Something knocked a chunk off the lunar surface

For a while, starting in the year 2016, it looked as if Earth might have a second, much-smaller moon. But, after preliminary studies of the object’s orbit, astronomers labeled 469219 Kamo’oalewa as a near-Earth asteroid (NEA) and a quasi-satellite to Earth.

So we know that, like our moon, Kamo’oalewa stays close to Earth over many orbital periods, in this case for centuries to come. Kamo’oalewa appears as if it circles the Earth. But it doesn’t, although its orbit around the sun is synchronized with Earth’s orbit.

But the moon does figure into Kamo’oalewa’s story. In 2021, astronomers using spectroscopy revealed that Kamo’oalwea might in fact be a piece of the moon. The asteroid and the moon are apparently made of identical stuff: space-weathered silicates.

Now there’s more.

Last Friday (April 19, 2024), another group of astronomers published data in Nature Astronomy supporting a lunar origin for Kamo’oalwea. They also believe they know the impact crater that formed when Kamo’oalewa was blasted from the moon’s surface.

They think they’ve found the scar left by the impact that sent Kamo’oalewa hurtling into space. The far side crater Giordano Bruno – named for the 16th century Italian philosopher, poet, cosmological theorist and esotericist – seems to be the “likely” source, they said.

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Rounding up the unusual suspects

In reporting the new evidence, Phys.org described the detective work that led an international team of scientists to the suspect crater:

The team began by creating a computer model to mimic the type of collision that could have resulted in a piece of the moon’s surface the size of Kamo’oalewa being flung into space. In so doing they were able to estimate the likely size of the asteroid that would have struck the moon, and from that, the size of the crater it would have left behind.

Knowing how large the impactor was, and that the impact had to be fairly recent, the team came up with a short list of possible suspects for craters that might match Kamo’oalwea’s origin. As it turned out, one crater had its fingerprints all over the asteroid. From Phys.org:

They then compared samples of moon material brought back to Earth that had been found near one prime possibility – the Giordano Bruno crater. They found spectral similarities between the samples and the asteroid Kamo’oalewa – they also found both had bits of the mineral pyroxene in them as well.

Bingo. Case closed. Or is it?

Space missions will continue investigating asteroid Kamo’oalewa

While it the mystery of Kamo’oalewa’s origin appears solved, a pair of upcoming space probes will test the team’s hypothesis.

First, launching in 2025, the Chinese Tianwen-2 mission will collect a sample of Kamo’oalewa and return it to Earth. According to the Planetary Society:

The spacecraft will rendezvous with asteroid Kamo’oalewa and carry out remote sensing, assessing the planetary body for potential landing sites. It will then attempt to collect samples from the small body using two different techniques — touch-and-go and anchor-and-attach — and return to Earth to deliver the samples for analysis. Altogether, this will take around 2.5 years.

A second mission – NASA’s NEO Surveyor space telescope launching in 2027 – should provide more useful data about the orbit of Kamo’oalwea. The NASA mission, however, isn’t about finding the origin of near-Earth objects (NEO). NEO Surveyor hopes to find potentially hazardous asteroids and comets before they find us.

From the NEO Surveyor website:

After launch, NEO Surveyor will carry out a five-year baseline survey to find at least two-thirds of the near-Earth objects larger than 140 meters (460 feet). These are the objects large enough to cause major regional damage in the event of an Earth impact. By using two heat-sensitive infrared imaging channels, NEO Surveyor can make accurate measurements of NEO sizes and gain valuable information about their composition, shapes, rotational states, and orbits.

Bottom line: A group of astronomers say their data point to a lunar origin for the near-Earth asteroid Kamo’oalewa.

Source: Asteroid Kamo‘oalewa’s journey from the lunar Giordano Bruno crater to Earth 1:1 resonance

Via Phys.org

Read more: Piece of the moon? Asteroid might have lunar origin

The post Was asteroid Kamo’oalewa blasted from this moon crater? first appeared on EarthSky.

• For the 1st time, astronomers have detected a methane emission on a brown dwarf. That is where methane is emitting light instead of absorbing it.
• Researchers say that auroras in the brown dwarf’s atmosphere may create the methane emission. They also found evidence for a temperature inversion on the brown dwarf.
• There’s no solar wind from a nearby star to create auroras or temperature inversions, so material coming from a moon might be responsible.

Methane is common on brown dwarfs, where it absorbs light, so it’s not seen visually. But now, scientists say they have detected methane on a brown dwarf that is glowing in infrared light. In other words, it is emitting light instead of absorbing it, as is typically seen on brown dwarfs. It’s puzzling and unexpected to visibly see the methane on a relatively cold body like a brown dwarf. And researches say that auroras may be creating this methane emission. Researchers at the American Museum of Natural History said on April 17, 2024, that they found the bright methane emission on the brown dwarf W1935, 47 light-years from Earth. They made the discovery using the James Webb Space Telescope.

The research team published their new peer-reviewed paper in Nature on April 17, 2024.

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Methane emission on a cold brown dwarf surprises astronomers

Even though methane is typically abundant on brown dwarfs, astronomers don’t visibly see it in their atmospheres. That’s because it absorbs rather than emits light. So seeing the methane signature in infrared on W1935 was a surprise. Plus, brown dwarfs are relatively cool; the temperature on W1935 is only about 400 degrees Fahrenheit (200 degrees Celsius). That’s hot by human standards, but cold compared to stars.

The researchers were studying 12 different brown dwarfs when they made the discovery. W1935 was the only one emitting methane. But why?

