The Starlink Incident — Revisited

Sept. 13, 2022: A minor geomagnetic storm is supposed to be minor. That’s why even experts were surprised on Feb. 4, 2022, when dozens of Starlink satellites started falling out of the sky. A weak CME had hit Earth’s magnetic field, and the resulting G1-class (minor) storm was bringing them down:

Above: A Starlink satellite falls from the sky over Puerto Rico on Feb. 7, 2022. Credit: the Sociedad de Astronomia del Caribe

How could this happen? A new paper published in the research journal Space Weather provides the answer.

“Although it was only ‘minor,’ the storm pumped almost 1200 gigawatts of energy into Earth’s atmosphere,” explains lead author Tong Dang of the University of Science and Technology of China. “This extra energy heated Earth’s upper atmosphere and sharply increased aerodynamic drag on the satellites.”

SpaceX launched the satellites from Cape Canaveral on Feb. 3, 2022. Forty-nine (49) Starlinks were crowded inside the Falcon 9 rocket; less than a quarter would survive.

Left: An Earth-directed CME implicated in the Starlink Incident. Right: Geomagnetic indices showing how two minor geomagnetic storms sandwiched the launch of the Starlink satellites.

As was SpaceX’s practice at the time, the satellites were deployed at an altitude of 210 km–their first stop en route to an operational altitude near 600 km. In the satellite business, 210 km is considered to be low, barely above the atmosphere. SpaceX starts there in case any satellite malfunctions after launch. From 210 km, a “bad sat” can be easily de-orbited.

A little too easily, as it turns out.

Using a physics-based computer model named “TIEGCM,” Dang and colleagues simulated conditions during the storm. As geomagnetic energy heated Earth’s atmosphere, the air density at 210 km increased globally by 20% with “hot spots” as high as 60%.  This movie shows what happened:

Starlink dodged the worst spots. “The satellites did not hit any of the 60% regions,” says Dang. “But that didn’t save them.” The weaker 20% enhancements were enough to bring down 38 out of 49 satellites.

To prevent this from happening again, SpaceX has started launching to 320 km instead of 210 km. Earth’s atmosphere has to reach that much higher to drag the satellites back during a geomagnetic storm. Since the change, more than 1200 additional Starlink satellites have been launched on 24 rockets without incident.

There’s still danger, though. “Air density at 320 km is an order of magnitude less (compared to 210 km), but it’s not completely safe,” cautions Dang’s co-author Jiuhou Lei, also from the University of Science and Technology of China. “During an extreme geomagnetic storm, density could increase from 200% to 800% even at these higher altitudes.”

Extreme storms may be in the offing. Young Solar Cycle 25 is just getting started. The profusion of minor storms we are observing today will intensify in the years ahead especially as we approach Solar Max around 2025.

Elon Musk’s note to self: Check the space weather forecast.

BlueWalker 3 is Huge

Sept. 10, 2022: Later today, SpaceX will launch an unusual satellite: BlueWalker 3. Designed to supply 4G cell phone signals from space, Bluewalker 3 will unfurl a large antenna spanning 64 square meters–the size of a squash court:

This flat surface orbiting 500 kilometers above Earth will reflect a lot of sunlight, which could make the satellite extremely visible to observers on the ground. It could become brighter than the planet Venus, outshining everything in the night sky except the Moon.

While this is only a single satellite for now, Bluewalker’s maker AST SpaceMobile plans to launch more than 100 larger satellites called BlueBirds. These satellites, which could be more than twice the size of BlueWalker 3, would appear even brighter in the sky.

For astronomers, the satellites could create bright streaks across images from ground-based telescope, potentially making them unusable for observing more distant objects.

Should we be concerned? Maybe. First let’s see how bright Bluewalker 3 actually is. It is scheduled to launch from Cape Canaveral on Sept 10th between 9:10 p.m. to 9:20 p.m. EDT. A batch of 34 Starlink satellites will share the ride.

Update: SpaceX successfully launched the huge BlueWalker 3 communications satellite and 34 Starlink satellites on Sept. 10th at 9:20 pm EDT.

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Dung Beetles Navigate Using the Milky Way — New Results

Sept. 1, 2022: When you hear the words “dung beetle” you probably think of poop. After you read this article, a different picture may come to mind: The Milky Way.

In 2009, entomologists made an astonishing discovery. Nocturnal dung beetles (Scarabaeus satyrus) can navigate using the Milky Way. Although the compound eyes of beetles cannot resolve individual stars, this species can see the Milky Way as a stripe across the sky and perhaps even sense features within it such as the galactic center and lanes of stardust.

“Currently, dung beetles are the only animals we know of that use the Milky Way for reliable orientation,” says James Foster of the University of Konstanz in Germany. “They are excellent little astronomers.”

