agencies
Friday, 07 April 2023 07:00 PM
Astronomers have discovered two new black holes that are closest to Earth, and also represent something astronomers have not seen before. The black holes, called Gaia BH1 and Gaia BH2, were found in data collected by the European Space Agency (ESA) Gaia spacecraft.
According to RT, Gaia BH1 is located only 1,560 light-years from Earth in the direction of the constellation Ophiuchus, while Gaia BH2 is located 3,800 light-years away in the constellation Centaurus. Cosmically speaking, both black holes are in Earth’s backyard.
However, it is not only the proximity of these black holes to Earth that makes them unusual, as stars orbit them at much greater distances than previously observed in black hole-companion double star systems.
“What distinguishes this new group of black holes from those we already knew is their wide separation from their companion stars,” discovery team leader Karim El-Badry, of the Harvard-Smithsonian Center for Astrophysics in Massachusetts and the Max Planck Institute for Astronomy in Germany, said in a statement.
Star systems associated with a “normal” black hole are called X-ray binaries (X-ray binaries) and are usually bright in high-energy X-ray and radio emissions. This is easier to find than black holes, which do not swallow matter and therefore do not emit strong signals of energy.
It is noteworthy that the black holes Gaia BH1 and Gaia BH2 are completely dark and were discovered through the gravitational influence on their companion stars.
“These black holes likely have a very different formation history than an X-ray binary,” El-Badri explained. “We suspected that black holes could exist in larger systems, but we weren’t sure how they formed. Their discovery means that we must adapt our theories about the evolution of binary star systems.” It is not yet clear how these systems form.
And Gaia is equipped to make such discoveries because it can precisely measure the position and motion of billions of stars against the background sky.
Scientists said that tracking this stellar movement accurately indicates the gravitational effects exerted on these stars by other stars, and planets orbiting planets and black holes.
“The accuracy of the Gaia data was essential to this discovery,” said Timo Prosti, Gaia project scientist at the European Space Agency. “The black holes are found by observing the tiny wobble of their companion star as it orbits it. No other instrument is capable of making such measurements.”
Gaia’s observations were supported by measurements of the motion of each companion star by other observatories. For example, follow-up investigations of Gaia BH2 with NASA’s Chandra X-ray Observatory and the South African MeerKAT radio telescope on Earth revealed that there is no detectable light coming from this black hole.
“Although we haven’t detected anything, this information is very valuable because it tells us a lot about the environment around the black hole,” said discovery team member Yvette Cendez, from the Harvard-Smithsonian Center for Astrophysics.
She added: “There are a lot of particles that come out of the companion star in the form of stellar winds. But since we did not see any radio light, this tells us that the black hole is not a great eater and that many particles do not cross its event horizon. We do not know the reason for this, But we want to know.”
Gaia BH1 and Gaia BH2 have the most sparse orbits of all known black holes. The fact that they are the closest known black holes to Earth indicates that many similar black holes in massive binaries are still waiting to be discovered.
The team will now try to detect similar systems in the next data file from Gaia, due for release in 2025. This new data will be based on 66 months of observations from the spacecraft and will contain more detailed information about the motion of the stars.
“This is very exciting,” Cendes concluded, “because it now indicates that these black holes in wide orbits are already common in space, and more common than binaries where the black hole and companion star are closer. But the problem is figuring them out. The good news is that Gaia is still It takes the data, and the next data release will contain many more of these stars that have mysterious black hole companions in them.”
The results of the discovery of these two black holes are published in the Monthly Notices of the Royal Astronomical Society.