Astronomers discover the closest black hole to Earth – in our cosmic backyard

Astronomers discover the closest black hole to Earth – in our cosmic backyard

Artist's impression of the closest black hole to Earth and its sun-like companion

Astronomers have discovered the closest known black hole to Earth with the help of the International Gemini Observatory. It is also the first unambiguous detection of a dormant stellar-mass black hole in the Milky Way. Its proximity to Earth, just 1,600 light-years away, provides an intriguing research goal to advance our understanding of the evolution of binary systems. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/J. da Silva/Spaceengine/M. Zamanic

Gemini North telescope in Hawaii reveals first dormant stellar mass[{” attribute=””>black hole in our cosmic backyard.

Using the International Gemini Observatory, astronomers have discovered the closest-known black hole to Earth. This is the first unambiguous detection of a dormant stellar-mass black hole in the Milky Way. Located a mere 1600 light-years away, its close proximity to Earth offers an intriguing target of study to advance our understanding of the evolution of binary systems.

“Take the Solar System, put a black hole where the Sun is, and the Sun where the Earth is, and you get this system.” — Kareem El-Badry

Black holes are the most extreme objects in the Universe. It is believed that supermassive versions of these unimaginably dense objects reside at the centers of all large galaxies. Stellar-mass black holes — which weigh approximately five to 100 times the mass of the Sun — are much more common. In fact, there are an estimated 100 million stellar-mass black holes in the Milky Way alone. However, only a handful have been confirmed to date, and nearly all of these are ‘active’. This means that they shine brightly in X-rays as they consume material from a nearby stellar companion, unlike dormant black holes which do not.

Astronomers have now discovered the closest black hole to Earth, which the researchers have dubbed Gaia BH1. To find it, they used the Gemini North telescope in Hawai‘i, one of the twin telescopes of the International Gemini Observatory, operated by NSF’s NOIRLab.

Gaia BH1 is a dormant black hole that is about 10 times more massive than the Sun and is located about 1600 light-years away in the constellation Ophiuchus. This means it is three times closer to Earth than the previous record holder, an X-ray binary in the constellation of Monoceros. The new discovery was made possible by making exquisite observations of the motion of the black hole’s companion, a Sun-like star that orbits the black hole at about the same distance as the Earth orbits the Sun.

This animation shows a Sun-like star orbiting Gaia BH1, the closest black hole to Earth, about 1,600 light-years away. Observations by Gemini North, one of the International Gemini Observatory’s twin telescopes operated by NSF’s NOIRLab, were crucial in limiting the orbital motion and thus the masses of the two components in the binary system, allowing the team to identify the central body. identify as a black hole about 10 times as massive as our sun. Credit: T. Müller (MPIA), PanSTARRS DR1 (KC Chambers et al. 2016), ESA/Gaia/DPAC

“Take the solar system, put a black hole where the sun is and the sun where the earth is, and you get this system,” explains Kareem El-Badry, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian and the Max Planck Institute for Astronomy, and the lead author of the paper describing this discovery, published Nov. 2 in Monthly Notices from the Royal Astronomical Society.

“While there have been many purported detections of these types of systems, nearly all of these discoveries have subsequently been refuted. This is the first unequivocal detection of a Sun-like star in broad orbit around a stellar-mass black hole in our Milky Way.”

While there are likely millions of stellar black holes roaming the Milky Way galaxy, the few that have been discovered were discovered through their energetic interactions with a companion star. When material from a nearby star whirls towards the black hole, it superheats and generates powerful X-rays and material beams. If a black hole isn’t actively feeding (that is, it’s dormant), it just blends into its environment.

“I’ve been searching for dormant black holes for the past four years using a wide variety of datasets and methods,” says El-Badry. “My previous efforts — as well as others — yielded a menagerie of binary systems masquerading as black holes, but this is the first time the search has paid off.”

