Researchers have built a small but powerful detector to find gravitational waves in a hidden frequency range. The discovery could expose unseen black hole activity and early-universe echoes.
Category: physics
A new attempt to explain the accelerated expansion of the universe
Why is the universe expanding at an ever-increasing rate? This is one of the most exciting yet unresolved questions in modern physics. Because it cannot be fully answered using our current physical worldview, researchers assume the existence of a mysterious “dark energy.” However, its origin remains unclear to this day.
An international research team from the Center for Applied Space Technology and Microgravity (ZARM) at the University of Bremen and the Transylvanian University of Brașov in Romania has come to the conclusion that the expansion of the universe can be explained—at least in part—without dark energy.
In physics, the evolution of the universe has so far been described by the general theory of relativity and the so-called Friedmann equations. However, in order to explain the observed expansion of the universe on this basis, an additional “dark energy term” must be manually added to the equations.
Not So Dead After All: Astronomers Reveal the Secret Behind Inflated White Dwarfs
White dwarfs are the dense, compact remains left behind when stars exhaust their nuclear fuel, a process that will one day occur to our own Sun. These stellar remnants are known as degenerate stars because their internal physics defy normal expectations: as they gain mass, they actually become smaller in size.
Many white dwarfs exist in pairs, forming what are known as binary systems, where two stars orbit each other. Most of these systems are ancient by galactic standards and have cooled over time to surface temperatures near 4,000 Kelvin.
Yet, astronomers have recently identified a remarkable group of short-period binary systems in which the stars complete an orbit in less than an hour. Surprisingly, these white dwarfs appear to be about twice as large as models predict, with much higher surface temperatures ranging from 10,000 to 30,000 Kelvin.
Can we hear gravitational-wave ‘beats’ in the rhythm of pulsars?
Pulsars suggest that ultra–low-frequency gravitational waves are rippling through the cosmos. The signal seen by international pulsar timing array collaborations in 2023 could come from a stochastic gravitational-wave background—the sum of many distant sources—or from a single nearby binary of supermassive black holes.
To tell these apart, Hideki Asada, theoretical physicist and Professor at Hirosaki University, and Shun Yamamoto, researcher at the Graduate School of Science and Technology, Hirosaki University, propose a method that exploits beat phenomena between gravitational waves at nearly the same frequency, searching for their imprint in the tiny shifts of pulsars’ radio-pulse arrival times.
Their work has been published in the Journal of Cosmology and Astroparticle Physics.
Astronomers uncover collisional signature of filamentary structures in galactic G34 molecular cloud
Using CO (J=1–0) molecular line data obtained from the 13.7-meter millimeter-wave telescope at the Purple Mountain Observatory’s Delingha Observatory, Sun Mingke, a Ph.D. student from the Xinjiang Astronomical Observatory of the Chinese Academy of Sciences and his collaborators conducted a systematic study of the galactic molecular cloud G34. They revealed the collisional signatures and dynamical mechanisms of filamentary structures in this region. The results are published in Astronomy & Astrophysics.
Star formation is one of the key processes that drive the evolution of galaxies and the interstellar medium. Recent observations and theoretical studies suggest that interactions and collisions between large-scale filamentary structures may play an important role in triggering high-mass star formation.
In this study, the researchers identified two giant filaments, designated F1 and F2, in the G34 region. By analyzing their spatial distribution and velocity field, the researchers found clear evidence of ongoing collisions between the filaments.
