stones.

Of all precious stones, it is opal that presents the greatest difficulties of description, it displaying at once the piercing fire of carbunculus, the purple brilliancy of amethystos, and the sea-green of smaragdus, the whole blended together and refulgent with a brightness that is quite incredible.

There is an Indian legend about the origin of the opal. As Willard Heaps wrote in Gemstones:

… the gods Brahma, Vishnu and Shiva once vied in jealous love for a beautiful woman. This angered the Eternal, who changed the fair mortal into a creature made of mist. Thereupon each of the three gods endowed her with his own color so as to be able to recognize her. Brahma gave her the glorious blue of the heavens, Vishnu enriched her with the splendor of gold and Shiva lent her his flaming red. But all this was in vain, since the lovely phantom was whisked away by the winds. Finally, the Eternal took pity on her and transformed her into a stone, the opal, that sparkles in all the colors of the rainbow.

Heaps also wrote that ancient cultures attached meaning to opals. Romans called opals the Cupid stone. Asians called it the anchor of hope. Arabs believed they fell from the sky. In Poland, people thought that opals made their wearer invisible; hence, the opal was the talisman of thieves and spies.

October birthstone: evil superstitions

During the medieval period, a change in color intensity of an opal was believed to indicate if its wearer was ill or in good health. Supposedly the opal maintained a strong heart, prevented fainting, protected against infection and cleansed foul-smelling air. The stone, as in ancient times, still represented a symbol of hope.

But the opal’s reputation changed in the mid-14th century. The Black Death swept across Europe, killing 1/4 of its population. People thought the gem was the cause of death. When worn by someone struck with the deadly plague, it would appear brilliant only until the person died. Then it would change in appearance, losing its luster. In reality, it was the sensitivity of this stone to changes in temperature that altered its appearance, as the heat from a burning fever gave way to the cold of death.

In Elizabethan England, people treasured the opal for its beauty. Shakespeare wrote of it in his play Twelfth Night as the queen of gems. Queen Victoria is said to have loved opals and presented them to her children, thus making the stone popular. But the stone continued to have a mixed reputation, chiefly due to a novel, Anne of Geierstein, written by Sir Walter Scott in 1829 that depicted it as a stone of evil.

In Australia, opals have long been a part of Australian Aboriginal cultures. In one story, set during the Dreamtime, a pelican was resting in an area of beautiful colors. When he pecked at the colored stones, a spark flew out and lit the dry grass on fire. As the fire spread, it reached his people who, for the first time, were able to cook fish and meat.

Tourmaline, an alternate October birthstone

An alternate October birthstone is tourmaline, a gemstone that exhibits the broadest spectrum of gemstone colors. Gem-quality forms of this mineral have in the past been misidentified as rubies, emeralds and sapphires. In fact, a famous tourmaline – the size of a pigeon’s egg – belonging to the Russian empress Catherine the Great was long thought to be a ruby.

The name of this gemstone is believed to derive from the Singhalese (Sri Lankan) word toramalli, a term applied to colorful stones.

A green elbaite crystal, a type of tourmaline, from Brazil. (The white crystal is another mineral, albite.) Image via Ivar Leidus/ Wikimedia Commons.

Tourmaline characteristics

Tourmaline is a complex boron-bearing silicate mineral that can also contain other elements such as aluminum, magnesium, sodium, iron and lithium. They come in a myriad of colors: yellow, green, red, blue, pink, brown and black. Metals within the crystal structure are responsible for the gemstone colors. Pink, for example, comes from the presence of manganese. Iron produces black to deep brown colors, while magnesium creates browns and yellows. Tourmalines rich in lithium can produce several different colors such as blues, greens and reds. Some crystals even have bicolored properties. One variety, called the watermelon tourmaline, has green outer edges that transition to a transparent white zone that gives way to a pink or light red interior. Tourmaline has a hardness of 7-7.5 on the Mohs scale.

When tourmalines are warmed or rubbed, they attract small bits of paper, lint and ash. This occurs because the gem becomes charged with static electricity. In fact, Benjamin Franklin used this gem in his studies of electricity. Maintaining a tourmaline exhibit at museums requires frequent cleaning of the gemstone because heat from lights of the display case create a charge in the stone that attracts dust.

Compared with other gemstones, tourmalines are a relatively recent discovery. Hence, it lacks the rich lore that accompanies many other precious gems. However, some people think of tourmaline as the peace stone, believed to dispel fear and make its wearer calm.

Schorl is the most commonly found form of tourmaline. In this specimen from Namibia, a small piece of green fluorite is perched atop the tourmaline crystals. Image via Robert M. Lavinsky/ Wikimedia Commons.

Find out about birthstones for the rest of the year

January birthstone
February birthstone
March birthstone
April birthstone
May birthstone
June birthstone
July birthstone
August birthstone
September birthstone
October birthstone
November birthstone
December birthstone

Bottom line: October has two birthstones, opal and tourmaline.

The post October birthstone: Colorful opal and tourmaline first appeared on EarthSky.

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Saturn at opposition – brightest for 2026 – on October 4

Earth goes between the sun and Saturn once in nearly every earthly year. That’s because we take a year to orbit the sun, while Saturn takes nearly 30 years. This nice gif from the Lowell Observatory (not to scale) shows you what “opposition” means. It means Saturn is opposite the sun as seen from Earth. So it rises when the sun sets and appears somewhere in our sky all night long.

Saturn at opposition

Date and time of opposition in 2026: 12 UTC (7 a.m. CDT) on October 4.
When and where to watch in 2026: Saturn was in the evening sky through February. It emerged in the morning sky in April. It’ll be visible all night when it reaches opposition on October 4. Planets at opposition are always opposite the sun. They rise in the east at sunset and are visible all night. So after its October 4 opposition, for the rest of 2026, Saturn will remain easily visible in the evening sky. It’ll finally disappear in the sunset glare in March 2027.
Brightness at opposition: Saturn is a bright planet. When it’s above our horizon, it’s easily visible to the unaided eye. It’s a bit brighter at opposition than usual, reaching magnitude 0.3. In other words, at opposition (and always), Saturn shines as brightly as the brightest stars.
Distance from Earth at opposition: Outer planets are always closest to Earth for the year at opposition. At the 2026 opposition, Saturn is approximately 784 million miles (1.26 billion kilometers) away. That’s 70 light-minutes (about 8.43 astronomical units).
Constellation at opposition: Saturn will be in front of Cetus the Whale at opposition.
Disk size at opposition: Saturn’s disk size is largest around opposition. That’s important to people looking through telescopes. At its largest, Saturn will appear through telescopes as 19.7 arcseconds across.
Ring tilt at opposition: We passed through the plane of Saturn’s rings in March 2025. That’s something we do every 13 to 15 years. The rings, which are exceedingly thin, can’t be seen in small amateur telescopes for a few weeks around the ring plane crossing. Now the rings are opening again. In October 2026, Saturn’s rings are tilted by -7.5 degrees south, relative to earthly viewers.

