Predictions indicate that wormholes and black holes may have nearly identical polarized light spectra, making these astrophysical objects difficult to distinguish.
Category: cosmology – Page 229
Predicting Black Hole Radio-Wave Hot Spots
Characterized by just three parameters—mass, spin, and charge—black holes could be considered one of the Universe’s simpler astrophysical objects. Yet, the number of open problems related to how the dark behemoths behave also marks them as one of the most enigmatic. One puzzle is why the plasma around black holes glows so brightly. Now, in 3D simulations of the magnetic fields within this plasma, Benjamin Crinquand of Princeton University and colleagues think they have found the answer: the breaking and reconnecting of magnetic-field lines [1]. The simulations predict that, under certain conditions, magnetic-field instabilities can induce radio-wave hot spots that rotate around the shadow of the black hole. This prediction could be tested by future versions of the Event Horizon Telescope (EHT)—the network of radio dishes used to capture the first black hole images (see Research News: First Image of the Milky Way’s Black Hole).
There are several mechanisms that physicists think could be behind a black hole’s light. One of those is so-called accretion power, where friction-like forces in the infalling plasma heat the plasma, leading to the emission of photons. Models of this process predict constant emission signals, which doesn’t seem to fit with observations of high-intensity bursts of gamma rays from black holes.
Another possibility—and the one that Crinquand and his colleagues consider—is that the energy needed to create this light is extracted from the magnetic field that threads through the plasma. When the lines associated with this field break apart and then reconnect—a process known as magnetic reconnection—magnetic-field energy can convert into plasma-kinetic energy that is then emitted as photons. This model would not replace the accretion one, but act in tandem with it.
Famous Stephen Hawking theory about black holes confirmed
One of Stephen Hawking’s most famous theories has been confirmed to be correct, thanks to space-time ripples caused by the merger of the two distant black holes.
The black hole area theorem, which Hawking derived from Einstein’s theory of general relativity in 1971, states that the surface area of a black hole cannot decrease over time. This rule is of importance to physicists because it appears to set time to run in a certain direction: the second law of thermodynamics, which states that the entropy, or disorder, of a closed system must always rise. Because the entropy of a black hole is proportional to its surface area, both must always increase.
The researchers’ confirmation of the area law, according to the new study, appears to suggest that the properties of black holes are crucial hints to the hidden laws that control the universe. Surprisingly, the area law appears to contradict another of the famous physicist’s proven theorems: that black holes should evaporate over incredibly long time scales, suggesting that determining the source of the conflict between the two theories might reveal new physics.
‘Spooky action at a distance’ can lead to a multiverse. Here’s how
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.
Searching for traces of dark matter with neutron spin clocks
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.
Black holes don’t always power gamma-ray bursts, new research shows
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.
Synthetic black holes radiate like real ones
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.
An early universe analog built in a lab in Germany
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.