Jackie Faherty at the American Museum of Natural History led the new study. She said:

Methane gas is expected in giant planets and brown dwarfs but we usually see it absorbing light, not glowing. We were confused about what we were seeing at first but ultimately that transformed into pure excitement at the discovery.

Every time an astronomer points JWST at an object, there’s a chance of a new mind-blowing discovery. Methane emission was not on my radar when we started this project but now that we know it can be there and the explanation for it so enticing I am constantly on the look-out for it. That’s part of how science moves forward.

Temperature inversion and auroras on W1935

The methane emission wasn’t the only surprise. When the researchers did computer modelling of the brown dwarf’s atmosphere, they found evidence for a temperature inversion. Normally, an atmosphere gets cooler the higher in altitude. But in an inversion, it gets warmer instead. The phenomenon can happen on planets, since their host stars warm their atmospheres. But brown dwarfs aren’t planets, and W1935 doesn’t orbit a star. It’s isolated in deep space. So how could a temperature inversion occur? As co-author Ben Burningham at the University of Hertfordshire noted:

We were pleasantly shocked when the model clearly predicted a temperature inversion. But we also had to figure out where that extra upper atmosphere heat was coming from.

So how does this happen on W1935? Jupiter and Saturn may provide the answer: auroras. Both giant planets have both methane emissions and temperature inversions. They also have auroras. On Jupiter and Saturn, the auroras are from high-energy particles from the sun hitting the planets’ magnetic fields. This creates heat and auroras in the planets’ upper atmospheres. This is the same as what happens on Earth.

Does W1935 have a moon?

But scientists aren’t sure yet how auroras on W1935 would be generated, since it has no star and therefore no solar wind containing the energetic particles. There is, however, another intriguing possible cause.

Both Jupiter and Saturn have moons that also eject material into space. Jupiter’s volcanic moon Io and Saturn’s ocean moon Enceladus in particular. That material helps enhance the auroras on both planets. So, could W1935 have a moon of its own? It’s an exciting, if still-unproven, possibility.

If W1935 does have auroras, they wouldn’t be the first ones discovered on a brown dwarf. On July 29, 2015, astronomers detected auroras on the brown dwarf LSR J1835+3259. And in 2018, astronomers found auroras on a rogue planet, SIMP J01365663+0933473. Rogue planets also do not orbit any stars. Instead they wander through space alone.

Those findings, plus W1935, show that auroras are probably quite common, not only on planets, but even brown dwarfs and rogue planets as well.

Bottom line: For the 1st time, astronomers have found a methane emission on a brown dwarf. The researchers say that auroras in the brown dwarf’s atmosphere may cause it.

Source: Methane emission from a cool brown dwarf

Via American Museum of Natural History (Eurekalert!)

Read more: Astronomers find weird rogue world with wild auroras

Read more: Found! First aurora beyond solar system

The post Methane emission on brown dwarf may be created by auroras first appeared on EarthSky.

• Over 1,000 new small asteroids have been found in Hubble Space Telescope images. They lie in the main asteroid belt between Mars and Jupiter.
• Researchers, along with over 11,000 volunteer citizen scientists, found the asteroids in older images from Hubble. The asteroid hunt relied on machine learning, a type of artificial intelligence (AI), to find the faint trails, or streaks, left by asteroids in the images.
• The results provide more clues about how the asteroid belt originated and evolved.

Astronomers have found over a million asteroids, mostly in the main asteroid belt between Mars and Jupiter. But many smaller asteroids, from the size of boulders to pebbles, are still waiting to be discovered. Recently, astronomers and citizen scientists have used archived images from the Hubble Space Telescope to search for small asteroids. They used machine learning and AI in their quest to identify the asteroids. And this asteroid hunt was a big success! Researchers from the U.S. and Europe said on April 18, 2024, that they discovered over 1,000 previously uncatalogued asteroids. About 400 of the objects were less than 1/2 mile (one km) in size.

The research team first published their peer-reviewed results in the journal Astronomy & Astrophysics on March 15, 2024.

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Hubble’s asteroid hunt

Hubble has provided incredible views of distant space objects, from planets to galaxies. But it can also see relatively nearby small objects, such as small asteroids in our own solar system.

The researchers, along with volunteer citizen scientists, searched through some 37,000 images, which spanned 19 years of Hubble observations. And the asteroid hunt paid off. They found 1,701 asteroid trails in the images. Asteroid trails appear as curved streaks in some Hubble images. They appear because the moving asteroids are closer to us than many of the objects being studied by Hubble.

Of the 1,701 asteroids detected, 1,031 were from small asteroids that were previously unknown and uncatalogued. Lead author Pablo García Martín at the Autonomous University of Madrid, Spain, said:

We are getting deeper into seeing the smaller population of main belt asteroids. We were surprised with seeing such a large number of candidate objects. There was some hint of this population existing, but now we are confirming it with a random asteroid population sample obtained using the whole Hubble archive.

This is important for providing insights into the evolutionary models of our solar system.

Citizen scientists

Hubble looked for smaller asteroids in the main asteroid belt, between Mars and Jupiter. These are ones that astronomers hadn’t yet detected. Most of the ones Hubble found are indeed in the asteroid belt. And they are extremely faint, about one forty-millionth the brightness of the faintest star that the human eye can see.

But this was a huge task, and the researchers needed help. So over 11,000 volunteer citizen scientists – 11,482 to be exact – also took part in the endeavor. As Martín noted:

Asteroid positions change with time, and therefore you cannot find them just by entering coordinates, because at different times, they might not be there. As astronomers we don’t have time to go looking through all the asteroid images. So we got the idea to collaborate with over 10,000 citizen-science volunteers to peruse the huge Hubble archives.

