Tag

General Relativity

All articles tagged with #general relativity

science2 days ago•27 min saved

LARES-2 tightens Earth's frame-dragging test to ~0.1% accuracy

The LARES-2 laser-ranging satellite, combined with LAGEOS and GRACE data, delivers the most precise measurement of Earth's frame-dragging to about one part in a thousand, providing a stringent confirmation of general relativity in the near-Earth environment and placing tight limits on alternative gravity models such as Chern–Simons gravity, while also improving the understanding of Earth tides through high-precision satellite analysis with GEODYN/UTOPIA and ILRS data.

via Nature|

#chern-simons-gravity #frame-dragging #general-relativity

science3 days ago•5 min saved

First Magnetar Birth Seen in Chirping Supernova

Astronomers monitored SN 2024afav for about 200 days and observed four distinct brightness bumps—the object's light curve chirp—best explained by a newborn magnetar with a tilted accretion disk that undergoes Lense-Thirring precession, a relativistic effect that modulates emitted light. This provides the first direct evidence that magnetars power some superluminous supernovae, supporting Dan Kasen's 2010 theory; the magnetar spins ~4.2 milliseconds with a magnetic field around 3×10^14 gauss. The discovery, published in Nature, confirms GR's role in a stellar explosion and suggests future surveys (e.g., Rubin Observatory) will uncover many more chirping events.

via ScienceDaily|

#general-relativity #lense-thirring #magnetar

space4 days ago•104 min saved

Einstein-powered microlensing uncovers a distant exoplanet in TESS data

NASA's TESS has detected Gaia23bra b using gravitational microlensing—a method based on Einstein's general relativity—marking a rare microlensing planet found in TESS data. Hints first appeared in Gaia data in 2023; Gaia23bra b weighs about 1.6 Jupiter masses and orbits an orange-dwarf star roughly 40,000 light-years away, far beyond TESS's typical transit range. This discovery shows microlensing can reveal planets that transit methods miss and foreshadows Roman Space Telescope-led microlensing surveys, which could uncover many more such worlds.

via Space|

#exoplanets #gaia23bra-b #general-relativity

space-and-spaceflight9 days ago•17 min saved

Gravastar Idea: A Dark-Energy ‘Mini-Universe’ Inside a Black Hole Mimic

Physicists propose gravastars—ultra-compact stars with a thin shell of ordinary matter and an interior powered by dark energy—that externally resemble black holes but lack singularities or event horizons. A new model shows how such objects could form from gravitational collapse and, in the process, trigger a Big Bang–like expansion inside a self-contained mini-universe. The scenario hinges on ideal, finely tuned conditions and does not replace black holes as the default outcome of collapse.

via Gizmodo|

#black-holes #dark-energy #general-relativity

space11 days ago•5 min saved

Star Collapse May Forge a Mini-Universe: Gravastars as Black Hole Alternatives

A new study proposes gravastars—ultra-compact objects formed when collapsing stars create a miniature universe inside, with dark-energy interiors that halt collapse and mimic black holes without horizons or singularities—offering a GR-consistent alternative to black holes. Yet the mechanism requires fine-tuning, questions of stability remain, and it’s unclear how such objects could be distinguished observationally; formation remains a key open problem.

via Universe Today|

#black-holes #but-we-only-need-five-ensure-only-five-so-remove-extra #cosmology

space13 days ago•43 min saved

Time Emerges from Quantum Entanglement, Not a Universal Backdrop

A theoretical study revisits the Page and Wootters idea and argues that time may not be a fundamental backdrop but arises from the entangled relationship between a clock and a system. Using a two-system model (a clock and an oscillator), the work shows that when these subsystems are properly entangled, ordinary quantum motion can emerge and, in the macroscopic/classical limit, the familiar time of classical physics and Schrödinger dynamics appears. The research also notes the clock’s limits in fully quantum regimes and emphasizes the need for the clock to behave classically for time to emerge, while stressing that experimental confirmation remains out of reach and the idea remains speculative.

via The Brighter Side of News|

#emergent-time #general-relativity #page-and-wootters-mechanism

science13 days ago•49 min saved

Loudest Black-Hole Merger Sheds Light on Event Horizons

Scientists analyzed GW250114—the loudest binary black-hole gravitational-wave signal observed to date, from a merger of two ~32-solar-mass black holes detected by LIGO, Virgo, and KAGRA. They identified a direct-waves component near the horizon and used it to measure the remnant black hole’s rotation and surface gravity, offering a new way to study event horizons and test general relativity in the extreme gravity regime.

