Mars mission to send Blue and Gold satellites to red planet

As seen in this artist’s concept, the Blue and Gold orbiters in the Mars mission ESCAPADE will launch in 2025. Scientists and engineers built the probes on a shoestring budget, to see if it could be done. The probes will take 11 months to reach the red planet and are designed to study Mars’ magnetosphere. Image via Rocket Lab/ UC Berkeley.

Mars mission to study magnetosphere on the cheap

NASA and its partners want to find out if they can study the solar system without breaking the bank. To this end, they’ll soon send a new, cost-effective Mars mission to the red planet. A pair of small satellites – called Blue and Gold – will fly into Earth orbit no earlier than spring 2025. They’ll ultimately go on an 11-month journey to Mars.

This 5-month mission to the red planet is officially called the Escape and Plasma Acceleration and Dynamics Explorers, or ESCAPADE. It represents a proof of concept, relying on new spaceflight technology to keep costs down. Mission leader Robert Lillis previously said in a talk with UC Berkeley News:

ESCAPADE and two other NASA missions recently approved are experiments to see whether advances in the space industry over the last five to 10 years can translate to a much better bang for the buck in terms of science per dollar. Sending two spacecraft to Mars for the total cost of under $80 million is just unheard of. But current NASA leadership is taking the risk.

The risk is a mission failure. But at 10% the normal cost for sending a spacecraft to Mars, NASA figures it can afford to roll the dice. Lillis put it this way:

Instead of spending $800 million for a 95% chance of success, can we spend $80 million for an 80% chance? This is what NASA is trying to find out with these missions, and we are lucky to be one of the guinea pigs.

Rob Lillis at UC Berkeley is the mission leader for ESCAPADE. Image via UC Berkeley/ SSL.

Going for the Gold and Blue on Mars

Lillis is also the University of California, Berkeley Space Sciences Laboratory (SSL) associate director for planetary science and astrobiology. The SSL – working in conjunction with NASA’s Goddard Space Flight Center – engineered the twin probes. In managing the mission, the SSL will run the onboard instruments and process the data. It’s also flying the craft.

And so that’s why the satellites are named Gold and Blue. They’re the official Berkeley colors. Sending two satellites to scan the same terrain will give ESCAPADE’s data an added dimension. Lillis said:

With simultaneous two-point observations of the solar wind and Mars’ ionosphere and magnetosphere, ESCAPADE will bring us the first stereo picture of this highly dynamic plasma environment.

The two orbiters will circle Mars in complementary orbits. They will sample the hot ionized plasma (yellow and green) and magnetic fields (blue lines) to understand how Mars’ atmosphere escapes into space. Image via UC Berkeley/ Robert Lillis.

Figuring out how Mars gets electrically charged

The Mars mission aims to track the internal workings of the planet’s magnetic environment, aka its magnetosphere. The mission scientists want to know how energy and matter from the solar wind makes its way in and out of Mars’ planetwide magnetic field.

Mars’ magnetic field is unlike those on other planets. It’s often called a hybrid. On the one hand, it’s a solar-induced magnetosphere, like that on Venus, created in part by the interaction of the solar wind with the Martian atmosphere. On the other hand, it also has localized areas of intrinsic magnetic fields from the planet’s crust. Plus there are larger-scale global influences.

NASA described the mission goals for probes:

ESCAPADE will analyze how Mars’ magnetic field guides particle flows around the planet, how energy and momentum are transported from the solar wind through the magnetosphere and what processes control the flow of energy and matter into and out of the Martian atmosphere.

ESCAPADE is part of the NASA Small Innovative Missions for Planetary Exploration (SIMPLEx) program. The spacecraft is relatively small, with a mass under 200 pounds (90 kg). Onboard are a magnetometer, an electrostatic analyzer to measure superthermal ions and electrons and a plasma density probe.

The end of the mission is planned for March 2027.

ESCAPADE will study Mars’ magnetosphere (depicted here), atmosphere and the solar wind, and how they interact. Image via Anil Rao/ University of Colorado/ MAVEN/ NASA GSFC/ NASA.

Bottom line: The Mars ESCAPADE mission will study the red planet’s magnetosphere using a pair of small satellites. ESCAPADE will launch no earlier than spring 2025.

Read more: Mars in 2024: Find it in the morning sky

The post Mars mission to send Blue and Gold satellites to red planet first appeared on EarthSky.

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As seen in this artist’s concept, the Blue and Gold orbiters in the Mars mission ESCAPADE will launch in 2025. Scientists and engineers built the probes on a shoestring budget, to see if it could be done. The probes will take 11 months to reach the red planet and are designed to study Mars’ magnetosphere. Image via Rocket Lab/ UC Berkeley.

Mars mission to study magnetosphere on the cheap

NASA and its partners want to find out if they can study the solar system without breaking the bank. To this end, they’ll soon send a new, cost-effective Mars mission to the red planet. A pair of small satellites – called Blue and Gold – will fly into Earth orbit no earlier than spring 2025. They’ll ultimately go on an 11-month journey to Mars.

This 5-month mission to the red planet is officially called the Escape and Plasma Acceleration and Dynamics Explorers, or ESCAPADE. It represents a proof of concept, relying on new spaceflight technology to keep costs down. Mission leader Robert Lillis previously said in a talk with UC Berkeley News:

ESCAPADE and two other NASA missions recently approved are experiments to see whether advances in the space industry over the last five to 10 years can translate to a much better bang for the buck in terms of science per dollar. Sending two spacecraft to Mars for the total cost of under $80 million is just unheard of. But current NASA leadership is taking the risk.

The risk is a mission failure. But at 10% the normal cost for sending a spacecraft to Mars, NASA figures it can afford to roll the dice. Lillis put it this way:

Instead of spending $800 million for a 95% chance of success, can we spend $80 million for an 80% chance? This is what NASA is trying to find out with these missions, and we are lucky to be one of the guinea pigs.

Rob Lillis at UC Berkeley is the mission leader for ESCAPADE. Image via UC Berkeley/ SSL.

Going for the Gold and Blue on Mars

Lillis is also the University of California, Berkeley Space Sciences Laboratory (SSL) associate director for planetary science and astrobiology. The SSL – working in conjunction with NASA’s Goddard Space Flight Center – engineered the twin probes. In managing the mission, the SSL will run the onboard instruments and process the data. It’s also flying the craft.

And so that’s why the satellites are named Gold and Blue. They’re the official Berkeley colors. Sending two satellites to scan the same terrain will give ESCAPADE’s data an added dimension. Lillis said:

With simultaneous two-point observations of the solar wind and Mars’ ionosphere and magnetosphere, ESCAPADE will bring us the first stereo picture of this highly dynamic plasma environment.

The two orbiters will circle Mars in complementary orbits. They will sample the hot ionized plasma (yellow and green) and magnetic fields (blue lines) to understand how Mars’ atmosphere escapes into space. Image via UC Berkeley/ Robert Lillis.

Figuring out how Mars gets electrically charged

The Mars mission aims to track the internal workings of the planet’s magnetic environment, aka its magnetosphere. The mission scientists want to know how energy and matter from the solar wind makes its way in and out of Mars’ planetwide magnetic field.

Mars’ magnetic field is unlike those on other planets. It’s often called a hybrid. On the one hand, it’s a solar-induced magnetosphere, like that on Venus, created in part by the interaction of the solar wind with the Martian atmosphere. On the other hand, it also has localized areas of intrinsic magnetic fields from the planet’s crust. Plus there are larger-scale global influences.

