The night sky above us is strewn with stars. An ordinary observer may get the impression that the stars are always shining and never disappear without a trace. Unless their luminosity can change, or if they are massive enough, they explode with the bright light of a supernova. However, astronomers have documented at least 800 cases of star disappearance over the past 70 years. Sometimes observers saw a star in the sky, and the next day it disappeared forever.
New research led by astronomers from the University of Copenhagen and published in the journal Physical Review Letters suggests that these stars, due to their massiveness, turn into a black hole, where any evidence of their existence instantly disappears.
“Were one to stand gazing up at a visible star going through a total collapse, it might, just at the right time, be like watching a star suddenly extinguish and disappear from the heavens. The collapse is so complete that no explosion occurs, nothing escapes and one wouldn’t see any bright supernova in the night sky,” explains study co-author Alejandro Vigna-Gómez from the Niels Bohr Institute.
When a massive star that is at least eight times heavier than the Sun dies, it collapses almost instantly under the weight of its own gravity. This usually causes a supernova, which releases so much energy that it can eclipse the galaxy. After that, a black hole or neutron star is formed. However, sometimes this explosive stage is bypassed. If a star turns out to be too massive, it collapses directly into a black hole.
This theory of “total collapse” is not new in astronomy. But new research provides some of the most compelling evidence to support it. The evidence comes from observations of the binary star system VFTS 243, where a star with ten times the mass of the Sun and a black hole orbit each other. According to Vigna-Gómez, this is an extraordinary system because it contains almost no signs of a supernova. “The orbit of the system has hardly changed since the collapse of the star into a black hole,” he added.
Astronomers have not found any signs of a natal kick, an acceleration that occurs during an explosion. In fact, there was no evidence of a violation of the orbit of the two objects. Instead, the researchers say, most of the energy is lost through neutrinos, subatomic particles that interact weakly with gravity.
Much more work is needed to finally solve this mystery, but these findings serve as an important test of stellar evolution models.
Earlier we explained why the stars were not visible in space photos.
According to sciencedaily.com
