NASA's newest satellite aims to solve a burning mystery about the sun's atmosphere, one that confounds scientists and seems to flout the laws of physics: why the temperature goes up as distance from the surface increases.

The outer layer of the solar atmosphere, called the corona, extends more than one million kilometres from the surface. Given the distance, that corona’s temperature should decrease, but it does the opposite: while the sun’s surface temperature reaches approximately 5,500 C, the corona temperature soars to over 1,000,000 degrees.

The satellite, dubbed IRIS (Interface Region Imaging Spectrograph), launched over the Pacific Ocean Wednesday to begin a two-year mission studying that unusual energy transfer from the surface to the outer atmosphere. It will aim an ultraviolet telescope at the "interface region" between the surface and the corona, which emits most of the sun’s ultraviolet radiation.

"We are thrilled to add IRIS to the suite of NASA missions studying the sun," NASA spokesman John Grunsfeld said in a press release. "IRIS will help scientists understand the mysterious and energetic interface between the surface and corona of the sun."

Deputy project scientist Adrian Daw added that NASA is "bound to see something we didn't expect to see."

NASA also hopes IRIS can shed new light on solar flares and other phenomena.

The seven-foot craft will orbit 620 kilometres above Earth, crossing from the south to the north pole in a circuit that allows for eight months of continuous viewing per year with minimal obstruction from eclipses.