Above: A nocturnal dung beetle at work. Photo credit: Chris Collingridge © 2017

A quick review of dung beetles: They are nature’s sanitation crew. Whenever a pile of brown material is dumped in the forest, dung beetles converge to clean up the mess. Each beetle sculpts a dung ball, which they roll away in a straight line. Far from the pile, the ball will be buried and eaten, and sometimes used as bedding for dung beetle eggs.

It sounds simple, but there’s a problem. Dung beetles are combative. If two beetles leaving the pile bump into one other, they can get into a brutal wrestling match often ending with overhead judo-style full body throws. Wandering around in circles (like lost humans do) boosts the odds of a fight even more. Dung beetles have therefore evolved the ability to navigate to safety in quick straight lines.

During the day they steer by the sun. Dung beetles can see polarization patterns in the daytime sky, and use these patterns to hold course. A single patch of blue sky is sufficient. The trick works at night, too. Dung beetles are the only known creatures who can see the polarization of moonlight, which is 100 million times weaker than daylight polarization. Studies show that dung beetles can walk straight as accurately at night as during the day, even when the Moon is a faint crescent.

Above: Dung beetle vision blurs the Milky Way, but no one is certain how much. These are four models used in the experiments of James Foster. Models in the 2o to 4o smoothing range seem to best represent how the beetles see the sky.

But what happens when there’s no sun or Moon? In the early 2000s, this question troubled two pioneers of dung beetle research, Eric Warrant and Marie Dacke of Lund University in Sweden. To find the answer, they took some beetles to the planetarium at the University of the Witwatersrand in Johannesburg, South Africa, and projected the Milky Way onto the domed ceiling. The beetles saw it, and navigated.

Their discovery prompted a veritable explosion in dung beetle research. James Foster is a leader in the field, publishing new results every few years.

Foster and colleagues have built a rudimentary planetarium just for dung beetles. It uses LED lights to mimic the Milky Way as beetles see it through their compound eyes. In 2017 they found that dung beetles were able to distinguish between north and south arms of the Milky Way, sensing intensity contrasts as low as 13%.  This threshold puts features such as the galactic center in Sagittarius and the Great Rift in Cygnus theoretically within range of beetle senses.

Next they added city lights to their experiment–and the results  were not good. “Light pollution may be forcing  beetles to abandon the Milky Way as their compass,” worries Foster.

Above: Claudia Tocco, a colleague of James Foster, performing experiments on the roof of the University of the Witwatersrand in central Johannesburg. A dung beetle is at the center of the red-lit arena. Photo credit Marcus Byrne

In a paper published July 2021, Foster’s team described how urban lights wipe out the Milky Way, reduce the polarization of moonlight by 60% to 70%, and “create anthropogenic celestial cues.” The last item is worst of all. Spotlights and brightly lit buildings mesmerize beetles who suddenly ignore the sky and make a beeline for manmade bulbs.

“These beacons draw beetles towards the most hostile regions of their environments,” says Foster. “After rolling their balls some distance, beetles need to find a patch of soft sand where they can dig in. They are unlikely to find that in the immediate vicinity of bright artificial lights, whether in cities or the countryside, since these are usually associated with concrete and tarmac.”

Dung beetles aren’t the only ones. Researchers believe they are only scratching the surface of this field with potentially thousands of species watching the stars. Everything from simple light bulbs to sophisticated satellite mega-constellations may be affecting these members of our ecosystem.

“Dung beetle!” What are you thinking of now?

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Major Farside CME and Radiation Storm

Sept. 6, 2002: Something just exploded on the farside of the sun. NASA’s STEREO-A spacecraft recorded a magnificent full-halo CME emerging during the late hours of Sept. 5th:

A NASA model of the CME shows it heading away from Earth and directly toward Venus. This will be the second time in a week that Venus has been hammered by a significant solar storm. An earlier CME struck on Sept. 1st, probably launched by the same farside sunspot.

“This is no run of the mill event,” says George Ho of the Johns Hopkins Applied Physics Lab. “Many science papers will be studying this for years to come.”

Ho is the principal investigator for an energetic particle detector onboard Europe’s Solar Orbiter spacecraft–and he is getting a lot of data right now. Solar Orbiter just performed a close flyby of Venus (only 6420 km away) to adjust its orbit around the sun. It is in the perfect position to observe the storm.

This plot shows a wave of energetic particles washing over the spacecraft:

Above: Data from Solar Orbiter’s EPD/Suprathermal Ion Spectrograph. These are quick-look data; they have not been checked for accuracy and are subject to revision

“I can safely say the Sept. 5th event is one of the largest (if not THE largest) Solar Energetic Particle (SEP) storms that we have seen so far since Solar Orbiter launched in 2020,” says Ho. “It is at least an order of magnitude stronger than the radiation storm from last week’s CME.”

