The surface temperature of the Sun is about 6,000 Kelvins, while the outer edge of the Sun’s atmosphere, called the corona, can reach millions of Kelvins. Normally, we think of things cooling down the farther they get from an energy source… So how can temperature increase with distance from the Sun’s surface?

The Interface Region Imaging Spectrograph (IRIS) spacecraft launches from the Vandenberg Air Force Base in California on June 27th, with the intention of studying how the corona gets so hot.

“I wonder if maybe we were staring too hard at the corona to understand the corona,” says IRIS scientist Charles Kankelborg, a physicist at Montana State University. “It may be that by backing out we can get some vital clues to what’s happening.”

Between the Sun’s surface and the corona lies a layer of plasma called the chromosphere. Scientists hope that studying this area of lower atmosphere will help them uncover the reason behind the Sun’s strange temperature patterns.

From Earth, we can only observe the layer in question during a total solar eclipse, when the Moon blocks the Sun, and observers can see the halo of glowing light behind the Moon. For IRIS to see this section of sun, it will take images at temperatures between 4,500 Kelvins and 65,000 Kelvins, and ultraviolet spectra between 4,5000 Kelvin and 107 Kelvin.

IRIS is specially designed to target this little understood region of the Sun’s atmosphere. The spacecraft will follow a polar orbit—always facing the Sun—to trace the flow of energy and plasma from the lower layer of the Sun’s surface through the chromosphere and into the corona. Detailed information on this process could give astronomers an archetype for other stellar atmospheres.

Dr. Alan Title, IRIS principal investigator and physicist at the ATC Solar and Astrophysics Laboratory in Palo Alto, is excited for the launch. “With IRIS, we have a unique opportunity to provide significant missing pieces in our understanding of energy transport on the Sun. The complex processes and enormous contrasts of density, temperature and magnetic field within this interface region require instrument and modeling capabilities that are now finally within our reach.”

The launch takes place on Thursday, so the newest data about our closest star are coming soon!

You can watch the launch here at 6:00pm PDT!

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA

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