(ORDO NEWS) — Stellar black holes are small but deadly
When a star burns through the rest of its fuel, it can collapse or fall into itself. For smaller stars (up to about 3 times the mass of the Sun), the star will become a neutron star or a white dwarf. But when a large star falls into itself, it continues to shrink and creates a stellar black hole.
The black holes formed by the collapse of stars are relatively small, but incredibly dense. One of these objects, three times the mass of the Sun, fits into the diameter of a city.
This results in a crazy amount of gravitational force pulling things around the object. Stellar black holes once formed begin to absorb dust and gas from their surrounding galaxies, allowing them to grow in size.
According to the Harvard-Smithsonian Center for Astrophysics, the Milky Way contains several hundred million stellar black holes.
Supermassive black holes – the birth of giants
Small black holes populate the universe, but their cousins, supermassive black holes, dominate. These huge black holes are millions or even billions of times more massive than the Sun, but their diameter is about the same. Such black holes are believed to lie at the center of almost every galaxy, including the Milky Way.
Scientists are not sure how such large black holes appear. Once these giants have formed, they begin to take on mass from the dust and gas around them, material found in abundance at the centers of galaxies, allowing them to grow to even greater sizes.
Supermassive black holes may be the result of the merger of hundreds or thousands of tiny black holes. Large gas clouds may also be responsible for this process, collapsing together and rapidly gaining mass.
The third option is a star cluster collapse, a group of stars falling together. Fourth, supermassive black holes can originate from large clumps of dark matter.
This is the substance that we can observe due to its gravitational effect on other objects; however, we do not know what dark matter is made of because it does not emit light and cannot be observed directly.
Intermediate black holes – stuck in the middle
Scientists once thought that black holes only came in small and large sizes, but recent research has revealed the possibility of medium or intermediate black holes (IMBHs).
Such bodies can form when stars in a cluster collide. Several of these intermediate black holes that form in the same region could eventually coalesce together at the center of a galaxy and create a supermassive black hole.
In 2014, astronomers discovered what appeared to be an intermediate-mass black hole in the arm of a spiral galaxy.
“Astronomers have been very diligent in their search for these medium-sized black holes,” study co-author Tim Roberts of the University of Durham in the United Kingdom said in a statement. “There have been hints that they exist, but they act like a long-lost relative who has no interest in being found.”
New research in 2018 has shown that these intermediate black holes may exist at the very heart of dwarf galaxies (or very small galaxies).
Observations of 10 such galaxies (five of which were previously unknown to science prior to this latest study) revealed X-ray activity – common for black holes – suggesting the presence of black holes with a mass between 36,000 and 316,000 suns.
The information comes from the Sloan Digital Sky Survey, which studies about 1 million galaxies and can detect the kind of signals that often come from black holes picking up nearby material from dust and gas.
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