The strange behavior of stars in the Sword of Orion may be due to the presence of a black hole about 200 times larger than our sun.
Overview image of the Orion Nebula with the star cluster at its center. The possible black hole would reside somewhere between the four bright stars which mark the cluster's center. These stars form the famous Trapezium of the Orion Nebula Cluster. (NASA/ESA/Hubble Space Telescope)
Using computer modelling, an international team of astronomers studied these fast-moving stars that form the Orion Nebula Cluster.
There appear to be too few high-mass stars in the cluster relative to low-mass stars, and they are moving at high speeds as if the whole group is flying apart.
“These properties have been a puzzle to astronomers, given all the knowledge that they have about how stars are formed and distributed,” said study co-author Holger Baumgardt at Australia’s University of Queensland in a press release.
The model consisted of a dense cloud of interstellar gas with the right proportion of heavy and light stars. Thus their motion could be calculated, showing that the cluster expands as the gas moves outwards.
Many heavy stars were thrown out, and some moved to the center, colliding with the most massive star there.
“Our scenario neatly accounts for virtually all observed properties of the Orion Nebula Cluster, that is, its low number of high-mass stars, and its rapidly-moving central stars, and suggests that the massive stars near the center of this cluster are bound by a black hole,” said study lead author Ladislav Subr at Charles University, Prague, in the release.
The black hole would have formed when the massive star became unstable.
“Having such a massive black hole at our doorstep would be a dramatic chance for intense studies of these enigmatic objects,” said study co-author Pavel Kroupa at Germany’s University of Bonn in the release.
The study was published in The Astrophysical Journal.