astronomy

COMET 3I/ATLAS IS NOT HIDING FROM EARTH

/ Dr.Tony Phillips / Leave a comment

This week the internet is buzzing with headlines like “Mysterious Object Is Up to No Good While It’s Hidden Behind the Sun.” They’re referring to interstellar Comet 3I/ATLAS. Harvard astronomer Avi Loeb and others have suggested it might be a spaceship deliberately hiding from humans. There’s just one problem with this argument: We can still see it from Earth.

For example, the CCOR-1 coronagraph onboard NOAA’s GOES-19 satellite is tracking the comet and monitoring its brightness:

So is NASA’s quartet of PUNCH spacecraft, and coronagraphs onboard the Solar and Heliospheric Observatory (SOHO, not far from Earth). Comet 3I/ATLAS is under constant surveillance.

“Unless 3I/ATLAS fades substantially in the next couple of days, we should be able to keep eyeballs on it right through its perihelion (closest approach to the sun),” says coronagraph expert Karl Battams.

Tracking the comet is not easy because it is so faint. Battams explains how it is done: “Objects at the threshold of detection like 3I/ATLAS are a challenge for coronagraphs. We often have to employ image stacking techniques. For this to work, we have to have a very precise understanding of the pointing and distortion of the telescopes so that we can find the exact pixels that correspond to the comet. It gets fiddly, but we make it work.”

If 3I/ATLAS changes direction or surges in brightness, we will know. So far, it’s acting like a comet. T. Marshall Eubanks from Space Initiatives Inc assembled this light curve, including recent data from CCOR-1 and PUNCH:

These data confirm that 3I/ATLAS is following a fairly standard model of comet brightness with contributions from gas and dust. If this is a spacecraft, it is wearing an uncanny disguise.

In December, 3I/ATLAS will emerge from the glare of the sun. Telescopes on Earth’s surface can then rejoin the monitoring effort. Our bet: They will see a comet, not a spaceship. Stay tuned.

The Centennial Gleissberg Cycle

/ Dr.Tony Phillips / Leave a comment

May 6, 2025: (Spaceweather.com) If you’ve been enjoying the auroras of Solar Cycle 25, we’ve got good news. The next few solar cycles could be even more intense–the result of a little-known phenomenon called the “Centennial Gleissberg Cycle.”

You’ve probably heard of the 11-year sunspot cycle. The Gleissberg Cycle is a slower modulation, which suppresses sunspot numbers every 80 to 100 years. For the past ~15 years, the sun has been near a low point in this cycle, but this is about to change.

New research published in the journal Space Weather suggests that the Gleissberg Cycle is waking up again. If this is true, solar cycles for the next 50 years could become increasingly intense.

“We have been looking at protons in the South Atlantic Anomaly,” explains the paper’s lead author Kalvyn Adams, an astrophysics student at the University of Colorado. “These are particles from the sun that come unusually close to Earth because our planet’s magnetic shield is weak over the south Atlantic Ocean.”


Above: The South Atlantic Anomaly (blue) is a weak spot in Earth’s magnetic field where particles from the sun can come relatively close to Earth [more]

It turns out that protons in the South Atlantic Anomaly are a “canary in a coal mine” for the Gleissberg Cycle. When these protons decrease, it means the Gleissberg Cycle is about to surge. “That’s exactly what we found,” says Adams. “The protons are clearly decreasing in measurements we obtained from NOAA’s Polar Operational Environmental Satellites.”

Protons in the South Atlantic Anomaly are just the latest in a growing body of evidence suggesting that the “Gleissberg Minimum” has passed. Current sunspot counts are up; the sun’s ultraviolet output has increased; and the overall level of solar activity in Solar Cycle 25 has exceeded forecasts. It all adds up to an upswing in the 100-year cycle.

It also means that Joan Feyman was right. Before she passed away in 2020, the pioneering solar physicist was a leading researcher of the Gleissberg Cycle, and she firmly believed that the centennial oscillation was responsible for the remarkable weakness of Solar Cycle 24 (2012-2013). In a seminal paper published in 2014, she argued that the minimum of the Gleissberg Cycle fell almost squarely on top of Solar Cycle 24, making it the weakest cycle in 100 years. The tide was about to turn.

The resurgence of the Gleissberg Cycle makes a clear prediction for the future: Solar Cycles 26 through 28 should be progressively intense. Solar Cycle 26, peaking in ~2036, would be stronger than current Solar Cycle 25, and so on. The projected maximum of the Gleissberg Cycle is around 2055, aligning more or less with Solar Cycle 28. That cycle could be quite intense.

