Astronomers Find A Black Hole Closest To Earth
Astronomers find a black hole closest to earthabout 1,600 light-years from Earth, making it the nearest such object yet found. On Friday, scientists announced that this black hole is 10 times bigger than our sun. That's a new record for proximity by a factor of three.
The black hole was discovered by tracking the orbit of a companion star that travels at about the same speed as Earth does around the sun. According to Kareem El-Badry of the Harvard-Smithsonian Center for Astrophysics, the European Space Agency's Gaia probe was responsible for the original discovery of the black hole.
Before publishing their results in Monthly Notices of the Royal Astronomical Society, El-Badry and his colleagues double-checked them with the International Gemini Observatory in Hawaii. Scientists can't say for sure what caused the Milky Way's system to develop. Gaia BH1 is a star in the constellation of Ophiuchus, the Serpent-Bearer.
Black Holes Are Not Common In Milky Way
Gas is often stolen from big companion stars and consumed by black holes. This gas clusters around the black hole to create a disk that emits strong X-ray light. However, black holes with an appetite for matter are not the most prevalent kind in the Milky Way.
Black holes that are calm when they are not in the middle of a meal are far more common than astronomers realize. So far, allegations that such black holes have been found have not been verified.
Astronomer Kareem El-Badry and his team needed an accurate map of the locations of billions of stars, so they consulted recently published data from the Gaia satellite. A star that orbits a black hole far enough away to avoid being devoured will still experience the back-and-forth tug of the black hole's gravity, though.
Supermassive black holes, which are millions or billions of times more massive than the sun, can be found in the center of almost every galaxy, but their origin is a mystery. Massive stars that have reached the end of their thermonuclear lifetimes and imploded are assumed to be the origin of smaller black holes.
It's estimated that the Milky Way is home to millions of black holes. In double-star systems, they often reveal themselves by their X-ray emissions when they siphon gas from their partners.
By observing the star's velocity, astronomers may infer the existence of a black hole. One star out of thousands that seemed to be being pulled by something invisible was a promising candidate for a black hole.
Evolution Of Black Holes
As it stands, astronomers' existing theories of the development of binary systems have a hard time explaining how the unique structure of the Gaia BH1 pair could have formed. This newly discovered black hole would have had a progenitor star at least 20 times as big as our Sun.
That limits its lifespan to only a few million years. If the two stars had formed at the same time, the more massive one would have expanded into a supergiant and swallowed the other before the latter could complete its evolution into a normal, hydrogen-burning, main-sequence star like our Sun.
As can be seen from the measurements of the black hole pair, it is not at all evident how the solar-mass star could have survived that incident and emerged as an apparently normal star. In all theoretical models that allow for survival, the solar-mass star is expected to wind up in a considerably more tightly confined orbit than is actually seen.
This implies the possibility of a population of latent black holes in binaries, which might be an indication of significant knowledge gaps on black hole formation and evolution in binary systems.
Final Thought
The next closest black hole to Earth is some 3,200 light-years distant, making Gaia BH1 the closest one yet detected. This is probably not the closest we'll find, and it may not even be the closest that exists.
The Milky Way is home to an estimated 100 million black holes, most of which are undetectable to the naked eye. Gaia's next data release is scheduled for 2025, and El-Badry anticipates that it will include a plethora of new black holes.