View at EarthSky Community Photos. | Steven Bellavia captured Saturn and 3 of its moons from Virginia on September 3, 2026, and wrote: “Saturn, with moons Dione, Tethys and Rhea (left-to-right).” Thank you, Steven! Read about Saturn at opposition in 2026 below.

Around opposition is the best time to see Saturn

Opposition marks the middle of the best time of the year to see an outer planet. You can’t see Saturn’s rings through binoculars, but good binoculars, steadily held or mounted on a tripod, will reveal Saturn as a bright oval-shaped disk. Meanwhile, any small backyard telescope will show the rings.

Saturn’s rings: Top tips for seeing those glorious rings

Saturn’s 2026 opposition comes at 12 UTC on October 4, when Earth will sweep between the sun and Saturn, placing the ringed planet opposite the sun in our sky. Saturn will be in an excellent place to observe through mid-October. It’s easily visible to the unaided eye all night. Right now it’s a bit brighter than usual at magnitude 0.3. In other words, at opposition (and always), Saturn shines as brightly as the brightest stars. Read about Saturn at opposition — when its closest and brightest in our sky — in 2026 here. Chart via EarthSky.

For precise sun and Saturn rising times at your location:

Old Farmer’s Almanac (U.S. and Canada)
timeanddate.com (worldwide).
Stellarium-Web (online planetarium program)
In-the-sky information and finder chart from your location

The Cassini spacecraft, which orbited Saturn from 2004 to 2017, obtained stunning images of the planet Saturn with its rings and moons. Here, a Saturnian moon called Rhea transits – or passes in front of – a crescent Saturn, with the rings (black line) seen edge on. Image via Cassini Imaging Team/ SSI/ ESA/ NASA-JPL. See more images of Saturn from Cassini.

How often is Saturn at opposition?

In fact, Saturn comes to opposition nearly every earthly year. A year is the length of time Earth takes to travel once around the sun. But Saturn’s orbit around the sun takes 29.4 Earth years. So each year we have to travel slightly farther in orbit to catch up to, and pass, Saturn again. Thus Saturn oppositions are roughly 378 days apart and Saturn’s opposition comes about two weeks later each year.

Dates are based on UTC time.

2024 Saturn opposition: September 8
2025 Saturn opposition: September 21
2026 Saturn opposition: October 4
2027 Saturn at opposition: October 18

View at EarthSky Community Photos. | Brian Martin in Riverside, California, captured this image. It’s Saturn on August 19, 2025, with the shadow of its large moon Titan on its surface. Over this past year, since 2025 was the year of a ring plane crossing, we’ve been seeing the shadows of Saturn’s moons on the giant planet’s surface. The final shadow transit involving Titan was on October 6, 2025. Afterwards, we won’t see shadow transits of Titan again until the next year of a ring plane crossing, in 2039-2040. Thank you, Brian!

View from above the solar system, October 2026

Heliocentric view of solar system, October 2026. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission. Plus Guy Ottewell explains heliocentric charts here.

Saturn is a world of rings and moons

Saturn is the 6th planet outward from the sun. People in ancient times saw it as a golden “star” that moved among the fixed stars: a wanderer. It wasn’t until astronomers began using telescopes in the 17th century that they saw its rings.

Astronomers used to speak of Saturn as having three rings. But spacecraft in the later part of the 20th century showed vastly more detail. In fact, they revealed that Saturn has thousands of thin, finely detailed rings made of tiny chunks of ice. Also, Saturn has at least 293 moons with confirmed orbits. And many of them don’t have names. Furthermore, only 13 of them have diameters larger than 30 miles (about 50 kilometers).

Certainly, Saturn is truly a wondrous world of rings and moons. Usually, it’s everyone’s favorite celestial object to gaze at through a small telescope. So if there’s a public astronomy night near you this month … go!

Contrasting the size of Saturn and its rings with our planet Earth. Image via NASA.

Saturn and its rings as seen by Hubble on September 12, 2021. Image via ESA/ NASA/ Amy Simon (NASA-GSFC)/ Michael H. Wong (UC Berkeley)/ Alyssa Pagan (STScI)/ NASA.

Read more: Saturn’s rings are weird and wonderful: 10 facts here

Saturn yearly changes

View at EarthSky Community Photos. | John Nelson of Puget Sound, Washington, submitted this composite image and wrote: “A composite of some of my images of Saturn over the last 6 years showing how the angle of Saturn’s rings to Earth have been slowly decreasing. In March 2025, the angle decreased to the point where the rings were edge-on but Saturn was too close to the sun to see. Saturn’s ring angle toward Earth cycles over a 13 to 15 year period going from nearly fully open to edge on then back again.” Thank you, John.

Bottom line: Saturn’s 2026 opposition comes on October 4, when Earth will sweep between the sun and Saturn, placing the ringed planet opposite the sun in our sky. Saturn will be in an excellent place to observe from late August through October.

Read more: What does opposition mean for an outer planet?

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

A planisphere is virtually indispensable for beginning stargazers. Order your EarthSky planisphere today.

See also: Geocentric ephemeris for Saturn 2026

See also: Geocentric ephemeris for the Sun: 2026

The post Saturn at opposition – brightest for 2026 – on October 4 first appeared on EarthSky.

from EarthSky https://ift.tt/voMYNCR

Earth goes between the sun and Saturn once in nearly every earthly year. That’s because we take a year to orbit the sun, while Saturn takes nearly 30 years. This nice gif from the Lowell Observatory (not to scale) shows you what “opposition” means. It means Saturn is opposite the sun as seen from Earth. So it rises when the sun sets and appears somewhere in our sky all night long.

Saturn at opposition

Date and time of opposition in 2026: 12 UTC (7 a.m. CDT) on October 4.
When and where to watch in 2026: Saturn was in the evening sky through February. It emerged in the morning sky in April. It’ll be visible all night when it reaches opposition on October 4. Planets at opposition are always opposite the sun. They rise in the east at sunset and are visible all night. So after its October 4 opposition, for the rest of 2026, Saturn will remain easily visible in the evening sky. It’ll finally disappear in the sunset glare in March 2027.
Brightness at opposition: Saturn is a bright planet. When it’s above our horizon, it’s easily visible to the unaided eye. It’s a bit brighter at opposition than usual, reaching magnitude 0.3. In other words, at opposition (and always), Saturn shines as brightly as the brightest stars.
Distance from Earth at opposition: Outer planets are always closest to Earth for the year at opposition. At the 2026 opposition, Saturn is approximately 784 million miles (1.26 billion kilometers) away. That’s 70 light-minutes (about 8.43 astronomical units).
Constellation at opposition: Saturn will be in front of Cetus the Whale at opposition.
Disk size at opposition: Saturn’s disk size is largest around opposition. That’s important to people looking through telescopes. At its largest, Saturn will appear through telescopes as 19.7 arcseconds across.
Ring tilt at opposition: We passed through the plane of Saturn’s rings in March 2025. That’s something we do every 13 to 15 years. The rings, which are exceedingly thin, can’t be seen in small amateur telescopes for a few weeks around the ring plane crossing. Now the rings are opening again. In October 2026, Saturn’s rings are tilted by -7.5 degrees south, relative to earthly viewers.