“With a major increase in launch rates, it’ll be important to plan for changes to the space environment that thousands of satellites and spacecraft are flying through from all sides,” says Adams. “Solar activity and particle fluxes could all be very different in the decades ahead.”

For more information, read Adams’s original research here.

The Tail of Comet ATLAS is Backwards

/ Dr.Tony Phillips / Leave a comment

Aug. 25, 2025 (Spaceweather.com) — In July, when astronomers used the Hubble Space Telescope to photograph 3I/ATLAS, they had a “Eureka!” moment. The mysterious interstellar visitor had a fuzzy atmosphere and a growing tail. Clearly, it was a comet. 

However, something was not quite right. Take a look, and see if you can spot the problem:

The tail of 3I/ATLAS points almost straight toward the sun. Normally, comet dust tails are pushed away from the sun by radiation pressure. 3I/ATLAS is doing the opposite—it’s backwards.

Why? Researchers led by David Jewitt of UCLA believe they have an explanation: “It is due to the preferential sublimation of ice on the hot day side of the nucleus and the near absence of sublimation on the night side,” they wrote in a paper reporting the observations.  

In other words, 3I/ATLAS *is* a comet, but only the sun-heated side is producing lots of dust. The emerging dust particles are too big for radiation pressure to bend them back into an ordinary tail.

This is unusual, but not unheard of. Solar system comets have been known to produce sunward fans or jets, typically from localized “hot spots” on their rotating nuclei. What makes 3I/ATLAS different is the dominance of its sunward plume, dwarfing a barely visible anti-solar tail behind it.

If 3I/ATLAS is indeed a comet, it may have been wandering through the galaxy for longer than our Solar System has existed. Billions of years of cosmic ray bombardment will have altered its surface–knocking hydrogen atoms out while heavier molecules remained behind. This process could create a hardened crust that might not sputter dust and gas like fresher comets from the Solar System. 

Researchers will be very interested to see how the tail of 3I/ATLAS evolves as it approaches the sun for a close encounter in October 2025. Will it remain backward? Or will the crust crumble and allow smaller particles to escape, forming a more normal anti-solar tail?

Of course, if it is a spaceship as Harvard professor Avi Loeb suggests, something completely different may occur. Either way, stay tuned.

Is 3I/ATLAS Really a Comet?

/ Dr.Tony Phillips / Leave a comment

August 26, 2025: (Spaceweather.com) The most intriguing mystery in astronomy today is the nature of interstellar object 3I/ATLAS. Most astronomers believe it is a comet. However, Avi Loeb of Harvard University famously makes the case that it might be something else–like alien tech.

Into this debate comes new data from the James Webb Space Telescope. A paper just submitted to the Astrophysical Journal Letters reports that 3I/ATLAS looks like a comet, albeit a strange one. Here are the images from JWST:

Above: These JWST images show the distribution of carbon dioxide (panel b), water (panel c) and carbon monoxide (panel d). Most of the light is coming from CO2.

The infrared space telescope found most of the ingredients we expect to find in comets. There’s a fuzzy coma, volatile ices, and all the usual molecules: water (H20), carbon dioxide (CO2), carbon monoxide (CO). If 3I/ATLAS is a spacecraft, it has an uncanny disguise.

However, there’s also something strange. The ratios of the different molecules are quite unexpected and don’t match what we see in Solar System comets. In particular, the CO2/H20 ratio of 8 ± 1 is extremely high. Only one other comet, C/2016 R2, is known to have similar chemistry, and astronomers have long considered it to be a “freak.”

Above: Carbon dioxide-to-water ratios in known comets. 3I/ATLAS does not fit the trend.

Typical comets have a lot more water in their atmospheres, with H20 almost always outnumbering CO2. It could be that water production in 3I/ATLAS has not yet fully “turned on” because it is still too cold. If so, solar heating might restore ratios to normal. 3I/ATLAS will reach its closest point to the sun (1.36 AU) on Oct. 29, 2025, potentially bringing forth a geyser of water vapor to mix with the other gases.

Or, maybe, 3I/ATLAS is just strange–like it came from another star system. Stay tuned for updates.

Space Hurricanes Are Real

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Aug. 1, 2025 (Spaceweather.com): Hurricane season just got worse. Chinese researchers have discovered a new kind of storm at the edge of space. They call it a “space hurricane.”

