(ORDO NEWS) — A bright tail emanating from a distant galaxy could indicate an invisible supermassive black hole that has been ejected from its center and is flying away, leaving behind regions of active star formation.
It is believed that at the centers of large galaxies, including ours, there are supermassive black holes, gaining millions and even billions of solar masses.
Actively absorbing matter, they accelerate and heat it, forcing it to radiate and partially throwing it away at great speed.
All this betrays the presence of supermassive black holes, allowing us to estimate their colossal size.
When several such galaxies merge, their black holes approach each other and spin around a common center of gravity.
As a result of these complex interactions, one of the holes can be ejected from the galaxy, as if launched by a gravitational sling.
Once in the void of intergalactic space, it becomes invisible to telescopes. However, sometimes you can notice the “orphan hole” by the trail that it leaves behind.
Pieter van Dokkum and his colleagues used the Hubble Space Telescope to study the dwarf galaxy RCP 28.
However, in the resulting images, they noticed something unusual – a bright and narrow line indicating the center of another, more distant and larger galaxy.
Therefore, scientists conducted additional observations at the Hawaiian Keck Observatory. This made it possible to estimate the distances to the strange line and the galaxy itself.
They were located together, at a distance of about 39 million light years, which means they are connected to each other.
The length of the tail itself, astronomers have estimated at 200,000 light years. In addition, it is inhomogeneous both in brightness and in the color of the outgoing radiation.
There are areas in the tail that look like shock waves.
All this may indicate the passage of a massive body moving at great speed and leaving behind areas of increased concentration of matter, in some of which new stars began to form.
Van Dokkum et al. associated this process with a supermassive black hole that was ejected from the center of a distant galaxy.
According to the hypothesis of the authors of the work, in the past this galaxy experienced a merger with another. Their black holes converged and began to rotate together.
Such a tandem could have stably existed for quite a long time, but then a merger with a third galaxy took place.
The appearance of a third supermassive black hole broke the stability of the pair, and soon one of them was ejected from the center of the galaxy, and then beyond.
Moving at high speed, it compresses the surrounding gas. As such regions of the intergalactic medium cooled, the birth of young stars was triggered in them.
Astronomers were able to see at least three star-forming regions in the tail. Calculations have shown that some of their stars may be less than 30 million years old.
Relativistic jets, narrow streams of plasma that are ejected from the active centers of galaxies at near-light speed, can also leave similar star-forming regions.
However, the version with the ejection of a supermassive black hole is also confirmed by the shape of the galaxy itself: it turned out to be severely disturbed due to the passage of a huge gravitating object through it.
Perhaps in the future, scientists will be able to find other such traces, which will become one of the ways to detect invisible black holes – “orphans”.
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