View at EarthSky Community Photos. | Steven Bellavia captured Saturn and 3 of its moons from Virginia on September 3, 2026, and wrote: “Saturn, with moons Dione, Tethys and Rhea (left-to-right).” Thank you, Steven! Read about Saturn at opposition in 2026 below.

Around opposition is the best time to see Saturn

Opposition marks the middle of the best time of the year to see an outer planet. You can’t see Saturn’s rings through binoculars, but good binoculars, steadily held or mounted on a tripod, will reveal Saturn as a bright oval-shaped disk. Meanwhile, any small backyard telescope will show the rings.

Saturn’s rings: Top tips for seeing those glorious rings

Saturn’s 2026 opposition comes at 12 UTC on October 4, when Earth will sweep between the sun and Saturn, placing the ringed planet opposite the sun in our sky. Saturn will be in an excellent place to observe through mid-October. It’s easily visible to the unaided eye all night. Right now it’s a bit brighter than usual at magnitude 0.3. In other words, at opposition (and always), Saturn shines as brightly as the brightest stars. Read about Saturn at opposition — when its closest and brightest in our sky — in 2026 here. Chart via EarthSky.

For precise sun and Saturn rising times at your location:

Old Farmer’s Almanac (U.S. and Canada)
timeanddate.com (worldwide).
Stellarium-Web (online planetarium program)
In-the-sky information and finder chart from your location

The Cassini spacecraft, which orbited Saturn from 2004 to 2017, obtained stunning images of the planet Saturn with its rings and moons. Here, a Saturnian moon called Rhea transits – or passes in front of – a crescent Saturn, with the rings (black line) seen edge on. Image via Cassini Imaging Team/ SSI/ ESA/ NASA-JPL. See more images of Saturn from Cassini.

How often is Saturn at opposition?

In fact, Saturn comes to opposition nearly every earthly year. A year is the length of time Earth takes to travel once around the sun. But Saturn’s orbit around the sun takes 29.4 Earth years. So each year we have to travel slightly farther in orbit to catch up to, and pass, Saturn again. Thus Saturn oppositions are roughly 378 days apart and Saturn’s opposition comes about two weeks later each year.

Dates are based on UTC time.

2024 Saturn opposition: September 8
2025 Saturn opposition: September 21
2026 Saturn opposition: October 4
2027 Saturn at opposition: October 18

View at EarthSky Community Photos. | Brian Martin in Riverside, California, captured this image. It’s Saturn on August 19, 2025, with the shadow of its large moon Titan on its surface. Over this past year, since 2025 was the year of a ring plane crossing, we’ve been seeing the shadows of Saturn’s moons on the giant planet’s surface. The final shadow transit involving Titan was on October 6, 2025. Afterwards, we won’t see shadow transits of Titan again until the next year of a ring plane crossing, in 2039-2040. Thank you, Brian!

View from above the solar system, October 2026

Heliocentric view of solar system, October 2026. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission. Plus Guy Ottewell explains heliocentric charts here.

Saturn is a world of rings and moons

Saturn is the 6th planet outward from the sun. People in ancient times saw it as a golden “star” that moved among the fixed stars: a wanderer. It wasn’t until astronomers began using telescopes in the 17th century that they saw its rings.

Astronomers used to speak of Saturn as having three rings. But spacecraft in the later part of the 20th century showed vastly more detail. In fact, they revealed that Saturn has thousands of thin, finely detailed rings made of tiny chunks of ice. Also, Saturn has at least 293 moons with confirmed orbits. And many of them don’t have names. Furthermore, only 13 of them have diameters larger than 30 miles (about 50 kilometers).

Certainly, Saturn is truly a wondrous world of rings and moons. Usually, it’s everyone’s favorite celestial object to gaze at through a small telescope. So if there’s a public astronomy night near you this month … go!

Contrasting the size of Saturn and its rings with our planet Earth. Image via NASA.

Saturn and its rings as seen by Hubble on September 12, 2021. Image via ESA/ NASA/ Amy Simon (NASA-GSFC)/ Michael H. Wong (UC Berkeley)/ Alyssa Pagan (STScI)/ NASA.

Read more: Saturn’s rings are weird and wonderful: 10 facts here

Saturn yearly changes

View at EarthSky Community Photos. | John Nelson of Puget Sound, Washington, submitted this composite image and wrote: “A composite of some of my images of Saturn over the last 6 years showing how the angle of Saturn’s rings to Earth have been slowly decreasing. In March 2025, the angle decreased to the point where the rings were edge-on but Saturn was too close to the sun to see. Saturn’s ring angle toward Earth cycles over a 13 to 15 year period going from nearly fully open to edge on then back again.” Thank you, John.

Bottom line: Saturn’s 2026 opposition comes on October 4, when Earth will sweep between the sun and Saturn, placing the ringed planet opposite the sun in our sky. Saturn will be in an excellent place to observe from late August through October.

Read more: What does opposition mean for an outer planet?

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

A planisphere is virtually indispensable for beginning stargazers. Order your EarthSky planisphere today.

See also: Geocentric ephemeris for Saturn 2026

See also: Geocentric ephemeris for the Sun: 2026

The post Saturn at opposition – brightest for 2026 – on October 4 first appeared on EarthSky.

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What are the world’s loudest birds? Here are 2 contenders

The University of Massachusetts Amherst said the bare-throated bellbird and the red-legged seriema are both contenders for the world’s loudest birds. The bare-throated bellbird, which lives in the Amazon, has a call of around 131 decibels. The red-legged seriema, which lives in a wide swath of eastern South America, has a call of more than 120 decibels. For comparison, 120-130 decibels is equal to a jet plane taking off or a chainsaw. Video via UMass Amherst.

Love wildlife and the natural world? Get the latest animal stories — as well as space and night sky updates delivered to your inbox.

What are the world’s loudest birds?

While the loudest birds might seem like the ones outside your window at sunrise, the University of Massachusetts Amherst shared two contenders for the world’s loudest birds. On September 29, 2026, researchers with UMass Amherst said two South American birds have calls that can rival a chainsaw.

The bare-throated bellbird, which lives in the Amazon, has a call of around 131 decibels. And the red-legged seriema, which lives in a wide swath of eastern South America, has a call of more than 120 decibels. For comparison, a chainsaw roars at about 120-130 decibels.

