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Category: cosmology

A 100-solar-mass black hole merger ripples spacetime, and may flash in gamma rays

An international team from China and Italy has reported a possible cosmic encore to the landmark 2017 multi-messenger discovery. In November 2024, the LIGO-Virgo-KAGRA observatories detected gravitational waves from a binary black hole merger, designated S241125n. Remarkably, just seconds later, satellites recorded a short gamma-ray burst (GRB) from the same region of the sky.

Typically, binary black hole mergers are not expected to produce electromagnetic counterparts. S241125n could be a very rare gravitational-wave event that has been linked to a GRB across multiple wavelengths, extending multi-messenger astronomy into a new regime. Although the association is not yet definitive and will require further follow-up, the probability of a chance coincidence appears low, making the result statistically intriguing while warranting caution.

The deep mystery physicists call “the problem of time” | Jim Al-Khalili: Full Interview

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Brian Cox: The quantum roots of reality | Full Interview ► • Brian Cox: The quantum roots of reality |…

Time feels obvious, but physics tells a stranger story about its existence: Theoretical physicist Jim Al-Khalili explores why our sense of time may be incredibly misleading, including the idea that past, present, and future might all exist at once.

0:00 Chapter 1: Does time flow?
2:42 Why Time Feels Faster as We Age.
3:56 Time and Change in Philosophy and Physics.
5:28 Einstein and the End of Absolute Time.
6:19 Time in the Equations of Physics.
7:50 Chapter 2: How do we reconcile quantum field theory with the general theory of relativity?
12:10 Evidence for Time Dilation: Muons.
14:29 Gravity Slows Time: General Relativity.
19:22 Space-Time and the Block Universe.
21:55 Does Time Really Exist?
26:33 The Debate: Eternalism vs Presentism.
34:12 Chapter 3: Is There a “Now”?
40:40 Chapter 4: Why Does Thermodynamics Have a Direction in Time?
49:38 Quantum Entanglement and the Direction of Time.
55:10 Did Time Begin at the Big Bang?
45:00 Will Time End?
1:05:40 Chapter 5: Is Time Travel Possible?

Strange ‘Chirp’ May Reveal What Powers The Brightest Supernovae in The Universe

A strange chirp appeared in the light from a massive stellar explosion.

Scientists think it may be the signature of a newborn magnetar 🧲⭐

Full story.

A never-before-seen ‘chirp’ in the light of an exploding star has revealed new clues about the engine powering some of the brightest supernovae in the Universe.

According to an analysis of the unprecedented signal, a superluminous supernova named SN 2024afav was most likely the violent birth of a magnetar – a rapidly spinning, extremely magnetic neutron star whose environment is ‘wobbling’ due to an effect predicted by general relativity.

The event, says a team led by astrophysicist Joseph Farah of Las Cumbres Observatory in the US, marks the first observational evidence of this effect, known as Lense-Thirring precession, in the environment of a magnetar.

Continue reading “Strange ‘Chirp’ May Reveal What Powers The Brightest Supernovae in The Universe” | >

The universe is humming with ripples in spacetime: Scientists just doubled our catalog of black hole and neutron star collisions

“The message from this catalog is: We are expanding into new parts of what we call ‘parameter space’ and a whole new variety of black holes,” LVK member Daniel Williams, of the University of Glasgow in the U.K., said in the statement. “We are really pushing the edges, and are seeing things that are more massive, spinning faster, and are more astrophysically interesting and unusual.”

The catalog also demonstrates just how sensitive the LVK detectors have become. Some of the neutron star mergers occurred up to 1 billion light-years away, while some of the black hole mergers occurred up to 10 billion light-years away. These detections have allowed scientists to test the theory that first predicted the existence of both black holes and gravitational waves, Einstein’s magnum opus theory of gravity, general relativity.

Cosmic microwave background

(CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dark. However, a sufficiently sensitive radio telescope detects a faint background glow that is almost uniform and is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the electromagnetic spectrum. Its energy density exceeds that of all the photons emitted by all the stars in the history of the universe. The accidental discovery of the CMB in 1964 by American radio astronomers Arno Allan Penzias and Robert Woodrow Wilson was the culmination of work initiated in the 1940s.