NASA described the mission goals for probes:

ESCAPADE will analyze how Mars’ magnetic field guides particle flows around the planet, how energy and momentum are transported from the solar wind through the magnetosphere and what processes control the flow of energy and matter into and out of the Martian atmosphere.

ESCAPADE is part of the NASA Small Innovative Missions for Planetary Exploration (SIMPLEx) program. The spacecraft is relatively small, with a mass under 200 pounds (90 kg). Onboard are a magnetometer, an electrostatic analyzer to measure superthermal ions and electrons and a plasma density probe.

The end of the mission is planned for March 2027.

ESCAPADE will study Mars’ magnetosphere (depicted here), atmosphere and the solar wind, and how they interact. Image via Anil Rao/ University of Colorado/ MAVEN/ NASA GSFC/ NASA.

Bottom line: The Mars ESCAPADE mission will study the red planet’s magnetosphere using a pair of small satellites. ESCAPADE will launch no earlier than spring 2025.

Read more: Mars in 2024: Find it in the morning sky

The post Mars mission to send Blue and Gold satellites to red planet first appeared on EarthSky.

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Equinox shadows trace a straight line from west to east

Note that the shape of your “gnomon” or stick doesn’t matter. The tip of this huge obelisk’s shadow at the Chinook Trails Elementary School in Colorado Springs, Colorado, traces a straight line from west to east, throughout the day of an equinox. Image via John Carmichael/ Wikimedia (public domain).

The September equinox will fall at 12:44 UTC (7:44 a.m. CDT) on September 22, 2024. Read about this equinox.

Equinox shadows are unique

Do you enjoy sundials, and shadows? Did you know that – on the day of an equinox, and only on the day of an equinox – the tip of an upright stick’s shadow follows a straight west-to-east path? If you track the shadow’s tip (aka its terminus) as it moves across the ground on the day of the equinox, you’ll see it tracing out that straight line, as shown – beginning around 00:20 – in the video below:

If you track the tip of an upright stick’s shadow on the day of the equinox, you’ll find that it follows a straight line. In this image, the larger stick is serving as the gnomon, and the smaller sticks are recording the shadow’s passing. Image via Woodland Ways. Used with permission.

Tracking the equinox sun

By tracking the sun’s shadow in this way, you’re making a simple kind of sundial. Sundials are the earliest type of timekeeping device.

This shadow fact – that is, the tip of a shadow traces a straight west-to-east path only at the equinoxes – applies everywhere worldwide, except at the North and South Poles.

In 2024, the equinox comes on September 22. So that’s a good day to see the equinox shadow for yourself.

Given a sunny day and an open sky, you can see the line traced by the moving shadow. Find a level spot, and pound your shadow stick (aka your gnomon) upright into the ground.

Alternatively, you could use an existing flagpole or utility pole as a makeshift shadow pole. Just be sure to have enough flat terrain to accommodate the moving shadow.

Try using spikes, coins or small rocks to record the shadow’s passing throughout the day. Remember, you’ll be recording the points struck by the shadow’s tip, or terminus. On the day of an equinox, these points will make a straight line, on or near a line from due west to due east.

Note that, in this video, what he labels as equinoctial line is the line from due east to due west.

About that word ‘gnomon’

A shadow pole or shadow stick, when used to track the sun by its shadow, is called a gnomon. Apparently, “gnomon” is from an ancient Greek root meaning “to know.”

So the term seems appropriate because – after all – the gnomon’s shadow knows! The gnomon of a sundial, for example, knows both the hour of the day and the season of the year.

More sophisticated than an upright stick, the washer-shaped eyelet creates a “pinhole” gnomon. On the equinoxes, the opening projects the pinpoint of light upon the straight equinox line. On the summer/winter solstices, this point of light travels along the respective curved solstice paths. Image via François Blateyron. Used with permission.

Curved shadow paths at other times of year

Then at other times of the year, but most especially at the solstices, the shadow paths follow a curve, as shown on the graphic below. Technically speaking, these nonlinear curves are called hyperbolas.

The Greenwich Royal Observatory presents a fine example of a pinhole sundial. In this instance, the vertical sundial faces south and records the meridian (noontime) passing of the sun in both sun time and clock time. Image via Wikimedia (CC BY-SA 3.0).

Worldwide similarities of shadow paths

In both the Northern and Southern Hemispheres, the morning’s longest shadow happens right after sunrise. Midway between sunrise and sunset, the shortest shadow of the day occurs at solar noon. Then, after noon, the shadow starts to elongate again, with the longest afternoon shadow happening just before sunset.

Once again, on the day of an equinox, the tip of an upright pole’s shadow travels in a straight line, from west to east.

Here are more experiments you can do yourself at home.

Northern and Southern Hemisphere differences

By the way, there are some major differences between the two hemispheres. On an equinox-day in the Northern Hemisphere, the straight shadow path passes to the north of the gnomon. In the Southern Hemisphere, the straight shadow path passes to the south of the gnomon.

And, at the equator, the shadow path goes neither north nor south of the gnomon. That’s because the noonday sun swings directly over the upright pole on the equinox, casting no midday shadow.

On the day of an equinox – and only on the day of an equinox – the tip of a shadow from an upright stick or “gnomon” traces a straight west-to-east path along the ground. In fact, you can watch the equinox shadows yourself. Illustration via John Jardine Goss/ EarthSky.

Bottom line: On the day of an equinox, the tip of an upright stick’s shadow follows a straight west-to-east path all day long.

Read more: September equinox 2024: All you need to know

The post Equinox shadows trace a straight line from west to east first appeared on EarthSky.

from EarthSky https://ift.tt/rwAcG1v

Note that the shape of your “gnomon” or stick doesn’t matter. The tip of this huge obelisk’s shadow at the Chinook Trails Elementary School in Colorado Springs, Colorado, traces a straight line from west to east, throughout the day of an equinox. Image via John Carmichael/ Wikimedia (public domain).

The September equinox will fall at 12:44 UTC (7:44 a.m. CDT) on September 22, 2024. Read about this equinox.

Equinox shadows are unique

Do you enjoy sundials, and shadows? Did you know that – on the day of an equinox, and only on the day of an equinox – the tip of an upright stick’s shadow follows a straight west-to-east path? If you track the shadow’s tip (aka its terminus) as it moves across the ground on the day of the equinox, you’ll see it tracing out that straight line, as shown – beginning around 00:20 – in the video below:

If you track the tip of an upright stick’s shadow on the day of the equinox, you’ll find that it follows a straight line. In this image, the larger stick is serving as the gnomon, and the smaller sticks are recording the shadow’s passing. Image via Woodland Ways. Used with permission.

Tracking the equinox sun

By tracking the sun’s shadow in this way, you’re making a simple kind of sundial. Sundials are the earliest type of timekeeping device.

This shadow fact – that is, the tip of a shadow traces a straight west-to-east path only at the equinoxes – applies everywhere worldwide, except at the North and South Poles.

In 2024, the equinox comes on September 22. So that’s a good day to see the equinox shadow for yourself.

Given a sunny day and an open sky, you can see the line traced by the moving shadow. Find a level spot, and pound your shadow stick (aka your gnomon) upright into the ground.

Alternatively, you could use an existing flagpole or utility pole as a makeshift shadow pole. Just be sure to have enough flat terrain to accommodate the moving shadow.

Try using spikes, coins or small rocks to record the shadow’s passing throughout the day. Remember, you’ll be recording the points struck by the shadow’s tip, or terminus. On the day of an equinox, these points will make a straight line, on or near a line from due west to due east.

Note that, in this video, what he labels as equinoctial line is the line from due east to due west.

