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Category: cosmology – Page 2

Possible ‘superkilonova’ exploded not once but twice

When the most massive stars reach the ends of their lives, they blow up in spectacular supernova explosions, which seed the universe with heavy elements such as carbon and iron. Another type of explosion—the kilonova—occurs when a pair of dense dead stars, called neutron stars, smash together, forging even heavier elements such as gold and uranium. Such heavy elements are among the basic building blocks of stars and planets.

So far, only one kilonova has been unambiguously confirmed to date, a historic event known as GW170817, which took place in 2017. In that case, two neutron stars smashed together, sending ripples in space-time, known as gravitational waves, as well as light waves across the cosmos.

The cosmic blast was detected in gravitational waves by the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO) and its European partner, the Virgo gravitational-wave detector, and in light waves by dozens of ground-based and space telescopes around the world.

Strange, Record-Breaking Gamma-Ray Explosion Lasted 7 Hours and Defies Explanation

Data collected using multiple NSF NOIRLab facilities reveal a gamma-ray burst that lasted more than seven hours and originated in a massive, extremely dust-rich galaxy. Gamma-ray bursts (GRBs) rank among the most extreme explosions known in the Universe, surpassed only by the Big Bang itself. Mos

Laser light and the quantum nature of gravity: Proposed experiment could measure graviton energy exchange

When two black holes merge or two neutron stars collide, gravitational waves can be generated. They spread at the speed of light and cause tiny distortions in space-time. Albert Einstein predicted their existence, and the first direct experimental observation dates from 2015.

Now, Prof. Ralf Schützhold, theoretical physicist at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), is going one step further. He has conceived an experiment through which gravitational waves can not only be observed but even manipulated. Published in the journal Physical Review Letters, the idea could also deliver new insights into the hitherto only conjectured quantum nature of gravity.

“Gravity affects everything, including light,” says Schützhold. And this interaction also occurs when gravitational waves and light waves meet.

Dark matter search narrows as detector sets new limits and spots solar neutrinos

Australian researchers have played a central role in a landmark result from the LUX-ZEPLIN (LZ) experiment in South Dakota—the world’s most sensitive dark matter detector. Today, scientists working on the experiment report they have further narrowed constraints on proposed dark matter particles. And, for the first time, the experiment has detected elusive neutrinos produced deep inside the sun.

Scientists hypothesize that dark matter makes up about a quarter of the universe’s mass (or 85% of its matter) but have yet to detect exactly what makes up this strange phenomenon. The result announced today by the LZ experiment is one of the world’s most sensitive measurements in the hunt for dark matter. It has expanded its search for WIMPs (weakly interacting massive particles) down to masses approximately between that of three and nine times that of a proton, the positively charged particle in the nucleus of an atom.

Dr. Theresa Fruth, from the University of Sydney’s School of Physics, is one of only two Australian-based researchers in the 250-member international collaboration.

Astronomers challenge 50-year-old quasar law

Compelling evidence that the structure of matter surrounding supermassive black holes has changed over cosmic time has been uncovered by an international team of astronomers.

If true, the research led by the National Observatory of Athens and published in the Monthly Notices of the Royal Astronomical Society would challenge a fundamental law which has existed for almost five decades.

Einstein’s theory comes wrapped up with a bow: Astronomers spot star ‘wobbling’ around black hole

The cosmos has served up a gift for a group of scientists who have been searching for one of the most elusive phenomena in the night sky. Their study, presented in Science Advances, reports on the very first observations of a swirling vortex in spacetime caused by a rapidly rotating black hole.

The process, known as Lense-Thirring precession or frame-dragging, describes how black holes twist the spacetime that surrounds them, dragging nearby objects like stars and wobbling their orbits along the way.

Neutrino observatories show promise for detecting light dark matter

Dark matter is an elusive type of matter that does not emit, reflect or absorb light, yet is estimated to account for most of the universe’s mass. Over the past decades, many physicists worldwide have been trying to detect this type of matter or signals associated with its presence, employing various approaches and technologies.

As it has never been directly detected before, the composition and properties of dark matter remain mostly unknown. Initially, dark matter searches focused on the detection of relatively heavy particles. More recently, however, physicists also started looking for lighter particles with masses below one giga-electron-volt (GeV), which would thus be lighter than protons.

Researchers at SLAC National Accelerator Laboratory and The Ohio State University recently showed that signatures of these sub-GeV dark matter particles could also be picked up by neutrino observatories, large underground detectors originally designed to study neutrinos (i.e., light particles that weakly interact with regular matter).

ALICE solves mystery of light-nuclei survival

Observations of the formation of light-nuclei from high-energy collisions may help in the hunt for dark matter.

Particle collisions at the Large Hadron Collider (LHC) can reach temperatures over one hundred thousand times hotter than at the center of the sun. Yet, somehow, light atomic nuclei and their antimatter counterparts emerge from this scorching environment unscathed, even though the bonds holding the nuclei together would normally be expected to break at a much lower temperature.

Physicists have puzzled for decades over how this is possible, but now the ALICE collaboration has provided experimental evidence of how it happens, with its results published today in Nature.

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