‘Black neutron star’ discovery changes astronomy
Scientists have discovered an astronomical object that has never been observed before.
It is more massive than collapsed stars, known as “neutron stars”, but has less mass than black holes, BBC News reported.
Such “black neutron stars” were not thought possible and will mean ideas for how neutron stars and black holes form will need to be rethought.
The discovery was made by an international team using gravitational wave detectors in the US and Italy.
Charlie Hoy, a PH.D. student from Cardiff University, UK, involved in the study, said the new discovery would transform our understanding.
“We can’t rule out any possibilities,” he told BBC News. “We don’t know what it is and this is why it is so exciting because it really does change our field.”
Hoy is part of an international team working for the Ligo-virgo Scientific Collaboration.
The international group has laser detectors several kilometers long that are able to detect minute ripples in spacetime caused by the collision of massive objects in the universe.
The collected data can be used to determine the mass of those objects involved.
Last August, the instruments detected the collision of a black hole 23 times the mass of our Sun with an object of 2.6 solar masses.
That makes the lighter object more massive than the heaviest type of dead star, or neutron star, previously observed — of just over two solar masses. But it was also lighter than the lightest black hole previously observed — of around five solar masses.
Astronomers have been searching for such objects in what they’ve come to call the “mass gap.”
Writing in the journal The Astrophysical Journal Letters, the research team believes that of all the possibilities, the object is most likely to be a light black hole, but they are not ruling out any other possibilities.
Having collided with the large black hole, the object no longer exists. However, there should be further opportunities to learn more about these mass-gap objects from future collisions, according to Professor Stephen Fairhurst, also at Cardiff.
“It is a challenge for us to determine what this is,” he told BBC News. “Is this the lightest black hole ever, or is it the heaviest neutron star ever?”
If it is a light black hole then there is no established theory for how such an object could develop. But Fairhurst’s colleague, Professor Fabio Antonioni, has proposed that a solar system with three stars could lead to the formation of light black holes. His ideas are receiving increased attention following the new discovery.
If, however, this new class of object is a heavy neutron star then theories for how they form may also need to be revised, according to Professor Bernard Schutz of the Max Planck Institute for Gravitational Physics in Potsdam, Germany.
“We don’t know a lot about the nuclear physics of neutron stars. So, people who are looking at exotic equations that explain what goes on inside them might be thinking, ‘maybe this is evidence that we can get much heavier neutron stars’.”
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