New images from NASA's NuSTAR telescope show the 'hidden' light of the Sun, produced by small flares too faint to be observed amid the blazing light of our star. The result, obtained with the contribution of the Italian Space Agency (ASI) to the mission, will help astronomers answer one of the greatest mysteries of the Sun, the paradox of having an atmosphere so much hotter than the surface, as if the air around a fire were hotter than the flames.
A possible explanation of this unexpected overheating could be found in the effects of flares and nanoflares, respectively large and small explosions, in the outermost part of the solar atmosphere (corona). In the case of flares, these eruptions of heat, light and particles are quite regular but not frequent enough to keep the corona at the observed high temperatures. For this reason, it is assumed that the real culprits are the nanoflares.
These small eruptions can occur much more often than flares, probably enough to warm the solar corona thanks to their collective action. However, a single nanoflare is too faint to be observed in the blazing light of the Sun, thus making it very difficult to investigate their actual role in solar activity.
The new mosaic image by NuSTAR, obtained by combining observations made in June 2022, shows (in the form of blue halos) the high-energy X-rays emitted by the high-temperature material that is thought to originate when multiple nanoflares occur close to each other. Now NuSTAR's observations allow solar physicists to study how often these small flares happen and how they release energy.
"NuSTAR is a small mission designed to observe the most violent phenomena that occur in the Universe in high-energy X-rays", explains Simonetta Puccetti, researcher at the Space Research Unit of the Italian Space Agency ASI. "Its high sensitivity has opened a new observational window that has allowed us to expand our knowledge of the physics of black holes, neutron stars and supernovae. Usually, this type of telescope does not directly observe the Sun to avoid damaging the on-board detectors. However, solar radiation is not particularly intense in the energy band of NuSTARr's instruments. Therefore, it was decided to add this new scientific goal to those already achieved by this little gem from NASA. The data obtained will allow us to better understand the physics that governs our star and are already an excellent result, but in the analysis of future
observations we could even identify traces of dark matter". The NuSTAR mission includes a strong contribution from ASI with its Space Science Data Center (SSDC), in the development of the scientific software for data calibration. ASI also supplies the ground station and hosts a mirror of the official data archive
© RIPRODUZIONE RISERVATA
