Are black holes and dark matter the same?

Date:
December 20, 2021
Source:
University of Miami
Summary:
Astrophysicists suggest that primordial black holes account for
all dark matter in the universe.



FULL STORY ========================================================================== Proposing an alternative model for how the universe came to be, a team
of astrophysicists suggests that all black holes -- from those as tiny as
a pin head to those covering billions of miles -- were created instantly
after the Big Bang and account for all dark matter.


========================================================================== That's the implication of a study by astrophysicists at the University
of Miami, Yale University, and the European Space Agency that suggests
that black holes have existed since the beginning of the universe and
that these primordial black holes could be as-of-yet unexplained dark
matter. If proven true with data collected from this month's launch of
the James Webb Space Telescope, the discovery may transform scientific understanding of the origins and nature of two cosmic mysteries: dark
matter and black holes.

"Our study predicts how the early universe would look if, instead of
unknown particles, dark matter was made by black holes formed during
the Big Bang -- as Stephen Hawking suggested in the 1970s," said Nico Cappelluti, an assistant professor of physics at the University of Miami
and first author of the study slated for publication in The Astrophysical Journal.

"This would have several important implications," continued Cappelluti,
who this year expanded the research he began at Yale as the Yale Center
for Astronomy and Astrophysics Prize Postdoctoral Fellow. "First, we
would not need 'new physics' to explain dark matter. Moreover, this
would help us to answer one of the most compelling questions of modern astrophysics: How could supermassive black holes in the early universe
have grown so big so fast? Given the mechanisms we observe today in the
modern universe, they would not have had enough time to form. This would
also solve the long-standing mystery of why the mass of a galaxy is always proportional to the mass of the super massive black hole in its center."
Dark matter, which has never been directly observed, is thought to be
most of the matter in the universe and act as the scaffolding upon which galaxies form and develop. On the other hand, black holes, which can be
found at the centers of most galaxies, have been observed. A point in
space where matter is so tightly compacted, they create intense gravity.

Co-authored by Priyamvada Natarajan, professor of astronomy and physics
at Yale, and Gu"nther Hasinger, director of science at the European
Space Agency (ESA), the new study suggests that so-called primordial
black holes of all sizes account for all black matter in the universe.



========================================================================== "Black holes of different sizes are still a mystery," Hasinger
explained. "We don't understand how supermassive black holes could have
grown so huge in the relatively short time available since the universe existed." Their model tweaks the theory first proposed by Hawking and
fellow physicist Bernard Carr, who argued that in the first fraction
of a second after the Big Bang, tiny fluctuations in the density of the universe may have created an undulating landscape with "lumpy" regions
that had extra mass. These lumpy areas would collapse into black holes.

That theory did not gain scientific traction, but Cappelluti,
Natarajan, and Hasinger suggest it could be valid with some slight modifications. Their model shows that the first stars and galaxies would
have formed around black holes in the early universe. They also propose
that primordial black holes would have had the ability to grow into supermassive black holes by feasting on gas and stars in their vicinity,
or by merging with other black holes.

"Primordial black holes, if they do exist, could well be the seeds from
which all the supermassive black holes form, including the one at the
center of the Milky Way," Natarajan said. "What I find personally super exciting about this idea is how it elegantly unifies the two really
challenging problems that I work on -- that of probing the nature of
dark matter and the formation and growth of black holes -- and resolves
them in one fell swoop." Primordial black holes also may resolve another cosmological puzzle: the excess of infrared radiation, synced with X-ray radiation, that has been detected from distant, dim sources scattered
around the universe. The study authors said growing primordial black
holes would present "exactly" the same radiation signature.

And, best of all, the existence of primordial black holes may be proven
-- or disproven -- in the near future, courtesy of the Webb telescope
scheduled to launch from French Guiana before the end of the year and
the ESA-led Laser Interferometer Space Antenna (LISA) mission planned
for the 2030s.

Developed by NASA, ESA, and the Canadian Space Agency to succeed the
Hubble Space Telescope, the Webb can look back more than 13 billion
years. If dark matter is comprised of primordial black holes, more stars
and galaxies would have formed around them in the early universe, which
is precisely what the cosmic time machine will be able to see.

"If the first stars and galaxies already formed in the so-called 'dark
ages,' Webb should be able to see evidence of them," Hasinger said.

LISA, meanwhile, will be able to pick up gravitational wave signals from
early mergers of primordial black holes.

========================================================================== Story Source: Materials provided by University_of_Miami. Note: Content
may be edited for style and length.


========================================================================== Related Multimedia:
* Diagram_of_2_possible_routes_of_evolution_of_the_universe ========================================================================== Journal Reference:
1. Nico Cappelluti, Gu"nther Hasinger, Priyamvada Natarajan. Exploring
the
high-redshift PBH-LCDM Universe: early black hole seeding, the
first stars and cosmic radiation backgrounds. The Astrophysical
Journal, 2021 [abstract] ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211220120813.htm

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