Using the Gemini International Observatory, astronomers have discovered the closest known black hole to Earth. It is also the first unequivocal detection of a dormant stellar-mass black hole in the Milky Way. Its proximity to Earth, just 1,600 light-years away, offers an intriguing target for study to advance our understanding of the evolution of binary systems. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/J. da Silva/Spaceengine/M. Zamani
The Gemini North telescope in Hawai’i reveals the first inactive 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, located about 1,600 light-years away. Observations from Gemini North, one of the Gemini International Observatory’s twin telescopes, operated by NSF’s NOIRLab, were crucial in constraining the orbital motion and thus the masses of the two components in the binary system, allowing the team identify the central body as a black hole about 10 times more massive than 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,” explained 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 that was published on November 2 in Royal Astronomical Society Monthly Notices.
“While there have been many detections of systems like this, 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.”
Although there are likely millions of stellar-mass black holes wandering the Milky Way, the few that have been detected were discovered by their energetic interactions with a companion star. As material from a nearby star spirals into the black hole, it superheats, generating powerful X-rays and jets of material. If a black hole is not actively feeding (i.e. it is inactive), it simply blends in with its surroundings.
“I have been searching for dormant black holes for the past four years using a wide range of data sets and methods,” El-Badry said. “My previous attempts, as well as those of others, have resulted in a collection of binary systems masquerading as black holes, but this is the first time the search has paid off.”
“While this bodes potential for future discoveries of the predicted dormant black hole population in our galaxy, 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 system is so normal?” — martin still
The team originally identified that the system potentially harbored a black hole by analyzing data from the of the European Space Agency gaia spaceship. Gaia captured the tiny irregularities in the star’s motion caused by the gravity of an unseen massive object. To explore the system in more detail, El-Badry and his team turned to the Gemini Multi-Object Spectrograph instrument on Gemini North, which measured the velocity of the companion star as it orbited the black hole and provided a precise measurement of its orbital period. . Gemini’s follow-up observations were crucial in constraining the 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 roughly 10 times more massive than our own. Sun.
“Our Gemini follow-up observations confirmed beyond reasonable doubt that the binary contains a normal star and at least one dormant black hole,” El-Badry explained. “We were unable to find any 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 outstanding observing capabilities, but also on Gemini’s ability to provide data on a tight schedule, as the team had only a short window to conduct their follow-up observations.
“When we had the first indications that the system contained a black hole, we only had a week before the two objects were at the closest separation in their orbits. Measurements at this point are essential for making accurate mass estimates in a binary system,” El-Badry said. “Gemini’s ability to provide observations on short notice was critical to the success of the project. If we had missed that narrow window, we would have had to wait another year.”
Astronomers’ current models of the evolution of binary systems are hard-pressed to explain how the peculiar configuration of the Gaia BH1 system could have arisen. Specifically, the progenitor star that later became the newly detected black hole would have been at least 20 times more massive than our Sun. This means that it would have lived for only a few million years. If both stars formed at the same time, this massive star would have quickly become a supergiant, swelling and engulfing the other star before it had time to become a hydrogen-burning main sequence star like our Sun.
It’s not entirely clear how the solar-mass star could have survived that episode, ending up as an apparently normal star, as observations of the black hole binary indicate. All theoretical models that allow for survival predict that the solar-mass star should have ended up in a much tighter orbit than is actually observed.
This could indicate that there are important gaps in our understanding of how black holes in binary systems form and evolve, and also suggests the existence of a still unexplored population of quiescent black holes in binary systems.
“It is interesting that this system does not fit easily into standard models of binary evolution,” El-Badry concluded. “It raises a lot of questions about how this binary system formed, as well as how many of these dormant black holes exist.”
“As part of a network of space and ground-based observatories, Gemini North has not only provided strong evidence of the closest black hole to date, but also of the first pristine black hole system, cleared by the usual hot gas that interacts with the hole. black. said Martin Still, NSF Gemini Program Officer. “While this bodes potential for future discoveries of the predicted dormant black hole population in our galaxy, 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 system is so normal?”
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, Royal Astronomical Society Monthly Notices.
DOI: 10.1093/mnras/stac3140
The Gemini North observations were conducted as part of a director’s discretionary time program (program ID: GN-2022B-DD-202).
The Gemini International 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 Research and Development Agency, Brazil through the Ministry of Science, Technology and Innovation, 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 maintain a “National Gemini Office” to support their local users.
