Press release: Odd behaviour of a star
Nr. 12/2018 - 17.01.2018
Researchers discover first inactive black hole in giant star cluster
(pug) An international team of astronomers led by the University of Göttingen has discovered the first inactive black hole in the heart of a giant star cluster. The researchers noticed the strange behaviour of a star that appears to be orbiting an invisible black hole with about four times the mass of the Sun. In addition, the observation marks the first time that a black hole has been found by directly detecting its gravitational pull. The results were published in Monthly Notices of the Royal Astronomical Society.
Globular star clusters are huge spheres of tens of thousands of stars that orbit most galaxies. They are among the oldest known stellar systems in the Universe and date back to near the beginning of galaxy growth and evolution. More than 150 are currently known to belong to the Milky Way. Using ESO’s MUSE instrument on the Very Large Telescope in Chile, the researchers studied star cluster NGC 3201 in the southern constellation of Vela. They noticed that one of the stars was behaving very oddly: It was being flung backwards and forwards at speeds of several hundred thousand kilometres per hour, with the pattern repeating every 167 days.
“The star was orbiting something that was completely invisible and which had a mass more than four times the Sun – this could only be a black hole,” says Benjamin Giesers, PhD student at Göttingen University’s Institute for Astrophysics and lead author of the study. With funding by the Federal Ministry of Education and Research, Göttingen University played a large role in constructing and building ESO’s MUSE instrument. The instrument provides astronomers with a unique ability to measure the motions of thousands of far away stars at the same time. The researchers were able to estimate the black hole’s mass through the movements of the star caught up in its enormous gravitational pull.
The relationship between black holes and globular clusters is an important but mysterious one. Because of their large masses and high ages, these clusters are thought to have produced a large number of stellar-mass black holes – created as massive stars within them exploded and collapsed over the long lifetime of the cluster. “Until recently, it was assumed that almost all black holes would disappear from globular clusters after a short time and that systems like this should not exist,” says Giesers. “Our findings help to understand the formation of globular clusters and the evolution of black holes and binary systems, which is vital in the context of understanding the sources of gravitational waves.”
Original publication: Benjamin Giesers et al. A detached stellar-mass black hole candidate in the globular cluster NGC 3201. Monthly Notices of the Royal Astronomical Society 2018. Doi: 10.1093/mnrasl/slx203.
Contact:
Benjamin Giesers
University of Göttingen
Faculty of Physics
Institute for Astrophysics
Phone +49 551 39-5045
Email: giesers@astro.physik.uni-goettingen.de
Prof. Dr. Stefan Dreizler
University of Göttingen
Faculty of Physics
Institute for Astrophysics
Phone +49 551 39-5041
Email: dreizler@astro.physik.uni-goettingen.de
Web: www.uni-goettingen.de/en/216891.html