The first known example appeared in Defense Meteorological Satellite (DMSP) images on Aug. 20, 2014. A massive swirl of charged particles appeared above the North Pole. Spinning silently, it resembled a terrestrial hurricane in shape, with spiral arms and a calm “eye” glowing with auroral light. A detailed study of this event was published in the July 2025 edition of Space Weather.

Above: A ‘ space hurricane’ observed by DMSP satellites. Note the eye and spiral arms.

“The space hurricane formed during very quiet conditions,” says lead author Sheng Lu of Shandong University. “Solar activity was low.” 

Most researchers had overlooked these events because they weren’t linked to solar storms. This team looked for auroras under calm conditions and found something new. The DMSP F17 satellite flew through the space hurricane’s center; ten minutes later, SWARM B crossed the edge. Their data confirmed the hurricane was an active electrodynamic storm, not just an auroral display.

The hurricane’s effects mimicked those of actual geomagnetic storms. Using GPS data from the Canadian High Arctic Ionospheric Network, the researchers found that satellite signals passing through the hurricane’s edge experienced strong phase scintillations–a type of “twinkling” that can reduce GPS accuracy. Meanwhile, ground-based magnetometers in Greenland recorded sharp shifts in Earth’s magnetic field as large as 400 nT–comparable to a G1-class geomagnetic storm.

Above: The anatomy of a space hurricane. Credit: Lu et al (2025) [Expand]

Savvy aurora chasers know that the best time to catch Northern Lights is when the interplanetary magnetic field (IMF) tilts south. This opens a hole in Earth’s magnetosphere, allowing solar wind to enter. We tend to ignore times when the IMF tilts north and closes the door. Yet that is precisely when space hurricanes form, according to the study. 

Space hurricanes are stealthy, appearing when traditional metrics of space weather forecasting indicate little of interest. Note to forecasters: Not all storms come from the sun.

Want to learn more? Read the original research here.

Moths Follow the Milky Way

/ Dr.Tony Phillips / Leave a comment

July 17, 2025 (Spaceweather.com): Astronomers come in all shapes and sizes–even invertebrates. A new study published in Nature reveals that Australian moths can see and decipher the night sky. They pay particular attention to the Milky Way and seem capable of navigating using the Carina nebula as a visual landmark.


Above: A male Bogong moth and a diagram of their annual migration.

Every spring in southeast Australia, billions of Bogong moths take flight under cover of darkness. It’s the beginning of an epic migration as much as 1,000 kilometers long. Their destination: a small cluster of caves in the Australian Alps–places the moths have never visited before, yet somehow navigate to with remarkable precision. Their compass, it turns out, is the night sky itself.

Reaching this conclusion required the researchers to do something you probably don’t want to think about too closely: They attached the moths to tiny little tethers. Moths could lift off and pick a direction, but not escape. 

The experiment unfolded inside a special moth planetarium (pictured right). Star patterns were projected onto an overhead screen, while the ambient magnetic field was nulled by Helmholtz coils, guaranteeing that the participants could not “cheat” using magnetic navigation. When shown a normal star field, the moths oriented in the correct direction. But when the stars were scrambled into random patterns, they lost their bearings.

To dig deeper, the researchers recorded activity from visual neurons in the moths’ brains as a projected night sky rotated overhead. Neurons fired most strongly when the stars aligned with the moth’s inherited migratory heading. Some neurons were tuned to the brightest region of the Milky Way (especially near the Carina nebula) suggesting that this band of starlight is a visual landmark.

Clouds produced the next revelation: Bogong moths remained oriented even when stars were hidden. In those cases, they relied on Earth’s magnetic field instead, revealing a dual-compass system similar to that of migratory birds. When both stellar and magnetic cues were removed, the moths became disoriented again. 

Upper row: Laboratory-projected night skies during spring and autumn, and an autumn sky with its stars randomly arranged. Lower row: The moths’ reaction to each sky.

In recent years, scientists have discovered that many creatures are guided by the stars. In addition to humans, the list includes migratory songbirds, possibly seals, dung beetles, cricket frogs, and now Bogong moths. The list of lifeforms guided by magnetism is even longer, ranging in size from microbes to whales. 

You can read the original research here.

The Bastille Day Event, 25 Years Later

/ Dr.Tony Phillips / Leave a comment

July 14, 2025: You know a solar flare is strong when even the Voyager spacecraft feel it. Twenty-five years ago, on July 14, 2000, the sun unleashed one of the most powerful solar storms of the Space Age—an event so intense, its shockwaves rippled all the way to the edge of the solar system.