But the goal behind studying these noisy birds was not to find a world record holder. Instead, the researchers studied them because they were looking to see if physical traits could predict a bird’s loudness.

Plus, they wanted to know if a bird’s loudness is related to its ecological niche and specific social organization.

The researchers published their peer-reviewed study in the journal Evolution on September 29, 2026.

How do you measure the volume of a bird?

To measure the volume of any bird, it’s best to do it in their natural habitat. So the researchers, João C.T. Menezes and Jeff Podos of UMass Amherst, set out to measure the sounds from birds in their own backyard along with birds in Brazil.

For tools, the researchers used golf rangefinders, which operate like a pair of binoculars with a laser that measures distance, plus portable sound meters. That’s because if you hear a loud bird, it also matters how close or far away from you the bird is.

Altogether, the pair measured 123 different bird species for their study. And amazingly, 113 of those species had never had their volume catalogued before. Podos said:

We’ve been able to vastly increase the number of species for which there is amplitude data. This is basic, foundational research that no one else has managed to do on this scale, and it points to all sorts of other questions that would be fun to follow up.

Listen to the call of the bare-throated bellbird. Video via UMass Amherst.

Why are some birds louder than others?

Overall, they found a huge range of volume among the different bird species. For example, one of the softest-voiced birds was the little hummingbird, with a song at a decibel level of 64. That’s about equal to human conversation.

And at the high end of the scale were the bare-throated bellbirds and red-legged seriemas, with songs that register 120+ decibels. So they are the world’s loudest birds.

Unsurprisingly, the smaller bird is quieter while the larger birds are louder. The researchers think big birds with bulky muscles might allow for greater air compression for explosive volume. They also have wider beak openings.

But so far, the data did not support obvious reasons for why loudness would have an ecological or evolutionary purpose. Menezes said:

We now know some of the hows. Bigger bodies and wider beaks, but we’ve yet to discover the whys, and we probably need much more data from many more species to be able to tease out what’s going on on the ecological and evolutionary front.

Now, the researchers are ready to go back out into the field to test some of their hypotheses. Podos said:

You can’t do this kind of work in the lab, or by scraping data from the internet. You have to get out into the world, you have to pay careful attention to what you’re seeing and hearing, and anything you do in the field that forces you to observe more carefully is really fun.

It takes you back to the roots of why we do science in the first place.

The bare-throated bellbird lives in South America. It is one of the contenders for world’s loudest bird. Image via Ben Tavener/ Wikimedia Commons.

The red-legged seriema is also a contender for world’s loudest bird. Image via Manfred Werner/ Tsui/ Wikimedia Commons.

Bottom line: Researchers at the University of Massachusetts Amherst said the bare-throated bellbird and red-legged seriema are two contenders for world’s loudest birds.

Source: Evolutionary drivers of vocal amplitude in birds

Via UMass Amherst

Read more: Do birds have accents? Regional differences in birdsong

Read more: Will fall migration 2026 bring a billion bird night?

The post What are the world’s loudest birds? Here are 2 contenders first appeared on EarthSky.

from EarthSky https://ift.tt/cFWyzS1

The University of Massachusetts Amherst said the bare-throated bellbird and the red-legged seriema are both contenders for the world’s loudest birds. The bare-throated bellbird, which lives in the Amazon, has a call of around 131 decibels. The red-legged seriema, which lives in a wide swath of eastern South America, has a call of more than 120 decibels. For comparison, 120-130 decibels is equal to a jet plane taking off or a chainsaw. Video via UMass Amherst.

Love wildlife and the natural world? Get the latest animal stories — as well as space and night sky updates delivered to your inbox.

What are the world’s loudest birds?

While the loudest birds might seem like the ones outside your window at sunrise, the University of Massachusetts Amherst shared two contenders for the world’s loudest birds. On September 29, 2026, researchers with UMass Amherst said two South American birds have calls that can rival a chainsaw.

The bare-throated bellbird, which lives in the Amazon, has a call of around 131 decibels. And the red-legged seriema, which lives in a wide swath of eastern South America, has a call of more than 120 decibels. For comparison, a chainsaw roars at about 120-130 decibels.

But the goal behind studying these noisy birds was not to find a world record holder. Instead, the researchers studied them because they were looking to see if physical traits could predict a bird’s loudness.

Plus, they wanted to know if a bird’s loudness is related to its ecological niche and specific social organization.

The researchers published their peer-reviewed study in the journal Evolution on September 29, 2026.

How do you measure the volume of a bird?

To measure the volume of any bird, it’s best to do it in their natural habitat. So the researchers, João C.T. Menezes and Jeff Podos of UMass Amherst, set out to measure the sounds from birds in their own backyard along with birds in Brazil.

For tools, the researchers used golf rangefinders, which operate like a pair of binoculars with a laser that measures distance, plus portable sound meters. That’s because if you hear a loud bird, it also matters how close or far away from you the bird is.

Altogether, the pair measured 123 different bird species for their study. And amazingly, 113 of those species had never had their volume catalogued before. Podos said:

We’ve been able to vastly increase the number of species for which there is amplitude data. This is basic, foundational research that no one else has managed to do on this scale, and it points to all sorts of other questions that would be fun to follow up.

Listen to the call of the bare-throated bellbird. Video via UMass Amherst.

Why are some birds louder than others?

Overall, they found a huge range of volume among the different bird species. For example, one of the softest-voiced birds was the little hummingbird, with a song at a decibel level of 64. That’s about equal to human conversation.

And at the high end of the scale were the bare-throated bellbirds and red-legged seriemas, with songs that register 120+ decibels. So they are the world’s loudest birds.

Unsurprisingly, the smaller bird is quieter while the larger birds are louder. The researchers think big birds with bulky muscles might allow for greater air compression for explosive volume. They also have wider beak openings.

But so far, the data did not support obvious reasons for why loudness would have an ecological or evolutionary purpose. Menezes said:

We now know some of the hows. Bigger bodies and wider beaks, but we’ve yet to discover the whys, and we probably need much more data from many more species to be able to tease out what’s going on on the ecological and evolutionary front.

Now, the researchers are ready to go back out into the field to test some of their hypotheses. Podos said:

You can’t do this kind of work in the lab, or by scraping data from the internet. You have to get out into the world, you have to pay careful attention to what you’re seeing and hearing, and anything you do in the field that forces you to observe more carefully is really fun.

It takes you back to the roots of why we do science in the first place.

The bare-throated bellbird lives in South America. It is one of the contenders for world’s loudest bird. Image via Ben Tavener/ Wikimedia Commons.

The red-legged seriema is also a contender for world’s loudest bird. Image via Manfred Werner/ Tsui/ Wikimedia Commons.

Bottom line: Researchers at the University of Massachusetts Amherst said the bare-throated bellbird and red-legged seriema are two contenders for world’s loudest birds.