About that word ‘gnomon’

A shadow pole or shadow stick, when used to track the sun by its shadow, is called a gnomon. Apparently, “gnomon” is from an ancient Greek root meaning “to know.”

So the term seems appropriate because – after all – the gnomon’s shadow knows! The gnomon of a sundial, for example, knows both the hour of the day and the season of the year.

More sophisticated than an upright stick, the washer-shaped eyelet creates a “pinhole” gnomon. On the equinoxes, the opening projects the pinpoint of light upon the straight equinox line. On the summer/winter solstices, this point of light travels along the respective curved solstice paths. Image via François Blateyron. Used with permission.

Curved shadow paths at other times of year

Then at other times of the year, but most especially at the solstices, the shadow paths follow a curve, as shown on the graphic below. Technically speaking, these nonlinear curves are called hyperbolas.

The Greenwich Royal Observatory presents a fine example of a pinhole sundial. In this instance, the vertical sundial faces south and records the meridian (noontime) passing of the sun in both sun time and clock time. Image via Wikimedia (CC BY-SA 3.0).

Worldwide similarities of shadow paths

In both the Northern and Southern Hemispheres, the morning’s longest shadow happens right after sunrise. Midway between sunrise and sunset, the shortest shadow of the day occurs at solar noon. Then, after noon, the shadow starts to elongate again, with the longest afternoon shadow happening just before sunset.

Once again, on the day of an equinox, the tip of an upright pole’s shadow travels in a straight line, from west to east.

Here are more experiments you can do yourself at home.

Northern and Southern Hemisphere differences

By the way, there are some major differences between the two hemispheres. On an equinox-day in the Northern Hemisphere, the straight shadow path passes to the north of the gnomon. In the Southern Hemisphere, the straight shadow path passes to the south of the gnomon.

And, at the equator, the shadow path goes neither north nor south of the gnomon. That’s because the noonday sun swings directly over the upright pole on the equinox, casting no midday shadow.

On the day of an equinox – and only on the day of an equinox – the tip of a shadow from an upright stick or “gnomon” traces a straight west-to-east path along the ground. In fact, you can watch the equinox shadows yourself. Illustration via John Jardine Goss/ EarthSky.

Bottom line: On the day of an equinox, the tip of an upright stick’s shadow follows a straight west-to-east path all day long.

Read more: September equinox 2024: All you need to know

The post Equinox shadows trace a straight line from west to east first appeared on EarthSky.

from EarthSky https://ift.tt/rwAcG1v

Did Earth have rings 466 million years ago?

View larger. | Did Earth have rings 466 million years ago? This is an artist’s concept of what Earth could have looked like with a ring system. Image via Kevin M. Gill/ Flickr (CC BY 2.0).

• Several planets in our solar system have rings. Even some asteroids have rings. But why not Earth?
• Earth did once have its own rings, according to a new study, some 466 million years ago.
• The rings may have had a cooling affect, lowering global temperatures.

Did Earth have rings 466 million years ago?

Ring systems are common in our solar system. Saturn, Jupiter, Uranus, Neptune and even some dwarf planets and asteroids have rings. Earth, sadly, does not. But it might have in the past. That’s what researchers at Monash University in Australia said on September 16, 2024. Their study of asteroid impact craters from 466 million years ago – during the middle Ordovician Period – shows Earth may have had its own ring system.

The researchers, led by Andy Tomkins from Monash University’s School of Earth, Atmosphere and Environment, published their peer-reviewed findings in Earth And Planetary Science Letters on September 12, 2024.

Did Earth have rings long ago?

Since both larger planets and smaller bodies like asteroids can have rings, why not Earth? Our planet never had rings gracing its skies. Or did it?

The researchers hypothesize that a large asteroid passed close to Earth about 466 million years ago. It passed close enough that it was within the Roche limit. That is the minimum distance to which a smaller body can approach a larger primary body without tidal forces overcoming the internal gravity holding the satellite together.

In other words, if the smaller body gets too close, it will be torn apart. In this case, Earth’s gravity ripped apart the asteroid. The resulting debris began to orbit Earth, forming a ring or rings.

Clues from asteroid impacts

How did the researchers determine that an asteroid formed a ring, and when it happened? They examined the locations of 21 known asteroid impacts, dating back to the Ordovician Period, 466 million years ago. And they noticed something unusual.

All the craters were located within 30 degrees of the equator. This seemed odd, since over 70% of Earth’s continental crust – that forms nearly all of Earth’s land surface – was outside of that region. Why were the craters confined to this region? The research team postulated that the craters formed from debris that gradually fell back to Earth from the rings over time. As Tomkins explained:

Over millions of years, material from this ring gradually fell to Earth, creating the spike in meteorite impacts observed in the geological record. We also see that layers in sedimentary rocks from this period contain extraordinary amounts of meteorite debris.

Random or non-random?

But were these impacts really non-random? To answer this, the researchers calculated the continental surface area capable of preserving craters from that time. They looked at cratons – large parts of the continental crust that have remained stable – with rocks older than the mid-Ordovician Period.

The researchers excluded areas buried under sediments or ice, eroded regions and areas affected by tectonic activity. They found suitable regions across various continents, including Western Australia, Africa, the North American Craton and small parts of Europe. Such areas should have preserved craters if they existed.

But all the impact craters were in the 30% of the cratons that were close to the equator. According to the researchers, this shows the distribution of craters was non-random. They likened it to tossing a three-sided coin and having it land on tails 21 times.

View larger. | Artist’s illustration of an asteroid approaching Earth. In the new study, scientists said the possible rings likely formed when as asteroid passed close to Earth and was torn apart by the planet’s gravity. Image via urikyo33/ Pixabay.

Effects on climate

The ring system may also have affected Earth’s climate. Tomkins said:

What makes this finding even more intriguing is the potential climate implications of such a ring system.

How would this happen? The rings could have had a cooling effect, which would also explain another aspect of the late Ordovician Period: It was cold. In fact, it was one of the coldest times in the last 500 million years. The rings system could have cast a shadow on Earth by partially blacking sunlight. The researchers said this may have contributed to a global cooling period called the Hirnantian. The Hirnantian was the final stage of the Ordovician Period.

Tomkins said:

The idea that a ring system could have influenced global temperatures adds a new layer of complexity to our understanding of how extraterrestrial events may have shaped Earth’s climate.

Also, if rings existed at that point in Earth’s history, could they have also existed at other times as well? We don’t know yet, but it’s possible.

View larger. | Saturn’s small moon Iapetus has a distinct mountain-like ridge that goes almost all the way around the equator. One theory is that it formed from a former ring that collapsed, depositing debris along the equator. This is a bit reminiscent of what may have happened on Earth, except that the debris didn’t form a ridge, just craters. Image via NASA/ JPL/ Space Science Institute.

Saturn’s moon Iapetus

The findings are also reminiscent of what scientists say has occurred on other bodies in the solar system. Saturn’s small moon Iapetus has an unusual, tall mountain-like ridge that goes almost all the way around it at the equator. How did it form? Scientists say one theory is that a former ring may have collapsed and deposited the debris on the moon, forming the ridge.

This is a bit reminiscent of what may have happened on Earth, except that the debris didn’t form a ridge, just craters.

Bottom line: Did Earth have rings eons ago? A new study suggests that Earth had its own ring system 466 million years ago, which formed from the breakup of an asteroid.

Source: Evidence suggesting that earth had a ring in the Ordovician

Via Monash University

Read more: Saturn’s rings are disappearing!

Read more: Webb sees Neptune’s rings and moons. Wow!

