A winged Pegasus rocket lifted a compact solar observatory into orbit around Earth’s poles Thursday, kicking off a $181 million mission to shed light on a major mystery: What heats up the sun’s outer atmosphere to extreme temperatures and how that, in turn, affects Earth’s space weather.
NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will focus on the dynamic zone between the sun’s 6,000-degree visible surface — the photosphere — and the tenuous corona, which is somehow heated to more than a million degrees over a span of a few thousand miles.
Scientists hope to gain insights into the energy transport mechanisms that drive the solar wind — the supersonic stream of atomic particles blasted away from the sun — solar flares and explosive eruptions known as coronal mass ejections that occasionally disrupt power grids, satellite operations and communications on Earth.
“What we want to discover is what the basic physical processes are that transfer energy and material from the surface of the sun to the outer atmosphere of the sun, the corona,” Alan Title, IRIS principal investigator at Lockheed Martin’s Advanced Technology Center, told reporters before launch.
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“The visible surface (is) the place where virtually all of the light that leaves the sun leaves from. Immediately above that, the temperature rises to the million-degree corona. How that happens is a mystery. What are the processes that occur there?”
Making the program’s 42nd flight, the Orbital Sciences Pegasus XL rocket was carried aloft from Vandenberg Air Force Base, Calif., by an L-1011 carrier jet.
The Orbital Sciences “Stargazer” jet carried the 51,000-pound rocket to a pre-determined drop point over the Pacific Ocean and, after final tests were completed, released the Pegasus at a planned altitude of 39,000 feet at 10:27 p.m. EDT (GMT-4; 7:27 p.m. local time).