The points of purple light in the image above are bright X-ray emissions, blazing from super-hot gas swirling within binary star systems in M51, the Whirlpool Galaxy. Over 232 hours of observation time with NASA’s Chandra X-ray Observatory have revealed hundreds of these X-ray binaries (XRBs) within M51 — the brightest of them being created by hungry black holes.
When matter spirals around a massive black hole, rapidly falling in toward its event horizon, it gets accelerated to near-relativistic velocities (that’s how astrophysicists say “close to the speed of light”) and gets so incredibly hot that it emits radiation in X-ray wavelengths, visible across vast distances of the Cosmos.
In XRBs, a super-dense supermassive object like a black hole or neutron star is partnered with a less massive star, from which it draws in material. This convenient and energetic source of food fuels the XRBs, making them exceptionally X-ray bright.
Because the Whirlpool Galaxy just happens to be angled top-down to ours we can get a good view into it — even from 30 million light-years away. These new observations have uncovered five times as many XRBs than had previously been observed in M51, and show that an imminent collision with a smaller galaxy (seen above at upper left) may be responsible for the continuing formation of more stars and thus more XRBs.
The more diffuse purple glow in the image is from interstellar gas and dust within the arms of M51 that has been heated by supernova explosions.
Source: Chandra X-ray Observatory