via Yahoo|

#black-hole #event-horizon #general-relativity

science22 days ago•9 min saved

Dying Stars May Spawn Tiny Universes to Form Gravastars Instead of Black Holes

A new dynamic solution to Einstein’s equations suggests that collapsing massive stars could birth a miniature expanding universe inside, creating a gravastar that counteracts collapse and avoids a singularity or event horizon, potentially explaining a theoretical alternative to black holes. The mechanism hinges on an outward-expanding mini-universe powered by dark energy, balancing gravity to produce a stable gravastar, though it remains a theoretical model and not observational evidence.

via SciTechDaily|

#black-holes #dark-energy #general-relativity

science26 days ago•6 min saved

Dying Stars Could Birth Tiny Universes to Form Gravastars

A new theoretical study proposes that when a massive star collapses, it might birth a miniature universe inside the collapsing matter, driven by dark energy, expanding to counter gravity and halt collapse, thereby forming a stable gravastar instead of a black hole.

via ScienceDaily|

#dark-energy #general-relativity #gravastar

space27 days ago•11 min saved

Milky Way’s Center Comes Into View: First Photo of Sagittarius A*

The Event Horizon Telescope released the first image of the Milky Way’s central black hole, Sagittarius A*, in 2022. The 4-million-solar-mass object lies about 27,000 light-years away. Eight linked radio observatories formed an Earth-sized telescope, and the ring around the shadow matches General Relativity despite the object’s minute-scale variability; researchers now plan time-resolved movies to study gravity in action.

via Space Daily|

#astronomy #black-holes #event-horizon-telescope

space1 month ago•97 min saved

Spacetime crystals could spawn miniature black holes

Goethe University and TU Wien physicists propose that if spacetime can crystallize into a regular four‑dimensional lattice, a tiny energy perturbation could trigger a critical collapse that births microscopic black holes. Their work provides simple, exact solutions to Einstein’s equations for this process and suggests a possible primordial-black-hole pathway, but it does not prove such holes exist and notes they would evaporate quickly via Hawking radiation.

via Space|

#black-holes #general-relativity #primordial-black-holes

space1 month ago•86 min saved

Space-time crystals as seeds for naked singularities and micro black holes, new theory suggests

A new theoretical study argues that a repeating pattern in space-time, called a space-time crystal, could mathematically give rise to naked singularities and microscopic black holes when general relativity is explored in higher dimensions. Using pen-and-paper methods and perturbation theory, the researchers derive analytic self-similar solutions that work in the limit of many dimensions, but in realistic finite dimensions the expressions require extra terms. Current numerical work only reaches up to about 14 dimensions, leaving a gap to fully connect the analytic results to a physical universe. The work shows mathematical possibility, not proof that such objects exist, revisiting Hawking’s historical debate about naked singularities and outlining future steps to bridge theory and numerics.

via Live Science|

#black-holes #dimensions #general-relativity

space1 month ago•2 min saved

Cosmic Acceleration Without Dark Energy? New GR-Based Model Claims Yes

A new paper argues that the universe’s accelerating expansion can be explained purely within Einstein’s general relativity by treating Friedmann spacetimes as unstable during the early radiation era, producing accelerations that mimic dark energy without needing a cosmological constant or exotic energy. If borne out, this approach could replace or modify the standard lambda-CDM model, though its adoption remains uncertain.

via Gizmodo|

#cosmology #dark-energy #friedmann-spacetime

science1 month ago•2 min saved

Quantum Research Opens Door to Time-Travel Messages via Post-Selected Loops

A new physics study suggests that, within general relativity, closed timelike curves (CTCs) and post-selected CTCs could, in principle, allow messages to travel back in time. The idea echoes Interstellar’s plot and remains theoretical, with researchers planning photon-based experiments to test the concept while avoiding paradoxes through post-selection.

via bgr.com|

#closed-timelike-curve #general-relativity #post-selected-ctc

space1 month ago•15 min saved

Ancient Moon Mirrors Still Test Gravity With Millimeter Precision

Apollo-era lunar retroreflectors remain functional, allowing Earth-based lasers to measure the Earth–Moon distance to millimeter precision. The Moon is slowly drifting away at about 3.8 cm/year due to tidal friction, enabling stringent tests of general relativity, with next-generation reflectors and DLLR aiming to improve measurements further.

via Space Daily|

#apollo-reflectors #general-relativity #lunar-laser-ranging