“In fact, the >10 MeV and >50 MeV particle intensity has not subsided since the beginning of the storm yesterday,” adds Ho. “This is indicative of a very fast and powerful interplanetary shock, and the inner heliosphere may be filled with these high-energy particles for a long time. I think I’ve only seen couple of these in the last couple solar cycles.”

Earth is not affected by the storm, which is happening on the opposite side of the sun. However, we may not be safe from its source. The underlying explosion almost certainly happened in the magnetic canopy of AR3088, an active sunspot that popped up on the Earthside of the sun in August. It is now transiting the farside, apparently bigger and angrier than before. The sun’s rotation will turn AR3088 toward us again in little more than a week, putting Earth back in the line of fire. Stay tuned.Solar flare alerts: SMS Text

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A Big CME Heads for Venus

Aug. 31, 2022: A CME billowed away from the farside of the sun yesterday, Aug. 30th, and it was spectacular. Coronagraphs onboard the Solar and Heliospheric Observatory (SOHO) recorded a full halo storm cloud:

If Earth were in the crosshairs, we would be bracing for a strong geomagnetic storm. Instead, Venus will absorb the blow. NASA models show the CME making a direct hit on the second planet.

The Venus impact on Sept. 1st (~0600 UT) will not cause a geomagnetic storm. It can’t. Venus has no internally-generated global magnetic field. Rather, the impact will erode some atmosphere from Venus’s unprotected cloudtops–a process that does not occur on Earth.

Above: A NASA model of the CME. Venus is the green dot. Earth is the yellow dot.

The source of the CME is probably active sunspot AR3088, which left the Earthside of the sun two days ago. This sunspot was extremely active while we could see it from Earth. Now Venus is in the line of fire.

Coincidentally, the European Space Agency’s Solar Orbiter spacecraft is currently very close to Venus. That means it can study the CME as it passes by. If explosions from AR3088 continue apace, Solar Orbiter could get great data in the next week as potentially many storm clouds wash over the spacecraft.

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Earth Just Dodged a lot of CMEs

Aug. 30, 2022: It seemed like sunspot AR3088 would never stop exploding. Over the past four days, the strangely-magnetized active region produced more than a dozen M-class solar flares:

Each X-ray peak in the graph above produced a corresponding shortwave radio blackout on Earth. No part of our planet was untouched.

More than half of the explosions also produced a coronal mass ejection (CME). Earth dodged them all. Only one and maybe two delivered glancing blows of no consequence. All the rest sailed harmlessly into space.

The simple reason why: AR3088 was never facing Earth. Most of the explosions occured while the sunspot was approaching or even rounding the sun’s western limb.

This movie from NASA’s Solar Dynamics Observatory is a good example. It shows a flare from AR3088 on Aug. 29th partially eclipsed by the edge of the sun. The explosion registered M9 on GOES satellite X-ray sensors, but the uneclipsed flare was probably much stronger–perhaps even an X-flare.

If the sunspot had been facing us, we might now be experiencing strong geomagnetic storms with spectacular low-latitude auroras. Maybe next time

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Artemis I is ‘GO’ for Launch

Aug. 28, 2022: We’re about to find out if NASA still has the right stuff. On Monday morning, Aug. 29th at 8:33 am EDT, the most powerful rocket ever built will blast off from Kennedy Space Center’s launch pad 39B. Destination: the Moon. This is the beginning of NASA’s Artemis program, named after the twin sister of Apollo.

Artemis I will not carry any astronauts. It’s a test flight. In fact, it’s the only test flight, a controversial decision that worries some experts. Astronauts will ride the next rocket, Artemis II, in 2024. NASA will have two years to fix any problems uncovered by Artemis I.

Propelled by a 32-story tall rocket with 8.8 million pounds of thrust, Artemis I will exit Earth’s atmosphere in only 2 minutes. Less than 2 hours after that, the unoccupied Orion crew capsule will be burning straight for the Moon.

Over the course of the 42 day mission, Orion will orbit the Moon for more than a week (approaching the lunar surface within 62 miles) and travel 40,000 miles beyond the far side of the Moon before turning back to Earth.

The capsule will stay in space longer than any human spacecraft has without docking to a space station and return home faster and hotter than ever before. Indeed, a key goal of the mission is to test Orion’s heat shield when it slams into Earth’s atmosphere at 25,000 mph and heats up to 5,000 degrees Fahrenheit.

If all goes well, future launches will carry crew. Astronauts will orbit the Moon in 2024 (Artemis II), then touch down near the Moon’s south pole in 2025 (Artemis III). The moonwalkers will include the first woman to step onto the lunar surface.

