Science

Scientists Just Discovered a Mysterious Object in Space That Could Change What We Know About Black Holes

It falls right in the puzzling “mass gap” where no other object has been found yet.
black hole mass gap
This is the first-ever image of a black hole and its shadow, taken by the Event Horizon Telescope (EHT) and revealed in April 2019. Now, our understanding of black holes and neutron stars might just expand. Image: EHT

Scientists have discovered a mysterious object in space that has never been seen before by humans. In a study published on June 23, scientists claim to have found an unprecedented object that weighs more than most neutron stars but less than black holes.

When the most massive stars die, they collapse under their gravity and leave behind black holes. When smaller stars die, they explode in a supernova and leave behind dense, dead remnants of stars called neutron stars. The heaviest known neutron star is no more than 2.5 times the mass of our sun (2.5 solar masses), and the lightest known black hole is about five times the mass. The gap between the masses of the two is immense. And for decades, astronomers wondered whether dying stars left anything behind that lay in this mysterious “mass gap”.

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This “black neutron star”, detected in August last year but published in a paper just now, falls right in that puzzling “mass gap”.

The object is 2.6 solar masses, putting it right in the middle of the gap between neutron stars and black holes. This mystery object was discovered when it merged with a black hole of 23 solar masses—an event that generated a splash of gravitational waves which were picked up from observatories on Earth.

This object was detected by Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US and the European Virgo observatory, and the paper was published in an international collaboration between the two. “Even though we can’t classify the object with conviction, we have seen either the heaviest known neutron star or the lightest known black hole,” said Vicky Kalogera, who coordinated the writing of the paper, in a statement. “Either way, it breaks a record.”

This exciting and unprecedented finding challenges all astrophysical models that try to explain the event, said Mario Spera, a co-author of the paper. “However, we are quite sure that the universe is telling us, for the umpteenth time, that our ideas on how compact objects form, evolve and merge are still very fuzzy.”

Gravitational waves form when massive objects distort spacetime surrounding them and send ripples out across the universe. Scientists caught the first-ever detection of such waves, formed by two colliding black holes, in 2015. Since then, gravitational wave detections have only gotten stranger. Now, this discovery opens up infinite possibilities for space. It also implies that these events occur much more often than the astronomers had originally predicted. Additionally, the vast disparity in the mass of the object and that of the companion black hole it merged with—which is nine times more massive—seems to challenge theories about how black holes and neutron stars are formed.

How will researchers know what the nature of the mystery object exactly was? The astronomers who conducted the study say they look forward to future observations that may catch similar events.

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