NASA’s newest high-energy X-ray telescope has released two stunning images of a stellar explosion and ravenous black holes.
NuSTAR is the first high-energy X-ray telescope capable of producing eye candy. Two new images released this week at the American Astronomical Society showcase the telescope’s hundredfold increase in sensitivity over previous instruments.
The first image shows Cassiopeia A, the remnant of a 300-year-old stellar explosion. Since it’s only 1,000 light-years away, the supernova remnant has been studied in beautiful detail at many wavelengths. The Chandra X-ray Telescope, for example, has previously imaged Cassiopeia A at low X-ray energies. But examining Cassiopeia A at higher energies has never been possible before: previous high-energy X-ray telescopes haven’t had NuSTAR’s spatial resolution at these energies, so when the scopes looked at Cas A they would have seen only a fuzzy dot. NuSTAR, on the other hand, shows a panorama of the wispy tendrils that surround the central cinder of a star.
NuSTAR’s view provides more than just a pretty picture. The NuSTAR team is mapping out the presence of titanium-44, a radioactive element produced in supernova explosions. Stars make titanium-44 in a critical layer, inside of which the star collapses into a neutron star or black hole, and outside of which the star throws material off in a spectacular display. Once the NuSTAR team completes Cas A’s titanium-44 map, they’ll be able to reconstruct the original explosion.
Ultraluminous X-ray Sources
NuSTAR’s second image release shows the glow of two feeding black holes in nearby galaxy IC 342. The purple hot spots in the spiral arms are termed ultraluminous X-ray sources because they shine with an intensity that can’t easily be explained. They could be “intermediate-mass” black holes weighing thousands of Suns, or they could be ordinary stellar-mass black holes feeding at enormous rates. Either way, ULXs represent something exotic because astronomers don’t understand how intermediate-mass black holes grow, nor do they understand how ordinary stellar-mass black holes could feed at such high rates.
NuSTAR didn’t discover these ULXs — the Chandra X-ray Observatory did that. But NuSTAR adds crucial high-energy information that is going to help sort out which exotic mechanism is behind these brilliant X-ray sources.