?The discovery of two black holes closest to Earth, what distinguishes them
April 8, 2023April 8, 2023 Gaia BH1, Gaia BH2, x-rays, star clusters, binary black hole, black holes, gravity, astrophysics, orbit, black hole, astronomy, x-ray astronomy, Gaia (spacecraft), binary star, double stars
A team of astronomers has made a groundbreaking discovery of two black holes that are the closest to Earth known to date. The black holes, named Gaia BH1 and Gaia BH2, were found in data collected by the European Space Agency's Gaia spacecraft. Gaia BH1 is located 1,560 light-years from Earth in the constellation Ophiuchus, while Gaia BH2 is located 3,800 light-years away in the constellation Centaurus. These black holes are unique in that they orbit stars much more distant than those observed in the black hole's other companion star pairs.
Discovery team leader Karim El-Badri from the Harvard-Smithsonian Center for Astrophysics and the Max Planck Institute for Astronomy in Germany explained that what distinguishes these black holes from others is their wide separation from their companion stars.
Classic black hole companion star systems are known as X-ray binaries, which are usually bright in high-energy X-ray and radio emissions. The discovery of Gaia BH1 and Gaia BH2 is significant because they are both completely dark and were detected through the gravitational influence they had on their companion stars.
The discovery team suspects that these black holes have a different formation history than X-ray binaries, which means that existing theories about the evolution of binary star systems must be adapted.
Gaia's data is crucial for discovering "invisible" black holes because it can accurately measure the position and motion of billions of stars in the background sky. This allows the detection of gravitational effects exerted by other stars, orbiting planets and black holes on these stars.
Gaia's precision in measuring the position and motion of these stars makes it the ideal tool for detecting these "invisible" black holes. The team plans to discover massively separated black hole binary systems in the next data dump obtained by Gaia, due to start this new study in 2025.
This discovery is exciting because it means that black holes with wide orbits are more common in space than binaries where the black hole and star are close together. However, detecting them remains a challenge. The team is optimistic that the next Gaia data release will contain many more of these stars along with their mysterious black hole companions.
The findings of this study are detailed in a paper published in Monthly Notices of the Royal Astronomical Society.
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