Using AI in the asteroid hunt

The effort also used a form of artificial intelligence (AI) called machine learning to more effectively go through the thousands of archived Hubble images. The citizen scientists used an automated algorithm to identify the very faint asteroid trails in the images. AI has distinct advantages for this kind of work, as the paper explained:

One of the advantages of applying machine learning to find solar system objects in complete astronomical archives is the large number of potential results obtained. This allows us to apply purposely strict filtering conditions to improve accuracy and still keep a large enough sample to obtain statistically meaningful results.

This work began in 2019, when an international group of astronomers launched the Hubble Asteroid Hunter project.

Researchers and engineers at the European Space Research and Technology Centre (ESTEC) and the ESAC Science Data Centre developed the initiative. They did so in collaboration with Zooniverse, a popular citizen-science platform, and Google.

Next, the researchers will study the asteroids to characterize their orbits and physical properties. However, most of them are in image taken years ago, so it is not possible to track them now in real time.

History of the asteroid belt

So why are these discoveries important? They provide valuable clues about the origin and evolution of the asteroid belt. One possibility that astronomers have favored is that the asteroid belt is like smashed pottery. The smaller asteroids are the remaining pieces of larger ones that have collided and were destroyed over billions of years. The asteroids we have now are the leftover debris.

The other primary theory is that the smaller asteroids formed the way they are. But scientists say if that is so, then they should have conglomerated together as they accumulated dust from the planet-forming disk of the early solar system, forming larger bodies. However, astronomers don’t know of any mechanism that would prevent them from doing so. Co-author Bruno Merín at the European Space Astronomy Centre (ESAC), in Madrid, Spain, said:

Collisions would have a certain signature that we can use to test the current main belt population.

Asteroids have also previously photobombed images of galaxy clusters, as EarthSky reported back in 2019. You can clearly see the tell-tale curved streaks in those images, too.

Bottom line: Astronomers used the Hubble Space Telescope to go on an asteroid hunt. They found over 1,000 previously unknown small asteroids in the asteroid belt.

Source: Hubble Asteroid Hunter: III. Physical properties of newly found asteroids

Via Hubblesite

Read more: How big are asteroids? Compare sizes in this video

Read more: Asteroids photobombed deep Hubble images

The post Asteroid hunt by Hubble telescope using AI first appeared on EarthSky.

On the mornings of April 26 and 27, 2024, the waning gibbous moon will lie close to the bright star Antares in Scorpius the Scorpion. They’ll be visible from early morning until dawn. Also, skywatchers in Asia and Africa will see the moon pass in front of – or occult – Antares near 21 UTC on April 26.

Our charts are mostly set for the northern half of Earth. To see a precise view – and time – from your location, try Stellarium Online.

Watch for the daytime moon

The moon takes a month to orbit Earth. So – though you might not realize it – the moon is up in the daytime exactly as often as it’s up at night. It’s just not as noticeable during the day, because the contrast between the moon and the sky isn’t as great. But now – in the days following full moon, which came on the night of April 23, 2024 – you can easily spot the daytime moon. It’ll be in the west after sunrise this week.

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The Big Dipper and Leo the Lion

April is a great time to look up overhead in the evening sky and find the well-known pattern of stars we call the Big Dipper. It’s an asterism – or obvious pattern of stars – and part of the constellation Ursa Major the Great Bear. Also, you can find the constellation Leo the Lion. Leo has another well-known asterism known as the Sickle. The Sickle looks like a backward question mark that is punctuated by the bright star Regulus. In fact, the Big Dipper can help you locate Leo and the Sickle. An imaginary line drawn southward from the pointer stars in the Big Dipper – the two outer stars in the Dipper’s bowl – points toward Leo the Lion.

The Big Dipper and Polaris

Plus, the Big Dipper can direct you to find Polaris, the North Pole Star. The two outer stars in the bowl of the Dipper point to Polaris. It’s at the end of the handle of Ursa Minor the Little Bear, commonly known as the Little Dipper. Look for the Big and Little Dippers high in the northern sky on spring evenings. This view is for the Northern Hemisphere.

Cancer the Crab

Cancer the Crab, with its Beehive star cluster, needs a dark sky to be seen. It lies between the Gemini twin stars Castor and Pollux, and the bright star Regulus in Leo the Lion.

Once you’ve found Cancer – if your sky is dark – you can see the wonderful open star cluster called the Beehive. It contains some 1,000 stars.

Have fun exploring the sky!

April evenings: Jupiter

Jupiter appears low in the west shortly after sunset in the first three weeks of April. During the month’s final week, it lies too low in the bright evening twilight to be easily seen. At the beginning of the month, Jupiter sets about three hours after sunset. At month’s end, Jupiter lies low in the evening twilight and may be challenging to spot. Jupiter will lie near the delicate Pleiades star cluster.

April mornings: Mars and Saturn

Mars and Saturn lie low in the morning twilight in April 2024. They shine with similar brightness and have a close pairing on the mornings of April 10 and 11. Saturn will climb a bit higher as the month goes on, and Mars will not move as much on the sky’s dome. By month’s end, Saturn will rise about two hours before sunrise and Mars will follow it about an hour later. Both planets will be easier to find in the coming months as they climb out of the morning glare.

Where’s Venus and Mercury?

Venus is too close to the sun to be visible this month, and it’ll emerge in the evening sky around the beginning of August. Mercury will disappear from the bright evening twilight at the beginning of April and return to the morning sky in May.

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Looking for a dark sky? Check out EarthSky’s Best Places to Stargaze.

