Author: Lisa Grossman / Source: Science News
LEESBURG, Va. — Astronomers watching the 2017 solar eclipse from the ground and from the air witnessed new, tantalizing features of the sun’s outer atmosphere.
Three teams have recently presented their first science results from the Great American Eclipse. Combined, the findings could help disentangle lingering solar puzzles, such as how bursts of plasma leave the sun, why the outer atmosphere, the solar corona, is so well organized and what is the nature of the corona’s magnetic field.
While thousands of eclipse watchers gathered across the country last August armed with special glasses and cameras, solar physicists Adalbert Ding and Shadia Habbal and their colleagues set up a specially designed spectrometer in Mitchell, Ore. (That was one of four sites from which their team monitored the eclipse.) The team had used an earlier version of the instrument, which takes in specific wavelengths of light that can trace different coronal temperatures, to watch a solar eclipse in March 2015 from Svalbard, Norway.
In both 2015 and 2017, the scientists observed evidence of relatively cool blobs of gas embedded in hot plasma in the outer corona.
(The sun’s surface simmers at about 6000° Celsius, but its corona roasts at millions of degrees — and no one knows why.) Ding, of the Institute for Optics and Atomic Physics in Berlin, and Habbal, of the University of Hawaii in Honolulu, measured wavelengths of light emitted by atoms and charged particles called ions in the corona, as a proxy for the plasma’s heat.To the researchers’ astonishment, they saw blobs of plasma during both eclipses that had maintained temperatures as low as 20,000° C embedded within material in the corona that was as hot as 3.7 million degrees Celsius, Ding said at the Triennial Earth-Sun Summit on May 23. “We were very surprised,” Ding says. He thinks the cooler material may be trapped within plasma bubbles and can’t get out. “The stunning thing is that they survive.”
The team also measured solar material’s Doppler shift, or the change in wavelength as the material moved toward or away from Earth. The…
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