A New Form of Space Weather on Betelgeuse

August 12, 2022: You’ve heard of a CME, a “coronal mass ejection.” They happen all the time. A piece of the sun’s tenuous outer atmosphere (corona) blows off and sometimes hits Earth. Something far more terrible has happened to Betegeuse. The red giant star produced an SME, or “surface mass ejection.”

Above: An artist’s concept of an SME on Betelgeuse. Credit: Elizabeth Wheatley (STScI)

Astronomers believe that in 2019 a colossal piece of Betelgeuse’s surface blew off the star. The mass of the SME was 400 billion times greater than a CME or several times the mass of Earth’s Moon. Data from multiple telescopes, especially Hubble, suggest that a convective plume more than a million miles across bubbled up from deep inside the star, producing shocks and pulsations that blasted a chunk off the surface.

“We’ve never before seen such a huge mass ejection from the surface of a star,” says Andrea Dupree of the Harvard-Smithsonian Center for Astrophysics, who is leading the study. “Something is going on that we don’t completely understand.”

After it left the star, the SME cooled, forming a dark cloud that famously dimmed Betelgeuse in 2019 and 2020. Even casual sky watchers could look up and see the change. Some astronomers worried that the dimming foreshadowed a supernova explosion. The realization that an SME is responsible has at least temporarily calmed those fears.

Above: A Hubble image of Betelgeuse located in the shoulder of Orion.

Betelgeuse’s brightness has since returned to normal, but something strange is still going on. Astronomers have long known that Betelgeuse is a variable star with a 430-day period. Its metronome-like change in brightness has been observed for more than 200 years. As Betelgeuse recovers, however, those pulsations are no longer regular: See the data. Spectra taken by Hubble and the Tillinghast telescope in Arizona imply that years later the surface of Betelgeuse is still bouncing like a plate of gelatin dessert–a testament to the ferocity of the blowout.

Betelgeuse is so large that if it replaced the sun at the center of our solar system, its atmosphere would extend past Jupiter. Dupree used Hubble to resolve hot spots on the star’s surface in 1996. This was the first direct image of a star other than the sun.

What’s happening now “is a totally new phenomenon that we can observe directly and resolve surface details with Hubble,” says Dupree. “We’re watching stellar evolution in real time.”

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Balloons Detect an Earthquake from the Stratosphere

August 10, 2022: If you want to detect an earthquake on Venus–good luck. The planet’s surface is hot enough to melt lead, and the atmospheric pressure is crushing. No ground-based seismometer could possibly survive.

What’s an extraterrestrial seismologist to do? Launch a balloon.

Above: Researchers prepare to launch a Strateole-2 balloon with sensors capable of detecting earthquakes from thousands of kilometers away.

A new paper just published in the Geophysical Research Letters reports the detection of a magnitude 7.3 earthquake by a fleet of balloons floating through the stratosphere above Indonesia’s Flores Sea. Onboard infrasound sensors registered acoustic waves rippling upward from the sea surface below, proving that, here on Earth, balloons can be used as seismometers.

“The same technique should work in the atmosphere of Venus,” says Raphael Garcia, the study’s lead author and a planetary scientist at the Institut Supérieur de l’Aéronatique et de l’Espace of the University of Toulouse. “Balloon-based sensors could float high above Venus’s deadly surface, collecting data at a safe distance.”

In the fall of 2021, the Centre National d’Etudes Spatiales (CNES) launched a fleet of 16 balloons from Mahé Island in the Seychelles archipelago. Unlike ordinary weather balloons, which explode in a matter of hours, these were “superpressure balloons,” which can remain aloft for months. Stratospheric winds carried them over the Flores Sea just in time for the temblor.

Above: Position of the quake in Flores Sea (blue square) with ground seismometers (purple stars) and the Strateole-2 balloons (red circles)

Four balloons picked up the undersea quake on Dec. 14, 2021. Combining their signals, researchers pinpointed the epicenter within 300 km, the magnitude of the quake within 0.8 units, and its onset within 50 seconds. Furthermore, waveforms recorded by the infrasound sensors were detailed enough to sense structures in the Earth 100 km deep.

Garcia would like to do the same thing on Venus. “We know nothing of its interior,” he says. “We don’t know how it’s made inside, and seismology is one of the best tools to figure that out.”

Seismic balloons could come in handy on our own planet, too. “Balloons could be used to cover ocean regions where conventional seismometers are not yet deployed,” notes Garcia.  “Another advantage: Balloons may be rapidly deployed just after a big quake for monitoring aftershocks.”

Above: Acoustic waves recorded by the four balloons during the Flores Sea earthquake.