The post Did Earth have rings 466 million years ago? first appeared on EarthSky.

from EarthSky https://ift.tt/ew5ioO8

View larger. | Did Earth have rings 466 million years ago? This is an artist’s concept of what Earth could have looked like with a ring system. Image via Kevin M. Gill/ Flickr (CC BY 2.0).

• Several planets in our solar system have rings. Even some asteroids have rings. But why not Earth?
• Earth did once have its own rings, according to a new study, some 466 million years ago.
• The rings may have had a cooling affect, lowering global temperatures.

Did Earth have rings 466 million years ago?

Ring systems are common in our solar system. Saturn, Jupiter, Uranus, Neptune and even some dwarf planets and asteroids have rings. Earth, sadly, does not. But it might have in the past. That’s what researchers at Monash University in Australia said on September 16, 2024. Their study of asteroid impact craters from 466 million years ago – during the middle Ordovician Period – shows Earth may have had its own ring system.

The researchers, led by Andy Tomkins from Monash University’s School of Earth, Atmosphere and Environment, published their peer-reviewed findings in Earth And Planetary Science Letters on September 12, 2024.

Did Earth have rings long ago?

Since both larger planets and smaller bodies like asteroids can have rings, why not Earth? Our planet never had rings gracing its skies. Or did it?

The researchers hypothesize that a large asteroid passed close to Earth about 466 million years ago. It passed close enough that it was within the Roche limit. That is the minimum distance to which a smaller body can approach a larger primary body without tidal forces overcoming the internal gravity holding the satellite together.

In other words, if the smaller body gets too close, it will be torn apart. In this case, Earth’s gravity ripped apart the asteroid. The resulting debris began to orbit Earth, forming a ring or rings.

Clues from asteroid impacts

How did the researchers determine that an asteroid formed a ring, and when it happened? They examined the locations of 21 known asteroid impacts, dating back to the Ordovician Period, 466 million years ago. And they noticed something unusual.

All the craters were located within 30 degrees of the equator. This seemed odd, since over 70% of Earth’s continental crust – that forms nearly all of Earth’s land surface – was outside of that region. Why were the craters confined to this region? The research team postulated that the craters formed from debris that gradually fell back to Earth from the rings over time. As Tomkins explained:

Over millions of years, material from this ring gradually fell to Earth, creating the spike in meteorite impacts observed in the geological record. We also see that layers in sedimentary rocks from this period contain extraordinary amounts of meteorite debris.

Random or non-random?

But were these impacts really non-random? To answer this, the researchers calculated the continental surface area capable of preserving craters from that time. They looked at cratons – large parts of the continental crust that have remained stable – with rocks older than the mid-Ordovician Period.

The researchers excluded areas buried under sediments or ice, eroded regions and areas affected by tectonic activity. They found suitable regions across various continents, including Western Australia, Africa, the North American Craton and small parts of Europe. Such areas should have preserved craters if they existed.

But all the impact craters were in the 30% of the cratons that were close to the equator. According to the researchers, this shows the distribution of craters was non-random. They likened it to tossing a three-sided coin and having it land on tails 21 times.

View larger. | Artist’s illustration of an asteroid approaching Earth. In the new study, scientists said the possible rings likely formed when as asteroid passed close to Earth and was torn apart by the planet’s gravity. Image via urikyo33/ Pixabay.

Effects on climate

The ring system may also have affected Earth’s climate. Tomkins said:

What makes this finding even more intriguing is the potential climate implications of such a ring system.

How would this happen? The rings could have had a cooling effect, which would also explain another aspect of the late Ordovician Period: It was cold. In fact, it was one of the coldest times in the last 500 million years. The rings system could have cast a shadow on Earth by partially blacking sunlight. The researchers said this may have contributed to a global cooling period called the Hirnantian. The Hirnantian was the final stage of the Ordovician Period.

Tomkins said:

The idea that a ring system could have influenced global temperatures adds a new layer of complexity to our understanding of how extraterrestrial events may have shaped Earth’s climate.

Also, if rings existed at that point in Earth’s history, could they have also existed at other times as well? We don’t know yet, but it’s possible.

View larger. | Saturn’s small moon Iapetus has a distinct mountain-like ridge that goes almost all the way around the equator. One theory is that it formed from a former ring that collapsed, depositing debris along the equator. This is a bit reminiscent of what may have happened on Earth, except that the debris didn’t form a ridge, just craters. Image via NASA/ JPL/ Space Science Institute.

Saturn’s moon Iapetus

The findings are also reminiscent of what scientists say has occurred on other bodies in the solar system. Saturn’s small moon Iapetus has an unusual, tall mountain-like ridge that goes almost all the way around it at the equator. How did it form? Scientists say one theory is that a former ring may have collapsed and deposited the debris on the moon, forming the ridge.

This is a bit reminiscent of what may have happened on Earth, except that the debris didn’t form a ridge, just craters.

Bottom line: Did Earth have rings eons ago? A new study suggests that Earth had its own ring system 466 million years ago, which formed from the breakup of an asteroid.

Source: Evidence suggesting that earth had a ring in the Ordovician

Via Monash University

Read more: Saturn’s rings are disappearing!

Read more: Webb sees Neptune’s rings and moons. Wow!

The post Did Earth have rings 466 million years ago? first appeared on EarthSky.

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Are day and night equal on the equinox?

Satellite views of Earth on the solstices and equinoxes. We are at the September equinox now. Are day and night equal on the equinox? Read below to find out. Images via NASA Earth Observatory.

More day than night

The September equinox will come on Sunday, September 22, 2024, at 12:44 UTC (7:44 a.m. CDT on September 22 for central North America). It’s the Northern Hemisphere’s autumn equinox and Southern Hemisphere’s spring equinox. You sometimes hear it said that, at the equinoxes, everyone receives about equal daylight and darkness. But there’s really more daylight than darkness at the equinox, eight more minutes or so at mid-temperate latitudes. Two factors explain why we have more than 12 hours of daylight on this day of supposedly equal day and night. They are:

1. The sun is a disk, not a point.

2. Atmospheric refraction.

Read more about the September 2024 equinox: All you need to know

The sun is a disk, not a point

Watch any sunset, and you know the sun appears in Earth’s sky as a disk.

It’s not point-like, as stars are, and yet – by definition – most almanacs regard sunrise as when the leading edge of the sun first touches the eastern horizon. They define sunset as when the sun’s trailing edge finally touches the western horizon.

This in itself provides an extra 2 1/2 to 3 minutes of daylight at mid-temperate latitudes.

Atmospheric refraction raises the sun about 1/2 degree upward in our sky at both sunrise and sunset. This advances the time of actual sunrise, while delaying the time of actual sunset. The result is several minutes of extra daylight, not just at an equinox, but every day. Image via Wikipedia (CC BY-SA 3.0).

Atmospheric refraction

The Earth’s atmosphere acts like a lens or prism, uplifting the sun about 0.5 degrees from its true geometrical position whenever the sun nears the horizon. Coincidentally, the sun’s angular diameter spans about 0.5 degrees, as well.

In other words, when you see the sun on the horizon, it’s actually just below the horizon geometrically.

What does atmospheric refraction mean for the length of daylight? It advances the sunrise and delays the sunset, adding nearly another six minutes of daylight at mid-temperate latitudes. Hence, more daylight than night at the equinox.

Astronomical almanacs usually don’t give sunrise or sunset times to the second. That’s because atmospheric refraction varies somewhat, depending on air temperature, humidity and barometric pressure. Lower temperature, higher humidity and higher barometric pressure all increase atmospheric refraction.

On the day of the equinox, the center of the sun would set about 12 hours after rising – given a level horizon, as at sea, and no atmospheric refraction.

