Hai-Bo Yu

Dark Matter Helped Solve This Milky Way Mystery

tomwt — Wed, 22 Jan 2025 15:53:50 +0000

Dark Matter Helped Solve This Milky Way Mystery tomwt Wed, 01/22/2025 - 07:53 More CNAS in the Media Emily Chan | MSN January 19, 2025

MSN - One of the most extensively studied stellar streams within the galactic halo of the Milky Way is the GD-1 stellar stream.

It is known for its long, thin structure and distinctive features. It exhibits spur and gap features that have puzzled scientists for many years.

A team of researchers led by Hai-Bo Yu, a professor of physics and astronomy from the University of California, Riverside, proposed that these strange features may result from a core-collapsing self-interacting dark matter (SIDM) subhalo, a smaller and denser satellite halo within the galactic halo.

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Dark matter may have caused a baffling break in this star stream

tomwt — Tue, 14 Jan 2025 16:42:04 +0000

Dark matter may have caused a baffling break in this star stream tomwt Tue, 01/14/2025 - 08:42 More CNAS in the Media Robert Lea | Space.com January 14, 2025

SPACE.COM - A perplexing "break" in a stream of stars around the Milky Way could be the result of dark matter — that is, if the mysterious cosmic stuff interacts with itself.

The feature in question is in the GD-1 stellar stream, a thin group of stars moving together on a shared trajectory through the Milky Way's all-encompassing halo. The GD-1 stellar stream has been well-studied by astronomers, but a gap in its structure has long been a puzzle.

Now, a team from the University of California, Riverside, proposes that the cause of this feature is a sub-halo of self-interacting dark matter within the larger halo of dark matter that envelops our galaxy.

"This work opens a promising new avenue for investigating the self-interacting properties of dark matter through stellar streams," team leader and University of California, Riverside researcher Hai-Bo Yu, said in a statement. "It marks an exciting step forward in our understanding of dark matter and the dynamics of the Milky Way."

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Astrophysicists offer explanation for origin of one of Milky Way’s largest satellites

tomwt — Wed, 12 Jun 2024 15:15:10 +0000

Astrophysicists offer explanation for origin of one of Milky Way’s largest satellites tomwt Wed, 06/12/2024 - 08:15 More CNAS in the Media Staff | Sci.News June 11, 2024

SCI.NEWS - “Since its discovery in 2016, there have been many attempts to reproduce Crater II’s unusual properties, but it has proved very challenging,” said University of California, Riverside’s Professor Hai-Bo Yu.

Dark matter makes up 85% of the Universe’s matter, and it can form a spherical structure under the influence of gravity called a dark matter halo.

Invisible, the halo permeates and surrounds a galaxy like Crater II. The fact that Crater II is extremely cold indicates its halo has a low density.

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Dark matter and Einstein rings solve ancient galaxy mystery

tomwt — Wed, 17 Apr 2024 17:10:20 +0000

Dark matter and Einstein rings solve ancient galaxy mystery tomwt Wed, 04/17/2024 - 10:10 More CNAS in the Media Eric Ralls | Earth.com April 13, 2024

EARTH.COM - A team of researchers led by Hai-Bo Yu, a professor of physics and astronomy at the University of California, Riverside, has shed new light on the enigmatic nature of dark matter through the lens of an ancient galaxy.

The study focuses on JWST-ER1g, a massive ancient galaxy discovered by the James Webb Space Telescope (JWST) last September, which formed when the universe was just a quarter of its current age.

Surprisingly, JWST-ER1g is associated with an Einstein ring, a phenomenon predicted by Einstein’s theory of general relativity. The galaxy acts as a lens, bending light from a distant source, which then appears as a ring.

This phenomenon, known as strong gravitational lensing, allows researchers to calculate the total mass enclosed within the ring, which consists of both stellar and dark matter components.

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Exotic 'Einstein ring' suggests that mysterious dark matter interacts with itself

tomwt — Wed, 17 Apr 2024 16:43:26 +0000

Exotic 'Einstein ring' suggests that mysterious dark matter interacts with itself tomwt Wed, 04/17/2024 - 09:43 More CNAS in the Media Sharmila Kuthunur | SPACE.COM April 16, 2024

SPACE.COM - A fresh analysis of a remarkably massive yet compact galaxy from the early universe suggests that dark matter interacts with itself.

The galaxy, JWST-ER1, which formed just 3.4 billion years after the Big Bang, was first spotted last October in images snapped by NASA's James Webb Space Telescope (JWST). At over 17 billion light-years from Earth, JWST-ER1g is the farthest-ever example of a perfect "Einstein ring" — an unbroken circle of light around the galaxy, a result of light rays from a distant, unseen galaxy being bent due to the space-warping mass of JWST-ER1.

