The NuStar observatory is usually used to find black holes far from our Solar System, but astronomers have now utilized the tool to examine our own sun. These observations reveal the pattern of X-rays emitted by our local star.
The Nuclear Spectroscopic Telescope Array (NuSTAR) , together with Japan's Hinode observatory, were used to create the new composite photograph. High-energy X-rays recorded by NuStar are seen in blue in the new images, while lower-energy radiation, recorded by Hinode, is seen in green.
Solar flares, massive eruptions of radiation and charged particles, can be seen in the regions where X-rays are prominent. However, NuStar would be overwhelmed by large flares, preventing direct observation of these features using that instrument. Instead, astronomers hope to use the tool to discover more about microflares, which produce one-millionth the energy of a typical flare.
Researchers also hope to utilize the instrument to see nanoflares, theoretical formations of gas 1,000 times smaller than microflares. These formations could emit electrons at extremely high velocities, producing X-rays that could be seen by NuStar. Some astrophysicists believe these nanoflares could be responsible for heating the atmosphere, or corona, of the sun, driving temperatures there significantly higher than the surface of our parent star. Astronomers have long wondered how the space surrounding the sun could be hotter than the surface of the star.
The sun goes through a 22-year-long cycle, as sunspots become more and less common over the course of 11 years, before the magnetic fields of these formations flip for another 11 years. Astronomers will need to wait until the sunspot cycle is at a minimum before nanoflares are likely to be detected.
"Our sun is quieting down in its activity cycle, but still has a couple of years before it reaches a minimum," Iain Hannah of the University of Glasgow said.
NuStar images of our sun could be used by astronomers to determine where energy is emitted by flares, as well as the process responsible for the release. Some researchers hope NuStar could be used to detect axions, a theoretical subatomic particle associated with dark matter. Such a finding could help astrophysicists learn more about this mysterious form of matter that is five times more common in the universe than the ordinary atoms that make up stars and planets.
"What's great about NuSTAR is that the telescope is so versatile that we can hunt black holes millions of light-years away and we can also learn something fundamental about the star in our own backyard," said Brian Grefenstette from the California Institute of Technology.
