Using sophisticated computer modeling programs, astrophysicists have shed light on the long-standing mystery of the binding force behind a cluster of unruly and rapidly swirling stars located in the famous Orion Nebula Cluster, also known as Messier 42 (M42).
A new study, published in the Astrophysical Journal (arXiv.org version), suggests that fast-moving stars in M42 are potentially held together through the powerful gravitational pull of a black hole up to 200 times the mass of the Sun.
Located about 1,300 light-years from Earth, M42 has long been known for its strange properties. The stars in this region of massive star formation move at a rapid speed, as if the whole cluster was flying apart. Compared to the number of low-mass stars that can be seen in the cluster, the number of high-mass stars is too few.
“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 Dr Holger Baumgardt of the University of Queensland’s School of Mathematics and Physics.
The astrophysicists set up a computer model of the Orion Nebula Cluster representing a tight cloud of inter-stellar gas containing the right combination of heavy and light stars. They then went on to calculate the movement of these stars in the system.
“In our model, we had to invent a new method of dealing with the gas and the way it is driven out from the cluster by the intensely radiating high-mass stars,” said lead author Dr Ladislav Subr of Charles University in Prague.
“Such dense star cluster models were a challenge to compute due to the large number of calculations that had to be made,” Dr Baumgardt added.
The results showed that, as the gas was being driven outwards, the cluster began to expand, explaining why most stars move rapidly. Many of the heavy stars were sling-shot out of the cluster, while some were driven into the center of the cluster and collided with the most massive star there. At some point, this massive star became unstable and imploded into a black hole, with a mass about 200 times larger than the Sun.
“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,” Dr Subr explained.
“Having such a massive black hole at our doorstep would be a dramatic chance for intense studies of these enigmatic objects,” said co-author Prof Pavel Kroupa of the University of Bonn in Germany.
Bibliographic information: Ladislav Šubr et al. 2012. Catch Me If You Can: Is There a “Runaway-mass” Black Hole in the Orion Nebula Cluster? ApJ 757, 37; doi: 10.1088/0004-637X/757/1/37