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Category: cosmology – Page 203

Over 50 percent of high-mass stars reside in multiple star systems. But due to their complex orbital interactions, physicists have a difficult time understanding just how stable and long-lived these systems are. Recently a team of astronomers applied machine learning techniques to simulations of multiple star systems and found a new way that stars in such systems can arrange themselves.

Classical mechanics has a notorious problem known as the three-body problem. While Newton’s laws of gravity can easily handle calculations of the forces between two objects and their subsequent evolution, there is no known analytic solution when you include a third massive object. In response to that problem, physicists over the centuries have developed various approximation schemes to study these kinds of systems, concluding that the vast majority of possible three-object arrangements are unstable.

But it turns out that there are a lot of multiple-star systems out there in the galaxy. Indeed, over half of all massive stars belong to at least a binary pair, and many of them belong to triple or quadruple star systems. Obviously, the systems last a long time. Otherwise, they would have flung themselves apart a long time ago before we had a chance to observe them. But because of the limitations of our tools, we have difficulty assessing how these systems organize themselves and what stable orbit options exist.

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Source of Dark Energy is black holes combined with Einstein’s gravity — experts Result potentially means nothing new has to be added to our picture of Universe It makes up most of the universe, yet hardly anything is known about the so-called Dark Energy that envelopes us. The unusual ‘something’ – one of the great mysteries of cosmology – is believed to be an unknown force that is pushing things apart more strongly than gravity and causing the universe’s expansion to accelerate.

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Measurements of the magnetic moment of the electron have achieved unprecedented accuracy, showing great potential for the search for physics beyond the standard model.

Despite its remarkable successes, the standard model of particle physics clearly isn’t complete—dark matter, dark energy, and the matter–antimatter asymmetry of the Universe are some of its most flagrant deficiencies. Experimenters thus eagerly search for anomalies that could provide hints on a theory that could complete or replace the standard model. The electron is a key player in this quest: its magnetic moment is both the most precisely measured elementary-particle property and the most accurately verified standard model prediction to date. New measurements by Gerald Gabrielse’s group at Northwestern University in Illinois [1] have determined the value of the electron’s magnetic moment 2.2 times more accurately than the previous best estimate, which was obtained in 2008 [2].

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Research in fundamental science has revealed the existence of quark-gluon plasma (QGP)—a newly identified state of matter—as the constituent of the early universe. Known to have existed a microsecond after the Big Bang, the QGP, essentially a soup of quarks and gluons, cooled down with time to form hadrons like protons and neutrons—the building blocks of all matter.

One way to reproduce the extreme conditions prevailing when QGP existed is through relativistic heavy-ion collisions. In this regard, particle accelerator facilities like the Large Hadron Collider (LHC) and the Relativistic Heavy Ion Collider have furthered our understanding of QGP with experimental data pertaining to such collisions.

Meanwhile, have employed multistage relativistic hydrodynamic models to explain the data, since the QGP behaves very much like a perfect fluid. However, there has been a serious lingering disagreement between these models and data in the region of low transverse momentum, where both the conventional and hybrid models have failed to explain the particle yields observed in the experiments.

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Last summer, the gravitational wave observatory known as LIGO caught its second-ever glimpse of two neutron stars merging. The collision of these incredibly dense objects — the hulking cores of long-ago supernova explosions — sent shudders through space-time powerful enough to be detected here on Earth. But unlike the first merger, which conformed to expectations, this latest event has forced astrophysicists to rethink some basic assumptions about what’s lurking out there in the universe. “We have a dilemma,” said Enrico Ramirez-Ruiz of the University of California, Santa Cruz.

The exceptionally high mass of the two-star system was the first indication that this collision was unprecedented. And while the heft of the stars alone wasn’t enough to cause alarm, it hinted at the surprises to come.

In a paper recently posted to the scientific preprint site arxiv.org, Ramirez-Ruiz and his colleagues argue that GW190425, as the two-star system is known, challenges everything we thought we knew about neutron star pairs. This latest observation appears to be fundamentally incompatible with scientists’ current understanding of how these stars form, and how often. As a result, researchers may need to rethink years of accepted knowledge.

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One of Albert Einstein’s theory of general relativity’s most fascinating predictions is the possibility of black holes, which are created after a massive star reaches the end of its life and collapses. Supermassive black holes as big as 100,000 or ten billion times the Sun are commonly found at the center of most galaxies.

Those are the biggest form of black holes, but it is also thought that primordial black holes (PBHs) also exist. Unlike the big ones, these tiny black holes emerged in the early cosmos through the gravitational collapse of extraordinarily dense areas.

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The global collaboration that delivered us not one but two pictures of supermassive black holes has now peered into one of the brightest lights in the Universe.

The Event Horizon Telescope (EHT), a telescope array comprising radio antennae around the world, studied a distant quasar named NRAO 530, whose light has traveled for 7.5 billion years to reach us.

The resulting data show us the quasar’s engine in incredible detail and will, astronomers say, help us understand the complex physics of these incredible objects, and how they generate such blazing light.

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It’s a hot new early dark energy summer.

We’re still not sure exactly what dark energy is, but it may have played a key role in the early universe.

Physicists can’t see or measure dark energy (hence the name). The only clue that it exists is how it affects the rest of the universe; dark energy is the force that’s driving the universe to keep expanding faster. Physicists Florian Niedermann of Stockholm University and Martin Sloth of the University of Southern Denmark propose that if dark energy formed bubbles in the dark plasma of the early universe, it could solve one of the biggest mysteries in modern physics.

They describe their idea in a recent paper in the journal Physics Letters B.

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These tiny black holes lose mass faster than their massive counterparts, emitting Hawking radiation until they finally evaporate.

One of the most intriguing predictions of Einstein’s general theory of relativity.

When a sufficiently massive star runs out of fuel, it explodes, and the remaining core collapses, leading to the formation of a stellar black hole (ranging from 3 to 100 solar masses).

Supermassive black holes also exist in the center of most galaxies.

So far, astronomers have captured images of two supermassive black holes: one in the center of the galaxy M87 and the most recent in our Milky Way (Sagittarius A*).

But it’s believed that another kind of black hole exists – the primordial or primitive black hole (PBHs). These have a different origin to other black holes, having formed in the early universe through the gravitational collapse of extremely dense regions.

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