Compilation / Li Wanhong
Astronomers have discovered a new black hole, about 10 times the mass of the sun, only 1,600 light-years away from the earth, making it the closest black hole to the earth so far. However, researchers believe that there must be closer black holes in the universe, but they have not been discovered yet.
Scientists have only found about 20 black holes in the Milky Way so far. It is estimated that there are more than 100 million black holes lurking in the Milky Way, with a mass between 5 and 100 times that of the sun.
A study published in the Monthly Notices of the Royal Astronomical Society pointed out that there are still a large number of black holes that have not yet been observed, and the newly discovered black holes cannot always have the title of “closest to the earth”.
“There may be many more black holes that are closer.” Astrophysicist Karim Karim of the Harvard-Smithsonian Center for Astrophysics El-Badri told Science News that “just finding one … means there are still a lot of black holes waiting to be discovered.”
NASA explains that most black holes are born from the death of massive stars. When stars about 10 times the mass of the sun or more come to the end of their lives, they disintegrate in powerful supernova explosions, leaving behind at least a few suns’ mass tightly packed into a relatively small space: a black hole. This dense object has an extremely strong gravitational force, and no matter, including light, can escape.
“Time” reported that since light is also swallowed by black holes, scientists cannot directly observe it. But active black holes devour surrounding matter and emit X-rays, which scientists have discovered their existence.
The newly discovered black holes are dormant black holes, which do not absorb matter and therefore do not emit X-rays. “Time” mentioned that dormant black holes are more common, but also harder to find. El-Badri and his research partners also detected clues to the existence of this dormant black hole from the data of the European Space Agency’s “Gaia” space telescope. The Gaia space telescope is currently tracking the positions and movements of stars in the Milky Way.
The National Optical, Infrared Astronomy Research Laboratory (NOIRLab) said scientists noticed that a star in the constellation Ophiuchus was moving in an unexpected way, and realized that there was a gravitational pull from an unknown and massive object behind it. The researchers then used observations from other telescopes, including those operated by the lab, to support the theory that the mysterious object is actually a black hole.
According to Time magazine, the stars near the black hole are about the same size as the sun, and the distance between the two is similar to the distance between the sun and the earth. Researchers aren’t sure why the star wasn’t consumed as its companion star expanded, died and formed a black hole.
“It raises a lot of questions about how binary star systems form, and how many dormant black holes there are,” El-Badri said. ◇