What happens when two dead stars meet in space? In this case one devours the other. At the first discovery of this kind, scientists believe they have discovered a black hole that swallows a neutron star. The ability to detect this distant collision was made possible by Earth's gravitational-wave observatories, a newer and novel astronomical observation made possible only in the last decade.
"Scientists have never discovered a black hole smaller than five solar masses or a neutron star larger than 2.5 times the mass of our Sun," said Susan Scott, director of the General Theory of Relativity and Data Analysis Group Australian National University and Chief Researcher at the ARC Center of Excellence for Gravitational Wave Discovery in a statement. "Because of this experience, we are very confident that we have just discovered a black hole that devours a neutron star.
The event occurred at an estimated distance of 8,550 million trillion kilometers from Earth and was discovered by discovery of gravitational waves in Italy and the United States, called LIGO and Virgo. These devices discovered waves in space and time.
"About 900 million years ago, this black hole ate a very dense star known as a neutron star, like Pac-man ̵
Neutron stars are small but incredibly dense. They arise when stars of a certain mass range collapse due to their own gravity and overcome the strong force that prevents the fusion of electrons and protons. In these breakdowns, the electrons and protons splinter into a sphere of neutrons as dense as an atomic nucleus. Neutron stars usually have a diameter of about 20 kilometers and a mass that is larger than our sun with a diameter of 1.39 million kilometers.
However, when larger stars collapse, not even the repulsive force between neutrons remains intact and the stars collapse into a singularity whose escape velocity is greater than the speed of light. These are known as black holes.
Collisions between black holes and other star objects such as neutron stars are among the most massive energy releases in the universe. The amount of released gravitational energy is so great that it spreads over the entire universe and can be detected by gravitational detectors on Earth. Black holes are notoriously difficult for physicists to understand because we can not "see" them. Their nature escapes such a test because they can not escape information. Discoveries such as these give astronomers a better insight into these difficult-to-understand space events.
"We have always thought that there should be binary systems of a black hole and a neutron star that are mutually confirmed orbiting in space, this would be the first evidence that such systems actually exist and that some of them are getting tighter and tighter grow together and eventually collapse, "said Scott.
However, since the event is unconfirmed, there are other possibilities. One is that the smaller object could be a very bright black hole.
"We do not know any black holes in the universe with masses less than about five solar masses," Scott told CNN. "This would raise many new questions about how to make such a bright black hole."
Scientists hope to discover other similar events to confirm or deny what they have observed.
"We can better estimate the population size of these systems in the universe and also better understand how these systems primarily" come together, "Scott said. "On the extended wish list, we soon hope to have a supernova that runs somewhere nearby so that we can capture the expected gravitational waves of this type of event and better model the supernova process."
This past decade has historically been advances in people's knowledge of black holes.
For example, early this summer, astrophysicists found indirect evidence that supermassive black holes can form without a very large imploding star. Rather, some supermassive black holes grow very quickly within a very short time and then suddenly stop growing.
Years of advances in imaging technology led to the first image of a black hole last spring.
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