Feeling Cosmically Small?

Black holes have been observed engulfing a neutron star for the first time ever, according to scientists.

Two of the extraordinarily rare events - that happened just 10 days apart - were witnessed by a team of researchers in January 2020, and the findings have just been published in the Astrophysical Journal Letters.


Black holes are the most extreme objects in the universe and are so dense that nothing can escape their enormous gravitational pull, not even light. They are formed when an enormous star many times the size of the Sun reaches the end of its lifespan and simultaneously explodes - a supernova - while its core collapses in on itself to form an ultra-dense entity.


Neutron stars are formed in a similar way, but only arise at the end of the lifespan of stars up to three times the mass of our Sun. These are big enough to go supernova, but small enough to avoid becoming a black hole.


In January last year, black holes were observed engulfing a neutron star for the first time ever, to the wild excitement of scientists.


"These collisions have shaken the Universe to its core and we've detected the ripples they have sent hurtling through the cosmos," said Prof Susan Scott, a co-author on the study based at the Australia National University.


"Each collision isn't just the coming together of two massive and dense objects. It's really like Pac-Man, with a black hole swallowing its companion neutron star whole. These are remarkable events and we have waited a very long time to witness them. So it's incredible to finally capture them. We've now seen the first examples of black holes merging with neutron stars, so we know that they're out there," said Dr Maya Fishbach, co-author of the paper from the LIGO Scientific Collaboration.

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"But there's still so much we don't know about neutron stars and black holes - how small or big they can get, how fast they can spin, how they pair off into merger partners. With future gravitational wave data, we will have the statistics to answer these questions, and ultimately learn how the most extreme objects in our universe are made."

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