The CMB is the key experimental evidence of the Big Bang theory for the origin of the universe. In the Big Bang cosmological models, during the earliest periods, the universe was filled with an opaque fog of dense, hot plasma of sub-atomic particles. As the universe expanded, this plasma cooled to the point where protons and electrons combined to form neutral atoms of mostly hydrogen. Unlike the plasma, these atoms could not scatter thermal radiation by Thomson scattering, and so the universe became transparent. Known as the recombination epoch, this decoupling event released photons to travel freely through space. However, the photons have grown less energetic due to the cosmological redshift associated with the expansion of the universe. The surface of last scattering refers to a shell at the right distance in space so photons are now received that were originally emitted at the time of decoupling.

The CMB is very smooth and uniform, but maps by sensitive detectors detect small but important temperature variations. Ground and space-based experiments such as COBE, WMAP and Planck have been used to measure these temperature inhomogeneities. The anisotropy structure is influenced by various interactions of matter and photons up to the point of decoupling, which results in a characteristic pattern of tiny ripples that varies with angular scale. The distribution of the anisotropy across the sky has frequency components that can be represented by a power spectrum displaying a sequence of peaks and valleys. The peak values of this spectrum hold important information about the physical properties of the early universe: the first peak determines the overall curvature of the universe, while the second and third peak detail the density of normal matter and so-called dark matter, respectively.

Fluid simulation at unprecedented scale provides toolkit for fundamental physics and applied fluid engineering

What governs the speed at which raindrops fall, sediment settles in river estuaries, and matter is ejected during a supernova? These questions circle around one, deceitfully simple factor: the rate at which a fluid filled with particles mixes with a particle-free one. Raindrops travel from one layer of air to another; sediment falls from river to seawater, and ejecta travels from the exploding star through the surrounding dust cloud. The same principle dictates sediment mixing in rising smoke, dust storms, nuclear explosions, hydrocarbon refining, metal smelting, wastewater treatment, and more.

New simulations have now provided researchers and engineers with unprecedented access to these fundamental fluid mechanics. While plainly visible in everyday life, the phenomenon has eluded scientific scrutiny due to their complexity. For the first time, researchers have derived a general formulation of how layers of heavy particles mix and described the common characteristics of the phenomena.

Simone Tandurella, study first author and Ph.D. student in the Complex Fluids and Flows Unit at OIST, explains, “Both the simulations and the model we obtain enable exciting research into a wide range of fundamental physics phenomena, as well as applied research in fluid engineering. They provide the basic puzzle pieces that can help us understand fluid-particle instabilities at large scales.”

Galaxy-group motion suggests slower expansion in our cosmic neighborhood

Two new studies have measured the expansion of the universe in our immediate cosmic neighborhood using a novel method that analyzes the motion of two nearby galaxy groups within their surrounding cosmic flow. The results indicate that the local universe is expanding more slowly than previously estimated, bringing measurements of nearby galaxies into close agreement with observations of the early universe. The findings also suggest that less dark matter is required to explain the dynamics of galaxies within these groups than previously assumed.

The two studies were recently published in Astronomy & Astrophysics by an international team including David Benisty from the Leibniz Institute for Astrophysics Potsdam (AIP). Each paper analyzes observational data for a different nearby galaxy group—the Centaurus A group and the M81 group—to determine both their masses and the value of the Hubble constant.

The Hubble constant describes how fast the universe expands, expressed as a ratio of the recessional velocity to the distance a galaxy has toward us. The Hubble constant is measured in km/s per Megaparsec, 1 Megaparsec being 3.3 million light years.

Oval orbit casts new light on black hole–neutron star mergers

Scientists have uncovered the first robust evidence of a black hole and neutron star crashing together but orbiting in an oval path rather than a perfect circle just before they merged. This discovery challenges long-standing assumptions about how these cosmic pairs form and evolve.

Researchers from the University of Birmingham, Universidad Autónoma de Madrid, and Max Planck Institute for Gravitational Physics published their findings today (11 Mar) in The Astrophysical Journal Letters.

Most neutron star-black hole pairs are expected to adopt circular orbits long before merging. But the analysis of the gravitational-wave event GW200105 shows that this system traveled on an oval orbit long before merging to form a black hole 13 times more massive than the sun. An oval orbit is something never seen before in this kind of collision.

Astronomers Spot Bizarre Supernova That Could Unlock the Secret of Dark Energy

A rare gravitationally lensed supernova could help astronomers determine how fast the universe is expanding and shed light on dark energy. Astronomers may be closer to understanding one of the greatest mysteries in cosmology: dark energy, the unknown force thought to be driving the accelerating e

JWST Detects Evidence of “Monster Stars” That May Have Created the Universe’s First Giant Black Holes

Using the James Webb Space Telescope, an international team of researchers has discovered chemical fingerprints from enormous primordial stars that were among the first to form after the Big Bang.

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