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Category: cosmology

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.

Largest ever radio sky survey maps the universe in unprecedented detail

An international collaboration using the Low Frequency Array (LOFAR) has published an exceptionally detailed radio sky map, revealing 13.7 million cosmic sources and delivering the most complete census yet of actively growing supermassive black holes. It showcases an extraordinary variety of systems powered by these black holes, whose radio emission can extend for millions of light-years.

The newly released LOFAR Two-meter Sky Survey (LoTSS-DR3) marks a major milestone in radio astronomy and international scientific collaboration. The results will be published in Astronomy & Astrophysics.

By observing the sky at low radio frequencies, the survey reveals a dramatically different view of the universe than that seen at optical wavelengths. Much of the detected emission arises from relativistic particles moving through magnetic fields, allowing astronomers to trace energetic phenomena such as powerful jets from supermassive black holes and galaxies undergoing extreme star formation across cosmic time.

Quantum entanglement offers route to higher-resolution optical astronomy

Researchers in the US have demonstrated how quantum entanglement could be used to detect optical signals from astronomical sources at the single-photon level. Published in Nature, a team led by Pieter-Jan Stas at Harvard University showed how extremely weak light signals could be detected across a fiber link spanning more than 1.5 km—possibly paving the way for optical telescopes with unprecedented resolution.

Interferometry is often used in astronomy to produce high-resolution images of distant objects. By combining light collected across networks of spatially separated detectors, the technique can achieve resolutions comparable to those of a single telescope with a diameter equivalent to the distance between them. In continent-spanning networks like the Event Horizon Telescope, it was used to create the first direct image of a black hole (Messier 87) in 2019.

Multi-wavelength observations track bright gamma-ray blazar’s three-year cycle

By analyzing the data from various space observatories and ground-based telescopes, European astronomers have performed a multiwavelength study of a bright gamma-ray blazar known as S5 1044+71. The new study, published Feb. 26 on the arXiv pre-print server, delivers a comprehensive view of this blazar, which could help us better understand its nature.

Blazars are very compact quasi-stellar objects (quasars) associated with supermassive black holes (SMBHs) at the centers of active, giant elliptical galaxies. They are the most luminous and extreme subclass of active galactic nuclei (AGNs). The characteristic features of blazars are highly collimated relativistic jets pointed almost exactly toward Earth.

Astronomers divide blazars into two classes, based on their optical emission properties: flat-spectrum radio quasars (FSRQs) that feature prominent and broad optical emission lines, and BL Lacertae objects (BL Lacs), which do not.

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