"The value for the dark matter mass seems higher than expected," Hai-Bo Yu, a professor of physics and astronomy at the University of California, Riverside (UCR) and a co-author of the new study, said in a statement. "This is puzzling."

In a new paper, Yu and his colleagues suggest that JWST-ER1g's unusually high density could be explained by a higher population of stars than currently thought. However, a contraction mechanism by which ordinary matter — the stuff that makes up gas and stars — "collapses and condenses" into JWST-ER1g's dark matter halo could be packing "more dark matter mass in the same volume, resulting in higher density," study lead author Demao Kong of UCR said in the same statement.

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Dark matter might keep itself company, and that helps solve 2 cosmic puzzles

tomwt — Mon, 22 Jan 2024 17:27:11 +0000

Dark matter might keep itself company, and that helps solve 2 cosmic puzzles tomwt Mon, 01/22/2024 - 09:27 More CNAS in the Media Paul Sutter | Astronomy January 22, 2024

ASTRONOMY - Maybe dark matter talks to itself, according to a new proposal, and that might just explain two cosmological mysteries at once.

Dark matter is the name astronomers give to the mysterious substance that makes up the bulk of all matter in the universe. Upwards of 80 percent of the mass of a galaxy exists in the form of this strange, invisible stuff. But despite our inability to directly identify it, we can see the effects it has on its environment, like providing the gravitational glue needed to keep stars in their orbits despite their incredibly rapid rotation around galactic centers.

According to Hai-Bo Yu, a professor of physics and astronomy at the University of California, Riverside and the leader of the research team, they felt that a more complex version of dark matter could explain these two galactic extremes.

“The first is a high-density dark matter halo in a massive elliptical galaxy,” Yu says. “The halo was detected through observations of strong gravitational lensing, and its density is so high that it is extremely unlikely in the prevailing cold dark matter theory. The second is that dark matter halos of ultra-diffuse galaxies have extremely low densities and they are difficult to explain by the cold dark matter theory.”

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Grant awarded to physicist to explore the dark sector

ilseu — Wed, 01 Jul 2020 22:30:15 +0000

Grant awarded to physicist to explore the dark sector ilseu Wed, 07/01/2020 - 15:30 More College News Iqbal Pittalwala | Inside UCR July 01, 2020

The John Templeton Foundation has supported research on a diverse range of subjects including creativity, forgiveness, and free will. Dark matter — nonluminous material in space that is understood to constitute 85 percent of the matter in the universe — can now be added to the list.

The foundation has awarded UC Riverside physicist Hai-Bo Yu a three-year grant of about $235,000 to explore a new dark matter theory, “Self-Interacting Dark Matter,” which posits dark matter particles have strong self-interactions. The project title, “Exploring the dark sector,” refers to the unknown portion of the universe outside standard physics, including dark matter and dark energy.

Dr. Hai-Bo Yu

Yu, an associate professor of physics and astronomy, will use numerical simulations and analytical modeling to study dark-sector interactions and compare their predictions with astrophysical observations of galactic systems, including spiral galaxies, satellite galaxies in the Milky Way, and newly discovered ultra-diffuse galaxies.

“In these systems, dark matter distributions exhibit a great diversity that seriously challenges the prevailing theory,” Yu said. “If dark matter is indeed hidden from the visible sector, our proposed method will be the only way to understand the nature of dark matter, one of the deepest mysteries in science.”

Unlike normal matter, dark matter does not absorb, reflect, or emit light, making it difficult to detect. Physicists have inferred its existence from the gravitational effect dark matter has on visible matter.

“Conventional dark matter searches are based on the assumption that it has sizable interactions with known particles in the visible sector,” Yu said. “Despite decades of effort, however, we have not observed positive signals. A pressing question confronts the dark matter research community: What’s the next step in tackling the dark matter problem?”

Yu recently collaborated with scientists to demonstrate the nature of dark matter can be unveiled even if it does not lead to detectable signals in conventional searches.

“The key observation is that microscopic interactions in the dark sector can affect dark matter distributions in galaxies over cosmological timescales, and thus leave their imprints on stellar kinematics and dynamics of galaxies,” Yu said.

A postdoctoral researcher and a graduate student at UCR will join Yu in the research.

The project is expected to result in research papers published in major peer-reviewed journals in the fields of astrophysics and cosmology. Findings will be also be presented at research conferences, workshops, and seminars.

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