If one were to land on the Sun in some mythical spacecraft resistant to two million or so degrees Fahrenheit, they might be surprised at the temperatures encountered. Passing through the upper layers of said star, our solar passenger would find temperatures plummeting as they came closer and closer to the boiling plasma surface, from many millions of degrees in the Sun’s upper atmosphere to a mere 10,000 or so degrees Fahrenheit as they entered the Sun’s “interior.” As solar material is ejected from that interior, it gains energy and heats up as it moves outward into space.
The atmospheric zones where this heating occurs are the chromosphere and the transition region. Together they form a volatile and rather mysterious zone of the Sun, where hot and cold (relatively) plasma mix together with explosive results in the forms of coronal mass ejections and solar flares, and less spectacular phenomenon like the solar winds (though all of the above can have impacts on human technology here on Earth). So far, deep looks at this region have been impossible, with technology unable to cover a wide range of temperatures and without the benefit of high-resolution imaging.
NASA’s Interface Region Imaging Spectrograph (IRIS) mission is the first to promise a deep look. In the agency’s own words: “In combination, IRIS’s resolution, wide temperature coverage and computer modeling will enable scientists to map plumes of solar material as they move throughout the region and to pinpoint where in their travels they gain energy and heat.”
The video below is the first CME captured by IRIS. It’s a difficult undertaking, as the satellite needs to be in position a full day in advance of the actual eruption. “We focus in on active regions to try to see a flare or a CME,” said Bart De Pontieu, the IRIS science lead, in a NASA announcement. “And then we wait and hope that we’ll catch something. This is the first clear CME for IRIS so the team is very excited.”