While surveying cluster NGC 3201, astronomers have spotted a strange star being flung backward and forwards by an invisible force at several hundred thousand kilometers per hour, with such pattern repeating every 167 days.
Using the ESO's MUSE instrument at the Very Large Telescope observatory, they determined that the star was actually orbiting an invisible black hole that is four times more massive than the sun.
It is the first of its kind that does not currently swallow matter and is surrounded by a spherical cluster of stars, instead of a disc of gas.
Based on observed properties, the ESO has determined the star is around 0.8 times the mass of the Sun while its counterpart is calculated to possess 4.36 times more.
The system was initially thought to be a binary star system, and a triple star system consisting of a double neutron star with a main star orbiting around it.
While it matches all the criteria of a triple star system, it could not be identified as such because a double neutron star binary has never been observed.
With this possibility ruled out and considering the size of the invisible object, astronomers concluded that it could only be a black hole.
Astronomers report through a study published Jan. 9, that this recent discovery suggests there are actually more stellar-mass binary black holes in the Universe than previously thought and confirms that such objects can exist within star clusters.
Formation Of Globular Star Clusters
A globular cluster is a spherical region in space comprised of tens of thousands of stars that are densely packed. Currently, astronomers have identified more than 150 globular clusters in the Milky Way and some of them are among the universe's oldest recorded star systems.
These systems are believed to produce a number of massive black holes as stars in such clusters explode and collapse over time.
Moreover, NGC 3201 has an unusual structural parameter due to its large cluster core radius. This indicates that the globular cluster contains an extensive black hole system within its core, with the radius expansion caused by the interaction between black holes and stars.
Astronomers are hoping that more observations using MUSE would reveal more systems similar to the recent discovery.
What Are Black Holes?
A black hole is an area in space with a gravitational field so powerful that even light or small particles could not get out. Because of this, it appears invisible to the naked eye. It could only be viewed through space telescopes.
NASA states that not all black holes are large. There are smaller ones the size of a single atom but with the mass of an entire mountain.
Meanwhile, the biggest black holes are called "supermassive." They have masses of a million times more than the Earth's Sun and are often located in the center of every large galaxy.
In the Milky Way, the supermassive black hole at the center is known as Sagittarius A. It has a mass of around four million Suns.