Voyager 2 felt the explosion 180 days later; Voyager 1, 245 days. The debris was still coherent and traveling faster than 600 km/s (1.9 million mph) when it slammed into the two spacecraft—then more than 9 billion kilometers from the sun.

Here on Earth, the effects were almost immediate. Within minutes, extreme ultraviolet and X-ray radiation bathed our planet and its satellites. Ground-based sensors registered a rare GLE (ground-level event) as energetic particles cascaded through the atmosphere.

“People flying in commercial jets at high latitudes would have received double their usual radiation dose,” recalled Clive Dyer of the University of Surrey Space Centre. “It was quite an energetic event—one of the strongest of its time.”

Because the flare happened on July 14th, it’s called “The Bastille Day Event” after France’s national holiday. However, auroras did not appear until the following day, July 15th, when a coronal mass ejection (CME) arrived. The 1500 km/s impact triggered an extreme geomagnetic storm (Kp=9).

Above: Auroras on July 15, 2000, photographed by (left) Ronnie Sherrill in North Carolina and (right) NASA’s IMAGE spacecraft.

In New York, Lou Michael Moure remembers his sky catching fire: “I was living on Long Island. A family member ran into my room, shouting about ‘the sky on fire.’ Sure enough, the sky blazed white, green, then red from horizon to horizon.” In North Carolina, Uwe Heine was doing yardwork when bright red auroras appeared straight overhead: “I told our neighbor those weren’t sunset colors. It was an aurora—and super rare this far south!”

By the time the storm ended on July 16th, auroras had been sighted as far south as Texas, Florida, and even Mexico.

The Bastille Day Event was important because, for the first time in history, spacecraft throughout the solar system were equipped with instruments capable of studying such a storm. Most notably, it was the first major solar storm observed by SOHO, the Solar and Heliospheric Observatory, which gave researchers an unprecedented look at how extreme flares unfold and evolve.

Above: SOHO images of the X5.7-class Bastille Day solar flare (left) and CME (right). “Snow” in the images is a result of energetic protons hitting the spacecraft

Later studies described how an X5.7-class flare, erupting near the center of the solar disk, released 10³³ ergs of magnetic energy—equivalent to a thousand billion WWII-era atomic bombs. The resulting CME generated a massive barrier of magnetic field and plasma, which swept away galactic cosmic rays as it raced through the heliosphere. Even the Voyagers felt this unusual dip in cosmic radiation, known as a Forbush Decrease.

Could it happen again? It could happen again this week. We’re currently near the peak of Solar Cycle 25, and another X-flare is well within the realm of possibility.

Happy Bastille Day.

A Warning From the Trees: Miyake Events

/ Dr.Tony Phillips / Leave a comment

Jan. 30, 2025: (Spaceweather.com) How bad can a solar storm be? Just ask a tree. Unlike human records, which go back hundreds of years, trees can remember solar storms for millennia.

Nagoya University doctoral student Fusa Miyake made the discovery in 2012 while studying rings in the stump of a 1900-year-old Japanese cedar. One ring, in particular, drew her attention. Grown in the year 774–75 AD, it contained a 12% jump in radioactive carbon-14 (14C), about 20 times greater than ordinary fluctuations from cosmic radiation. Other teams confirmed the spike in wood from Germany, Russia, the United States, Finland, and New Zealand. Whatever happened, trees all over the world experienced it.

Most researchers think it was a solar storm—an extraordinary one. Often, we point to the Carrington Event of 1859 as the worst-case scenario for solar storms. The 774-75 AD storm was at least 10 times stronger; if it happened today, it would floor modern technology. Since Miyake’s initial discovery, she and others have confirmed five more examples (12,450 BC, 7176 BC, 5259 BC, 664-663 BC, 993 AD). Researchers call them “Miyake Events.”

Right: The 774-775 AD carbon-14 spike. [more]

It’s not clear that all Miyake Events are caused by the sun. Supernova explosions and gamma-ray bursts also produce carbon-14 spikes. However, the evidence tilts toward solar storms. For each of the confirmed Miyake Events, researchers have found matching spikes of 10Be and 36Cl in ice cores. These isotopes are known to trace strong solar activity. Moreover, the 774-75 AD Miyake Event had eyewitnesses; historical reports of auroras suggest the sun was extremely active around that time.