NASA, we are rooting for you!

Live coverage of the launch begins on Monday, Aug. 29th, at 6:30 am EDT.

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A Strangely Magnetized (Perpendicular) Sunspot

Aug. 25, 2022: New sunspot AR3088 is emerging in the sun’s southern hemisphere. Its magnetic field is not normal:

Shown above is a map of magnetic fields on the sun. AR3088 is inset. According to Hale’s Law, the sunspot’s magnetic poles should be arranged +/-, that is, positive (+) on the left and negative (-) on the right. Instead, they are rotated 90 degrees; positive (+) is on top and negative (-) is on the bottom.

This is a rare “perpendicular sunspot,” with magnetic poles orthogonal to the sun’s equator. What’s going on? Something unusual may be happening to the sun’s magnetic dynamo beneath the surface where this sunspot is growing. We’ll keep an eye on AR3088 to see what happens next. Solar flare alerts: SMS Text

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Auroras on Jupiter

Aug. 23, 2022: Yesterday, NASA released the first James Webb Space Telescope (JWST) images of auroras on Jupiter. The red rings of light circling Jupiter’s poles were big enough to swallow Earth:

Image credit: JWST’s Near-Infrared Camera (NIRCam). The camera’s F360M filter picked up the 3.3 – 3.6 micron glow of excited H3+ in Jupiter’s auroral zone.

But Jupiter’s auroras are more then just oversized versions of our own. They are formed in a completely different way. One of the key ingredients is volcanoes, and–so much for space weather–solar activity is not required.

For the most part, Jupiter makes its own Northern and Southern Lights. It does this by spinning–like crazy. Jupiter turns on it axis once every 10 hours, dragging its giant planetary magnetic field around with it. Spinning a magnet is a great way to generate a few volts; kids do it all the time for science fair projects. Jupiter’s spin produces 10 million volts around its poles.

These voltages set the stage for non-stop auroras. The fuel comes from Jupiter’s volcanic moon Io, where active vents spew ions such as O+ and S+ into Jupiter’s magnetosphere. Polar electric fields grab these ions and slam them into Jupiter’s upper atmosphere. The resulting glow can be seen almost anytime JWST wants to look. Jupiter’s volcano-powered auroras are usually “on.”

Above: This JWST image of Jupiter and its surroundings uses a different color table, so the auroras look blue. They are still infra-red.

Solar wind and CMEs can also help. However, solar storm clouds are naturally weakened by the time they travel all the way to Jupiter, five times farther from the sun than Earth. Also, Jupiter’s powerful magnetic field forms a potent shield. Io is already inside Jupiter’s “defenses,” so it can be more effective.

Two distinct auroras coexist over the poles of Jupiter: Ultraviolet auroras created by atmospheric hydrogen in its molecular form (H2) and infrared auroras created by the hydrogen ion H3+. JWST saw the infrared variety. In fact, the telescope is well instrumented to monitor these auroras. Its Near-Infrared Camera (NIRCam) has a filter that nicely captures the 3.3 to 3.6 micron glow of H3+.

NASA, we want more!

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Dark Plasma Eruption from a Reversed Polarity Sunspot

Aug. 14, 2022: The sun just hurled a plume of cool, dark plasma into space following an explosion around sunspot AR3076. NASA’s Solar Dynamics Observatory recorded the blast on August 14th:

Traveling faster than 600 km/s (1.3 million mph), the plume tore through the sun’s outer atmosphere, creating a coronal mass ejection (CME). Coronagraph images from the Solar and Heliospheric Observatory (SOHO) confirm that the CME has an Earth-directed component. It could sideswipe Earth’s magnetic field on Aug. 18th, producing minor to moderate geomagnetic storms.

REVERSED POLARITY SUNSPOT: The sunspot that produced the dark plasma explosion is a little unusual. It has its signs backwards.

Above: A magnetic map of the sun’s surface from NASA’s Solar Dynamics Observatory.

According to Hale’s Law, Solar Cycle 25 sunspots in the sun’s northern hemisphere should have a -/+ polarity; negative on the left, positive on the right. However, the magnetogram above shows the opposite. AR3076 is a reversed polarity sunspot.

Studies show that about 3% of all sunspots violate Hale’s Law. In many ways, reversed polarity sunspots are just like other sunspots. For instance, they have the same lifespan and tend to be about the same size as normal sunspots. In one key way they are different: According to a 1982 survey by Frances Tang of the Big Bear Solar Observatory, reversed polarity sunspots are more than twice as likely to develop complex magnetic fields mixing + and – together. Reversed polarity sunspots are therefore more likely to explode.

This one sure did, and a CME is now heading for Earth. Don’t miss the impact.

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