Gaia has discovered a mysterious new type of black hole – and two Earths are hiding in the cosmic backyard -Se

ESA’s Gaia mission helped make a new discovery black hole. The new family already has two members, and both are closer to Earth than any other black hole we know of.

A team of astronomers studied the orbits of stars tracked by Gaia and noticed that some of them were wobbly in the sky, as if they were gravitationally affected by the massive object. Several telescopes searched for the object, but no light was found, leaving only one possibility: black holes.

An ambitious mission to chart a three-dimensional map of our galaxy, the Milky Way, in the process of revealing the galaxy’s formation, formation and evolution. Credit: ESA-D. Ducros, 2013

A new population of black holes

Using data from ESA’s Gaia mission, astronomers have discovered not only the closest, but also the second-closest black hole to Earth. The black holes, Gaia BH1 and Gaia BH2, are located just 1560 light-years away in the Ophiuchus constellation and 3800 light-years away in the Centaurus constellation, respectively. In galactic parlance, these black holes reside in our cosmic backyard.

Two black holes were discovered by studying the motions of their companion stars. A strange ‘double’ in the movement of the stars in the sky indicates that they are orbiting a very massive object. In both cases, the objects are about ten times more massive than our Sun. Other explanations for these massive companions, such as double-star systems, were ruled out because they did not appear to emit any light.

Star ‘doubles’ in the sky are caused by the gravitational pull of other stars, exoplanets or black holes. The attractor in this image is an exoplanet. Credit: ESA

Until recently, all black holes astronomers knew were discovered through the emission of light — usually at X-ray and radio wavelengths — produced by reading material. New black holes are truly black and can only be detected by their gravitational effects. The distance of stars from black holes and the orbits of stars around them is much greater than that of black holes and other known binary systems of stars. These nearby star-black hole pairs, called X-ray binaries, are very bright in X-ray and radio light and thus easy to find. But new discoveries suggest that black holes are more common in massive binaries.

“What distinguishes this new group of black holes from the ones we already knew about is their wide separation from their companion stars. These black holes probably have a completely different formation history than X-ray binaries,” explained Karim El-Badri, the discoverer of the new black hole and a researcher at the Harvard-Smithsonian Center for Astrophysics and the Max-Planck Institute for Astronomy in Heidelberg, Germany.

ESA’s Gaia mission helped discover a new type of black hole. The new family already has two members, and both are closer to Earth than any other black hole we know of. Two black holes were discovered by studying ultra-precise measurements of stellar positions and motions in Gaia’s third data release. A strange ‘double’ in the movement of two stars in the sky indicates that they are orbiting a very massive object. In both cases, the objects are about ten times more massive than our Sun. Other explanations for these massive companions, such as double-star systems, were ruled out because they did not appear to emit any light. Gaia’s second black hole, BH2, is located 3800 light-years from Earth. It is a binary system consisting of a red giant star and possibly a black hole. In this animation of Gaia BH2 made in Gaia Sky, the orbits are scaled correctly, but the diameter of the back hole is not to scale. Credit: ESA/Gaia/DPAC, CC BY-SA 3.0 IGO

Movement of billions of stars

Black holes were discovered using Gaia data. Gaia accurately measures the positions and motions of billions of stars. The movement of stars against the sky can provide essential clues about the objects that gravitationally influence these stars. These objects may include other stars, exoplanets, and black holes.

“The correctness Gaia data were essential for this discovery. Black holes have been detected by observing the tiny wobbles of their companion stars as they orbit around them. No other instrument is capable of such measurements,” said Timo Prousti, ESA’s Gaia project scientist.

Gaia provided accurate measurements of motion in three directions, but to understand more precisely how stars move away and toward us, additional radial velocity measurements were needed. Ground-based observers provided these for newly found black holes, and this led to the conclusion that astronomers had detected the black hole.

Invisible black holes

Black holes often do not disappear completely. When material falls on them, they can emit radio and X-ray light. For Gaia’s second black hole, NASAIts Chandra X-ray Observatory and South Africa’s Meerkat radio telescope looked for this light on the ground, but they found no signal.

“Even though we didn’t detect anything, this information is incredibly valuable because it tells us a lot about the environment around a black hole. There’s a lot of particles coming from the companion star in the form of the stellar wind. But since we didn’t see any radio light, that tells us the black hole is a massive “It’s not a eater and many particles aren’t crossing its event horizon. We don’t know why that is, but we want to find out!” said Yvette Sandes who helped discover the second black hole and is an astronomer at the Harvard-Smithsonian Center for Astrophysics in the US.

The new type of black hole emits no light, making them virtually invisible, possibly because they are so far away from their companion stars. Gaia BH1 and Gaia BH2 have the most widely separated orbits of all known black holes. The fact that they are also the closest black holes to Earth suggests that many more similar black holes in wide binaries still await discovery.

“This is very exciting because it now implies that these wide-orbiting black holes are actually common in space—where black holes and stars are more common than nearby binaries. But the problem is detecting them. The good news is that Gaia is still taking data, and its next data release ( 2025) will contain many more stars, including a companion to a mysterious black hole,” Yvette explained.

Gaia’s next data release will be based on 66 months of observations and will contain improved information on the star’s orbit. In the meantime, astronomers will be busy trying to figure out where these wide-orbiting black holes come from.

Karim El-Badri noted: “We suspected that black holes might exist in extended systems, but we weren’t sure how they formed. Their discovery means that our theories about the evolution of binary star systems need to be adapted because it is still not clear how these systems form.”

“Gaia’s Data Processing and Analysis Consortium is developing methods to detect astrometric binaries with compact companions. We hope to provide a good sample of candidates in the next Gaia data release,” said team member Sevi Mazeh of Tel Aviv University. The scientific community looks forward to further expanding this new population of dormant black holes.

On June 13, 2022, Gaia released, for the first time, the results of its non-single star processing. The Gaia binary star survey surpasses all work on binary stars in the past two centuries. These two black holes were found by searching for two solutions from this catalog of over 813,000 binary star systems. The Gaia data release is expected to further increase the accuracy of 4 binary star solutions, possibly revealing many more exciting candidates for follow-up.

References: Karim El-Badri, Hans-Walter Ricks, Yvette Sandes, Antonio C. Rodriguez, Charlie Conroy, Eliot Quatert, Keith Hawkins, Eleonora Zari, Melissa Hobson, Katelyn Breivik, Arne Renu, by “A Red Giant Orbiting a Black Hole” ” Edo Berger, Sahar Shahaf, Rhys Seeberger, Kevin B. Berg, David W. Latham, Lars A. Buchave, Alison Biarilla, Dolev Bashi, Sevi Mazeh, and Simchon Feigler, 30 Mar. 2023, Monthly Bulletin of the Royal Astronomical Society.
DOI: 10.1093/mnras/stad799