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Scientists thought there was a black hole at the centre of our Galaxy. It turns out it may be something even stranger
https://www.skyatnightmagazine.com/news/...ark-matter
INTRO: Astronomers have proposed a radical alternative to the long-held belief that a supermassive black hole sits at the centre of the Milky Way, suggesting that instead a dense clump of dark matter could generate the same gravitational effects. The new study, published in Monthly Notices of the Royal Astronomical Society, argues that an ultra-compact dark matter core can explain both the rapid motions of stars near our galactic centre and the larger-scale rotation of our Galaxy.
For decades, the object known as Sagittarius A* has been interpreted as a black hole more than four million times the mass of the Sun, largely because stars in its vicinity, called S-stars, whirl around
it at enormous speeds. However, an international team have put forward a fermionic dark matter model that could reproduce the same stellar motions without a black hole.
“This is the first time a dark matter model has successfully bridged these vastly different scales and various object orbits, including modern rotation curve and central stars data,” says the study’s co-author Dr Carlos Argüelles. “We are not just replacing the black hole with a dark object; we are proposing that the supermassive central object and the Galaxy’s dark matter halo are two manifestations of the same substance.” (MORE - details)
Eurekalert (excerpts): The international team of researchers have instead put forward an alternative idea – that a specific type of dark matter made up of fermions, or light subatomic particles, can create a unique cosmic structure that also fits with what we know about the Milky Way's core. It would in theory produce a super-dense, compact core surrounded by a vast, diffuse halo, which together would act as a single, unified entity.
The inner core would be so compact and massive that it could mimic the gravitational pull of a black hole and explain the orbits of S-stars that have been observed in previous studies, as well as the orbits of the dust-shrouded objects known as G-sources which also exist nearby.
Of particular importance to the new research is the latest data from the European Space Agency's GAIA DR3 mission, which has meticulously mapped the rotation curve of the Milky Way's outer halo, showing how stars and gas orbit far from the centre.
It observed a slowdown of our galaxy's rotation curve, known as the Keplerian decline, which the researchers say can be explained by their dark matter model's outer halo when combined with the traditional disc and bulge mass components of ordinary matter.
This, they add, strengthens the 'fermionic' model by highlighting a key structural difference. While traditional Cold Dark Matter halos spread out following an extended 'power law' tail, the fermionic model predicts a tighter structure, leading to more compact halo tails.
[...] "Our model not only explains the orbits of stars and the galaxy's rotation but is also consistent with the famous 'black hole shadow' image. The dense dark matter core can mimic the shadow because it bends light so strongly, creating a central darkness surrounded by a bright ring."
The researchers statistically compared their fermionic dark matter model to the traditional black hole model. They found that while current data for the inner stars cannot yet decisively distinguish between the two scenarios, the dark matter model provides a unified framework that explains the galactic centre (central stars and shadow), and the galaxy at large.
The new study paves the way for future observations. [...] The outcome of these findings could potentially reshape our understanding of the fundamental nature of the cosmic behemoth at the heart of the Milky Way. (MORE - missing details, no ads)
https://www.skyatnightmagazine.com/news/...ark-matter
INTRO: Astronomers have proposed a radical alternative to the long-held belief that a supermassive black hole sits at the centre of the Milky Way, suggesting that instead a dense clump of dark matter could generate the same gravitational effects. The new study, published in Monthly Notices of the Royal Astronomical Society, argues that an ultra-compact dark matter core can explain both the rapid motions of stars near our galactic centre and the larger-scale rotation of our Galaxy.
For decades, the object known as Sagittarius A* has been interpreted as a black hole more than four million times the mass of the Sun, largely because stars in its vicinity, called S-stars, whirl around
it at enormous speeds. However, an international team have put forward a fermionic dark matter model that could reproduce the same stellar motions without a black hole.
“This is the first time a dark matter model has successfully bridged these vastly different scales and various object orbits, including modern rotation curve and central stars data,” says the study’s co-author Dr Carlos Argüelles. “We are not just replacing the black hole with a dark object; we are proposing that the supermassive central object and the Galaxy’s dark matter halo are two manifestations of the same substance.” (MORE - details)
Eurekalert (excerpts): The international team of researchers have instead put forward an alternative idea – that a specific type of dark matter made up of fermions, or light subatomic particles, can create a unique cosmic structure that also fits with what we know about the Milky Way's core. It would in theory produce a super-dense, compact core surrounded by a vast, diffuse halo, which together would act as a single, unified entity.
The inner core would be so compact and massive that it could mimic the gravitational pull of a black hole and explain the orbits of S-stars that have been observed in previous studies, as well as the orbits of the dust-shrouded objects known as G-sources which also exist nearby.
Of particular importance to the new research is the latest data from the European Space Agency's GAIA DR3 mission, which has meticulously mapped the rotation curve of the Milky Way's outer halo, showing how stars and gas orbit far from the centre.
It observed a slowdown of our galaxy's rotation curve, known as the Keplerian decline, which the researchers say can be explained by their dark matter model's outer halo when combined with the traditional disc and bulge mass components of ordinary matter.
This, they add, strengthens the 'fermionic' model by highlighting a key structural difference. While traditional Cold Dark Matter halos spread out following an extended 'power law' tail, the fermionic model predicts a tighter structure, leading to more compact halo tails.
[...] "Our model not only explains the orbits of stars and the galaxy's rotation but is also consistent with the famous 'black hole shadow' image. The dense dark matter core can mimic the shadow because it bends light so strongly, creating a central darkness surrounded by a bright ring."
The researchers statistically compared their fermionic dark matter model to the traditional black hole model. They found that while current data for the inner stars cannot yet decisively distinguish between the two scenarios, the dark matter model provides a unified framework that explains the galactic centre (central stars and shadow), and the galaxy at large.
The new study paves the way for future observations. [...] The outcome of these findings could potentially reshape our understanding of the fundamental nature of the cosmic behemoth at the heart of the Milky Way. (MORE - missing details, no ads)