The weather forecast on the sun: rainy with a chance of space fireballs.
Astronomers have discovered a phenomenon that causes the sun to form enormous objects similar to meteors or “shooting stars” in its corona, the outer layer of its atmosphere, that then fall back toward the surface at nearly 225,000 mph.
“If humans were alien beings capable of living on the Sun’s surface, we would constantly be rewarded with amazing views of shooting stars,” said Patrick Antolin, the astrophysicist who led the discovery, in a statement.
The objects are formed in the so-called “coronal rain,” made of fiery plasma — not water — that has gone through a drastic cooling and condensation process like precipitation. Scientists have found that sudden patchy temperature drops in the sun’s corona can cause the material to clump together in tightly packed balls over 150 miles wide.
Gravity then pulls the clumps back to the sun, heating the gas under them up to a million degrees for a few minutes as they fall, according to new research that will be published in the science journal Astronomy & Astrophysics. The paper will be included in a special issue of the publication dedicated to the Solar Orbiter, a collaborative mission of the European Space Agency and NASA.
The spacecraft made a close approach to the sun last spring, taking the sharpest photo yet of the jacket of gasses enveloping the star, including the first detailed images of the coronal rain clumps.
“Just detecting coronal rain is a huge step forward for solar physics because it gives us important clues about the major solar mysteries, such as how it is heated to millions of degrees,” Antolin said.
The orbiter is studying the sun’s magnetic activity and so-called solar wind, gasses flowing off the sun that cause “space weather.” Right now, scientists have a limited ability to forecast space weather events, which can disrupt power grids, telecommunications, and GPS systems.
The orbiter is also trying to get to the bottom of what causes the corona’s extreme heat. Despite the corona being millions of miles from the sun’s surface, this outer atmosphere is hundreds of times hotter. This defies most physics: Usually temperature drops as you move farther from a heat source.
“Just detecting coronal rain is a huge step forward for solar physics because it gives us important clues about the major solar mysteries, such as how it is heated to millions of degrees.”
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Credit: Patrick Antolin / ESA / Solar Orbiter / EUI / HRI
Though Antolin and the team have compared these coronal rain clumps to meteors, here’s how they differ:
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A meteor could be as tiny as a pebble or grit of sand that has flown through space and smacked into Earth’s atmosphere. The ephemeral streak is caused by a rock moving so fast — an average of 45,000 mph, according to NASA — that it blazes as it bombards the air surrounding the planet. Usually, meteors burn up before they ever touch the ground. They reach around 3,000 degrees Fahrenheit due to air friction as they fall through the atmosphere, disintegrating. But the sun’s corona is thin and low in density and does not boil off much material from the clumps. Scientists think most of the solar “shooting stars” make it all the way to the sun’s surface.
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The coronal clumps probably don’t have the bright tails associated with meteors, making them harder to observe on the sun. In Earth’s atmosphere, the falling space rocks leave behind a heated trail of vaporized material. In the sun’s corona, falling gas follows magnetic field lines. The compression and heat underneath the clumps keep them intact.
Credit: Patrick Antolin / ESA / Solar Orbiter / EUI / HRI
Still, the Solar Orbiter has revealed these raining clumps make quite a show, causing brief, strong brightening, blasting material up, and sending shock waves that reheat the gas above. Guess it’s a good thing we can’t experience these solar meteor showers on the sun, as Antolin imagined.
“We would need to watch out for our heads,” he quipped.
