Picture is the most sensitive solar portrait ever taken in high-energy X-rays.
US Space agency NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, has taken its first picture of the sun, a recent press release by the agency said.
The telescope was launched into space in 2012. Originally, its purpose was to set its eyes on black holes and other objects far from our solar system. But now, it has been able to turn its gaze closer, to the sun and in the process, has taken the most sensitive solar portrait ever taken in high-energy X-rays, the press release noted.
"NuSTAR will give us a unique look at the sun, from the deepest to the highest parts of its atmosphere," said David Smith, a solar physicist and member of the NuSTAR team at University of California, Santa Cruz, US.
While the sun is too bright for other telescopes such as NASA's Chandra X-ray Observatory, NuSTAR can safely look at it without the risk of damaging its detectors. The sun is not as bright in the higher-energy X-rays detected by NuSTAR, a factor that depends on the temperature of the sun's atmosphere.
According to NASA’s press release, the solar image taken by NuSTAR has given insight into questions about the remarkably high temperatures that are found above sunspots—cool, dark patches on the sun. Future images will provide even better data as the sun winds down in its solar cycle. The solar cycle is the periodic change in the Sun's activity (including changes in the levels of solar radiation and ejection of solar material) and appearance (visible in changes in the number of sunspots, flares, and other visible manifestations). Solar cycles have an average duration of about 11 years. They have been observed for hundreds of years.
"We will come into our own when the sun gets quiet," Smith was quoted in the press release, explaining that the sun's activity will dwindle over the next few years.
With NuSTAR's high-energy views, it has the potential to capture hypothesized nanoflares -- smaller versions of the sun's giant flares that erupt with charged particles and high-energy radiation. Nanoflares, should they exist, may explain why the sun's outer atmosphere, called the corona, is sizzling hot, a mystery called the "coronal heating problem." The corona is, on average, 1.8 million degrees Fahrenheit (1 million degrees Celsius), while the surface of the sun is relatively cooler at 10,800 Fahrenheit (6,000 degrees Celsius). It is like a flame coming out of an ice cube. Nanoflares, in combination with flares, may be sources of the intense heat.
If NuSTAR can catch nanoflares in action, it may help solve this decades-old puzzle.
"NuSTAR will be exquisitely sensitive to the faintest X-ray activity happening in the solar atmosphere, and that includes possible nanoflares," said Smith.
NuSTAR, according to the release, can also search for hypothesised dark matter particles called axions. Dark matter is five times more abundant than regular matter in the universe. While dark matter has been indirectly detected through its gravitational pull, its composition remains unknown. The axions would appear as a spot of X-rays in the center of the sun.
NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Virginia.
NuSTAR's mission operations center is at UC Berkeley, and equatorial ground station located at Malindi, Kenya.
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