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Category: cosmology

Gravitational wave signal tests Einstein’s theory of general relativity

For those who watch gravitational waves roll in from the universe, GW250114 is a big one. It’s the clearest gravitational wave signal from a binary black hole merger to date, and it gives researchers an opportunity to test Albert Einstein’s theory of gravity, known as general relativity.

“What’s fantastic is the event is pretty much identical to the first one we observed 10 years ago, GW150914. The reason it’s so much clearer is purely because our detectors have become much more accurate in the past 10 years,” said Cornell physicist Keefe Mitman, a NASA Hubble Postdoctoral Fellow at the Cornell Center for Astrophysics and Planetary Science in the College of Arts and Sciences.

Mitman is a co-author of the paper analyzing the wave, “Black Hole Spectroscopy and Tests of General Relativity with GW250114,” published in Physical Review Letters. It was written by the LIGO Scientific Collaboration, the Virgo Collaboration in Italy and the KAGRA Collaboration in Japan. Cornell researchers have been leading contributors to the LIGO-VIRGO-KAGRA project since its beginning in the early 1990s.

Massive runaway stars in the Milky Way: Observational study explores origins and ejection process

Researchers from the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) and the Institute of Space Studies of Catalonia (IEEC), in collaboration with the Institute of Astrophysics of the Canary Islands (IAC), have led the most extensive observational study to date of runaway massive stars, which includes an analysis of the rotation and binarity of these stars in our galaxy.

This study, published in the journal Astronomy & Astrophysics, sheds new light on how these stellar “runaways” are ejected into space and what their properties reveal about their fascinating origins.

Runaway stars are stars that move through space at unusually high speeds, drifting away from the places where they were born. For a long time, the way massive runaway stars acquire these high velocities has remained a mystery to astronomers, who have considered two main scenarios: a violent kick when a companion explodes as a supernova in a binary system, or a gravitational ejection during close encounters in dense, young star clusters.

Webb pushes boundaries of observable Universe closer to Big Bang

The NASA/ESA/CSA James Webb Space Telescope has topped itself once again, delivering on its promise to push the boundaries of the observable Universe closer to cosmic dawn with the confirmation of a bright galaxy that existed 280 million years after the Big Bang.

By now Webb has established that it will eventually surpass virtually every benchmark it sets in these early years, but the newly confirmed galaxy, MoM-z14, holds intriguing clues to the Universe’s historical timeline and just how different a place the early Universe was than astronomers expected.

“With Webb, we are able to see farther than humans ever have before, and it looks nothing like what we predicted, which is both challenging and exciting,” said Rohan Naidu of the Massachusetts Institute of Technology’s (MIT) Kavli Institute for Astrophysics and Space Research, lead author of a paper on galaxy MoM-z14 published in the Open Journal of Astrophysics.

NASA Webb Pushes Boundaries of Observable Universe Closer to Big Bang

NASA’s James Webb Space Telescope has topped itself once again, delivering on its promise to push the boundaries of the observable universe closer to cosmic dawn with the confirmation of a bright galaxy that existed 280 million years after the big bang. By now Webb has established that it will eventually surpass virtually every benchmark it sets in these early years, but the newly confirmed galaxy, MoM-z14, holds intriguing clues to the universe’s historical timeline and just how different a place the early universe was than astronomers expected.

“With Webb, we are able to see farther than humans ever have before, and it looks nothing like what we predicted, which is both challenging and exciting,” said Rohan Naidu of the Massachusetts Institute of Technology’s (MIT) Kavli Institute for Astrophysics and Space Research, lead author of a paper on galaxy MoM-z14 published in the Open Journal of Astrophysics.

Due to the expansion of the universe that is driven by dark energy, discussion of physical distances and “years ago” becomes tricky when looking this far. Using Webb’s NIRSpec (Near-Infrared Spectrograph) instrument, astronomers confirmed that MoM-z14 has a cosmological redshift of 14.44, meaning that its light has been travelling through (expanding) space, being stretched and “shifted” to longer, redder wavelengths, for about 13.5 of the universe’s estimated 13.8 billion years of existence.

Scientists may be approaching a ‘fundamental breakthrough in cosmology and particle physics’ — if dark matter and ’ghost particles’ can interact

Astronomers found evidence that dark matter and neutrinos may interact, hinting at a “fundamental breakthrough” that challenges our understanding of how the universe evolved.

‘The dream has come true’: Standard model of cosmology holds up in massive 6-year study of the universe — with one big caveat

The six-year Dark Energy Survey has released its full results, showing that two leading models of cosmology are equally valid — but both fail to explain one key observation.

Milky Way is embedded in a ‘large-scale sheet’ of dark matter, which explains motions of nearby galaxies

Computer simulations carried out by astronomers from the University of Groningen in collaboration with researchers from Germany, France and Sweden show that most of the (dark) matter beyond the Local Group of galaxies (which includes the Milky Way and the Andromeda galaxy) must be organized in an extended plane. Above and below this plane are large voids. The observed motions of nearby galaxies and the joint masses of the Milky Way and the Andromeda galaxy can only be properly explained with this “flat” mass distribution. The research, led by Ph.D. graduate Ewoud Wempe and Professor Amina Helmi, is published in Nature Astronomy.

Almost a century ago, astronomer Edwin Hubble discovered that virtually all galaxies are moving away from the Milky Way. This is important evidence for the expansion of the universe and for the Big Bang. But even in Hubble’s time, it was clear that there were exceptions. For example, our neighboring galaxy, Andromeda, is moving toward us at a speed of about 100 kilometers per second.

In fact, for half a century, astronomers have been wondering why most large nearby galaxies—with the exception of Andromeda—are moving away from us and do not seem to be affected by the mass and gravity of the so-called Local Group (the Milky Way, the Andromeda galaxy and dozens of smaller galaxies).

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