(ORDO NEWS) — The universe is full of bizarre objects, and now astronomers have discovered a bogeyman – super-heavy neutron stars that only lasted a fraction of a second before collapsing into black holes.
When stars of a certain mass range explode as supernovae, they leave behind a dense core known as a neutron star.
These strange stars fit more than the mass of the sun into a ball the size of a city. They often end up in binary systems, where eventually two neutron stars will spiral inward until they collide to form one object.
What kind of object it is depends on the total mass. A neutron star can have a maximum mass of just over two suns before it collapses under its own gravity and forms a black hole.
Therefore, if the sum of two neutron stars falls below this limit, they form a new neutron star. If the mass is greater, the collision will create a black hole.
In a new study, astronomers have discovered two neutron star mergers that resulted in the formation of black holes.
However, they also detected signals from an intriguing intermediate stage – superheavy neutron stars that exist for only milliseconds.
According to computer simulations of neutron star mergers, if a superheavy neutron star forms, there should be a special pattern in the gravitational waves emitted during the event, known as quasi-periodic oscillations (QPOs).
Although current observatories are not sensitive enough to detect them in gravitational waves, the new study’s team determined that their fingerprints should also show up in gamma rays.
To test this idea, astronomers looked at archived data on 700 short gamma-ray bursts (GRBs) recorded by three observatories over the past few decades.
And, of course, gamma-ray QPOs were detected in two events captured by the Compton Gamma Observatory – one in July 1991 and the other in November 1993.
The team calculated that the discovered superheavy neutron stars would have a mass of more than 2.5 times that of the Sun and would last no more than 300 milliseconds before collapsing into black holes.
They would also spin very fast nearly 78,000 rpm if they lasted that long. By comparison, the fastest pulsar runs at less than 43,000 rpm.
The team says that future gravitational wave detectors should become sensitive enough to directly detect the signatures of superheavy neutron stars, which could help provide new information about these short-lived objects.
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