The black hole watchers find a dormant black hole outside our galaxy
In addition, they have found that the star that gave rise to the black hole disappeared without any sign of a powerful explosion
The finding is published in an article in the journal Nature Astronomy, with the participation of researcher Mark Gieles from the Institute of Cosmos Sciences (ICCUB) and the IEEC
An international team of astronomers, dubbed the ‘black hole police’, has found an inactive stellar-mass black hole in the Large Magellanic Cloud, a galaxy close to the Milky Way. Named VFTS 243, the black hole was discovered thanks to six years of observations carried out with the Fibre Large Array Multi-Element Spectrograph (FLAMES) instrument on the European Southern Observatory's (ESO) Very Large Telescope (VLT). The discovery has been recently published in the prestigious journal Nature Astronomy.
"For the first time, our team came together to report the discovery of a black hole, rather than to deny one," says Tomer Shenar, the lead researcher of the study who started at the Catholic University of Leuven (Belgium) and who is now a Marie-Curie fellow at the University of Amsterdam (the Netherlands). "We have found a needle in a haystack," he adds. Although other similar black holes have been proposed, the team claims that this is the first ‘dormant’ stellar-mass black hole to be unambiguously detected outside our galaxy.
Stellar-mass black holes form when massive stars reach the end of their lives and collapse under their own gravity. A black hole is considered to be ‘dormant’ when it does not emit high levels of X-ray radiation (the most common way to detect black holes). These types of black holes are particularly difficult to detect, as they do not interact much with their surroundings.
To find VFTS 243, the collaboration analysed approximately 1,000 massive stars in the Tarantula Nebula region of the Large Magellanic Cloud to find those that might be accompanied by black holes. Identifying these companions as black holes is very difficult as there are many alternative options. The one that has now been discovered, VFTS 243, is at least nine times the mass of the Sun and orbits a hot, blue star (O-type) that weighs twenty-five times the mass of our star.
On the background, a VISTA (Visible and Infrared Survey Telescope for Astronomy) telescope
image of a segment of the Large Magellanic Cloud (LMG), marking the region in which the
black hole VFTS 243 resides. The zoom-in shows an artist's impression of the binary system:
an O star + a black hole with a (near-)circular orbit. The sizes of the star, black hole, and orbits
are not to scale. Credits: background image, ESO / M.-R.Cioni / VISTA LMG survey; visualization,
Isca Mayo / Sara Pinilla.
This finding gives the team a unique insight into the processes that accompany the formation of black holes: astronomers believe that a stellar-mass black hole forms when the core of a massive dying star collapses, but it is not yet known whether this is accompanied by a supernova explosion. The team has also found that the star that gave rise to the now-discovered black hole disappeared without any sign of a violent explosion.
In a binary system, a system of two stars orbiting each other, there is the possibility of finding a black hole from the motion of a luminous companion star. "From the nearly circular orbit of the binary in which we found VFTS 243, we could conclude that this black hole did not receive a velocity bump when it formed in a supernova explosion, something that helps us to better understand the origin of the gravitational waves observed by the LIGO-Virgo detectors,” says ICREA professor Mark Gieles, researcher at the Institute of Cosmos Sciences of the Universitat de Barcelona (UB), member of the Institute of Space Studies of Catalonia (IEEC — Institut d'Estudis Espacials de Catalunya) and of the Department of Quantum Physics and Astrophysics of the UB. Gieles is co-author of the paper and leads the ICCUB's Virgo gravitational wave research group, which analyses and interprets the increasing number of detected collisions of compact objects, such as binary black holes.
"The star that formed the black hole VFTS 243 appears to have collapsed completely, with no sign of any previous explosion," explains Shenar. "Recently, evidence for this ‘direct collapse’ scenario has emerged, but our study offers what is surely one of the most direct indications. This has major implications for the origin of black hole mergers in the Cosmos."
Despite the nickname ‘black hole police’, the team actively encourages scrutiny, and hopes that this work will lead to finding other stellar-mass black holes orbiting massive stars, of which there are predicted to be thousands in the Milky Way and Magellanic Clouds.
Researchers of the Instituto de Astrofísica de Canarias (IAC) and of the Universidad de La Laguna (UL) are also participating in the work, carried out by around forty experts from all over the world.
Press release prepared in collaboration with the Institutional Communication Unit of the Universitat de Barcelona (UB).
Main Image
Binary system with black hole
Caption: Artist's rendering of a binary system in which one of the two objects is a black hole.
Credit: ESO/L. Calçada.
Links
More information
This research is presented in a paper entitled “An X-ray-quiet black hole born with a negligible kick in a massive binary within the Large Magellanic Cloud”, by Shenar, T. et al., that appears published in the journal Nature Astronomy on 17 July 2022. Doi: 10.1038/s41550-022-01730-y.
The Institute of Space Studies of Catalonia (IEEC — Institut d’Estudis Espacials de Catalunya) promotes and coordinates space research and technology development in Catalonia for the benefit of society. IEEC fosters collaborations both locally and worldwide and is an efficient agent of knowledge, innovation and technology transfer. As a result of 25 years of high-quality research, done in collaboration with major international organisations, IEEC ranks among the best international research centers, focusing on areas such as: astrophysics, cosmology, planetary science, and Earth Observation. IEEC’s engineering division develops instrumentation for ground- and space-based projects, and has extensive experience in working with private or public organisations from the aerospace and other innovation sectors.
IEEC is a private non-profit foundation, governed by a Board of Trustees composed of Generalitat de Catalunya and four other institutions that each have a research unit, which together constitute the core of IEEC R&D activity: the Universitat de Barcelona (UB) with the research unit ICCUB — Institute of Cosmos Sciences; the Universitat Autònoma de Barcelona (UAB) with the research unit CERES — Center of Space Studies and Research; the Universitat Politècnica de Catalunya · BarcelonaTech (UPC) with the research unit CTE — Research Group in Space Sciences and Technologies; the Spanish Research Council (CSIC) with the research unit ICE — Institute of Space Sciences. IEEC is a CERCA (Centres de Recerca de Catalunya) center.
Contacts
IEEC Communication Office
Barcelona, Spain
E-mail: comunicacio@ieec.cat
Lead Researcher at IEEC
Barcelona, Spain
Mark Gieles
Institute of Space Studies of Catalonia (IEEC)
Institute of Cosmos Sciences of the Universitat de Barcelona (ICCUB)
E-mail: mgieles@ieec.cat, mgieles@icc.ub.edu