Source: Evolutionary drivers of vocal amplitude in birds

Via UMass Amherst

Read more: Do birds have accents? Regional differences in birdsong

Read more: Will fall migration 2026 bring a billion bird night?

The post What are the world’s loudest birds? Here are 2 contenders first appeared on EarthSky.

from EarthSky https://ift.tt/cFWyzS1

Stargazing tips! 10 great tips for beginning astronomers

Watch a video of the EarthSky’s stargazing tips for beginning astronomers.

Our top 10 stargazing tips for beginners

Stargazing is for everybody. It’s for people who view the night sky with a sense of wonder … and people who just like being outside at night. Maybe that’s you. If so – and if you’re a beginner – here are some tips to help you get started. And remember that, like anything, stargazing takes practice. Soon you’ll be able to point out stars, constellations and planets.

View at EarthSky Community Photos. | Stojan Stojanovski in Bitola, North Macedonia, captured this image on August 30, 2023. Stojan wrote: “My friend shows you the super Blue Moon tonight on the top of the mountain.” Thank you, Stojan! Anyone at any age can enjoy the night sky. Read our top 10 stargazing tips for beginners here.

Tip 1: Watch the moon

Earth’s companion moon is visible from city streets, suburban decks and wide-open rural pastures. The moon connects you to everybody on the planet, because, generally speaking, we all see the moon at the same phase (although, because we live on a round Earth with 24 time zones, not exactly at the same time). The moon’s orbit around Earth is regular and predictable. So the moon waxes and wanes in our sky in a way that’s about as satisfyingly regular and predictable as anything on Earth can be.

Try following it for one lunar cycle. Start looking for a crescent moon in the sunset direction a day or two after new moon and then check it out every night at about the same time. What do you notice? Is it getting fatter or thinner in phase? Does it move from night to night with respect to nearby bright stars or planets?

Then what happens after the full moon? You’ll notice it rises later each day and soon it’ll be visible only after midnight. And eventually it’ll appear above the horizon closer to the sunrise. That’s because during one complete lunar cycle, the moon spends half of its time in the night sky and half of the time in the daytime. So yes, you can sometimes see the moon in daylight. Track it for a month and see how it changes.

Read more: 4 keys to understanding moon phases.

And remember, the moon can help you locate stars and planets. Check our visible planet and night sky guide to see what’s currently visible in the night sky.

View at EarthSky Community Photos. | Chuck Reinhart from Indiana, shared this photo of Mars, Venus and the crescent moon with some earthshine. Thank you, Chuck!

Tip 2: Watch the sun

Our stargazing tips including watching the sun. Don’t look directly at it, of course. But do notice the point on the horizon where the sun rises or sets as seen from your kitchen window, balcony or yard. Does that rising or setting point change as the seasons pass? Does the path of the sun from east to west during the day change?

The sun rises due east and sets due west at every equinox. If you identify east and west, you’ll have a jump on our next activity. By the way, try this great custom calendar at Sunrise Sunset Calendars. Don’t forget to check the moon phase box, too!

View at EarthSky Community Photos. | Iaroslav Kourzenkov of Halifax, Nova Scotia, Canada, captured this image of the sunset on the March equinox. Thank you, Iaroslav!

Tip 3: Use a chart

The Internet is great, but a computer is an unwieldy companion on stargazing adventures. What you want is a printed chart. Start with the easy-to-use charts at EarthSky Tonight. These daily charts are geared toward beginners, and each one presents something interesting to spot in that night’s sky. Then take the plunge and purchase a printed chart, maybe one of the planispheres in our store.

In just a few weeks of using our daily EarthSky Tonight charts – plus a planisphere – you will quickly raise your stargazing IQ. Still want an online chart? Try Stellarium.

A planisphere will teach you what stars and constellations are overhead for any night of the year. Image via EarthSky.

Tip 4: Don’t buy a telescope yet

Remember that pair of binoculars you stuck way at the top of your closet? Point them at the moon and bright objects in the night sky. Do you see anything you hadn’t noticed before? Point them at noticeable star patterns; for example, the second star from the end of the Big Dipper’s handle is really two stars.

If you’re in a dark location, use your binoculars to sweep along the Milky Way and to check out any hazy patches in the night sky. These patches may be actual named star clusters, or they may be clouds of gas and dust where new stars are forming. You don’t need to know what you’re seeing to enjoy the beauty of it all.

This chart of the Big Dipper includes a label for Mizar, while its companion star, Alcor, appears next to it without a label. Can you see both stars with or without binoculars?

Tip 5: Notice patterns among the stars

Here’s how most stargazers learn constellations. They find a noticeable pattern, and then they notice another pattern nearby. They build outward, going from stars and patterns they know to new ones. Notice triangles, curves and straight lines of stars. Some of these patterns are the same ones our ancestors noticed while sitting around a campfire telling stories. Some of their stories ended up being passed down to us. Make up your own stories!

View at EarthSky Community Photos. | Cecille Kennedy captured this shot of the Northern Cross from Oregon. Thank you, Cecille! The Northern Cross is a clipped version of the constellation Cygnus the Swan. It’s an asterism, or pattern of stars. It lies embedded within another much larger asterism: the Summer Triangle, made up of the 3 brightest stars you can see in Cecille’s picture.

Tip 6: Find a dark-sky site

Try a state park or a national park. You won’t be sorry. Visit EarthSky’s Best Places to Stargaze page for dark locations around the world. Check also for an astronomy club in your area. Experienced members are good sources of advice, and some groups loan out telescopes.

Many societies also have libraries stocked with specialized books and atlases often not found in public libraries. Astronomy is also a good hobby to enjoy with a friend or family member. The delight of discovery is infectious.

And leave electronics in your pocket or vehicle. Even night mode is too bright under a dark sky and will ruin your night vision. Use a red flashlight to read your star charts or planisphere.

View at EarthSky Community Photos. | Thomas Frazier in Virginia took this wonderful image of his daughter while contemplating the amazing Milky Way. He wrote: “My daughter and I went to Sky Meadows State Park. After viewing various galaxies, nebulae and globular clusters on my telescope, we tried this shot. Sky Meadows was recently named an International Dark Skies site. The glow on the horizon is the Washington, D.C., metro area.” Thank you, Thomas!

Tip 7: Link up with astro-friends

If you live in a college town, keep an eye out for astronomy community enrichment courses. Local schools, museums and planetariums might also host public programs.

Universities often hold public observing nights at their observatories. Pictured here, Washburn Observatory at the University of Wisconsin-Madison. Image via Wikimedia Commons.

Tip 8: Take the telescope plunge carefully

Have you been watching the night sky for half a year at least? Can you recognize some major constellations? Have you identified a planet or two? The time to buy a telescope is when you’ve given yourself time to acclimate to the sky around you and all its nuances. Before that, if you want more optical power, buy binoculars. Once you’re ready to take the plunge, check these things to know before buying a telescope from High Point Scientific.