Sky dome maps for visible planets and night sky

The sky dome maps come from master astronomy chart-maker Guy Ottewell. You’ll find charts like these for every month of 2024 in his Astronomical Calendar.

Guy Ottewell explains sky dome maps

Heliocentric solar system visible planets and more

The sun-centered charts come from Guy Ottewell. You’ll find charts like these for every month of 2024 in his Astronomical Calendar.

Guy Ottewell explains heliocentric charts.

Some resources to enjoy

For more videos of great night sky events, visit EarthSky’s YouTube page.

Watch EarthSky’s video about Two Great Solar Eclipses Coming Up

Don’t miss anything. Subscribe to daily emails from EarthSky. It’s free!

Visit EarthSky’s Best Places to Stargaze to find a dark-sky location near you.

Post your own night sky photos at EarthSky Community Photos.

Translate Universal Time (UTC) to your time.

See the indispensable Observer’s Handbook, from the Royal Astronomical Society of Canada.

Visit Stellarium-Web.org for precise views from your location.

Almanac: Bright visible planets (rise and set times for your location).

Visit TheSkyLive for precise views from your location.

Bottom line: Visible planets and night sky guide for April 2024. On the mornings of April 26 and 27, watch for the moon close to the bright star Antares in Scorpius the Scorpion.

The post Visible planets and night sky guide for April first appeared on EarthSky.

? ? Sun news for Apr 25, 2024: High activity, auroras on the way

? ?Solar activity high, 6 M flares over the past day.

?G1/higher geomagnetic storms are still expected.

?? MORE at EarthSky: https://t.co/xD29wLfm4e pic.twitter.com/fZEw5h5mWT

— Dr. C. Alex Young (@TheSunToday) April 25, 2024

Sun news for April 25, 2024: High activity, auroras on the way

Today’s top story: Solar activity remains high after an impressive 6 M flares were fired over the past 24 hours. All but one of these M flares came from a huge complex of sunspot groups in the sun’s southwest. This complex has brought us some great action this week, but it’s soon to rotate out of view over the western limb (edge). Meanwhile, action is expected at Earth today, with G1 (minor) or higher geomagnetic storms expected later today through tomorrow. And that means possible auroral displays! The disturbance is due to the effects of coronal mass ejections (CMEs) flying past our planet, combined with fast solar wind from one of the three coronal holes currently on the sun’s visible face. Good luck, aurora-watchers!
Last 24 hours: We’ve observed long, beautiful jets in the northwest over the past day, while prominences have been dancing all around the solar limb (edge). The sun produced 21 flares between 11 UTC yesterday and 11 UTC today: 6 M flares and 15 C flares. The largest event was an M2.0 flare by active region AR3637 at 22:59 UTC on April 24. The list of the M flares of the past 24 hours is:
M1.5 by AR3645, 12:14 UTC on April 24. R1 (minor) radio blackout over the west coast of Africa.
M1.1 by AR3647 at 22:50 UTC on April 24. R1 (minor) radio blackout over the Pacific Ocean.
M2.0 by AR3637 at 22:59 UTC on April 24. R1 (minor) radio blackout over the Pacific Ocean.
M1.0 by AR3645 at 1:49 UTC on April 25. R1 (minor) radio blackout over the Philippine Sea.
M1.0 by AR3645 at 2:27 UTC on April 25. R1 (minor) radio blackout over the Philippine Sea.
M1.1 by AR3648 at 3:15 UTC on April 25. R1 (minor) radio blackout over the Philippine Sea.
The lead flare producer of the day was AR3648 with 6 C flares. All 12 active regions on the Earth-facing solar disk are currently showing simple alpha or beta magnetic configurations, indicating a low potential for flaring in the coming day. They all are stable or in decay. A newcomer sunspot region has emerged on the southwest quadrant, now numbered AR3658.
Next 24 hours: The chance for C flares is 99%. The chance for M flares is 75%. The chance for an X flare is 15%.
Next expected CME: No new coronal mass ejections (CMEs) were observed in available imagery during the past day.
Current geomagnetic activity: Earth’s magnetic field is quiet at the time of this writing (11 UTC on April 25). Quiet up to unsettled levels are anticipated today through tomorrow due to the effects of high-speed solar wind from the three coronal holes now on the sun’s visible face, combined with CMEs passing in the vicinity of Earth. G1 or greater geomagnetic storming is expected, despite no obvious Earth-directed events.

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Sun news for April 24, 2024: HIGH activity, with sun-stuff coming

The EarthSky sun news team created this 1-minute video summary for you.
Activity remains high today! Over the past day, we had 5 M flares, four fewer than the day before. All the M flares came from the big sunspot complex in the sun’s southwest quadrant. This region is also continuing to produce long, beautiful jets. In the past day, we saw prominences dancing all around the visible sun. And a filament erupted in the sun’s northeast, which sent material northward away from Earth. Meanwhile, starting tonight, we are anticipating glancing blows to Earth from perhaps up to a dozen smaller coronal mass ejections, aka CMEs. These chunks of sun-stuff will likely only sideswipe us. And, because there are multiple chunks, the timing of their effects is difficult to pin down. But any effects will be combined with fast solar wind from one of the three coronal holes currently on the sun’s visible face. So we’re anticipating geomagnetic storming at the G1 (minor) level, or higher, starting tonight and into April 26. Good luck, aurora-watchers!
Last 24 hours: Overall activity has decreased with 5 M flares in the past day (11 UTC yesterday to 11 UTC today). The sun released 20 flares in all: 5 M flares and 15 C flares. The largest event was an M2.9 flare at 17:33 UTC on April 23 from AR3638. Here’s the breakdown of the M flares from the past 24 hours:
M1.0, AR3647, 16:23 UTC on April 23. R1 (minor) radio blackout over the Atlantic Ocean.
M2.9, AR3638, 17:33 UTC on April 23. R1 (minor) radio blackout over the Atlantic Ocean (the largest flare.)
M1.8, AR3645, 00:13 UTC on April 24. R1 (minor) radio blackout over the Pacific Ocean.
M1.6, AR3645, 00:38 UTC on April 24. R1 (minor) radio blackout over the Pacific Ocean.
M1.8, AR3638, 02:30 UTC on April 24. R1 (minor) radio blackout over the Pacific Ocean.
The lead flare producer of the day was AR3645 with 7 flares: 2 Ms plus 5 Cs. Sunspot region AR3638 produced 2 M flares. All active regions now have either an alpha or beta magnetic configuration, indicating a lowered potential for flaring in the coming day. The sun currently has 13 sunspot groups on its Earth-facing side.

