Scientists have studied the closest, largest, brightest galaxies to Earth for centuries.
Messier 51, the Whirlpool Galaxy, is one of astronomy’s most spectacular objects.
This enormous, face-on galaxy was the first one ever to reveal its spiral structure.
The small object alongside it, the galaxy NGC 5195, is interacting and merging with the Whirlpool galaxy.
Such mergers trigger new waves of star formation, create grand spiral arms, and activate supermassive black holes.
Both galaxies pull on each other, funneling gas onto each central black hole.
This matter then accelerates and gets ejected along powerful jets, producing X-ray emissions.
Prior studies with NASA’s Chandra X-ray telescope showed fewer X-rays than expected.
Exploring higher energies, NuSTAR still showed the same missing X-ray problem.
Excessive emission isn’t present in these cores; the galactic centers are even outshone by outlying neutron stars.
This is problematic, according to lead author Murray Brightman:
Galactic mergers are supposed to generate black hole growth, and the evidence of that would be strong emission of high-energy X-rays. But we’re not seeing that here.
These results imply black holes flicker on and off more rapidly than anticipated.
Further research is needed; the mystery remains unsolved for now.