A mysterious object about 800 million light-years from Earth detected by gravitational wave sensors is one of the smallest black holes or one of the largest neutron stars discovered so far, scientists said Wednesday.
Virgo’s advanced detector at the European Gravitational Observatory (EGO) in Italy and two wave observatories in the United States discovered the object last year and calculated it to weigh about 2.6 times our own Sun.
That places him in the “mass gap” of the Universe, referring to the virtually complete lack of observed objects between 2.6-5 solar masses.
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They said the object was formed when another unknown body merged with a large black hole about 800 million years ago, emitting a huge detectable gravitational wave on Earth.
Both neutron stars and black holes form when very massive stars burn their nuclear fuel and explode in phenomena known as supernovae.
Stars with lighter nuclei tend to form neutron stars. However, the heaviest ones collapse into black holes, the mass of which is so condensed that its gravity absorbs dust and gas from the surrounding galaxies.
The team behind the investigation, published in The Astrophysical Journal Letters, said there were several possible explanations for the object’s unique nature.
Chief among them is that the original object may have been a relatively small neutron star that was effectively “swallowed whole” by a black hole.
“I think of Pac-Man eating a little point,” said Vicky Kalogera, a researcher at the LIGO network of observatories and a professor at Northwestern University.
“When the masses are highly asymmetric, the smallest neutron star can be eaten in one bite,” said Kalogera.
Gravitational waves, whose existence was predicted by Albert Einstein, carry energy as gravitational radiation, allowing detection teams to extrapolate the mass of what created them.
Since its gravitational wave is evidence of its formation, the researchers said the discovery of the object questions the existence of the mass gap.
“The Universe firmly tells us that we are still missing most of the history of compact object formation and evolution and that we may need to revisit some of our current ideas about compact object formation,” said Mario Spera, a researcher at the Padua University.
