The universe is full of strange objects. And now, astronomers have discovered a superheavy neutron star that existed for only a fraction of a second before collapsing into a black hole.
When a star of a certain mass range explodes as a supernova, it leaves behind a dense core known as a neutron star. These strange stars weigh more than the mass of the Sun and are packed into balls the size of cities. They often end up in binary star systems, eventually spiraling inward until two neutron stars collide and he forms a single celestial body.
What that object is depends on its total mass. A neutron star can have a maximum mass of slightly more than her two Suns before collapsing under its own gravity to form a black hole. So if the sum of two neutron stars falls below that limit, they will form a new neutron star. If the mass is large, the collision will create a black hole instead.
In a new study, astronomers have detected two mergers between neutron stars that lead to black holes. But they also found an intriguing intermediate-stage signal – a superheavy neutron star that only exists for a few milliseconds.
According to computer simulations of neutron star mergers, if a superheavy neutron star were to form, a specific pattern known as quasi-periodic oscillations (QPOs) should occur in the gravitational waves emitted during the event. Current observatories are not sensitive enough to detect these in gravitational waves, but a new team of researchers determined that their fingerprints should also appear in gamma rays.
To test this idea, astronomers scanned archival data of 700 short gamma-ray bursts (GRBs) captured by three observatories over the past few decades. And sure enough, the gamma-ray QPO appeared in two of his events (July 1991 and November 1993) captured by the Compton Gamma-ray Observatory.
The team calculated that the detected superheavy neutron star had more than 2.5 times the mass of the Sun and lasted no more than 300 milliseconds before collapsing into a black hole. It should also have been spinning at a very high speed. If it had lasted this long, it would have made about 78,000 revolutions per minute. By comparison, the fastest spinning pulsar clocks less than 43,000 rpm.
The team said future gravitational-wave detectors should be sensitive enough to find direct traces of superheavy neutron stars, which could help provide new information about these short-lived objects. I’m here.
A study was published in a journal NatureA simulation of the merger of two neutron stars can be seen in the video below.
Neutron star merger simulation by gamma-ray observation
Source: NASA
