What happens when two dead stars meet in deep space? In this case, one swallows the other. At the first discovery of its kind, scientists believe they noticed a black hole engulfing a neutron star. The ability to detect this distant collision was given by the Earth's gravity observatories of gravitational waves, a recent and new kind of astronomical observations that has only become possible in the last decade.
"Scientists have never found a black hole smaller than five solar masses or a neutron star larger than about 2.5 times the mass of our Sun," says Susan Scott, group leader for a general theory of relativity and data analysis at the Australian National University and a principal investigator at the Center for Excellence in Gravity Wave ARC, said in a statement . "Based on this experience, we are very confident that we have just discovered a black hole that raises a neutron star.
The event occurred approximately 8.550 million trillion kilometers from Earth and was discovered by gravitationally detecting wave machines in Italy and the United States called LIGO and Virgo. These devices 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 a human from Pak – it is possible to remove the star immediately," Scott said. "The ANU SkyMapper telescope responded to the opening warning and scanned the entire probable area of the space where the event occurred, but we did not find any visual confirmation."
The neutron stars are small in size but incredibly dense. They are formed when stars of a certain mass range collapse on their own gravity, overcoming the powerful force that protects electrons and protons from fusion; at these breakdowns, the electrons and protons are smashed together into a neutron ball as tightly as an atomic nucleus. Neutron stars tend to be about 20 kilometers in diameter with a mass larger than our Sun, which is 1.39 million kilometers in diameter.
However, when the larger stars collapse, even the repulsive force between the neutrons remains intact, and the said stars collapse into a singularity whose escape velocity is greater than the speed of light. They are known as black holes.
Collisions between black holes and other star objects, such as neutron stars, represent some of the most massive energy releases in the universe. The gravitational energy released is so huge and pulsating throughout the universe that it can be detected by ground gravity detectors. Black holes are notoriously difficult to understand for physicists, provided we cannot "see" inside them; their nature refutes such a study as information cannot escape them. Detections like these give astronomers more insight into these difficult to understand cosmic events.
"We have always thought that there should be binary black hole and neutron star systems circling each other in space, so if this event is confirmed, this would be the first proof that such systems actually exist and that some of them spin closer and closer and eventually break up together, "Scott said.
However, since the event is unconfirmed, there are other possibilities, one is that the smaller object can be a very light black hole.
"We are not aware of any black holes in a universe with masses of less than about five solar masses, "Scott said through CNN." This would raise many new questions such as: "how is such a bright black hole formed?"
Scientists hope to find more
"We can better assess the population of these systems in the universe and also better understand how these systems" come together "in the first place," Scott said . "In the expanded wish list, we would soon hope to have a supernova that comes out somewhere close so that we can capture the expected gravitational waves of this type of event and better model the supernova process."
This last decade there is historical progress in terms of human knowledge about black holes.
For example, earlier this summer astrophysicists discovered circumstantial evidence suggesting that it is possible to form supermassive black holes without a very large star being deposited. Rather, some supermassive black holes grow very fast for a very short period of time and then suddenly stop growing.
Years of advancement in imaging technology also led to the first image of a black hole last spring.