Sun news for April 23, 2024: 9 M flares in the past day!

Wow! Sun activity has reached high levels after 9 M flares were blasted over the past 24 hours. Equally exciting is that some of the flares were sympathetic. That’s when flares in seemingly unrelated locations on the sun occur nearly simultaneously, because they are actually connected to each other by invisible magnetic fields. We saw some of this yesterday with the active sunspot complex in the southwest. On top of the M flare fiesta, it’s been a crazy day for sunspots. As of yesterday, we reached a daily sunspot number of 278, the highest in 22 years, since it reached 281 in August 2002. And we now have 14 sunspot groups on the Earth-facing side, the highest – along with one other day – that it’s been in Solar Cycle 25 so far. What a day on the sun!
Last 24 hours: We observed lots of filament activity over the past day, with some of these filaments participating in the sympathetic flaring. Between 11 UTC yesterday and 11 UTC today, the sun released 26 flares: 9 M flares and 17 C flares. The largest was an M3.6 flare produced at 3:19 UTC by AR3654 on April 23. Here’s the breakdown of the M flares from the past 24 hours:
M1.7, AR3647, 13:35 UTC on April 22. R1 (minor) radio blackout over Africa.
M1.1, AR3645, 14:55 UTC on April 22. R1 (minor) radio blackout off the west coast of Africa.
M1.6, AR3646, 15:19 UTC on April 22. R1 (minor) radio blackout over the Atlantic Ocean.
M2.8, AR3656, 15:50 UTC on April 22. R1 (minor) radio blackout over the Atlantic Ocean.
M1.1, AR3656, 16:30 UTC on April 22. R1 (minor) radio blackout over the Atlantic Ocean.
M1.5, AR3638, 21:16 UTC on April 22. R1 (minor) radio blackout over the Pacific Ocean east of Hawaii.
M1.1, AR3645, 23:18 UTC on April 22. R1 (minor) radio blackout over the Pacific Ocean west of Hawaii.
M3.6, AR3654, 3:19 UTC on April 23. R1 (minor) radio blackout over the Philippine Sea (the largest flare).
M3.0, AR3654, 8:21 UTC on April 23. R1 (minor) radio blackout over the Arabian Sea.
The lead flare producer of the day was AR3645, which fired off 9 flares: 2 Ms plus 7 Cs. Sunspot regions AR3656 and AR3654 also produced 2 M flares. There are four active regions showing potential with beta-gamma magnetic configurations: AR3639, AR3645, AR3646 and AR3647. The sun currently has 14 sunspot groups on its Earth-facing side, including newcomer AR3657. The sun has two coronal holes on its Earth-facing side, one near the disk’s center and one in the southeast.

Sun news for April 22, 2024: Bang! Activity is up

After a fairly calm Sunday, the sun has kicked it up a notch today. The sunspot region complex AR3638-AR3647 (AR3638, AR3643, AR3645 and AR3647) started firing off M flares at midday April 21 UTC time. There were also some near M flares, a C9.0 and C8.6. During the last 24-hour observation period from 11 UTC April 21 to 11 UTC April 22, these M and larger C flares had 6 coronal mass ejections (CMEs) associated with them. Current analysis has shown that all these CMEs were southward directed and do not have Earth-directed components. Additional data may update these determinations. This complex is the region that started producing continuous jets earlier this week. AR3638 has a beta magnetic classification and AR3647 has a beta-gamma magnetic classification. None of the regions in this larger group are especially complex magnetically. Nevertheless, they are producing some interesting action. Stay tuned for what’s next.
Last 24 hours: Solar flare activity increased over the current observation period (11 UTC yesterday to 11 UTC today). Sun activity is now at moderate levels due to 4 M flares. The total flare count is 18, 4 M flares and 14 C flares. The largest event of the period was an M3.4 flare at 21:44 UTC on April 21 from sunspot region AR3638. The region also produced an M2.2 at 15:07 UTC on April 21. Region AR3645 produced the other 2 M flares, an M1.0 at 12:39 UTC on April 21 and an M1.1 at 7:58 UTC on April 22. All of the M flares appear to have produced CMEs, but none of these eruptions have an obvious Earth-directed component. AR3638 and AR3645 have both shown slight growth in size. Other regions have either remained the same or decayed slightly. New regions AR3652, AR3653, AR3654, AR3655 and AR3656 were numbered this period. The sun has 13 sunspot groups on its Earth-facing side.

The sun in recent days

Sun images from our community

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Bottom line: Sun news April 25, 2024. Sun activity is high after 6 M flares. Geomagnetic storming likely tonight through tomorrow – get ready, aurora-chasers!

