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Discovering Dark Matter: New Clue From Mysterious Clouds Circling Spinning Black Holes

Gravitational waves are cosmic ripples in the fabric of space and time that emanate from catastrophic events in space, like collisions of black holes and neutron stars — the collapsed cores of massive supergiant stars. Extremely sensitive gravitational-wave detectors on Earth, like the Advanced LIGOThe Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory supported by the National Science Foundation and operated by Caltech and MIT. It’s designed to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. It’s multi-kilometer-scale gravitational wave detectors use laser interferometry to measure the minute ripples in space-time caused by passing gravitational waves. It consists of two widely separated interferometers within the United States—one in Hanford, Washington and the other in Livingston, Louisiana.”>LIGO and Virgo detectors, have successfully observed dozens of gravitational-wave signals, and they’ve also been used to search for dark matter: a hypothetical form of matter thought to account for approximately 85% of all matter in the Universe. Dark matter may be composed of particles that do not absorb, reflect, or emit light, so they cannot be detected by observing electromagnetic radiation. 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 directly.

Ultralight boson particles are a new type of subatomic particle that scientists have put forward as compelling dark matter candidates. However, these ultralight particles are difficult to detect because they have extremely small mass and rarely interact with other matter — which is one of the key properties that dark matter seems to have.

Lilli Sun

Dr. Lilli Sun is on the hunt for boson clouds – a key contender for dark matter. Credit: Tracey Nearmy/ANU

The detection of gravitational wavesGravitational waves are distortions or ripples in the fabric of space and time. They were first detected in 2015 by the Advanced LIGO detectors and are produced by catastrophic events such as colliding black holes, supernovae, or merging neutron stars.”>gravitational waves provides a new approach to detecting these extremely light boson particles using gravity. Scientists theorize that if there are certain ultralight boson particles near a rapidly spinning black holeA black hole is a place in space where the pull of gravity is so strong not even light can escape it. Astronomers classify black holes into three categories by size: miniature, stellar, and supermassive black holes. Miniature black holes could have a mass smaller than our Sun and supermassive black holes could have a mass equivalent to billions of our Sun.”>black hole, the extreme gravity field causes the particles to be trapped around the black hole, creating a cloud around the black hole. This phenomenon can generate gravitational waves over a very long lifetime. By searching for these gravitational-wave signals, scientists can finally discover these elusive boson particles, if they do exist, and possibly crack the code of dark matter or rule out the existence of some types of the proposed particles. 

In a recent international study in the LIGO-Virgo-KAGRA collaboration, with OzGrav Associate Investigator Dr. Lilli Sun from the Australian National UniversityFounded in 1946, the Australian National University (ANU) is a national research university located in Canberra, the capital of Australia. Its main campus in Acton encompasses seven teaching and research colleges, in addition to several national academies and institutes.”>Australian National University being one of the leading researchers, a team of scientists carried out the very first all-sky search tailored for these predicted gravitational wave signals from boson clouds around rapidly spinning black holes. 

“Gravitational-wave science opened a completely new window to study fundamental physics. It provides not only direct information about mysterious compact objects in the Universe, like black holes and neutron stars, but also allows us to look for new particles and dark matter,” says Dr. Sun.

Although a signal was not detected, the team of researchers was able to draw valuable conclusions about the possible presence of these clouds in our Galaxy. In the analysis, they also took into consideration that the strength of a gravitational wave signal depends on the age of the boson cloud:  the boson cloud shrinks as it loses energy by sending out gravitational waves, so the strength of the gravitational wave signal would decrease as the cloud ages. 

“We learned that a particular type of boson clouds younger than 1000 years is not likely to exist anywhere in our Galaxy, while such clouds that are up to 10 million years old are not likely to exist within about 3260 light-years from Earth,” says Dr. Sun.

“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 more on this research see Ghostly Boson Clouds Could Solve the Mystery of Dark Matter.

Reference: “All-sky search for gravitational wave emission from scalar boson clouds around spinning black holes in LIGO O3 data” by The LIGO Scientific Collaboration, the Virgo Collaboration, the KAGRA Collaboration: R. Abbott, H. Abe, F. Acernese, K. Ackley, N. Adhikari, R. X. Adhikari, V. K. Adkins, V. B. Adya, C. Affeldt, D. Agarwal, M. Agathos, K. Agatsuma, N. Aggarwal, O. D. Aguiar, L. Aiello, A. Ain, P. Ajith, T. Akutsu, S. Albanesi, R. A. Alfaidi, A. Allocca, P. A. Altin, A. Amato, C. Anand, S. Anand, A. Ananyeva, S. B. Anderson, W. G. Anderson, M. Ando, T. Andrade, N. Andres, M. Andrés-Carcasona, T. Andrić, S. V. Angelova, S. Ansoldi, J. M. Antelis, S. Antier, T. Apostolatos, E. Z. Appavuravther, S. Appert, S. K. Apple, K. Arai, A. Araya, M. C. Araya, J. S. Areeda, M. Arène, N. Aritomi, N. Arnaud, M. Arogeti, S. M. Aronson, K. G. Arun, H. Asada, Y. Asali, G. Ashton, Y. Aso, M. Assiduo, S. Assis de Souza Melo, S. M. Aston, P. Astone, F. Aubin, K. AultONeal, C. Austin, S. Babak, F. Badaracco, M. K. M. Bader, C. Badger, S. Bae, Y. Bae, A. M. Baer, S. Bagnasco, Y. Bai, J. Baird, R. Bajpai, T. Baka, M. Ball, G. Ballardin, S. W. Ballmer, A. Balsamo, G. Baltus, S. Banagiri, B. Banerjee, D. Bankar, J. C. Barayoga, C. Barbieri, B. C. Barish, D. Barker, P. Barneo, F. Barone, B. Barr, L. Barsotti, M. Barsuglia, D. Barta, J. Bartlett, M. A. Barton, I. Bartos, S. Basak, R. Bassiri et al., 30 November 2021, Astrophysics > High Energy Astrophysical Phenomena.

Source: SciTechDaily