This image depicts coronal rain. Encircled are two plasma streamers, one hitting the sun's surface and another incoming behind it.
A massive eruption on the surface of the sun that sent tons of plasma raining down our nearest star has been caught on camera by NASA's new solar observatory.
The aftermath of the eruption, which occurred on April 19, can be seen in video from the sun-watching observatory.
"SDO has just observed a massive eruption on the sun ? one of the biggest in years," said Lika Guhathakurta of NASA headquarters in Washington, D.C. "The footage is not only dramatic, but also could solve a longstanding mystery of solar physics."
The movie spans four hours of actual time while observing the eruption in a view that spanned about 62,137 miles (100,000 km) of linear space.
"It's huge," said Karel Schrijver of Lockheed Martin's Solar and Astrophysics Lab. In fact, the entire planet Earth could fit between the plasma streamers with room to spare.
Stunning sun eruption view
Astronomers have seen eruptions like this before, but rarely so large and never in such fluid detail.
"We can see a billion tons of magnetized plasma blasting into space while debris from the explosion falls back onto the sun surface. These may be our best data yet," Schrijver said.
Schrijver says his favorite part of the movie is the coronal rain: "Blobs of plasma are falling back to the surface of the sun, making bright splashes where they hit," he explained. "This is a phenomenon I've been studying for years."
Coronal rain has long been a mystery. It's not surprising that plasma should fall back to the sun. After all, the sun's gravity is powerful. The puzzle of coronal rain is how slowly it seems to fall.
"The sun's gravity should be pulling the material down much faster than it actually moves. What's slowing the descent?" Schrijver said.
SDO is beginning to answer this question for the first time.
"The rain appears to be buoyed by a 'cushion' of hot gas," Schrijver said. "Previous observatories couldn't see it, but it is there."
Rain on the sun
SDO was also able to take the temperature of the coronal rain.
Using an array of ultraviolet telescopes called the Atmospheric Imaging Assembly (AIA), the observatory can remotely measure the temperature of gas in the sun's atmosphere. NASA launched the SDO spacecraft in February to take unprecedented HD-quality images and videos of the entire sun.
Coronal rain turns out to be relatively cool ? "only" about 107,000 degrees Fahrenheit (60,000 Celsius). When the rains falls, it is supported, in part, by an underlying cushion of much hotter material that has a temperature between 1.8 million and 4 million F (1 million and 2.2 million C).
"You can see the hot gas in the color-coded temperature movie," says Schrijver. "Cool material is red, hotter material is blue-green. The hot gas effectively slows the descent of the coronal rain."
Dick Fisher, the head of NASA's Heliophysics Division in Washington DC, has been working in solar physics for nearly forty years. "In all that time," he says, "I've never seen images like this."
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