The post Sun news April 25: High activity, auroras on the way first appeared on EarthSky.

The constellation of the Chamaeleon lies deep in the Southern Hemisphere sky. In fact, you have to be south of the equator to spot it. Accordingly, as a south circumpolar constellation, it circles closely around the south celestial pole. Therefore, it does not set. Thus, if you’re in the Southern Hemisphere, you can see it on any evening of the year.

The origin of the Chamaeleon

Pieter Dirkszoon Keyser and Frederick de Houtman created the Chamaeleon, along with 11 other Southern Hemisphere constellations, in the late 1500s. These Dutch navigators explored the Southern Hemisphere and took astronomical observations, naming the new constellations after creatures they met on their travels. The chameleon is a type of lizard, and the northern sky has its own lizard constellation: Lacerta.

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Locating the constellation of the Chameleon

You can find the constellation Chamaeleon any time of year in the Southern Hemisphere between the south celestial pole and the flowing river of the Milky Way. Also, if you can find the Southern Hemisphere’s prominent constellation of the Southern Cross, or Crux, and draw a line to the south celestial pole, you’ll pass through Chamaeleon.

The stars of the Chamaeleon

The stars of the constellation are all 4th magnitude and dimmer. Alpha Chamaeleontis and Theta Chamaeleontis lie a mere 1/2 degree from each other, with Alpha at magnitude 4.06 and Theta at magnitude 4.35. They lie 63 and 155 light-years away, respectively.

Delta Chamaeleontis is a double star near the center of the constellation. Its two components, four arcminutes apart, are magnitude 4.45 and 5.46, averaging 350 light-years distant. Then two degrees away is Gamma Chamaeleontis, magnitude 4.12 and 413 light-years away. Lastly is Beta Chamaeleontis at magnitude 4.24 and 271 light-years distant, found at the opposite end of the constellation as Alpha.

Bottom line: The constellation Chamaeleon is a dark patch of sky that lies deep in the Southern Hemisphere and is visible any night of the year.

The post Meet the Chamaeleon, a southern constellation first appeared on EarthSky.

• Jupiter’s rocky moon Io is the most volcanically active world in the solar system. It has hundreds of volcanoes, some with erupting lava fountains dozens of miles (kilometers) high.
• Io’s volcanoes have been active for billions of years, a new study says, ever since Io first formed.
• How do they know? The researchers studied the ratio of different light and heavy sulfur isotopes in Io’s thin atmosphere. The results suggest the volcanoes’ age, and also provide clues about how much sulfur Io has lost since its formation.

Jupiter’s moon Io is famous for the hundreds of volcanoes dotting its surface. It’s the most volcanically active world in our solar system. But how long has Io had its active volcanoes? Researchers at the California Institute of Technology (Caltech), New York University and NASA’s Goddard Space Flight Center said on April 18, 2024, that Io’s volcanoes have been erupting for billions of years, since just after the little moon 1st formed, along with our sun, Jupiter, Earth and the rest of our solar system.

The conclusions are based on new analysis of sulfur in Io’s thin atmosphere. That makes sense, because sulfur plays a key role on Io’s surface and in its atmosphere. Some of Io’s volcanoes spew sulfur and sulfur dioxide in great plumes extending miles (kilometers) above Io’s surface. Extensive plains of sulfur lie in a frosty coating on most of Io’s surface.

If you could stand on Io without a spacesuit (not literally possible since Io is bathed in extreme radiation from Jupiter), you’d find it smells like rotten eggs, due to its sulfur. Now that sulfur has provided clues to the history of Io’s active volcanoes.

The researchers published their peer-reviewed findings in two new papers on April 18, one in Science and the other in JGR Planets.

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New analysis of sulfur isotopes from Io’s volcanoes

So, Io’s volcanoes emit a lot of sulfur. And Io’s atmosphere is 90% sulfur dioxide. The research team conducted an analysis of isotopes of Io’s atmospheric sulfur. This provided clues as to how long Io has been in orbital Laplace resonance with two other moons: Europa and Ganymede.

In other words, Io completes four orbits of Jupiter for every two orbits of Europa and one orbit of Ganymede. As a result, the moons all pull on each other gravitationally. This causes their orbits to be elliptical rather than circular. And in turn, Jupiter’s strong gravity then heats the interiors of the moons. This is why Europa and Ganymede have subsurface oceans and Io has magma and volcanism.

By analyzing the isotopes, scientists could tell how long Io has been in orbital resonance and, therefore, volcanically active. To do this, they used the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile.

The sulfur atoms on Io have various isotopes. That is, they have varying numbers of neutrons. Sulfur-32 and sulfur-34 both have 16 protons, but the first has 16 neutrons, while the second has 18. The more neutrons an atom has, the heavier it is. On Io, the heaviest sulfur atoms are at the bottom of the atmosphere, while the lightest are near the top.

Ever-changing surface and atmosphere

Even though Io overall is billions of years old, just like all the other bodies in the solar system, its surface is only about a million years old. This is because its surface is always being replenished by new material from its numerous volcanoes.

Io’s atmosphere is always changing, too. Collisions with charged particles in Jupiter’s magnetic field strip away the already-thin atmosphere into space. This happens at a rate of one ton per second. Therefore, the lighter sulfur isotope at the top of the atmosphere, sulfur-32, gets depleted faster. By calculating how much sulfur-32 is missing, the researchers can determine how long Io has been volcanically active.