The test flights have already unearthed a curiosity in South America. On Nov. 28, 2021, just one of the balloons detected a magnitude 7.5 earthquake in northern Peru. The infrasound frequency, 0.23 Hz, was higher than expected; for comparison, the Flores Sea quake registered a more typical 0.085–0.125 Hz. Garcia’s team believes the high pitch may have been caused by a “ringing” of sediments in the Amazonian basin.

Sensing earthquakes from the stratosphere is relatively new. Researchers at Caltech and the Jet Propulsion Laboratory did it for the first time in July 2019. Garcia’s study marks the first time an earthquake was detected by more than one balloon. It won’t be the last.

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Surprise Geomagnetic Storm

Aug. 8, 2022: A solar wind stream hit Earth’s magnetic field on August 7th. At first, the stream’s velocity was low, but during the day it sped up to more than 600 km/s, ultimately triggering a G2-class (moderately strong) geomagnetic storm. This event was not in the forecast, so the resulting auroras came as a surprise.

“I was already in bed getting ready for sleep when the storm began,” says Ruslan Merzlyakov. “Rushing to the beach in Nykøbing Mors, I was able to photograph the first summer auroras in Denmark in 5 years.”

“Seeing the lights dance on a warm summer night was a great experience!” he says.

In North American, auroras spilled across the Canadian border as far south as Pennsylvannia. In Wayne County, PA, Sujay Singh photographed both red auroras and STEVE. Auroras were also sighted in Montana and the Dakotas.

The solar wind stream that sparked this display is a bit of a puzzle. It might be the early arrival of a stream originally expected on Aug. 9th, flowing from an equatorial hole in the sun’s atmosphere. Or, perhaps, a CME was involved. A discontinuity in solar wind data at 0045 UT on Aug. 7th hints at a shock wave embedded in the solar wind. These days, the active sun is producing so many minor explosions, it is easy to overlook faint CMEs heading for Earth.

“Earth’s magnetic field is still reverberating on August 8th,” reports Stuart Green, who recorded the event using a backyard magnetometer in the UK:

Despite the surprise, subscribers to our Space Weather Alert Service were aware of the storm. Instant text alerts announced the arrival of the solar wind and the subsequent G2 event. Aurora alerts: SMS Text

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Blue Jet Lightning Sighted Over Texas

August 4, 2022: Seeing one blue jet is rare. Photographer Matthew Griffiths just caught several of them over the Big Bend National Park in Texas. “This is by far the best,” he says:

Above: A blue jet emerges from a thunderhead in Big Bend National Park, photographed by Matthew Griffiths in Marfa, Texas: more.

Griffiths is an amateur photographer, primarily interested in wildlife and the Milky Way. “On July 28th, I was starting a five night West Texas road trip to capture the Milky Way,” he says. “But with thunderstorms in the distance I decided to try for red sprites instead.”

He ended up photographing the sprite’s elusive cousin, the blue jet. First recorded by cameras on the space shuttle in 1989, blue jets are part of a growing menagerie of cloudtop “transient luminous events” such as sprites, ELVES and green ghosts. They are all elusive, but blue jets may be the hardest of all to catch.

“We’re not sure why ground-based observers see them so rarely,” says Oscar van der Velde of the Lightning Research Group at the Universitat Politècnica de Catalunya. “It might have something to do with their blue color. Earth’s atmosphere naturally scatters blue light, which makes them harder to see. Blue jets might be more common than we think.”

A rookie mistake might have helped Griffiths. “This is only my second time trying for sprites. I might have aimed my camera too close to the cloud tops where bright lightning washed out the sprites; in fact, I couldn’t find any sprites in my photos. But I think my camera angle was just right for catching the bright blue jet.”

Above: A zoomed-in view showing the jet’s sharp lance-like core and a diffuse fan of electric-blue overhead.

Blue jets might look like lightning, but they are not the same. Normal lightning carves a scorching-hot path through the atmosphere, heating the air to 30,000 degrees Celsius. Blue jets are made of cold plasma akin to gas inside a fluorescent light bulb. You could touch one with your hand and it might not hurt.

And, of course, they go up instead of down. Photos taken from the International Space Station (ISS) show that blue jets reach astonishing altitudes, as high as 170,000 feet. This is high enough to touch the ionosphere, possibly forming a new and poorly understood branch of Earth’s global electrical circuit.

“Also,” says van der Velde, “there can be considerable production of NOx and ozone by these discharges, potentially affecting the chemistry of the upper atmosphere.”

Clearly, it is important to study blue jets. Photographers, now you know where to look.