An international team of astronomers has discovered the closest black hole to earthlocated about 1,600 light-years away, using the Gemini North telescope in Hawaii.
According to scientists, this is the first detection of a stellar-mass black hole in the Milky Way, whose proximity offers a unique study target to advance the understanding the evolution of binary systemsThe NoirLab research center, which operates the telescope, reported in a statement.
Black holes are the most extreme objects in the universe. Supermassive versions of these unimaginably dense astronomical objects may lie at the center of the largest galaxies. However, stellar-mass black holes, weighing approximately five to 100 times the mass of the Sun, are much more common in the universewith an estimated number of them around 100 million in the Milky Way alone.
However, to date only a few have been confirmed, almost all of them active, which means that “glow” brightly in X-rays as they consume material from a nearby stellar companion, unlike dormant black holes that don’t, like the newly discovered one.
Astronomers have named this dormant black hole as BH1. It weighs about 10 times the mass of the Sun and is located in the constellation Ophiuchus. At 1,600 light-years, it is three times closer to our planet than the previous record holder, an X-ray binary located in the constellation Monoceros.
The discovery was made possible by precise observations of the movement of the black hole companiona Sun-like star that orbits the Sun at roughly the same distance as Earth from the Sun.
Astronomers’ current models of the evolution of binary systems cannot fully explain how the peculiar configuration of the Gaia BH1 system came to be, because the original star that later became this black hole should have been at least 20 times more massive than our Sun.
This means that it would have lived only a few million years. If both stars formed at the same time, this massive star would have quickly become a supergiant, inflating and engulfing the other star before it had time to become a proper main-sequence star, which it burns hydrogen just like our Sun.
It’s not entirely clear how the solar-mass star survived that episode, ending up an apparently normal star, as observations indicate. All theoretical models that allow for this survival predict that the solar-mass star should be in a much narrower orbit than is actually observed.
This could indicate that there are important gaps in our understanding of the formation and evolution of black holes in binary systems, and suggests the existence of a still unexplored population of dormant black holes in binary systems.