Miyake Events have placed dendrochronologists (scientists who study tree rings) in the center of space weather research. After Miyake’s initial discovery in 2012, the international tree ring community began working together to look for evidence of solar superstorms. Their collaboration is called “the COSMIC initiative.” First results published in a 2018 edition of Nature confirm that Miyake Events in 774-75 AD and 993 AD were indeed global. Trees on five continents recorded carbon spikes.


Above: A global map of COSMIC tree ring and ice core measurements [more]

“There could be additional Miyake Events throughout the Holocene” says Irina Panyushkina, a member of the COSMIC initiative from the University of Arizona’s Laboratory for Tree-Ring Research. “An important new source of data are floating tree-ring records from Eurasia and the Great Lakes region. These are very old rings that could potentially capture 14C spikes as far back as 15,000 years. Eventually, I believe we will have a complete record of Miyake Events throughout that period.”

Four more candidates for Miyake Events have recently been identified (5628 BC, 5410 BC, 1052 C, and 1279 C). Confirmation requires checking trees on many continents and finding matching spikes of 10Be and 36Cl in ice cores. It’s all part of the “slow and systematic process” of radiocarbon tree ring research, says Dr. Panyushkina.

A complete survey of Miyake Events could tell us how often solar superstorms occur and how much peril the sun presents to a technological society. Stay tuned for updates from the trees.

Solar Maximum in the Sun’s Southern Hemisphere

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Nov. 4, 2024: At the end of October, amateur astronomer Senol Sanli made a composite 31-day image of the month’s sunspots. Take a look. Notice anything?

The two hemispheres of the sun are not the same. There’s a lopsided distribution of sunspots, with three times more in the south compared to the north. According to hemispheric sunspot data from the Royal Observatory of Belgium (WDC-SILSO), October was the fifth month in a row the sun’s southern hemisphere significantly outperformed the north. You can see the same pattern visually in composite images from September, August, July, and, to a lesser extent, June 2024.

What’s going on? Solar physicists have long known that the two hemispheres of the sun don’t always operate in sync. Solar Max in the north can be offset from Solar Max in the south by as much as two years, a delay known as the “Gnevyshev gap.” The assymetry is illustrated in this graph of north-vs-south sunspot numbers from the last 6 solar cycles:

Is the sun’s southern hemisphere experiencing its Solar Max right now? Maybe. We won’t know for sure until years from now when we can look back and see the final shape of Solar Cycle 25. Meanwhile, stay tuned for more southern sunspots.

Major Farside Solar Flare

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July 25, 2024: The biggest flare of Solar Cycle 25 just exploded from the farside of the sun. X-ray detectors on Europe’s Solar Orbiter (SolO) spacecraft registered an X14 category blast:

Solar Orbiter was over the farside of the sun when the explosion occured on July 23rd, in perfect position to observe a flare otherwise invisible from Earth.

“From the estimated GOES class, it was the largest flare so far,” says Samuel Krucker of UC Berkeley. Krucker is the principal investigator for STIX, an X-ray telescope on SolO which can detect solar flares and classify them on the same scale as NOAA’s GOES satellites. “Other large flares we’ve detected are from May 20, 2024 (X12) and July 17, 2023 (X10). All of these have come from the back side of the sun.”

Meanwhile on the Earthside of the sun, the largest flare so far registered X8.9 on May 14, 2024. SolO has detected at least three larger farside explosions, which means our planet has been dodging a lot of bullets.

The X14 farside flare was indeed a major event. It hurled a massive CME into space, shown here in a coronagraph movie from the Solar and Heliospheric Observatory (SOHO):

The CME sprayed energetic particles all over the solar system. Earth itself was hit by ‘hard’ protons (E > 100 MeV) despite being on the opposite side of the sun.

“This is a big one–a 360 degree event,” says George Ho of the Southwest Research Institute, principal investigator for one of the energetic particle detectors onboard SolO. “It also caused a high dosage at Mars.”

SolO was squarely in the crosshairs of the CME, and on July 24th it experienced a direct hit. In a matter of minutes, particle counts jumped almost a thousand-fold as the spacecraft was peppered by a hail storm energetic ions and electrons.

“This is something we call an ‘Energetic Storm Particle’ (ESP) event,” explains Ho. “It’s when particles are locally accelerated in the CME’s shock front [to energies higher than a typical solar radiation storm]. An ESP event around Earth in March 1989 caused the Great Quebec Blackout.”

So that’s what might have happened if the CME hit Earth instead of SolO. Maybe next time. The source of this blast will rotate around to face our planet a week to 10 days from now, so stay tuned. Solar flare alerts: SMS Text