Invisible to the naked eye lies a mighty force at the center of a starry metropolis.
The brilliant star cluster Messier 4, the closest cluster to Earth some 6,000 light-years away, contains hundreds of thousands of stars. It’s a sight to behold. Now NASA has used its legendary Hubble Space Telescope to reveal what is likely a black hole, about 800 times the mass of the sun, at the center of the star cluster.
“You can’t do this kind of science without Hubble,” Eduardo Vitral of the Space Telescope Science Institute, which manages the instrument’s science missions, said in a statement.
Black holes aren’t evil cosmic vacuum cleaners, and other misconceptions
This black hole is rare: it’s not a small black hole, the type of rogue object that roams our galaxy (scientists believe there’s a huge one 100 million of these in our Milky Way galaxy alone). And it’s not one of the monstrous “supermassive” black holes that sit at the center of galaxies – like Sagittarius A* – weighing millions of times more than the sun (astronomers have captured a rare image of this object giant of the Milky Way). Rather, the new observation is a curious “intermediate-mass” black hole, an oddity that scientists have many questions about – like why could they be so rare?
Black holes contain unimaginable mass, with gravitational forces so strong that not even light can escape. How, then, did the researchers reveal evidence of an invisible object? They looked at Hubble’s observations of Messier 4 over a 12-year period, observing how stars moved near the cluster’s core, “like bees swarming around a hive,” NASA explained.
Credit: NASA/ESA/Hubble
The research, recently published in the Royal Astronomical Society Monthly Notices, determined that the motions of stars were likely influenced by a strong center of gravity. They could not realistically explain the behavior of stars from other forces, such as dense stars near the core. The evidence points to a singular black hole, something relatively small in the middle of the larger Messier 4.
“It’s too small for us to otherwise explain that it’s a single black hole,” Vitral noted.
You can see the stars dance around the core of the star cluster in the NASA video below, 50 seconds in:
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The case of the curious force at the center of Messier 4 is still ongoing, however. Although the evidence for a black hole is compelling, there is always a chance that other forces are at play, such as previously unknown star activity and physics.
Hubble will monitor.
