Astronomers discover Gaia BH3, the largest “sleeping giant” black hole ever discovered in the Milky Way

Astronomers discover Gaia BH3, the largest “sleeping giant” black hole ever discovered in the Milky Way

This dormant black hole, which apparently hasn’t torn apart its companion star, is 1,926 light-years from Earth. Pasquale Panuzzo of France’s National Center for Scientific Research (CNRS) is part of a team of astronomers who regularly process data from Gaia, Europe’s star-mapping observatory. However, I noticed a recurring wobble. It appeared as if a constant gravitational pull from an unknown companion star was interfering with the star’s movement. And indeed, follow-up observations from Earth-based observatories have confirmed that the star is wobbling thanks to a very large but previously undetected black hole. This cosmic monster weighs about 33 times the mass of the Sun, making it the most massive stellar black hole ever discovered in the Milky Way. “It was a really big surprise when we found it,” recalls Panuzzo, lead author of the new study that describes the discovery. “When [the team] saw it, there was a constant ‘wow’.” Gaia BH3 is the second-closest known black hole to Earth The newly discovered black hole, a powerful light-trapping abyss named Gaia BH3, lurks just 1,926 light-years from Earth in the constellation Aquila. (It’s the second-closest black hole to Earth after Gaia BH1, which is 1,500 light-years away and three times lighter than Gaia BH3.) Unlike its companions, the so-called “sleeping giant” — as it’s called — is dormant and black. The hole isn’t a sparkling companion star ripping apart, but rather a manifestation of the imminent collapse of a once-massive star. The new study, published in April in the journal Astronomy and Astrophysics, marks the first direct connection between a black hole and a protostar that lacks any metals heavier than hydrogen or helium.

The discovery supports an influential theory of stellar evolution that suggests that supermassive black holes are the remains of stars with little to no metal. These metal-poor stars have weaker mass-eroding winds than metal-rich stars, so they have more material to form more massive black holes. Astronomers typically announce scientific discoveries at the same time they release data, in this case by early 2026, but “you can’t hide this kind of discovery from the community for two years,” Panuzzo said. says. “This is a unique case of publication based on preliminary data, as the data are exceptional and of great interest to the community.” Stars near Gaia BH3 Analyzing the star’s spectrum, they found that the star rocked by Gaia BH3 was a “completely peaceful, metal-poor, ancient star” that likely formed in the first billion years after the Big Bang. paper. The chemical composition of the companion star revealed from its spectra shows that it is composed primarily of hydrogen and helium. Many other elements are present, such as calcium, carbonium, and europium, but their abundance is several hundred times smaller than that found in the Sun. Because stars in binary systems usually form in the same star cluster, the black hole’s progenitor star would also have been metal-poor, Kafour said.

Surprisingly, the companion star does not appear to be “polluted” by the collapse of the black hole’s massive progenitor as would be expected when one star in a binary system dies, says Caffau. “We don’t see anything.”

She predicts the companion star, which has already evolved to its penultimate puffy nature, will eventually shed its outer layers and leave behind a tiny white dwarf, following the same fate that awaits our sun about 6 billion years from now after it runs out of fuel.

Panuzzo says there are other dormant black holes his team spotted while processing the latest Gaia data, although “none of those we saw are as spectacular as this one,” he says. A survey by Gaia of faint stars in our galaxy they are currently reviewing “will for sure have surprises.”