The sun in stereo

The twin spacecraft of the STEREO mission will be launched from Cape Canaveral on a Delta rocket like this one.

by Deane Morrison

From M, fall 2006

Every so often, the sun flings a gigantic blob of hot gas in our direction, wreaking havoc with satellites and power grids and sending astronauts in orbit scurrying for the safety of their radiation shields. It's hard to tell when one of these blobs of gas, or coronal mass ejections (CMEs), is brewing, or which ones are heading our way. But NASA's twin STEREO spacecraft-now scheduled for launch in October on a Delta rocket similar to the one above-will give researchers a 3-D view of the sun, revealing the directions of CME movements and, thanks to instruments designed and built by University physicists, clues for predicting them.

"As our society becomes more electronic and sophisticated, these outbursts become more disruptive," says Paul Kellogg, a retired University physics professor. "STEREO will allow us to see when one is coming to Earth."

The two spacecraft will be sent into different orbits, one in front of Earth and one behind. The University-built instruments will detect waves of energy and charged particles emitted by the sun via processes that may help cause CMEs.

"It's all to understand and predict how the sun works," says University physicist Keith Goetz. "We want to be able to look at the surface of the sun and say, for example, 'There's going to be an eruption-right there, in that spot.'"

Goetz, Kellogg and other University physicists worked with researchers at the Paris Observatory to design and build the instruments.