NASA’s NuSTAR telescope has revealed the 'hidden light' of the Sun!

Human eyes cannot see all the light that our nearest Star emits. A new image shows part of this hidden light, including high-energy X-rays emitted by the hottest material in the Sun’s atmosphere, as observed by NASA’s Nuclear Spectroscopic Telescope Array (nustar). Although the telescope typically studies objects outside our solar system, such as huge black holes and collapsed stars, it has also provided astronomers with information about our Sun.

Credits, NASA/JPL-Caltech/JAXA

In the image above, the nustar data is represented in blue and is superimposed on the observations of the X-ray Telescope (XRT) on the Hinode mission of the Japanese Aerospace Exploration Agency, represented in green, and the Atmospheric Imaging Assembly ( AIA ) on NASA’s Solar Dynamics Observatory (SDO), shown in red. The relatively small field of view of nustar does not allow it to observe the entire Sun from its position in Earth orbit, so the image is actually a mosaic of 25 images, taken in June 2022. The high-energy X-rays observed by nustar appear only at a few points in the solar atmosphere. In contrast, Hinode’s XRT detects low-energy X-rays, and SDO’s AIA detects ultraviolet light.

The mysteries of our Star

The point of view of nustar could help scientists solve one of the greatest mysteries about our nearest star: because the outer atmosphere of the Sun, called the corona, reaches more than a million degrees, at least 100 times warmer than its surface. This has puzzled scientists because the heat of the Sun originates in its core and travels outwards. It’s like the air around a fire is 100 times hotter than the flames.

The heat source of the corona may be small eruptions in the Sun’s atmosphere called nanoflares. Regular flares do not occur often enough to maintain the corona at the high temperatures observed by scientists, but nanoflares can occur much more frequently, perhaps often enough to massively heat the corona. Although individual nanoflares are too weak to be observed in sunlight, nustar is able to detect light from the high-temperature material that is thought to be produced when large numbers of nanoflares occur close to each other. This ability allows physicists to study the frequency with which nanoflares occur and how they release energy.

Source: NASA