This animation is an artist’s concept of Loki Patera, a lava lake on Io, made by using data from the JunoCam imager onboard NASA’s Juno spacecraft. With multiple islands in its interior, Loki is a depression filled with magma and rimmed with molten lava. Video via NASA/ JPL-Caltech/ SwRI/ MSSS/ YouTube.

Sulfur ratios

The researchers looked at the ratio of sulfur-32 to sulfur-34 in Io’s atmosphere. In the early solar system, the ratio was about 23 atoms of sulfur-32 for every one atom of sulfur-34. That ratio is the same today for any body that has remained unchanged since it first formed. But that’s not the case with Io. By far, most of its original sulfur – 92 to 99% – has been lost. Even though so much of the original sulfur – the lighter isotope sulfur-32 in particular – has been lost, this also shows Io must have been volcanically active since soon after its formation.

And that, in turn, shows Io has been in a Laplace orbital resonance with Europa and Ganymede for just as long.

History of Io’s volcanoes

While the new findings show Io has always been volcanically active, there are still various possible specific scenarios for the history of the moon. This includes the possibility that Io was once even more volcanically active early on than it is now. As Ery Hughes, formerly from Caltech and co-author of the first paper in Science, explained:

Because lots of the light sulfur is missing, the atmosphere we measure today is relatively ‘heavy’ in terms of sulfur. Key to achieving such heavy sulfur in Io’s atmosphere is the process of burying the heavy sulfur back into Io’s interior, so that it can be released by volcanoes over and over again. Our modeling shows that sulfur gets trapped in the crust of Io by reactions between the sulfur-rich frosts, which are deposited from the atmosphere and the magma itself, allowing it to be eventually buried into Io’s interior.

On April 18, 2024, NASA also released new video animations of a lava lake and steeple-like mountain on Io. Check them out!

Bottom line: A new study reveals Io’s volcanoes have been erupting for billions of years, ever since the small moon of Jupiter first formed.

Source: Isotopic evidence of long-lived volcanism on Io

Source: Using Io’s Sulfur Isotope Cycle to Understand the History of Tidal Heating

Via Caltech

Read more: Jupiter’s moon Io as you’ve never seen it

Read more: Jupiter’s moon Io: Global magma ocean, or hot metal core?

The post Io’s volcanoes have been erupting for billions of years first appeared on EarthSky.

Watch for a daytime moon

This month’s full moon came on the night of April 23, 2024. By April 25, the moon is in a waning gibbous phase, rising later and later each successive night. For those at temperate latitudes in the Northern Hemisphere, there’s an especially long time between moonrises on successive evenings around now. The April 25 moon will rise more than two hours after sunset. The April 26 moon will rise roughly to three hours after sunset.

And, of course, a later rising time means a later setting time. That’s why the mornings after a full moon are a good time to catch a nearly full daytime moon over your western horizon after sunrise. Watch for it!

The moon is up in the daytime half of the time. But, because it’s pale against the blue sky, it’s not as noticeable during the day as at night. Still, there are certain windows each month during which the daytime moon is most noticeable.

The rest of April 2024 presents one of those windows. It’s a good time to watch for a daytime moon.

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By April 26 and 27 mornings, moon near Antares

By the mornings of April 26 and 27, 2024 (or late evening April 25 and 26), the moon will be near the bright star Antares in the constellation Scorpius the Scorpion. At that time, the moon will be rising a little before midnight at mid-northern latitudes. And it’ll still be up after the sun rises, but appearing thinner in phase and higher in the sky with each new dawn.

Because of Earth’s motion around the sun, Antares – like all the fixed stars (stars that appear not to move relative to one another) – will rise about four minutes earlier each evening. Meanwhile, because of its own motion around Earth, the moon will be rising later and later each evening and thus moving away from Antares’ location in the sky.

Day by day, in the days ahead, the lighted portion of the waning gibbous moon will shrink. The half-lit last quarter moon will come late at 10:15 p.m. CDT April 30 (03:15 UTC on May 1), 2024.

Bottom line: You can easily spot the moon in the morning sky – after sunrise – for a few days after full moon. Look west after the sun comes up!

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The post Daytime moon is up after sunrise now first appeared on EarthSky.

Cor Caroli

Cor Caroli – aka Alpha Canum Venaticorum – is the brightest star in the constellation Canes Venatici the Hunting Dogs. This star, and Chara, Canes Venatici’s 2nd-brightest star, are probably the only two stars you’ll ever come to know within the boundaries of this tiny constellation. You can pick out the pair easily if your sky is dark enough.

Although they aren’t among the sky’s brightest stars, Cor Caroli and Chara are relatively easy to find, due to their relationship on the sky’s dome to the famous Big Dipper. This well-known asterism is ascending in the northeast on spring evenings. The two stars of Canes Venatici appear snuggled together, near the handle of the Dipper.

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Heart of Charles

Cor Caroli means Heart of Charles. Some say the star was named to honor King Charles I of England, who was beheaded in 1649 during the English Civil War. These sources claim Cor Caroli was labeled on old star charts as Cor Caroli Regis Martyris, or Heart of Charles the Martyr King.

Not everyone agrees, however. Others say the star was named for Charles I’s son, Charles II. Sir Charles Scarborough, physician to Charles II, is sometimes given credit for having coined the name. It’s said Scarborough claimed the star shone with exceptional brilliance on the night of Charles II’s return to England in 1660 to restore the monarchy.

It’s really 2 stars

If you use a small telescope, you’ll see that Cor Caroli is a double star. So it’s easy to imagine father and son peacefully reunited in the heavens, after all their tumultuous years on Earth.

