Two of the closest black holes to Earth have been discovered.

The locations of two black holes in the Milky Way galaxy. Image: ESA

Two recently discovered black holes are located very close to Earth and may represent a mysterious, previously unknown group of massive objects. An international team of astronomers discovered the black holes using data from the European Space Agency's (ESA) Gaia mission, combined with data from a range of ground-based telescopes around the world . They published their research in the journal Monthly Notices of the Royal Astronomical Society, Live Science reported on April 4th.

Named Gaia BH1 and Gaia BH2, these two black holes are the closest to Earth ever discovered, according to the ESA. Gaia BH1 is located 1,560 light-years from the Solar System, in the constellation Ophiuchus, more than three times closer than the previous record held by black hole A0620-00. Gaia BH2 is located 3,800 light-years in the constellation Centaurus. Both black holes are approximately 9-10 times the size of the Sun and are located within the Milky Way galaxy.

Astronomers take a long time to detect such large black holes because they are almost invisible. In the past, scientists searched for black holes by examining the remnants of their most recent meal. When a star or interstellar gas cloud falls into a black hole, it leaves behind bursts of electromagnetic radiation. This allows astronomers to detect the existence of the black hole, according to NASA.

But unlike previous findings, Gaia BH1 and 2 were completely dark. They appeared to be not consuming anything in the present and were utterly motionless. Instead, the research team found the black hole by carefully tracking the movement of two sun-like stars orbiting them. The stars oscillated slightly as they moved through space, indicating that something with strong gravitational pull was drawing them in. When the researchers examined the area with telescopes, they couldn't identify anything emitting radiation. The only explanation was the existence of a black hole.

Although both black hole systems were discovered in late 2022, the astronomy team began to appreciate their uniqueness. New research indicates that, unlike X-ray binary systems, where star-black hole pairs orbit very close together, emitting X-rays and radio waves, Gaia BH1 and Gaia BH2 likely represent a previously unseen group of black holes. They are located far from their companion star, according to Kareem El-Badry, a researcher at the Harvard-Smithsonian Center for Astrophysics. The research team hopes that Gaia's next data release in 2025 will help uncover more dormant black holes and how they form.

Source: VNE

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