Coronal Hole In Sun: NASA's SOHO Satellite Captures Amazing Dark Spot Above Solar Surface [VIDEO]
But fear not, for the coronal hole is nothing to be alarmed about. A coronal hole is simply a cooler region of the sun's atmosphere, or corona, where solar wind and particles are released from the sun at a speed of 500 miles per second.
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First discovered in the 1970s, coronal holes appear as a dark spot on the sun. The current hole covers about a quarter of the sun -- it's about 400,000 miles across, or the equivalent of 50 Earths lined up.
According to NASA, coronal holes in the sun are typical, though their number, size and location changes from time to time. Though scientists do know what coronal holes are, they aren't sure why they occur in the first place.
"While it's unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere," said Karen Fox at NASA's Goddard Space Flight Center in Greenbelt, Md.
The SOHO project, a joint effort between the European Space Agency and NASA, was launched in December 1995 to study the sun's internal structure and outer atmosphere, as well as solar winds. The $1.27 billion satellite monitors the sun while orbiting around Lagrange Point 1, a spot between the Earth and sun about 932,000 miles from Earth.
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