New research could have delivered bad news to scientists who thought that they had discovered the “missing link” of a black hole in a dense star cluster within the Milky Way.
The new findings suggest just that, not a rare intermediate mass black holethere may be a cluster of stellar-mass black holes there Omega Centauribelieved to be the stays of an ancient galaxy destroyed by Milky Way.
“The search for the elusive intermediate-mass black holes continues,” said research team member Justin Read, a scientist on the University of Surrey in England. “There may still be one at the center of Omega Centauri, but our work shows that it must have a mass of less than about 6,000 solar masses and be next to a cluster of stellar-mass black holes.”
Astronomers were the primary to find out about it to the possible presence of a black hole in Omega Centauri, which incorporates an estimated 10 million stars, once they noticed that some of these stars were moving faster than expected.
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Last yr, a team of astronomers conducted a study using Hubble Space Telescope and believed that they had found an intermediate-mass black hole with a mass akin to about 8,200 suns.
However, a reanalysis of this star cluster shows that this was not the case.
Why do “missing link” black holes matter?
As their name suggests, intermediate-mass black holes occupy the region between stellar-mass black holes (10 to 1,000 solar masses) and the supermassive black holes on the hearts of galaxies, with masses equal to thousands and thousands and even billions of suns.
The alleged discovery of an intermediate-mass black hole so near Earth was exciting because these black holes, regarded as a key link within the chain of mergers that help black holes achieve supermassive status, have been notoriously elusive. This is despite the very fact that scientists imagine they needs to be common within the universe.
This is because, like all black holes, they’re bounded by a one-way light-catching surface called an event horizon. This means that black holes can only be seen once they are surrounded by material, which they feed on to grow, and which heats up as a consequence of tidal forces, generating vibrant light.
Intermediate black holes are regarded as “stuck” or “frozen in time” because there is no such thing as a gas and dirt around them to feed on. This also means that they’re effectively invisible, for the reason that only approach to infer their presence is thru the effect of gravity on the celebs surrounding them.
Interactions with the gravity of the intermediate-mass black hole at the guts of Omega Centauri are thought to have accelerated the celebs at the middle of this dense cluster to high speeds.
“We have long known about supermassive black holes in the centers of galaxies and smaller, stellar-mass black holes in our galaxy,” team member and Instituto de Astrofísica de Canarias researcher Andrés Bañares Hernández said in a statement.
“However, the concept of black holes with intermediate masses that could fill the gap between these extremes remains unconfirmed,” he added. “By studying Omega Centauri – a remnant of a dwarf galaxy – we were able to refine our methods and take a step forward in understanding whether such black holes exist and what role they might play in the evolution of star clusters and galaxies.
“This work helps resolve a two-decade-old debate and opens new doors for future research.”
Another possible explanation for the observed stellar velocities is a cluster of stellar-mass black holes that are predicted to grow in dense star clusters like this one.
However, astronomers imagine that interactions with other stars would likely “kick” these smaller black holes out of the system. This made an intermediate-mass black hole the more than likely explanation for the high-speed stars at the guts of Omega Centauri – until now.
In the new study, scientists included one other necessary source of data when considering Omega Centauri, which modified the situation significantly.
Keeping time with space beacons
Additional data got here from the so-called “space lighthouses”. pulsars.
Pulsars rapidly spin cosmic remnants of the so-called neutron stars they form when massive stars run out of fuel and collapse under their very own gravity.
As these dead stars spin at 700 times per second, in addition they emit beams of radiation from their poles. These rays sweep across the universe like the sunshine of a cosmic beacon.
When they turn to point Earthpulsars brighten, making them look like pulsating. Because this pseudopulsing is extremely periodic, when included en masse in what scientists call a pulsar timing system, these cosmic beacons transform into a highly accurate timekeeping tool.
Changes in pulsar timing may indicate the presence of intense gravitational fields accelerating these dead stars. The addition of pulsar data allowed the team to study the gravitational fields at the guts of Omega Centauri in additional detail.
This enabled the team to tell apart the influence of an intermediate black hole from a cluster of stellar-mass black holes. The team determined that the latter is the more than likely explanation for the speed of the celebs in the middle of Omega Centauri.
The team is not too discouraged by their findings. Read, for instance, thinks it’s only a matter of time before astronomers start discovering intermediate-mass black holes.
“There’s a good chance we’ll find one [an intermediate-mass black hole] coming soon,” Read said. “Pulsars are accelerating more and more, which will allow us to peer into the centers of dense star clusters and hunt for black holes with greater precision than ever before.”
In the meantime, the team’s research may help astronomers better understand the mechanisms by which pulsars form.
” formation of pulsars can be an lively field of research because a large number of them have recently been detected,” Hernández concluded. “Omega Centauri is an ideal environment to study models of their formation, which we were able to do for the first time in our history of analysis.”
The team’s research has been accepted for publication within the journal Astronomy and astrophysics.