View at EarthSky Community Photos. | Dr Ski at Valencia Observatory, Central Philippines, took this image and wrote: “The Omega Centauri globular cluster is the only deep sky object I can capture at high magnification with a pocket camera and no tracking mount! It’s that spectacular. Unlike many astrophotographs, this image is exactly what you can expect to see thru a small telescope at 40x. No embellishments here.” Thank you, Dr Ski!

Tip 9: Just look up

Most of us go through life looking straight ahead. But you’ve got to look up to see stars. Standing outside at a bus stop? Look at the sky. In your car? Look out the window, carefully. Going outside before sunup to take the garbage out? Gaze toward the sunrise horizon. Notice bright objects in the sky. Notice patterns among the stars. Just start looking up and noticing.

View at EarthSky Community Photos. | Prateek Pandey in Bhopal, Madhya Pradesh, India, captured this photo of Boötes, Virgo and Corona Borealis. He wrote: “Spring constellations twinkling in the eastern horizon.” Thank you, Prateek!

Tip 10: Be faithful to the sky

One of the great things about becoming a stargazer is that you make a lifelong friend: the sky itself. It’s a friend that lives right next door. And like any friend, the sky changes in subtle ways from day to day and year to year. So once you start watching it, be patient. And you can’t learn everything about your friend at once. Be persistent. Watch the sky a lot and watch regularly. You’ll learn by looking! And you’ll make a connection with nature that’ll last your whole life long.

View at EarthSky Community Photos. | Steve Price in the Last Chance Desert, Utah, took this image and wrote: “New moon phase … Approximately 15 miles into The Last Chance Desert near Solomon’s Temple sandstone monolith … a great night to be alone in the desert with the stars and a few mammals scurrying around.” Thank you, Steve!

Bottom line: If you’re new to observing the night sky, check out our top 10 stargazing tips for beginners. We’ll help you explore and expand your love for astronomy.

Ready to begin exploring the night sky? Check out our Astronomy kit for beginners.

The post Stargazing tips! 10 great tips for beginning astronomers first appeared on EarthSky.

from EarthSky https://ift.tt/bRH84dh

Watch a video of the EarthSky’s stargazing tips for beginning astronomers.

Our top 10 stargazing tips for beginners

Stargazing is for everybody. It’s for people who view the night sky with a sense of wonder … and people who just like being outside at night. Maybe that’s you. If so – and if you’re a beginner – here are some tips to help you get started. And remember that, like anything, stargazing takes practice. Soon you’ll be able to point out stars, constellations and planets.

View at EarthSky Community Photos. | Stojan Stojanovski in Bitola, North Macedonia, captured this image on August 30, 2023. Stojan wrote: “My friend shows you the super Blue Moon tonight on the top of the mountain.” Thank you, Stojan! Anyone at any age can enjoy the night sky. Read our top 10 stargazing tips for beginners here.

Tip 1: Watch the moon

Earth’s companion moon is visible from city streets, suburban decks and wide-open rural pastures. The moon connects you to everybody on the planet, because, generally speaking, we all see the moon at the same phase (although, because we live on a round Earth with 24 time zones, not exactly at the same time). The moon’s orbit around Earth is regular and predictable. So the moon waxes and wanes in our sky in a way that’s about as satisfyingly regular and predictable as anything on Earth can be.

Try following it for one lunar cycle. Start looking for a crescent moon in the sunset direction a day or two after new moon and then check it out every night at about the same time. What do you notice? Is it getting fatter or thinner in phase? Does it move from night to night with respect to nearby bright stars or planets?

Then what happens after the full moon? You’ll notice it rises later each day and soon it’ll be visible only after midnight. And eventually it’ll appear above the horizon closer to the sunrise. That’s because during one complete lunar cycle, the moon spends half of its time in the night sky and half of the time in the daytime. So yes, you can sometimes see the moon in daylight. Track it for a month and see how it changes.

Read more: 4 keys to understanding moon phases.

And remember, the moon can help you locate stars and planets. Check our visible planet and night sky guide to see what’s currently visible in the night sky.

View at EarthSky Community Photos. | Chuck Reinhart from Indiana, shared this photo of Mars, Venus and the crescent moon with some earthshine. Thank you, Chuck!

Tip 2: Watch the sun

Our stargazing tips including watching the sun. Don’t look directly at it, of course. But do notice the point on the horizon where the sun rises or sets as seen from your kitchen window, balcony or yard. Does that rising or setting point change as the seasons pass? Does the path of the sun from east to west during the day change?

The sun rises due east and sets due west at every equinox. If you identify east and west, you’ll have a jump on our next activity. By the way, try this great custom calendar at Sunrise Sunset Calendars. Don’t forget to check the moon phase box, too!

View at EarthSky Community Photos. | Iaroslav Kourzenkov of Halifax, Nova Scotia, Canada, captured this image of the sunset on the March equinox. Thank you, Iaroslav!

Tip 3: Use a chart

The Internet is great, but a computer is an unwieldy companion on stargazing adventures. What you want is a printed chart. Start with the easy-to-use charts at EarthSky Tonight. These daily charts are geared toward beginners, and each one presents something interesting to spot in that night’s sky. Then take the plunge and purchase a printed chart, maybe one of the planispheres in our store.

In just a few weeks of using our daily EarthSky Tonight charts – plus a planisphere – you will quickly raise your stargazing IQ. Still want an online chart? Try Stellarium.

A planisphere will teach you what stars and constellations are overhead for any night of the year. Image via EarthSky.

Tip 4: Don’t buy a telescope yet

Remember that pair of binoculars you stuck way at the top of your closet? Point them at the moon and bright objects in the night sky. Do you see anything you hadn’t noticed before? Point them at noticeable star patterns; for example, the second star from the end of the Big Dipper’s handle is really two stars.

If you’re in a dark location, use your binoculars to sweep along the Milky Way and to check out any hazy patches in the night sky. These patches may be actual named star clusters, or they may be clouds of gas and dust where new stars are forming. You don’t need to know what you’re seeing to enjoy the beauty of it all.

This chart of the Big Dipper includes a label for Mizar, while its companion star, Alcor, appears next to it without a label. Can you see both stars with or without binoculars?

Tip 5: Notice patterns among the stars

Here’s how most stargazers learn constellations. They find a noticeable pattern, and then they notice another pattern nearby. They build outward, going from stars and patterns they know to new ones. Notice triangles, curves and straight lines of stars. Some of these patterns are the same ones our ancestors noticed while sitting around a campfire telling stories. Some of their stories ended up being passed down to us. Make up your own stories!

