Astronomers discovered an inactive black hole in a massive star cluster called NGC 3201 in the Vela constellation.
The black hole was identified thanks to the European Southern Observatory’s Very Large Telescope in Chile. This telescope is equipped with an instrument called MUSE which detected unusual behavior coming from a star as it was “being flung backward and forwards at speeds of several hundred thousand kilometers per hour”. According to the scientists, this pattern would repeat every 167 days.
The paper published in the journal, Monthly Notices of the Royal Astronomical Society, states how the black hole is the first of its kind to ever be detected in this type of star cluster.
Globular star clusters consist of tens of thousands of stars collected in a spherical shape. They are considered to be the most ancient types of stellar systems.
While the star was being moved by the black hole 4.36 times the Sun’s mass, it was not being swallowed by the behemoth. This made scientists assume that the black hole is inactive, meaning that it is not currently eating up matter.
According to the lead author of the study, Benjamin Gieser, previous scientific consensus established that black holes would disappear from a globular star cluster after a period of time. Giesers said that the newest discovery sheds light on the formation of globular clusters and the evolution of black holes.
NGC 3201 is just one of the many star clusters orbiting the Milky Way. The globular formation is located at an estimated 16.300 light-years away from the sun. So far, scientists have been able to pinpoint 150-star clusters in our galaxy. According to the paper, NGC 3201 is over 10.2 billion years old.
There are other theories that would suggest that the cause behind the star’s unusual behavior is not a black hole but rather two tightly bound neutron stars, with the observed star orbiting around them. However, according to the study, the neutron stars would have to be at least twice the sun’s mass.
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