Are day and night equal?

So, no, day and night are not exactly equal at the equinox.

And here’s a new word for you, equilux. The word is used to describe the day on which day and night are equal. The equilux happens a few to several days after the autumn equinox, and a few to several days before the spring equinox.

Much as earliest sunrises and latest sunsets vary with latitude, so the exact date of an equilux varies with latitude. That’s in contrast to the equinox itself, which is a whole-Earth event, happening at the same instant worldwide. At and near the equator, there is no equilux whatsoever, because the daylight period is over 12 hours long every day of the year.

Visit timeanddate.com for the approximate date of equal day and night at your latitude

Illustrations like this one make it seem as if day and night should be equal at the equinox. In fact, they aren’t exactly equal. Image via Wikimedia Commons (CC BY-SA 3.0).

Bottom line: There’s slightly more day than night on the day of an equinox. That’s because the sun is a disk, not a point of light, and because Earth’s atmosphere refracts (bends) sunlight.

The post Are day and night equal on the equinox? first appeared on EarthSky.

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Satellite views of Earth on the solstices and equinoxes. We are at the September equinox now. Are day and night equal on the equinox? Read below to find out. Images via NASA Earth Observatory.

More day than night

The September equinox will come on Sunday, September 22, 2024, at 12:44 UTC (7:44 a.m. CDT on September 22 for central North America). It’s the Northern Hemisphere’s autumn equinox and Southern Hemisphere’s spring equinox. You sometimes hear it said that, at the equinoxes, everyone receives about equal daylight and darkness. But there’s really more daylight than darkness at the equinox, eight more minutes or so at mid-temperate latitudes. Two factors explain why we have more than 12 hours of daylight on this day of supposedly equal day and night. They are:

1. The sun is a disk, not a point.

2. Atmospheric refraction.

Read more about the September 2024 equinox: All you need to know

The sun is a disk, not a point

Watch any sunset, and you know the sun appears in Earth’s sky as a disk.

It’s not point-like, as stars are, and yet – by definition – most almanacs regard sunrise as when the leading edge of the sun first touches the eastern horizon. They define sunset as when the sun’s trailing edge finally touches the western horizon.

This in itself provides an extra 2 1/2 to 3 minutes of daylight at mid-temperate latitudes.

Atmospheric refraction raises the sun about 1/2 degree upward in our sky at both sunrise and sunset. This advances the time of actual sunrise, while delaying the time of actual sunset. The result is several minutes of extra daylight, not just at an equinox, but every day. Image via Wikipedia (CC BY-SA 3.0).

Atmospheric refraction

The Earth’s atmosphere acts like a lens or prism, uplifting the sun about 0.5 degrees from its true geometrical position whenever the sun nears the horizon. Coincidentally, the sun’s angular diameter spans about 0.5 degrees, as well.

In other words, when you see the sun on the horizon, it’s actually just below the horizon geometrically.

What does atmospheric refraction mean for the length of daylight? It advances the sunrise and delays the sunset, adding nearly another six minutes of daylight at mid-temperate latitudes. Hence, more daylight than night at the equinox.

Astronomical almanacs usually don’t give sunrise or sunset times to the second. That’s because atmospheric refraction varies somewhat, depending on air temperature, humidity and barometric pressure. Lower temperature, higher humidity and higher barometric pressure all increase atmospheric refraction.

On the day of the equinox, the center of the sun would set about 12 hours after rising – given a level horizon, as at sea, and no atmospheric refraction.

Are day and night equal?

So, no, day and night are not exactly equal at the equinox.

And here’s a new word for you, equilux. The word is used to describe the day on which day and night are equal. The equilux happens a few to several days after the autumn equinox, and a few to several days before the spring equinox.

Much as earliest sunrises and latest sunsets vary with latitude, so the exact date of an equilux varies with latitude. That’s in contrast to the equinox itself, which is a whole-Earth event, happening at the same instant worldwide. At and near the equator, there is no equilux whatsoever, because the daylight period is over 12 hours long every day of the year.

Visit timeanddate.com for the approximate date of equal day and night at your latitude

Illustrations like this one make it seem as if day and night should be equal at the equinox. In fact, they aren’t exactly equal. Image via Wikimedia Commons (CC BY-SA 3.0).

Bottom line: There’s slightly more day than night on the day of an equinox. That’s because the sun is a disk, not a point of light, and because Earth’s atmosphere refracts (bends) sunlight.

The post Are day and night equal on the equinox? first appeared on EarthSky.

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Neptune at opposition on September 20-21, 2024

The 8th planet from our sun, Neptune, can’t be seen with the eye alone. Here’s how NASA’s Voyager 2 spacecraft – the 1st and only craft ever to visit Neptune – saw it in 1989. Image via NASA. See more images from Voyager.

• Earth will sweep between the sun and the 8th planet Neptune – outermost major planet in our solar system – at 0 UTC on September 21, 2024 (7 p.m. CDT on September 20), placing the distant planet opposite the sun in our sky.
• Astronomers call this an opposition of Neptune because, at this time, Neptune appears opposite the sun in our sky, rising in the east when the sun sets in the west.
• Neptune is closest and brightest at opposition. Yet it is still much too faint to see with the eye alone, at 30 times Earth’s distance from our sun.

Neptune at opposition in 2024

When and where to watch in 2024: Neptune emerged in the east before sunrise by April 2024 and was visible in good binoculars or a telescope in the morning sky through August. By the time of its September 21 opposition, Neptune is rising in the east at sunset and visible all night. For the rest of 2024, Neptune is up in the evening. It remains visible in good binoculars or a telescope in the evening sky through February of 2025.
Opposition for Neptune will fall at 0 UTC on September 21, 2024 (7 p.m. CDT on September 20).
Constellation at opposition: Neptune is in front of the constellation Pisces the Fish.
Brightness at opposition: The 8th planet shines at magnitude +7.8.
Distance from Earth: Neptune is at its shortest distance from Earth for 2024, 240 light-minutes or 28.9 AU from Earth on September 21.
Through a telescope: Neptune appears 2.3 arcseconds across. Neptune’s brightest moon, Triton, is visible in medium-size telescopes.
Through binoculars: Through binoculars, Neptune will appear as a starlike object if you know where to find it.

View from above the solar system, September 2024

Heliocentric view of solar system, September 2024. Chart via Guy Ottewell’s 2024 Astronomical Calendar. Used with permission.

What is opposition?

Opposition marks the middle of the best time of the year to see an outer planet. Neptune reaches a yearly maximum in brightness at or near opposition. From mid-July to mid-November, Neptune will be at its brightest but it won’t be visible to the unaided eye. Think of us on Earth, sweeping between the sun and Neptune in our smaller, faster orbit. Around the same time as Neptune reaches opposition, it is also making its closest approach to Earth.

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

For precise sun and Neptune rising times at your location:

Old Farmer’s Almanac (U.S. and Canada)

Timeanddate.com (worldwide).

Stellarium (online planetarium program)

In-the-sky’s information with finder chart from your location

How often is Neptune at opposition?

Neptune is the 8th planet from our sun. A year on Neptune is 165 Earth years long. Because Neptune’s orbit around the sun is so gigantic, and because Earth whips around the sun so quickly in comparison, Neptune’s opposition date comes only a few days later each year.

