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A study co-led by physicists at UC Riverside and UC Irvine has found that dark matter halos of ultra-diffuse galaxies are very odd, raising questions about physicists’ understanding of galaxy formation and the structure of the universe.

Ultra-diffuse galaxies are so called because of their extremely low luminosity. The distribution of baryons—gas and stars—is much more spread out in ultra-diffuse galaxies compared to “normal” galaxies with similar masses.

In the following Q&A, Hai-Bo Yu, an associate professor of physics and astronomy at UCRhis thoughts on the findings he and UCI’s Manoj Kaplinghat, his long-term collaborator, have published in The Astrophysical Journal about newly discovered ultra-diffuse galaxies and their dark matter halos.

With the help of ESO’s Very Large Telescope (VLT), astronomers have found six galaxies lying around a supermassive black hole when the Universe was less than a billion years old. This is the first time such a close grouping has been seen so soon after the Big Bang and the finding helps us better understand how supermassive black holes, one of which exists at the centre of our Milky Way, formed and grew to their enormous sizes so quickly. It supports the theory that black holes can grow rapidly within large, web-like structures which contain plenty of gas to fuel them.

“This research was mainly driven by the desire to understand some of the most challenging astronomical objects —supermassive black holes in the early Universe. These are extreme systems and to date we have had no good explanation for their existence,” said Marco Mignoli, an astronomer at the National Institute for Astrophysics (INAF) in Bologna, Italy, and lead author of the new research published today in Astronomy & Astrophysics.

The new observations with ESO’s VLT revealed several galaxies surrounding a supermassive black hole, all lying in a cosmic “spider’s web” of gas extending to over 300 times the size of the Milky Way. “The cosmic web filaments are like spider’s web threads,” explains Mignoli. “The galaxies stand and grow where the filaments cross, and streams of gas—available to fuel both the galaxies and the central supermassive black hole—can flow along the filaments.”

This places Drake in the company of towering physicists with equations named after them, including James Clerk Maxwell and Erwin Schrödinger. Unlike those, Drake’s equation does not encapsulate a law of nature. Instead, it combines some poorly known probabilities into an informed estimate.

Whatever reasonable values you feed into the equation (see image below), it is hard to avoid the conclusion that we shouldn’t be alone in the galaxy. Drake remained a proponent and a supporter of the search for extraterrestrial life throughout his days, but has his equation taught us anything?

Continue reading “61 years ago, the founding father of SETI fundamentally altered the search for aliens” »

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Why does our universe appear so exquisitely tuned to create the conditions necessary for life? This is a question that has troubled cosmologists and physicists for decades.

Continue reading “Did God Create The Universe? Brian Greene on The Multiverse & The Fine Tuning Argument” »

It’s difficult to describe the state of the universe’s affairs back when the whole of everything was compressed to a size slightly smaller than the period at the end of this sentence — on account that the concepts of time and space literally didn’t yet apply. But that challenge hasn’t stopped pioneering theoretical astrophysicist, Dr. Laura Mersini-Houghton, from seeking knowledge at the edge of the known universe and beyond. In her new book, Before the Big Bang, Mersini-Houghton recounts her early life in communist Albania, her career as she rose to prominence in the male-dominated field of astrophysics and discusses her research into the multiverse which could fundamentally rewrite our understanding of reality.

Excerpted from Before The Big Bang: The Origin of the Universe and What Lies Beyond by Laura Mersini-Houghton. Published by Mariner Books. Copyright © 2022 by Laura Mersini-Houghton. All rights reserved.

Scientific investigations of problems like the creation of the universe, which we can neither observe nor reproduce and test in a lab, are similar to detective work in that they rely on intuition as well as evidence. Like a detective, as pieces of the puzzle start falling into place, researchers can intuitively sense the answer is close. This was the feeling I had as Rich and I tried to figure out how we could test our theory about the multiverse. Rationally, it seemed like a long shot, but intuitively, it seemed achievable.

https://youtu.be/pDSEjaDCtOU?t=2526

Ian Hutchinson’s concerns for existential risk after minute 42.

Ian Hutchinson is a nuclear engineer and plasma physicist at MIT. He has made a number of important contributions in plasma physics including the magnetic confinement of plasmas seeking to enable fusion reactions, which is the energy source of the stars, to be used for practical energy production. Current nuclear reactors are based on fission as we discuss. Ian has also written on the philosophy of science and the relationship between science and religion.

Continue reading “Ian Hutchinson: Nuclear Fusion, Plasma Physics, and Religion” »

University of Cambridge physicists have developed a theoretical foundation for the existence of wormholes, which are pipelines that connect two dissimilar places in space-time. Time travel and instant communication across great distances may become possible if a piece of data or a physical object could pass through the wormhole.

“But there’s a problem: Einstein’s wormholes are extremely unsteady, and they don’t stay open long enough for something to pass over.”

In 1988, physicists reached the deduction that a type of negative energy called Casimir energy might keep wormholes open.

Black holes are astronomical objects with extremely strong gravitational pulls from which not even light can escape. While the idea of bodies that would trap light has been around since the 18th century, the first direct observation of black holes took place in 2015.

Since then, physicists have conducted countless theoretical and experimental studies aimed at better understanding these fascinating cosmological objects. This had led to many discoveries and theories about the unique characteristics, properties, and dynamics of black holes.

Researchers at Ludwig-Maximilians-Universität and Max-Planck-Institut für Physik have recently carried out a theoretical study exploring the possible existence of vortices in black holes. Their paper, published in Physical Review Letters, shows that black holes should theoretically be able to admit vortex structures.

With the upgraded detectors at the Laser Interferometer Gravitational-Wave Observatory (LIGO) and its sister facility Virgo, researchers can now measure significantly finer details of the gravitational-wave signals released from black hole mergers. This progress opens tantalizing prospects for black hole spectroscopy, a technique that involves analyzing the signal-frequency spectra of gravitational waves and that could be used to test the limits of the general theory of relativity. In 2019, an analysis of the first detected gravitational-wave signal (GW150914) indicated that it contained multiple tones, or “overtones” (see Synopsis: Hunting for Hair on Coalescing Black Holes), a finding that could lead to novel spectroscopy approaches. Now a new analysis of GW150914 by Roberto Cotesta of Johns Hopkins University in Baltimore and colleagues challenges that previous claim. Cotesta and his colleagues find that the suspected overtones could be caused by noise [1].

The overtones presented in the 2019 study were extracted from the “ringdown” phase of the merger, when the remnant black hole shakes like a struck bell. Cotesta and his colleagues wanted to test whether that 2019 conclusion was robust to the input assumptions used for the extraction. These assumptions include the time at which the gravitational-wave signal peaks and the noise that contributes to the measured signal. The team finds that the procedure is not robust and that some noise patterns—such as fluctuations occurring right around the signal peak—produce artifacts in the data that resemble overtones.

Theoretical physicist Swetha Bhagwat at the University of Birmingham, UK, who wasn’t involved in either study, says that while neither analysis has obvious faults, the fact that slight differences in the parameters used by the two teams lead to opposing conclusions highlights the need for further scrutiny. The detection of overtones has exciting implications for black hole spectroscopy, so it’s very important that the community debates this issue, she says.