First detection of a “sleeping” black hole in our immediate vicinity

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In October, the closest X-ray black hole to us was discovered. Recently, the Gemini North telescope in Hawaii discovered a new black hole just 1,600 light-years from Earth. This is the first inactive stellar mass black hole in our backyard. Its proximity to Earth offers an interesting target to study to further our understanding of the evolution of binary systems.

Black holes are the most extreme objects in the universe. It is generally accepted that at the center of all galaxies there is probably a supermassive black hole, millions or billions of times more massive than the Sun, but scientists do not know their exact origin.

However, the latter believe that smaller black holes are formed from massive stars that have collapsed after the thermonuclear phase of life. Because of this, these stellar-mass black holes — roughly 5 to 100 solar masses — are much more common, with about 100 million in the Milky Way alone.

Note that they can be identified by the X-rays emitted when they consume material from a nearby stellar companion in binary star systems. Despite such intense brightness, only a few have been confirmed so far. Unlike these “active” black holes, dormant black holes do absolutely nothing: they don’t attract nearby stars or material. So no x-rays come out, they remain invisible.

Recently, astronomers using the Northern Gemini Telescope in Hawaii, one of the twin telescopes of the International Gemini Observatory operated by NSF’s NOIRLab, discovered the closest sleeping black hole to Earth, dubbed Gaia BH1. It is about 10 times more massive than the Sun and is located about 1600 light-years away in the constellation of Ophiuchus, making it three times closer to Earth than the previous record holder, an X-ray binary located in the constellation of Ophiuchus. Unicorn. The study was published in the Monthly Notices of the Royal Astronomical Society.

sleeping black hole

The team was able to determine the presence of the black hole by observing the movement of its companion, a sun-like star that orbits the black hole at about the same distance as the Earth orbits the sun.

Karim El-Badri, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics and the Max Planck Institute for Astronomy and lead author of the study, explains in a press release: “Take the solar system, put a black hole where the Sun is, and the Sun is where the Earth is, and you get this system. Although there have been many claims about the discovery of such systems, almost all of these discoveries have subsequently been refuted. This is the first unequivocal detection of a sun-like star in a wide orbit around a stellar-mass black hole in our galaxy.”

As mentioned earlier, while there are probably millions of stellar-mass black holes in the Milky Way, those that have been detected were discovered due to their energetic interactions with a companion star that generates powerful X-rays and jets of matter. If a black hole is not actively feeding (that is, idle), it simply merges with the environment.

Time limited search

The team initially identified the system as potentially containing a black hole by analyzing data from the European Space Agency’s Gaia spacecraft. This image captures tiny bumps in the motion of a star caused by the gravity of an invisible massive object.

To study the system in more detail, El-Badri and his team turned to the Gemini Multi-Object Spectrograph instrument at Gemini North, which has good observational qualities and speed. This was due to the fact that the team had very little time for follow-up observations.

El-Badri notes: “When we had the first signs that there was a black hole in the system, we had only one week before the two objects were as close as possible in their orbits. Measurements at this stage are necessary for accurate estimates of the mass in the binary system. Gemini’s ability to make observations over a short period of time was essential to the success of the project. If we missed this narrow window, we would have to wait another year.”

In this way, the team was able to measure the speed of the companion star as it orbited the black hole and get an accurate measurement of its orbital period. The researchers also identified the central body as a black hole about 10 times as massive as the Sun.

Valuable information about binary systems

Unfortunately, modern astronomical models of the evolution of binary systems cannot explain how a particular configuration of the Gaia BH1 system could have arisen. In particular, the star that gave rise to the newly discovered black hole must have been at least 20 times more massive than the Sun. This means that he would have lived for only a few million years.

The authors explain that if two stars were to form at the same time, this massive star would quickly become a supergiant, inflating and engulfing the other star before it could become a true mainstream hydrogen-burning sequence star like our Sun.

Scientists are stumped as to whether a solar-mass star was able to survive this episode, turning into a seemingly normal star. All theoretical survival models conclude that the latter must have ended up in a much narrower orbit than the observed one.

Thus, it becomes obvious that there are significant gaps in our understanding of the formation and evolution of black holes in binary systems, which also suggests the existence of an as yet unexplored population of dormant black holes in binary systems.

Monthly Notices of the Royal Astronomical Society.

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