2023 Neptune opposition – September 19
2024 Neptune opposition – September 20
2025 Neptune opposition – September 23
2026 Neptune opposition – September 25

Neptune events in 2024

March 22, 2024: Neptune at solar conjunction
July 2, 2024: Neptune begins retrograde motion
September 21, 2024: Neptune at opposition
December 7, 2024: Neptune ends retrograde motion

You need optical aid to see Neptune

Planets are brightest when at opposition. But Neptune, the 8th planet, is never truly bright. It’s the only major solar system planet that’s never visible to the unaided eye. This world is about five times fainter than the dimmest star you can see on a moonless night under dark skies. You’ll need binoculars or a telescope for Neptune, plus a detailed sky chart.

Because we’re more or less between Neptune and the sun around opposition, Neptune is rising in the east around the time of sunset, climbing highest up for the night around midnight and setting in the west around sunrise. As viewed from Earth now, this world is in front of the constellation Pisces the Fish and near the planet Saturn.

Even with optical aid, Neptune may look like a faint star. You need to magnify Neptune by about 200 times and have a steady night of seeing to view this distant world as a small disk.

During opposition, an outer planet or solar system object is opposite the sun in Earth’s sky. Neptune at opposition occurs on September 21, 2024. Chart via EarthSky.

Bottom line: Neptune at opposition – when it’s 180 degrees from the sun on the sky’s dome – comes early on September 21, 2024. You need optical aid to spot it.

See also: Geocentric Ephemeris for the Sun: 2024

See also: Geocentric Ephemeris for Neptune: 2024

The post Neptune at opposition on September 20-21, 2024 first appeared on EarthSky.

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The 8th planet from our sun, Neptune, can’t be seen with the eye alone. Here’s how NASA’s Voyager 2 spacecraft – the 1st and only craft ever to visit Neptune – saw it in 1989. Image via NASA. See more images from Voyager.

• Earth will sweep between the sun and the 8th planet Neptune – outermost major planet in our solar system – at 0 UTC on September 21, 2024 (7 p.m. CDT on September 20), placing the distant planet opposite the sun in our sky.
• Astronomers call this an opposition of Neptune because, at this time, Neptune appears opposite the sun in our sky, rising in the east when the sun sets in the west.
• Neptune is closest and brightest at opposition. Yet it is still much too faint to see with the eye alone, at 30 times Earth’s distance from our sun.

Neptune at opposition in 2024

When and where to watch in 2024: Neptune emerged in the east before sunrise by April 2024 and was visible in good binoculars or a telescope in the morning sky through August. By the time of its September 21 opposition, Neptune is rising in the east at sunset and visible all night. For the rest of 2024, Neptune is up in the evening. It remains visible in good binoculars or a telescope in the evening sky through February of 2025.
Opposition for Neptune will fall at 0 UTC on September 21, 2024 (7 p.m. CDT on September 20).
Constellation at opposition: Neptune is in front of the constellation Pisces the Fish.
Brightness at opposition: The 8th planet shines at magnitude +7.8.
Distance from Earth: Neptune is at its shortest distance from Earth for 2024, 240 light-minutes or 28.9 AU from Earth on September 21.
Through a telescope: Neptune appears 2.3 arcseconds across. Neptune’s brightest moon, Triton, is visible in medium-size telescopes.
Through binoculars: Through binoculars, Neptune will appear as a starlike object if you know where to find it.

View from above the solar system, September 2024

Heliocentric view of solar system, September 2024. Chart via Guy Ottewell’s 2024 Astronomical Calendar. Used with permission.

What is opposition?

Opposition marks the middle of the best time of the year to see an outer planet. Neptune reaches a yearly maximum in brightness at or near opposition. From mid-July to mid-November, Neptune will be at its brightest but it won’t be visible to the unaided eye. Think of us on Earth, sweeping between the sun and Neptune in our smaller, faster orbit. Around the same time as Neptune reaches opposition, it is also making its closest approach to Earth.

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

For precise sun and Neptune rising times at your location:

Old Farmer’s Almanac (U.S. and Canada)

Timeanddate.com (worldwide).

Stellarium (online planetarium program)

In-the-sky’s information with finder chart from your location

How often is Neptune at opposition?

Neptune is the 8th planet from our sun. A year on Neptune is 165 Earth years long. Because Neptune’s orbit around the sun is so gigantic, and because Earth whips around the sun so quickly in comparison, Neptune’s opposition date comes only a few days later each year.

2023 Neptune opposition – September 19
2024 Neptune opposition – September 20
2025 Neptune opposition – September 23
2026 Neptune opposition – September 25

Neptune events in 2024

March 22, 2024: Neptune at solar conjunction
July 2, 2024: Neptune begins retrograde motion
September 21, 2024: Neptune at opposition
December 7, 2024: Neptune ends retrograde motion

You need optical aid to see Neptune

Planets are brightest when at opposition. But Neptune, the 8th planet, is never truly bright. It’s the only major solar system planet that’s never visible to the unaided eye. This world is about five times fainter than the dimmest star you can see on a moonless night under dark skies. You’ll need binoculars or a telescope for Neptune, plus a detailed sky chart.

Because we’re more or less between Neptune and the sun around opposition, Neptune is rising in the east around the time of sunset, climbing highest up for the night around midnight and setting in the west around sunrise. As viewed from Earth now, this world is in front of the constellation Pisces the Fish and near the planet Saturn.

Even with optical aid, Neptune may look like a faint star. You need to magnify Neptune by about 200 times and have a steady night of seeing to view this distant world as a small disk.

During opposition, an outer planet or solar system object is opposite the sun in Earth’s sky. Neptune at opposition occurs on September 21, 2024. Chart via EarthSky.

Bottom line: Neptune at opposition – when it’s 180 degrees from the sun on the sky’s dome – comes early on September 21, 2024. You need optical aid to spot it.

See also: Geocentric Ephemeris for the Sun: 2024

See also: Geocentric Ephemeris for Neptune: 2024

The post Neptune at opposition on September 20-21, 2024 first appeared on EarthSky.

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We’re getting better at seeing asteroids that may hit Earth

Spot the asteroid, save the world? Astronomers are getting better at spotting asteroids, which can guard against future collisions with Earth. Artist’s concept via NASA/ JPL/ Caltech.

• Astronomers are getting better at spotting asteroids that could potentially collide with Earth.
• We’ve now spotted nine asteroids before impact with Earth’s atmosphere. The most recent space rock spotted before it struck burned in the atmosphere up above the Philippines on September 5, 2024.
• By identifying hazardous asteroids sooner, we have a better chance to mitigate potential impacts and reduce the risk of a catastrophe.

By Daniel Brown, Nottingham Trent University

Astronomers are getting better at spotting asteroids

On September 4, 2024, astronomers discovered an asteroid, 3 feet (1 m) in diameter, heading toward Earth. The space rock burned up harmlessly in the atmosphere near the Philippines later that day, officials announced. Nevertheless, it produced a spectacular fireball that people shared in videos posted on social media.

The object, known as RW1, was only the ninth asteroid to be spotted before impact. But what of much bigger, more dangerous asteroids? Would our warning systems be able to detect all the asteroids that are capable of threatening us on the ground?

Asteroid impacts have influenced every large body in the solar system. They shape their appearance, alter their chemical abundance and – in the case of our own planet at the very least – they helped kickstart the formation of life. But these same events can also disrupt ecosystems, wiping out life, as they did 66 million years ago when a 6-mile (10-km) space rock contributed to the extinction of the dinosaurs (excluding birds).

What are asteroids?

Asteroids are the material left over from the formation of our solar system that did not become part of planets and moons. Asteroids come in all shapes and sizes. Gravity determines their paths and they can, to some extent, be predicted. Of particular interest are the objects that are close to Earth’s orbit called near-Earth objects (NEOs). As of September 2024, we know of approximately 36,000 such objects, ranging in size from several meters to a few kilometers.

