Sun Dazzles In First-Ever NuSTAR High-Energy X-Ray Portrait

The sun dazzled like a Christmas tree in hues of reds, greens and blues in its first-ever portrait taken in high-energy X-rays this week. NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, was built in 2012, chiefly to observe distant high-energy phenomena like supernovas and black holes. But the extraordinary image released by the space agency on Monday proved the supersensitive telescope can also capture our home star and could potentially solve a long-standing mystery.

"At first I thought the whole idea was crazy," Fiona Harrison, NuSTAR’s lead scientist, said in a statement this week. "Why would we have the most sensitive high-energy X-ray telescope ever built, designed to peer deep into the universe, look at something in our own back yard?"

The sun is too bright for other telescopes, like NASA’s Chandra X-ray Observatory. But NuSTAR’s mirrors and detectors block out much of the glare. This is the first solar portrait ever taken by NuSTAR, according to a press release from NASA. “It’s just a fluke that because of the way that NuSTAR is designed … it is able to look at the sun without damaging it,” Harrison of the California Institute of Technology in Pasadena told the Los Angeles Times.

The different colors in the solar portrait reveal the varying high-energy emissions detected by the supersensitive telescope, though NuSTAR can detect up to 79 kiloelectron volts. The green shades depict energies between 2 and 3 kiloelectron volts, while the blues show energies between 3 and 5 kilo electron volts. These high-energy X-rays that stream off the sun come from gas heated to above 3 million degrees.

The red represents ultraviolet light and lower-temperature material at 1 million degrees captured by NASA’s Solar Dynamics Observatory. The NuSTAR’s green and blue image was then overlaid onto the Solar Dynamics Observatory’s red, according to NASA. “That’s what resulted in this really beautiful image, which I think I’m going to make on my Christmas card next year,” Harrison told the Los Angeles Times on Thursday.

The space telescope’s high-energy views could finally determine how the sun’s corona — the thin, pearly atmosphere that surrounds the star — somehow heats to an average of 1.8 million degrees Fahrenheit, while the sun’s surface heats to a mere 10,800 degrees. Scientists suspect tiny solar flares — or nanoflares— jumping off the sun’s surface could be the reason, according to research by the Harvard-Smithsonian Center for Astrophysics. NuSTAR could help get to the bottom of this so-called “coronal heating problem” and other mysteries which have baffled scientists, like dark matter, according to NASA.

"NuSTAR will be exquisitely sensitive to the faintest X-ray activity happening in the solar atmosphere, and that includes possible nanoflares," David Smith, solar physicist and member of the NuSTAR team, said in a statement this week.