View at EarthSky Community Photos. | Cecille Kennedy captured this shot of the Northern Cross from Oregon. Thank you, Cecille! The Northern Cross is a clipped version of the constellation Cygnus the Swan. It’s an asterism, or pattern of stars. It lies embedded within another much larger asterism: the Summer Triangle, made up of the 3 brightest stars you can see in Cecille’s picture.

Tip 6: Find a dark-sky site

Try a state park or a national park. You won’t be sorry. Visit EarthSky’s Best Places to Stargaze page for dark locations around the world. Check also for an astronomy club in your area. Experienced members are good sources of advice, and some groups loan out telescopes.

Many societies also have libraries stocked with specialized books and atlases often not found in public libraries. Astronomy is also a good hobby to enjoy with a friend or family member. The delight of discovery is infectious.

And leave electronics in your pocket or vehicle. Even night mode is too bright under a dark sky and will ruin your night vision. Use a red flashlight to read your star charts or planisphere.

View at EarthSky Community Photos. | Thomas Frazier in Virginia took this wonderful image of his daughter while contemplating the amazing Milky Way. He wrote: “My daughter and I went to Sky Meadows State Park. After viewing various galaxies, nebulae and globular clusters on my telescope, we tried this shot. Sky Meadows was recently named an International Dark Skies site. The glow on the horizon is the Washington, D.C., metro area.” Thank you, Thomas!

Tip 7: Link up with astro-friends

If you live in a college town, keep an eye out for astronomy community enrichment courses. Local schools, museums and planetariums might also host public programs.

Universities often hold public observing nights at their observatories. Pictured here, Washburn Observatory at the University of Wisconsin-Madison. Image via Wikimedia Commons.

Tip 8: Take the telescope plunge carefully

Have you been watching the night sky for half a year at least? Can you recognize some major constellations? Have you identified a planet or two? The time to buy a telescope is when you’ve given yourself time to acclimate to the sky around you and all its nuances. Before that, if you want more optical power, buy binoculars. Once you’re ready to take the plunge, check these things to know before buying a telescope from High Point Scientific.

View at EarthSky Community Photos. | Dr Ski at Valencia Observatory, Central Philippines, took this image and wrote: “The Omega Centauri globular cluster is the only deep sky object I can capture at high magnification with a pocket camera and no tracking mount! It’s that spectacular. Unlike many astrophotographs, this image is exactly what you can expect to see thru a small telescope at 40x. No embellishments here.” Thank you, Dr Ski!

Tip 9: Just look up

Most of us go through life looking straight ahead. But you’ve got to look up to see stars. Standing outside at a bus stop? Look at the sky. In your car? Look out the window, carefully. Going outside before sunup to take the garbage out? Gaze toward the sunrise horizon. Notice bright objects in the sky. Notice patterns among the stars. Just start looking up and noticing.

View at EarthSky Community Photos. | Prateek Pandey in Bhopal, Madhya Pradesh, India, captured this photo of Boötes, Virgo and Corona Borealis. He wrote: “Spring constellations twinkling in the eastern horizon.” Thank you, Prateek!

Tip 10: Be faithful to the sky

One of the great things about becoming a stargazer is that you make a lifelong friend: the sky itself. It’s a friend that lives right next door. And like any friend, the sky changes in subtle ways from day to day and year to year. So once you start watching it, be patient. And you can’t learn everything about your friend at once. Be persistent. Watch the sky a lot and watch regularly. You’ll learn by looking! And you’ll make a connection with nature that’ll last your whole life long.

View at EarthSky Community Photos. | Steve Price in the Last Chance Desert, Utah, took this image and wrote: “New moon phase … Approximately 15 miles into The Last Chance Desert near Solomon’s Temple sandstone monolith … a great night to be alone in the desert with the stars and a few mammals scurrying around.” Thank you, Steve!

Bottom line: If you’re new to observing the night sky, check out our top 10 stargazing tips for beginners. We’ll help you explore and expand your love for astronomy.

Ready to begin exploring the night sky? Check out our Astronomy kit for beginners.

The post Stargazing tips! 10 great tips for beginning astronomers first appeared on EarthSky.

from EarthSky https://ift.tt/bRH84dh

Alpha Cephei, or Alderamin, is a fast-spinning star

Astronomers used the CHARA array at Georgia State University – an optical interferometer – to learn the fast rotational speed of Alpha Cephei, aka Alderamin. Read about this work here. Image via M. Zhao.

You deserve a daily dose of good news. For the latest in science and the night sky, subscribe to EarthSky’s free daily newsletter.

Alpha Cephei, also known as Alderamin, is the brightest star in the constellation Cepheus the King. Astronomers are intrigued by this star because it spins at such a fast rate. Unlike our almost-round sun, Alderamin is distorted by its rapid spin into an oblate form, like a partly deflated beach ball.

This star isn’t the brightest one around, but it’s pretty bright. It shines at about magnitude 2.5.

Its faint constellation, Cepheus, is surprisingly easy to spot in a dark sky because the stars of Cepheus trace out the shape of a child’s stick house.

Science of Alpha Cephei

Alpha Cephei, 49 light-years away, is a white star that is twice the mass of our sun and about 17 times its luminosity. It is considered a Class A star, which is now evolving off the main sequence into a subgiant. It’s thought that this star is now on its way to becoming a red giant as its internal supply of hydrogen fuel runs low.

Alpha Cephei rotates rapidly; observations suggest it could be as fast as 152 miles a second (246 km/s). In comparison, the sun’s rotation speed at the equator is not quite 1.2 miles a second (2 km/s). As a result of its rapid rotation, Alpha Cephei appears slightly flattened. That’s because the star’s surface rotation speed gets progressively faster as you move away from its rotation axis towards its equator.

And, as surface rotation speed increases, the star’s surface is increasingly pushed out. As a result, Alpha Cephei bulges along the equator.

A closer look at Alpha Cephei

The image at the top of this article is a model of Alpha Cephei based on data from the CHARA telescope array. It shows Alpha Cephei’s oblate shape. It also shows a darker equatorial region, shaded to indicate that these are cooler regions of the star.

Meanwhile, a section near the pole appears brighter. That’s because the surface gravity is higher around the “flattened” poles compared to the bulging equator, and as a result, higher temperatures and pressure are needed to maintain an equilibrium. These differences in brightness across rapidly rotating stars result in a phenomenon scientists call gravity darkening.

Astronomer Jim Kaler wrote about this rapidly spinning star:

The spin may also be related to the star’s activity. [Our] sun is magnetically active in broad part because its outer third is churning up and down in huge convective currents, the movement helping to generate a magnetic field. Such outer zones are supposed to disappear in class A stars like Alderamin. Yet Alderamin emits about the same amount of X-ray radiation as does the sun and has other features that together suggest considerable magnetic activity. No one really knows why. Such anomalies, of course, drive the science. Understanding Alderamin will someday help us understand our own star, on which we depend for life.