But statistical models predict nearly 1 billion such objects should exist. And we only know of very few of them.

Monitoring asteroids

We have been monitoring these asteroids since the 1980s and setting up more detailed surveys of them since the 1990s. The surveys use telescopes to make observations of the entire sky every night. Then they compare images of the same region on different dates.

Astronomers are interested in whether, in the same area of the sky, something has moved with respect to the stars from one night to another. Anything that has moved could be an asteroid. Observing its positions over a longer period allows team members to determine its exact path. This, in turn, enables them to predict where it will be in future, though such data collection and analysis is a time-consuming process that requires patience.

It is made even more challenging by the fact that there are many more smaller objects out there than bigger ones. Some of these smaller objects are nevertheless of sufficient size to cause damage on Earth, so we still need to monitor them. They are also faint and therefore harder to see with telescopes.

It can be difficult to predict the paths of smaller objects long into the future. This is because they have gravitational interactions with all the other objects in the solar system. Even a small gravitational pull on a smaller object can, over time, alter its future orbit in unpredictable ways.

The DART asteroid mission tested whether crashing a spacecraft into an asteroid was an effective way to change its course. Artist’s concept via NASA/ Johns Hopkins APL/ Steve Gribben.

More help to find the next killer asteroid

Funding is crucial in this effort to detect dangerous asteroids and predict their paths. In 2023, NASA allocated US$90 million (£68 million) to hunt for near Earth objects (NEOs). There are several missions in development to detect hazardous objects from space. Examples include the Sutter Ultra project and NASA’s NEOsurveyor infrared telescope mission.

There are even space missions to explore realistic scenarios for altering the paths of asteroids such as the DART mission. DART crashed into an asteroid’s moon so scientists could measure the changes in its path. DART showed it was possible in principle to alter the course of an asteroid by crashing a spacecraft into it. But we’re still far from a concrete solution that could be used in the event of a large asteroid that was really threatening Earth.

Detection programs create a huge amount of image data every day, which is challenging for astronomers to work through quickly. However, AI could help: advanced algorithms could automate the process to a greater degree. Citizen science projects can also open up the task of sorting through the data to the public.

Our current efforts are working, as demonstrated by the detection of the relatively small asteroid RW1. Astronomers only discovered it briefly before it struck Earth. But it gives us hope that we are on the right track.

Bigger asteroids mean greater destruction

Asteroids less than 80 feet (25 meters) in diameter generally burn up before they can cause any damage. But objects of 80 to 3,300 feet (25 to 1,000 meters) in diameter are large enough to get through our atmosphere and cause localized damage. The extent of this damage depends upon the properties of the object and the area where it will hit. But an asteroid of 460 feet (140 meters) in size could cause widespread destruction if it hit a city.

Luckily, collisions with asteroids in this size range are less frequent than for smaller objects. A 460-foot (140-meter) diameter object should hit Earth every 2,000 years.

As of 2023, statistical models suggest we know of 38% of all existing near Earth objects with a size of 460 feet (140 meters) or larger. With the new Vera Rubin 8.5-meter telescope, we hope to increase this fraction to roughly 60% by 2025. NASA’s NEOsurveyor infrared telescope could identify 76% of asteroids 460 feet (140 meters) in size or bigger by 2027.

Asteroids larger than 1 kilometer in size have the ability to cause damage on a global scale, similar to the one that helped to wipe out the dinosaurs. These asteroids are much rarer but easier to spot. Since 2011, we think we have detected 93% of these objects.

After detection, then what?

Less comforting is the fact that we have no current realistic proposal for diverting its path, though missions like DART are a start. We might eventually be able to compile a near-complete list of all possible asteroids that could cause global impacts on Earth.

It’s much less likely that we will ever detect every object that could cause localized damage on Earth, such as destroying a city. We can only continue to monitor what’s out there, creating a warning system that will allow us to prepare and react.

Daniel Brown, Lecturer in Astronomy, Nottingham Trent University

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

Bottom line: Astronomers are getting better at spotting asteroids, such as the asteroid that hit Earth near the Philippines on September 5, 2024. New observatories will help spot more asteroids. But what happens after we spot them?

The post We’re getting better at seeing asteroids that may hit Earth first appeared on EarthSky.

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Spot the asteroid, save the world? Astronomers are getting better at spotting asteroids, which can guard against future collisions with Earth. Artist’s concept via NASA/ JPL/ Caltech.

• Astronomers are getting better at spotting asteroids that could potentially collide with Earth.
• We’ve now spotted nine asteroids before impact with Earth’s atmosphere. The most recent space rock spotted before it struck burned in the atmosphere up above the Philippines on September 5, 2024.
• By identifying hazardous asteroids sooner, we have a better chance to mitigate potential impacts and reduce the risk of a catastrophe.

By Daniel Brown, Nottingham Trent University

Astronomers are getting better at spotting asteroids

On September 4, 2024, astronomers discovered an asteroid, 3 feet (1 m) in diameter, heading toward Earth. The space rock burned up harmlessly in the atmosphere near the Philippines later that day, officials announced. Nevertheless, it produced a spectacular fireball that people shared in videos posted on social media.

The object, known as RW1, was only the ninth asteroid to be spotted before impact. But what of much bigger, more dangerous asteroids? Would our warning systems be able to detect all the asteroids that are capable of threatening us on the ground?

Asteroid impacts have influenced every large body in the solar system. They shape their appearance, alter their chemical abundance and – in the case of our own planet at the very least – they helped kickstart the formation of life. But these same events can also disrupt ecosystems, wiping out life, as they did 66 million years ago when a 6-mile (10-km) space rock contributed to the extinction of the dinosaurs (excluding birds).

What are asteroids?

Asteroids are the material left over from the formation of our solar system that did not become part of planets and moons. Asteroids come in all shapes and sizes. Gravity determines their paths and they can, to some extent, be predicted. Of particular interest are the objects that are close to Earth’s orbit called near-Earth objects (NEOs). As of September 2024, we know of approximately 36,000 such objects, ranging in size from several meters to a few kilometers.

But statistical models predict nearly 1 billion such objects should exist. And we only know of very few of them.

Monitoring asteroids

We have been monitoring these asteroids since the 1980s and setting up more detailed surveys of them since the 1990s. The surveys use telescopes to make observations of the entire sky every night. Then they compare images of the same region on different dates.

Astronomers are interested in whether, in the same area of the sky, something has moved with respect to the stars from one night to another. Anything that has moved could be an asteroid. Observing its positions over a longer period allows team members to determine its exact path. This, in turn, enables them to predict where it will be in future, though such data collection and analysis is a time-consuming process that requires patience.

It is made even more challenging by the fact that there are many more smaller objects out there than bigger ones. Some of these smaller objects are nevertheless of sufficient size to cause damage on Earth, so we still need to monitor them. They are also faint and therefore harder to see with telescopes.

It can be difficult to predict the paths of smaller objects long into the future. This is because they have gravitational interactions with all the other objects in the solar system. Even a small gravitational pull on a smaller object can, over time, alter its future orbit in unpredictable ways.

The DART asteroid mission tested whether crashing a spacecraft into an asteroid was an effective way to change its course. Artist’s concept via NASA/ Johns Hopkins APL/ Steve Gribben.

More help to find the next killer asteroid

Funding is crucial in this effort to detect dangerous asteroids and predict their paths. In 2023, NASA allocated US$90 million (£68 million) to hunt for near Earth objects (NEOs). There are several missions in development to detect hazardous objects from space. Examples include the Sutter Ultra project and NASA’s NEOsurveyor infrared telescope mission.

