What happens when two dead stars meet in a deep space? In this case, one devours the other. During the first detection of this type, scientists think they have spotted a black hole swallowing a neutron star. The ability to detect this far-away collision has been made possible by Earth's gravitational wave observatories, a new and recent type of astronomical observation that has become possible only in the last decade.
"Scientists have never detected a black hole lower than five solar masses or neutron star greater than about 2.5 times the mass of our Sun," said Susan Scott, head of the General Theory group. of Relativity and Data Analysis from the Australian National University and Principal Investigator with the ARC Excellence Center for Gravitational Wave Discovery, said in a statement. "Based on this experience, we are confident that we have just detected a black hole engulfing a neutron star.
The event occurred about 8 550 billion kilometers from Earth and was detected by gravitational wave discovery machines in Italy and the United States, called LIGO and Virgo. These devices have detected ripples 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 – eventually smothering the star instantly," said Scott. "The ANU SkyMapper telescope responded to the detection alert and swept the entire area of probable space where the event occurred, but we did not find any visual confirmation. "
Neutron stars are small but incredibly dense. They are formed when stars of a certain mass range collapse under their own gravity, thus overcoming the powerful force that prevents electrons and protons from melting; in these collapses, electrons and protons merge into a neutron ball as dense as an atomic nucleus. Neutron stars generally have a diameter of about 20 kilometers and a mass greater than that of our sun, whose diameter is 1.39 million kilometers.
However, when larger stars collapse, even the neutron repulsion force does not remain intact and said stars collapse into a singularity whose output speed is greater than the speed of light. These are known as black holes.
Collisions between black holes and other stellar objects, such as neutron stars, are one of the most powerful releases of energy from the universe. The amount of gravitational energy released is so vast and it ripples throughout the universe, so that it can be detected by gravitational sensors based on the Earth. Black holes are notoriously difficult for physicists to understand, since we can not "see" them inside; their nature defies such questions because the information can not escape them. Such detections allow astronomers to better understand these difficult-to-understand spatial events.
"We have always thought that there should be binary systems consisting of a black hole and a neutron star going around in space. Therefore, if this event were to be confirmed, it would be the first evidence of such systems and they are getting closer and closer and eventually break, "Scott said.
However, since the event is not confirmed, there are other possibilities. The first is that the smallest object could be a very light black hole.
"We are not aware of any black holes in the universe with masses lower than about five solar masses," Scott said via CNN. "This would raise many new questions such as:" How does a black hole form so light? "
Scientists hope to detect more similar events, to confirm or deny what they observed.
"We can better estimate the size of the population of these systems in the universe and also better understand how these systems" come together "in the first place," Scott said. "On the extended wish list, we were hoping soon to have a supernova that would disappear somewhere in order to capture the gravitational waves expected from this type of event and better model the supernova process."
The last decade has seen historic advances in the knowledge of black holes by humans.
For example, earlier this summer, astrophysicists discovered indirect evidence suggesting that it is possible for supermassive black holes to form without imploding a very large star. Some supermassive black holes develop very quickly in a short period of time, then suddenly stop growing.
Years of advances in imaging technology have also led to the first image of a black hole last spring.
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