Cygnus X-1 has intrigued astronomers since it was discovered — and IXPE is uncovering its secrets.
Category: cosmology – Page 213
Some interpretations of quantum mechanics propose that our entire universe is described by a single universal wave function that constantly splits and multiplies, producing a new reality for every possible quantum interaction. That’s quite a bold statement. So how do we get there?
One of the earliest realizations in the history of quantum mechanics is that matter has a wave-like property. The first to propose this was French physicist Louis de Broglie, who argued that every subatomic particle has a wave associated with it, just like light can behave like both a particle and a wave.
Cosmological observations of the orbits of stars and galaxies enable clear conclusions to be drawn about the attractive gravitational forces that act between the celestial bodies.
The astonishing finding: Visible matter is far from sufficient for being able to explain the development or movements of galaxies. This suggests that there exists another, so far unknown, type of matter. Accordingly, in the year 1933, the Swiss physicist and astronomer Fritz Zwicky inferred the existence of what is known now as dark matter. Dark matter is a postulated form of matter which isn’t directly visible but interacts via gravity, and consists of approximately five times more mass than the matter with which we are familiar.
Recently, following a precision experiment developed at the Albert Einstein Center for Fundamental Physics (AEC) at the University of Bern, an international research team succeeded in significantly narrowing the scope for the existence of dark matter. With more than 100 members, the AEC is one of the leading international research organizations in the field of particle physics. The findings of the team, led by Bern, have now been published in Physical Review Letters.
Gamma-ray bursts (GRBs) have been detected by satellites orbiting Earth as luminous flashes of the most energetic gamma-ray radiation lasting milliseconds to hundreds of seconds. These catastrophic blasts occur in distant galaxies, billions of light years from Earth.
A sub-type of GRB known as a short-duration GRB starts life when two neutron stars collide. These ultra-dense stars have the mass of our sun compressed down to half the size of a city like London, and in the final moments of their life, just before triggering a GRB, they generate ripples in space-time—known to astronomers as gravitational waves.
Until now, space scientists have largely agreed that the “engine” powering such energetic and short-lived bursts must always come from a newly formed black hole (a region of space-time where gravity is so strong that nothing, not even light, can escape from it). However, new research by an international team of astrophysicists, led by Dr. Nuria Jordana-Mitjans at the University of Bath, is challenging this scientific orthodoxy.
Research led by the University of Amsterdam has demonstrated that elusive radiation coming from black holes can be studied by mimicking it in the lab.
Black holes are the most extreme objects in the universe, packing so much mass into so little space that nothing—not even light—can escape their gravitational pull once it gets close enough.
Understanding black holes is key to unraveling the most fundamental laws governing the cosmos, because they represent the limits of two of the best-tested theories of physics: the theory of general relativity, which describes gravity as resulting from the (large-scale) warping of spacetime by massive objects, and the theory of quantum mechanics, which describes physics at the smallest length scales. To fully describe black holes, we would need to stitch these two theories together and form a theory of quantum gravity.
The IceCube observatory detected 80 of the elusive particles from the heart of spiral galaxy NGC 1,068, also called the Squid Galaxy.
A team of researchers at Universität Heidelberg has built an early universe analog in their laboratory using chilled potassium atoms. In their paper published in the journal Nature, the group describes their simulator and how it might be used. Silke Weinfurtner, with the University of Nottingham, has published a News & Views piece in the same journal issue outlining the work done by the team in Germany.
Understanding what occurred during the first few moments after the Big Bang is difficult due to the lack of evidence left behind. That leaves astrophysicists with nothing but theory to describe what might have happened. To give credence to their theories, scientists have built models that theoretically represent the conditions being described. In this new effort, the researchers used a new approach to build a physical model in their laboratory to simulate conditions just after the Big Bang.
Beginning with the theory that that the Big Bang gave rise to an expanding universe, the researchers sought to create what they describe as a “quantum field simulator.” Since most theories suggest it was likely that the early universe was very cold, near absolute zero, the researchers created an environment that was very cold. They then added potassium atoms to represent the universe they were trying to simulate.
Like Garfield and lasagna.
AT 2020neh is one of a handful of intermediate-mass black holes identified, and the recent “tidal disruption event” saw it feast on a star.
The scientists said their spacetime simulation “agrees very well with theory.”
A team of physicists used a “quantum field simulator” to simulate a tiny expanding universe made out of ultracold atoms, a report from VICE
Simulating spacetime.
Pixelparticle/iStock.
The scientists conducted the experiment to simulate the early rapid expansion of the universe following the Big Bang. Their work could lead to accurate representations of the universe in future experiments, allowing for the testing of countless models of the early evolution of the cosmos.
A tantalizing signal reported by the XENON1T dark matter experiment has sparked theorists to investigate explanations involving new physics.
On June 16, 2020, the collaboration running XENON1T—one of the world’s most sensitive dark matter detectors—reported a signal it couldn’t explain (see today’s accompanying article, Viewpoint: Dark Matter Detector Delivers Enigmatic Signal). The signal has yet to reach the “5-sigma” bar for discovery, and a mundane explanation could still be the culprit. But theorists have been quick to explore whether exotic particles or interactions might be involved. Physical Review Letters followed a special procedure to get a coherent expert review of the proposals it received. Now, the journal is publishing five papers that represent the breadth of theories being pursued.
All of the reported scenarios explain two aspects of the signal, which was produced in the huge vat of ultrapure xenon that makes up XENON1T’s detector. First, the signal looks like it came from particles that collided mostly with the xenon atoms’ electrons. And second, each of these interactions dumped a few keV into the atom.