There are even space missions to explore realistic scenarios for altering the paths of asteroids such as the DART mission. DART crashed into an asteroid’s moon so scientists could measure the changes in its path. DART showed it was possible in principle to alter the course of an asteroid by crashing a spacecraft into it. But we’re still far from a concrete solution that could be used in the event of a large asteroid that was really threatening Earth.

Detection programs create a huge amount of image data every day, which is challenging for astronomers to work through quickly. However, AI could help: advanced algorithms could automate the process to a greater degree. Citizen science projects can also open up the task of sorting through the data to the public.

Our current efforts are working, as demonstrated by the detection of the relatively small asteroid RW1. Astronomers only discovered it briefly before it struck Earth. But it gives us hope that we are on the right track.

Bigger asteroids mean greater destruction

Asteroids less than 80 feet (25 meters) in diameter generally burn up before they can cause any damage. But objects of 80 to 3,300 feet (25 to 1,000 meters) in diameter are large enough to get through our atmosphere and cause localized damage. The extent of this damage depends upon the properties of the object and the area where it will hit. But an asteroid of 460 feet (140 meters) in size could cause widespread destruction if it hit a city.

Luckily, collisions with asteroids in this size range are less frequent than for smaller objects. A 460-foot (140-meter) diameter object should hit Earth every 2,000 years.

As of 2023, statistical models suggest we know of 38% of all existing near Earth objects with a size of 460 feet (140 meters) or larger. With the new Vera Rubin 8.5-meter telescope, we hope to increase this fraction to roughly 60% by 2025. NASA’s NEOsurveyor infrared telescope could identify 76% of asteroids 460 feet (140 meters) in size or bigger by 2027.

Asteroids larger than 1 kilometer in size have the ability to cause damage on a global scale, similar to the one that helped to wipe out the dinosaurs. These asteroids are much rarer but easier to spot. Since 2011, we think we have detected 93% of these objects.

After detection, then what?

Less comforting is the fact that we have no current realistic proposal for diverting its path, though missions like DART are a start. We might eventually be able to compile a near-complete list of all possible asteroids that could cause global impacts on Earth.

It’s much less likely that we will ever detect every object that could cause localized damage on Earth, such as destroying a city. We can only continue to monitor what’s out there, creating a warning system that will allow us to prepare and react.

Daniel Brown, Lecturer in Astronomy, Nottingham Trent University

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

Bottom line: Astronomers are getting better at spotting asteroids, such as the asteroid that hit Earth near the Philippines on September 5, 2024. New observatories will help spot more asteroids. But what happens after we spot them?

The post We’re getting better at seeing asteroids that may hit Earth first appeared on EarthSky.

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Year’s fastest sunsets happen around equinoxes

View at EarthSky Community Photos. | Jim Grant caught this sunset with a green flash at the Ocean Beach Pier in San Diego, California, on July 19, 2023. Jim wrote: “I knew the sunset was going to be stunning and I started tracking the boat hoping to get it centered in the sun. The green rim and green flash above were a bonus.” Thank you, Jim! Read more about the fastest sunsets below.

Year’s fastest sunsets and sunrises

The September equinox happens at 12:44 UTC on September 22, 2024 (7:44 a.m. CDT). And here’s a little-known equinox phenomenon: the sun sets faster around the time of an equinox. The fastest sunsets (and sunrises) occur at or near the equinoxes. On the other hand, the slowest sunsets (and sunrises) occur at or near the solstices. It’s true whether you live in the Northern or Southern Hemisphere.

And, by the way, when we say sunset here, we’re talking about the actual number of minutes it takes for the body of the sun to sink below the western horizon.

So, why does the sun set so quickly around the equinoxes? It’s because, at every equinox, the sun rises due east and sets due west. That means – on the day of an equinox – the setting sun hits the horizon at its steepest possible angle.

EarthSky’s Raúl Cortés caught the March equinox sun at sunrise. Thanks, Raúl! See more of Raúl’s photos here.

Year’s slowest sunsets and sunrises

Meanwhile, at a solstice, the sun is setting farthest north or farthest south of due west. And, the farther the sun sets from due west along the horizon, the shallower the angle of the setting sun. So that means a longer duration for sunset at the solstices.

Also, the sunset duration varies by latitude. Farther north or south on the Earth’s globe, the duration of sunset lasts longer. So, closer to the equator, the duration is shorter. But let’s just consider one latitude, 40 degrees north, the latitude of Denver or Philadelphia in the United States; parts of Spain; and Beijing, China.

At that latitude, on the day of equinox, the sun sets in about 2 3/4 minutes.

On the other hand, the solstice sun sets in roughly 3 1/4 minutes at 40 degrees latitude.

The equinox is an event that takes place in Earth’s orbit around the sun. Image via National Weather Service/ weather.gov.

Bottom line: The fastest sunsets of the year are happening now, around the time of the September equinox.

September equinox 2024: Everything you need to know

Are day and night equal on the equinox?

Help support EarthSky! Visit the EarthSky store for to see the great selection of educational tools and team gear we have to offer.

The post Year’s fastest sunsets happen around equinoxes first appeared on EarthSky.

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View at EarthSky Community Photos. | Jim Grant caught this sunset with a green flash at the Ocean Beach Pier in San Diego, California, on July 19, 2023. Jim wrote: “I knew the sunset was going to be stunning and I started tracking the boat hoping to get it centered in the sun. The green rim and green flash above were a bonus.” Thank you, Jim! Read more about the fastest sunsets below.

Year’s fastest sunsets and sunrises

The September equinox happens at 12:44 UTC on September 22, 2024 (7:44 a.m. CDT). And here’s a little-known equinox phenomenon: the sun sets faster around the time of an equinox. The fastest sunsets (and sunrises) occur at or near the equinoxes. On the other hand, the slowest sunsets (and sunrises) occur at or near the solstices. It’s true whether you live in the Northern or Southern Hemisphere.

And, by the way, when we say sunset here, we’re talking about the actual number of minutes it takes for the body of the sun to sink below the western horizon.

So, why does the sun set so quickly around the equinoxes? It’s because, at every equinox, the sun rises due east and sets due west. That means – on the day of an equinox – the setting sun hits the horizon at its steepest possible angle.

EarthSky’s Raúl Cortés caught the March equinox sun at sunrise. Thanks, Raúl! See more of Raúl’s photos here.

Year’s slowest sunsets and sunrises

Meanwhile, at a solstice, the sun is setting farthest north or farthest south of due west. And, the farther the sun sets from due west along the horizon, the shallower the angle of the setting sun. So that means a longer duration for sunset at the solstices.

Also, the sunset duration varies by latitude. Farther north or south on the Earth’s globe, the duration of sunset lasts longer. So, closer to the equator, the duration is shorter. But let’s just consider one latitude, 40 degrees north, the latitude of Denver or Philadelphia in the United States; parts of Spain; and Beijing, China.

At that latitude, on the day of equinox, the sun sets in about 2 3/4 minutes.

On the other hand, the solstice sun sets in roughly 3 1/4 minutes at 40 degrees latitude.

The equinox is an event that takes place in Earth’s orbit around the sun. Image via National Weather Service/ weather.gov.

Bottom line: The fastest sunsets of the year are happening now, around the time of the September equinox.

September equinox 2024: Everything you need to know

Are day and night equal on the equinox?

Help support EarthSky! Visit the EarthSky store for to see the great selection of educational tools and team gear we have to offer.

The post Year’s fastest sunsets happen around equinoxes first appeared on EarthSky.

from EarthSky https://ift.tt/oSMV3sG