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Category: cosmology – Page 4

Event Horizon Telescope images reveal new dark matter detection method

According to a new Physical Review Letters study, black holes could help solve the dark matter mystery. The shadowy regions in black hole images captured by the Event Horizon Telescope can act as ultra-sensitive detectors for the invisible material that makes up most of the universe’s matter.

Dark matter makes up roughly 85% of the universe’s matter, but scientists still don’t know what it actually is. While researchers have proposed countless ways to detect it, this study introduces black hole imaging as a fresh detection method—one that comes with some distinct benefits.

The Event Horizon Telescope’s stunning images of supermassive black holes have revealed more than just the geometry of spacetime; they’ve opened an unexpected window into the search for .

Astronomers detect lowest mass dark object ever measured using gravitational lensing

Dark matter is an enigmatic form of matter not expected to emit light, yet it is essential to understanding how the rich tapestry of stars and galaxies we see in the night sky evolved. As a fundamental building block of the universe, a key question for astronomers is whether dark matter is smooth or clumpy, as this could reveal what it is made of. Since dark matter cannot be observed directly, its properties can only be determined by observing the gravitational lensing effect, whereby the light from a more distant object is distorted and deflected by the gravity of the dark object.

“Hunting for dark objects that do not seem to emit any light is clearly challenging,” said Devon Powell at the Max Planck Institute for Astrophysics and lead author of the study. “Since we can’t see them directly, we instead use very distant galaxies as a backlight to look for their gravitational imprints.”

The research is published in the journal Nature Astronomy.

Simulations unveil the electrodynamic nature of black hole mergers and other spacetime collisions

Gravitational waves are energy-carrying waves produced by the acceleration or disturbance of massive objects. These waves, which were first directly observed in 2015, are known to be produced during various cosmological phenomena, including mergers between two black holes that orbit each other (i.e., binary black holes).

Viscous Stars Can Reflect Gravitational Waves like Black Holes Do

A neutron star’s viscosity determines how the star interacts with gravitational waves, a behavior that could be useful to the study of neutron-star interiors.

The detection of gravitational waves from mergers of black holes and neutron stars has opened a window onto the strong-gravitational-field regime, allowing physicists to put constraints on various gravitational theories [1, 2]. These observations also have the power to probe the ways in which such compact objects interact with gravitational waves hitting their boundaries or, in the case of neutron stars, passing through their interiors [3]. Valentin Boyanov at the University of Lisbon in Portugal and his colleagues have now investigated such interactions in detail, analyzing how an object’s response to passing gravitational waves is influenced by its viscosity [4]. Their results could allow researchers to extract information about the internal structure of neutron stars from future gravitational-wave measurements.

Boyanov and colleagues tackle the following questions: Under what conditions do viscous compact objects such as neutron stars reflect or absorb gravitational waves? And to what extent do these interactions mimic those of black holes? At first, it might seem that black holes in particular cannot be reflective―after all, their defining feature is that they absorb everything that falls on them. But in practice, whether a black hole absorbs or reflects gravitational waves depends on the frequency of those waves. High-frequency gravitational waves cross the event horizon and are absorbed, adding to the black hole’s mass and angular momentum. For low-frequency waves, on the other hand, the curved space time around the black hole constitutes a potential barrier to the wave propagation: The waves are “reflected,” meaning that they scatter off this region with their phase or their propagation direction altered.

Physicists Predict When The Universe Will End in a Reverse Big Bang

If recent discoveries that dark energy is evolving hold any water, our Universe will collapse under its own gravity on a finite timeline, new calculations suggest.

Based on several recent dark energy results, a new model finds that the Universe has a lifespan of just 33.3 billion years. Since we are now 13.8 billion years after the Big Bang, this suggests that we have a smidge less than 20 billion years left.

For another 11 billion years, the Universe will continue to expand, before coming to a halt and reversing direction, collapsing down to the hypothetical Big Crunch, say physicists Hoang Nhan Luu of Donostia International Physics Center in Spain, Yu-Cheng Qiu of Shanghai Jiao Tong University in China, and corresponding author Henry Tye of Cornell University in the US.

Astronomers discover the most ‘pristine’ star in the known universe

Not all stars are created equally. Astronomers believe that the first stars to form after the Big Bang were mostly made of only hydrogen and helium with trace amounts of lithium, as the heavier elements formed later on by nuclear fusion inside the stars. When these stars went supernova, heavier elements spread throughout space and formed more stars. Each successive generation contained more heavy elements, and these elements also became successively heavier.

While most stars still contain mostly hydrogen and helium, they now contain many as well, especially as they get older. These elements show up in spectrographic data when astronomers gather light from these . Stars are considered “pristine” when the data shows a lack of heavy elements—meaning they are likely very rare, older stars from earlier generations. And now, a group of astronomers, led by Alexander Ji from the University of Chicago, believe they have found the most pristine star on record. The group has documented their findings on the arXiv preprint server.

The star, referred to as SDSS J0715-7334, is a red giant purported to have the lowest metallicity—or heavy element content—ever found. The team’s detailed spectral and shows that SDSS J0715-7334 has a total metallicity “Z” of less than 7.8 × 10-7. This is compared to the next lowest metallicity star currently known, a star located in the Milky Way with a total metallicity of around 1.4 × 10-6.

Dark Matter and Dark Energy Don’t Exist, New Study Claims

A new study argues that dark matter and dark energy might be illusions caused by the universe’s forces fading over time. For many years, scientists have thought that dark matter and dark energy make up most of the cosmos. A new study, however, challenges that long-held belief by proposing that th

Rethinking Our Place in the Universe

The new map of the Universe’s expansion history released by the DESI Collaboration offers hints at a breakdown of the standard model of cosmology.

For nearly a century, we have known that our Universe is expanding. For the past quarter-century, we have also known that this expansion is accelerating, a discovery that earned the 2011 Nobel Prize in Physics [1, 2]. But what is the mysterious “dark energy” that drives this acceleration? The simplest explanation involves what Einstein dubbed a “cosmological constant” (Λ) and implies that dark energy is a constant energy inherent to spacetime itself. This idea is the cornerstone of the standard model of cosmology, the Λ cold dark matter (ΛCDM) model, which for decades has consistently explained all available astronomical observations. Now high-precision measurements of the Universe’s expansion history are putting this model to its most stringent test yet. The Dark Energy Spectroscopic Instrument (DESI) has created a cosmic map of unprecedented scale (Fig. 1) [3–9].

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