NASA Probe to Fly Into the Sun

June 16, 2008 -- Scientists have studied the sun for decades, sending probes to unravel its 11-year cycles, watching its outbursts and measuring how its winds shape the outer edges of the solar system.

But we've never actually dared a house call: The technology simply wasn't available -- until now.

NASA is starting work on a mission called Solar Probe Plus that will plunge deeply into the sun's atmosphere in an attempt to answer two long-standing questions: why the sun's outer atmosphere, or corona, is about 2 million degrees Fahrenheit hotter than its surface, and why the solar wind -- streams of electrically charged particles that permeate the solar system -- seems to have no organizing force.

Finding the answers will require a spacecraft that can weather temperatures exceeding 2,550 degrees Fahrenheit and radiation levels higher than any other probe has ever faced.

"Solar Probe Plus will actually enter the corona -- that's where the action is," said NASA program scientist Lika Guhathakurta.

At closest approach, the spacecraft would be about 4.3 million miles from the sun -- eight times closer than previous probes -- a vantage point that makes the star appear 23 times wider than it does from Earth. It will be powered by the sun, of course, with liquid-cooled panels that can duck behind a heat shield when the sunlight becomes too intense.

Scientists hope to time the mission so that it launches in 2015, which would be in the waning years of the present solar cycle, and last through the peak of Solar Cycle 25 so that it can sample the sun's corona and winds during different phases.