“While this may portend future discoveries of the predicted dormant population of black holes in our Milky Way, the observations also leave a mystery to be solved — despite a shared history with its exotic neighbor, why is the companion star in this binary star system so common? ” — Martin Still

The team originally identified that the system may be harboring a black hole through data from the European Space Agency Gaia spacecraft. Gaia captured the tiny irregularities in the star’s motion caused by the gravity of an invisible massive object. To examine the system in more detail, El-Badry and his team turned to the Gemini Multi-Object Spectrograph instrument on Gemini North, which measured the speed of the companion star as it orbited the black hole and provided an accurate reading. of its orbital period. The Gemini follow-up observations were crucial in limiting orbital motion and thus the masses of the two components in the binary system, allowing the team to identify the central body as a black hole about 10 times the mass of our Sun.

“Our follow-up observations of Gemini confirmed beyond a reasonable doubt that the binary star contains a normal star and at least one sleeping black hole,” explains El-Badry. “We could not find a plausible astrophysical scenario that could explain the observed orbit of the system that does not involve at least one black hole.”

The team relied not only on Gemini North’s excellent observation capabilities, but also on Gemini’s ability to provide data within a tight deadline, as the team had only a short period of time to conduct their follow-up observations.

“When we had the first indications that the system contained a black hole, we had only a week left before the two objects were at the closest separation in their orbit. Measurements at this point are essential to make accurate mass estimates in a binary system,” said El-Badry. “Gemini’s ability to make short-term observations was critical to the project’s success. Had we missed that narrow window , we should have waited another year.”

Astronomers’ current models of the evolution of binary systems are difficult to explain how the peculiar configuration of the Gaia BH1 system could have arisen. In particular, the precursor star that later turned into the newly discovered black hole would have been at least 20 times as massive as our sun. This means that it would have only lived a few million years. If both stars formed at the same time, this massive star would have quickly turned into a supergiant, blowing up and engulfing the other star before it had time to become a true, hydrogen-burning main sequence star like our sun.

It’s not at all clear how the solar-mass star survived that episode and eventually ended up as an apparently normal star, as the observations of the black hole’s binary star indicate. Theoretical models that allow for survival all predict that the solar-mass star should have entered a much tighter orbit than what is actually observed.

This could indicate that there are important gaps in our understanding of how black holes form and evolve in binary systems, and also suggests the existence of a still untapped population of dormant black holes in binary systems.

“Interestingly, this system cannot be easily accommodated in standard binary evolution models,” El-Badry concluded. “It raises a lot of questions about how this binary system formed and how many of these dormant black holes exist.”

“As part of a network of space and ground observatories, Gemini North has provided strong evidence not only for the closest black hole to date, but also for the first pristine black hole system, unperturbed by the usual hot gas. interacting with the black hole,” said NSF Gemini Program Officer Martin Still. “While this may portend future discoveries of our Milky Way galaxy’s predicted dormant population of black holes, the observations also leave a mystery to be solved — despite a shared history with its exotic neighbor, why is the companion star in this binary star system so common?”

Reference: “A Sun-Like Star Orbiting a Black Hole” by Kareem El-Badry, Hans-Walter Rix, Eliot Quataert, Andrew W Howard, Howard Isaacson, Jim Fuller, Keith Hawkins, Katelyn Breivik, Kaze WK Wong, Antonio C Rodriguez , Charlie Conroy, Sahar Shahaf, Tsevi Mazeh, Frédéric Arenou, Kevin B Burdge, Dolev Bashi, Simchon Faigler, Daniel R Weisz, Rhys Seeburger, Silvia Almada Monter and Jennifer Wojno, November 2, 2022, Monthly Notices from the Royal Astronomical Society.
DOI: 10.1093/mnras/stac3140

Gemini North sightings were made as part of a director’s discretionary time schedule (Program ID: GN-2022B-DD-202).

The International Gemini Observatory is operated by a partnership of six countries, including the United States through the National Science Foundation, Canada through the National Research Council of Canada, Chile through the National Agency for Research and Development, Brazil through the Ministry of Science and Technology and innovations, Argentina through the Ministry of Science, Technology and Innovation, and Korea through the Korea Astronomy and Space Science Institute. These participants and the University of Hawaii, which has regular access to Gemini, each have a “National Gemini Office” to support their local users.





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