From The Australian National University (AU) : “Mysterious clouds could offer new clues on dark matter” 

ANU Australian National University Bloc

From The Australian National University (AU)

1 December 2021
James Giggacher
+61 2 6125 7979
media@anu.edu.au

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Dr. Lilli Sun is on the hunt for boson clouds. Photo Tracey Nearmy/ ANU.

The hunt for gravitational waves, ripples in space and time caused by major cosmic cataclysms, could help solve one of the Universe’s other burning mysteries – boson clouds and whether they are a leading contender for dark matter.

Researchers are using powerful instruments, like the advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), advanced Virgo, and KAGRA, that detect gravitational waves up to billions of light years away to locate potential boson clouds.
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LIGOVIRGOKAGRA

Caltech /MIT Advanced aLigo

Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA.

Caltech/MIT Advanced aLigo Hanford, WA, USA installation.

VIRGO Gravitational Wave interferometer, near Pisa, Italy

KAGRA Large-scale Cryogenic Gravitational Wave Telescope Project (JP)
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LIGO Virgo Kagra Masses in the Stellar Graveyard. Credit: Frank Elavsky and Aaron Geller at Northwestern University(US)

Boson clouds-made up of ultralight subatomic particles that are almost impossible to detect-have been suggested as a possible source of Dark Matter – which accounts for about 85 per cent of all matter in the Universe.

Now a major new international study [see science paper below] carried out in the LIGO-Virgo-KAGRA collaboration and co-led by researchers from The Australian National University (ANU), offers one of the best leads yet to hunt down these subatomic particles by searching for gravitational waves caused by boson clouds circling black holes.

Dr Lilli Sun, from the ANU Centre for Gravitational Astrophysics, said the study was the first all-sky survey in the world tailored to look for predicted gravitational waves coming from possible boson clouds near rapidly spinning black holes.

“It is almost impossible to detect these ultralight boson particles on Earth,” Dr Sun said.

“The particles, if they exist, have extremely small mass and rarely interact with other matter — which is one of the key properties that dark matter seems to have. Dark matter is material that cannot be seen directly, but we know that dark matter exists because of the effect it has on objects that we can observe.

“But by searching for gravitational waves emitted by these clouds we may be able to track down these elusive boson particles and possibly crack the code of dark matter. Our searches could also allow to rule out certain ultralight boson particles that our theories say could exist but actually don’t.”

Dr Sun, also an Associate Investigator at the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), said gravitational wave detectors allowed researchers to examine the energy of rapidly rotating black holes extracted by such clouds if they exist.

“We believe these black holes trap a huge number of boson particles in their powerful gravity field, creating a cloud corotating with them. This delicate dance continues for millions of years and keeps generating gravitational waves that hurtle through space,” she said.

While the researchers haven’t yet detected gravitational waves from boson clouds, Dr Sun said gravitational wave science had “opened doors that were previously locked to scientists”.

“Gravitational-wave discoveries not only provide information about mysterious compact objects in the Universe, like black holes and neutron stars, they also allow us to look for new particles and dark matter,” she said.

“Future gravitational wave detectors will certainly open more possibilities. We will be able to reach deeper into the Universe and discover more insights about these particles.

“For example, the discovery of boson clouds using gravitational wave detectors would bring important insights about dark matter and help advance other searches for dark matter. It would also advance our understanding of particle physics more broadly.”

In another significant breakthrough, the study also shed more light on the chance of boson clouds existing in our own galaxy by taking into consideration their ages.

Dr Sun said the strength of any gravitational wave depends on the age of the cloud, with older ones sending out weaker signals.

“The boson cloud shrinks as it loses energy by sending out gravitational waves,” Dr Sun said.

“We learnt that a particular type of boson cloud younger than 1,000 years is not likely to exist anywhere in our galaxy, while clouds that are up to 10 million years old are not likely to exist within about 3,260 light years from Earth.”

Science paper:
All-sky search for gravitational wave emission from scalar boson clouds aroundspinning black holes in LIGO O3 data

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Dark Matter Background
Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM, denied the Nobel, some 30 years later, did most of the work on Dark Matter.

Fritz Zwicky.
Coma cluster via NASA/ESA Hubble, the original example of Dark Matter discovered during observations by Fritz Zwicky and confirmed 30 years later by Vera Rubin.
In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.

Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.

Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.
Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science).

Vera Rubin measuring spectra at the Department of Terrestrial Magnetism at the Carnegie Institution in Washington in about 1970. (Emilio Segre Visual Archives AIP SPL).

Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970.

Dark Matter Research

LBNL LZ Dark Matter Experiment (US) xenon detector at Sanford Underground Research Facility(US) Credit: Matt Kapust.

Lamda Cold Dark Matter Accerated Expansion of The universe http scinotions.com the-cosmic-inflation-suggests-the-existence-of-parallel-universes. Credit: Alex Mittelmann.

DAMA at Gran Sasso uses sodium iodide housed in copper to hunt for dark matter LNGS-INFN.

Yale HAYSTAC axion dark matter experiment at Yale’s Wright Lab.

DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB (CA) deep in Sudbury’s Creighton Mine

The LBNL LZ Dark Matter Experiment (US) Dark Matter project at SURF, Lead, SD, USA.

DAMA-LIBRA Dark Matter experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS) located in the Abruzzo region of central Italy.

DARWIN Dark Matter experiment. A design study for a next-generation, multi-ton dark matter detector in Europe at the University of Zurich.

PandaX II Dark Matter experiment at Jin-ping Underground Laboratory (CJPL) in Sichuan, China.

Inside the Axion Dark Matter eXperiment U Washington (US) Credit : Mark Stone U. of Washington. Axion Dark Matter Experiment.
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