And Cor Caroli doesn’t just appear double. It’s a true binary star, consisting of two stars revolving around a common center of mass. The pair lies some 115 light-years away. This is slightly farther away from us than the stars in the Big Dipper.

One orbital period may take as long as 8,300 years. The fainter star lies 19 arcseconds away and to the southwest of the brighter star. The stars are about 5 light-years apart, with the brighter star closer to us than the fainter star. The brighter star varies in brightness every 5.47 days from magnitude 2.84 to 2.98. The fainter companion shines at magnitude 5.6.

You can see this double star for yourself on the next clear evening. Binoculars won’t magnify enough to split the star into its two components. But a small telescope using at least 40 power will show the object as two stars. A large telescope using even more magnification will reveal the colors of the two stars. The brighter star is white or blue-white. The fainter star is more difficult to discern, but some observers see it as mild lilac in color.

The 2 stars are very different

The fainter star is Alpha-1 and the brighter star is Alpha-2. One would think that the brighter star would be #1 and the fainter star would be #2. But stars are numbered from west to east and the fainter star is west of the brighter star.

Alpha-2 is a hot star, spectral type A, with a temperature of 11,600 kelvins or 20,420 degrees Fahrenheit or 11,326 degrees Celsius (in contrast with our sun’s surface temperature of 6,000 kelvins or 10,340 F or 5,726 C). In other words, Cor Caroli shines 100 times brighter than our sun and is nearly three times larger than our sun.

This bright variable star is the namesake for a certain class of stars known as Alpha² Canum Venaticorum variables. These are heavy metal stars with very strong magnetic fields. “Metals,” in a star, refers to elements more complex than hydrogen or helium. In Cor Caroli, the metals are concentrated in starspots, and are not evenly distributed in the star’s atmosphere. And so, as the star rotates, its brightness varies from our point of view.

The fainter of the two stars in Cor Caroli, Alpha-1, is nearly as cool as our sun at 7,800 kelvins (12,284 F/ 6,806 C). It’s only five times brighter than our sun, and nearly twice as large. Its spectral class is F.

Bottom line: The star Cor Caroli, or Alpha Canum Venaticorum, is a binary star and the brightest star in the northern constellation Canes Venatici the Hunting Dogs. Both components are visible in a small telescope.

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The post Cor Caroli, named for the heart of a king first appeared on EarthSky.

• NASA’s Voyager 1 spacecraft has been traveling outward from Earth for 46 years and 7 months, as of today. It is now 15 billion miles (24 billion km) from Earth, making communications with its Earthly controllers nearly a 2-day round trip.
• In November 2023, Voyager 1 began sending back only gibberish. As of late last month, the Voyager 1 team was trying various things to prompt the craft to respond, including a special command, called a “poke” by the team. Following the “poke,” the team was able to decipher a message from the spacecraft, although with difficulty.
• Now Voyager 1 has begun sending an intelligible signal back to Earth again. The signal contains engineering updates. Scientists hope they can prompt the craft to resume sending science data again.

On April 22, 2024, Naomi Hartono posted this update on the status of Voyager 1 at NASA blogs. Edits by EarthSky.

Voyager 1 has phoned home

For the first time since November, NASA’s Voyager 1 spacecraft is returning usable data about the health and status of its onboard engineering systems. The next step is to enable the spacecraft to begin returning science data again. The probe and its twin, Voyager 2, are the only earthly spacecraft to ever fly in interstellar space (the space between stars).

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Voyager 1 stopped sending readable science and engineering data back to Earth on November 14, 2023, even though mission controllers could tell the spacecraft was still receiving their commands and otherwise operating normally. In March, the Voyager engineering team at NASA’s Jet Propulsion Laboratory in Southern California confirmed that the issue was tied to one of the spacecraft’s three onboard computers, called the flight data subsystem (FDS). The FDS is responsible for packaging the science and engineering data before it’s sent to Earth.

The team discovered that a single chip responsible for storing a portion of the FDS memory – including some of the FDS computer’s software code – isn’t working. The loss of that code rendered the science and engineering data unusable. Unable to repair the chip, the team decided to place the affected code elsewhere in the FDS memory. But no single location is large enough to hold the section of code in its entirety.

Here’s how they fixed it

So they devised a plan to divide the affected code into sections and store those sections in different places in the FDS. To make this plan work, they also needed to adjust those code sections to ensure, for example, that they all still function as a whole. Any references to the location of that code in other parts of the FDS memory needed to be updated as well.

The team started by singling out the code responsible for packaging the spacecraft’s engineering data. They sent it to its new location in the FDS memory on April 18. A radio signal takes about 22 1/2 hours to reach Voyager 1, which is over 15 billion miles (24 billion kilometers) from Earth, and another 22 1/2 hours for a signal to come back to Earth. When the mission flight team heard back from the spacecraft on April 20, they saw that the modification worked: for the first time in five months, they have been able to check the health and status of the spacecraft.

During the coming weeks, the team will relocate and adjust the other affected portions of the FDS software. These include the portions that will start returning science data.

Meanwhile, Voyager 1’s twin spacecraft – Voyager 2 – continues to operate normally. Launched over 46 years ago, the twin Voyager spacecraft are the longest-running and most distant spacecraft in history. Before the start of their interstellar exploration, both probes flew by Saturn and Jupiter, and Voyager 2 flew by Uranus and Neptune.

Bottom line: Now Voyager 1 has begun sending an intelligible signal back to Earth again. The signal contains engineering updates. Scientists hope they can prompt the craft to resume sending science data again.

Via NASA

The post Hurray! Voyager 1 has phoned home with engineering updates first appeared on EarthSky.