When we gaze up at the night sky, we are likely expecting to see stars, planets and constellations. But, perhaps not black holes.
In a groundbreaking finding, astronomers have discovered the presence of a previously unknown black hole within the Milky Way galaxy, over 33 times heavier than our sun. Gaia BH3, the “sleeping giant” – which it seems astronomers have been “sleeping on ” for years – is now being deemed the second closest black hole to Earth in the Milky Way, situated only 2,000 light-years away from our planet.
The giant is not to be confused with the notorious “Sagittarius A”; the most massive black hole known to scientists at the center of our galaxy. Rather, Gaia BH3 is the biggest “stellar” black hole in the Milky Way. The difference between the two black holes traces back to their births, when stellar black holes, like Gaia BH3, form when massive stars die. Supermassive black holes, like Sagittarius A, have more murky beginnings, though likely are born when massive cosmic clouds of dust and gas collapse.
Gaia BH3 is also not the only stellar black hole known by scientists, as roughly 10 million are expected to exist in the Milky Way alone. Its sheer size, however, and more importantly rarity to spot, makes the discovery so remarkable. “Most [stellar black holes] don’t have a star orbiting around them, so they are almost invisible to us,” says Dr. Pasquale Panuzzo, an astronomer and member of the Gaia collaboration at the Observatoire de Paris. The lack of light generated by the black holes causes them to be nearly impossible to spot, until now.
Astronomers discovered the black hole while covering observations taken by the European Space Agency’s (ESA’s) Gaia space telescope for an upcoming data release. The astronomers were not intending to find anything new until a “peculiar motion” garnered their attention, caused by Gaia BH3’s gravitational influence on a nearby companion star. While stellar black holes usually remain invisible, material from companion stars and exchanges of matter can release X-rays that can be spotted through telescopes, causing the discovery of black holes like Gaia BH3.
Gaia BH3, though a seemingly scary neighbor, poses no threat to Earth’s citizens. Rather, it sparks a new curiosity and excitement for ordinary stargazers and Astronomers alike, piquing interest in what other “giants” could lurk in our galaxy. The finding has especially caused ripples in the Astronomy community and is considered so important that scientists released details of the hole earlier than intended to enable other astronomers to collect further observations as soon as possible. While humans may have already stepped foot on the moon over half a century ago, we are not nearly close to unearthing all the secrets that our galaxy holds.