How to find Alpha Cephei

On a dark night, Alpha Cephei is easily visible and relatively easy to find. Look northward for this star. It is circumpolar — meaning it never sets — throughout all of Europe, northern Asia, Canada and American cities as far south as San Diego, California. Its constellation, Cepheus, has the shape of the stick house we all drew as children.

Or you might prefer to see the shape of Cepheus as a point on the King’s crown. Cepheus is a rather faint constellation, but Alpha Cephei is by far its brightest star and is easily observable to the unaided eye, even in cities.

If you know the W or M-shaped constellation Cassiopeia the Queen, you can use the Cassiopeia stars Schedar and Caph to star-hop to Alderamin.

A close-up of Cassiopeia and Cepheus. Notice that a line from Schedar and Caph will lead you to Alderamin, or Alpha Cephei, the brightest star in the King.

A once and future pole star

Alpha Cephei has been a pole star in the past. That is, a bright star close to the sky’s north pole. This is because a slow, constant wobble in Earth’s movement — known as precession — makes the stars shift in relation to our planet’s axis.

The last time Alpha Cephei was the nearest bright star to the north celestial pole was in 18,000 BCE. It will again be a pole star some 5,500 years from now. No matter what is going on at that time on Earth, the heavens will pursue their long and predictable cycles.

And Alpha Cephei will lie some 3 degrees from the sky’s north pole around the year 7500 CE. That means it won’t be as good a pole star as our present-day Polaris, which will be 0.4525 degrees from the north celestial pole on March 24, 2100. But it’ll be pretty good.

This star’s proper name, Alderamin, is from Arabic and means “the right arm,” presumably of Cepheus the King, father of Andromeda in Greek mythology.

Alpha Cephei is resplendent in this image from the STScI Digital Sky Survey. Image via Mikulski Archive.

Bottom line: Alpha Cephei, or Alderamin, is the brightest star in the faint constellation Cepheus the King. It’s spinning so fast that it appears like a slightly flattened beach ball.

The post Alpha Cephei, or Alderamin, is a fast-spinning star first appeared on EarthSky.

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Astronomers used the CHARA array at Georgia State University – an optical interferometer – to learn the fast rotational speed of Alpha Cephei, aka Alderamin. Read about this work here. Image via M. Zhao.

You deserve a daily dose of good news. For the latest in science and the night sky, subscribe to EarthSky’s free daily newsletter.

Alpha Cephei, also known as Alderamin, is the brightest star in the constellation Cepheus the King. Astronomers are intrigued by this star because it spins at such a fast rate. Unlike our almost-round sun, Alderamin is distorted by its rapid spin into an oblate form, like a partly deflated beach ball.

This star isn’t the brightest one around, but it’s pretty bright. It shines at about magnitude 2.5.

Its faint constellation, Cepheus, is surprisingly easy to spot in a dark sky because the stars of Cepheus trace out the shape of a child’s stick house.

Science of Alpha Cephei

Alpha Cephei, 49 light-years away, is a white star that is twice the mass of our sun and about 17 times its luminosity. It is considered a Class A star, which is now evolving off the main sequence into a subgiant. It’s thought that this star is now on its way to becoming a red giant as its internal supply of hydrogen fuel runs low.

Alpha Cephei rotates rapidly; observations suggest it could be as fast as 152 miles a second (246 km/s). In comparison, the sun’s rotation speed at the equator is not quite 1.2 miles a second (2 km/s). As a result of its rapid rotation, Alpha Cephei appears slightly flattened. That’s because the star’s surface rotation speed gets progressively faster as you move away from its rotation axis towards its equator.

And, as surface rotation speed increases, the star’s surface is increasingly pushed out. As a result, Alpha Cephei bulges along the equator.

A closer look at Alpha Cephei

The image at the top of this article is a model of Alpha Cephei based on data from the CHARA telescope array. It shows Alpha Cephei’s oblate shape. It also shows a darker equatorial region, shaded to indicate that these are cooler regions of the star.

Meanwhile, a section near the pole appears brighter. That’s because the surface gravity is higher around the “flattened” poles compared to the bulging equator, and as a result, higher temperatures and pressure are needed to maintain an equilibrium. These differences in brightness across rapidly rotating stars result in a phenomenon scientists call gravity darkening.

Astronomer Jim Kaler wrote about this rapidly spinning star:

The spin may also be related to the star’s activity. [Our] sun is magnetically active in broad part because its outer third is churning up and down in huge convective currents, the movement helping to generate a magnetic field. Such outer zones are supposed to disappear in class A stars like Alderamin. Yet Alderamin emits about the same amount of X-ray radiation as does the sun and has other features that together suggest considerable magnetic activity. No one really knows why. Such anomalies, of course, drive the science. Understanding Alderamin will someday help us understand our own star, on which we depend for life.

How to find Alpha Cephei

On a dark night, Alpha Cephei is easily visible and relatively easy to find. Look northward for this star. It is circumpolar — meaning it never sets — throughout all of Europe, northern Asia, Canada and American cities as far south as San Diego, California. Its constellation, Cepheus, has the shape of the stick house we all drew as children.

Or you might prefer to see the shape of Cepheus as a point on the King’s crown. Cepheus is a rather faint constellation, but Alpha Cephei is by far its brightest star and is easily observable to the unaided eye, even in cities.

If you know the W or M-shaped constellation Cassiopeia the Queen, you can use the Cassiopeia stars Schedar and Caph to star-hop to Alderamin.

A close-up of Cassiopeia and Cepheus. Notice that a line from Schedar and Caph will lead you to Alderamin, or Alpha Cephei, the brightest star in the King.

A once and future pole star

Alpha Cephei has been a pole star in the past. That is, a bright star close to the sky’s north pole. This is because a slow, constant wobble in Earth’s movement — known as precession — makes the stars shift in relation to our planet’s axis.

The last time Alpha Cephei was the nearest bright star to the north celestial pole was in 18,000 BCE. It will again be a pole star some 5,500 years from now. No matter what is going on at that time on Earth, the heavens will pursue their long and predictable cycles.

And Alpha Cephei will lie some 3 degrees from the sky’s north pole around the year 7500 CE. That means it won’t be as good a pole star as our present-day Polaris, which will be 0.4525 degrees from the north celestial pole on March 24, 2100. But it’ll be pretty good.

This star’s proper name, Alderamin, is from Arabic and means “the right arm,” presumably of Cepheus the King, father of Andromeda in Greek mythology.

Alpha Cephei is resplendent in this image from the STScI Digital Sky Survey. Image via Mikulski Archive.

Bottom line: Alpha Cephei, or Alderamin, is the brightest star in the faint constellation Cepheus the King. It’s spinning so fast that it appears like a slightly flattened beach ball.

The post Alpha Cephei, or Alderamin, is a fast-spinning star first appeared on EarthSky.

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