Black hole

Oct 19 2021

Black holes determine the evolution of the universe

In principle, they can only be recognized by what you can't see - and yet black holes have a decisive effect on the evolution of the universe. That's according to a new study by an international team of researchers from the University of Bologna and elsewhere. The work, published in Nature Astronomy, focuses on the Nest200047 system - a group of about 20 galaxies at a distance of about 200 million light-years from Earth. The central galaxy of this system hosts an active black hole, around which the researchers observed many pairs of gas bubbles of different ages, some unknown…

Let there be light: How to generate photons from nothing

Astrophysics

Sep 10 2021

Let there be light: How to generate photons from nothing

From black holes we know the effect of Hawking radiation: If in vacuum a pair of photons is born in a random way and one of them falls into the black hole, the other one remains: light from nothing. The energy debt to the universe must be paid by the black hole, which is why it evaporates over many billions of years. But there is a second trick. With the black hole the gravity plays the role of the magician who makes the one photon disappear. But according to the equivalence principle of the general relativity, the wizard can…

The birth of supermassive black holes from dark matter – and their growth

Astrophysics

Jun 17 2021

The birth of supermassive black holes from dark matter – and their growth

The universe is about 13.8 billion years old. In the beginning, there were no stars in it. But 600 to 800 million years later already mighty galaxies existed with gigantic black holes in their center, which are millions to billions times heavier than our sun. But where did these giants come from? For a long time it was assumed that they could have been formed by the collapse of gas clouds in protogalaxies. But the result is unsatisfactory. In this way, the black holes simply don't grow fast enough. A team led by a theoretical physicist at the University…

Merging boson stars instead of colliding black holes?

Astrophysics

Feb 27 2021

Merging boson stars instead of colliding black holes?

Bosons are particles with an even spin. They include the fundamental particles that mediate the individual interactions (such as photons for electromagnetism), but also composite particles such as helium-4 atoms. Their peculiarity is that any number of them can occupy the same ground state. They are then indistinguishable from each other and form a Bose-Einstein condensate with unusual properties. Among other things, the density of the condensate can approach infinity. This would make bosons good candidates for very heavy celestial bodies, where huge masses crowd into a small space. Who doesn't think of a black hole? But a celestial…

Astrophysics

Feb 22 2021

When a star rips apart …

... a muon deep under the ice of Antarctica creates a trace in a gigantic detector. The muon was created because a high-energy neutrino interacted with an atom in the detector. The neutrino began its journey about 700 million years ago, around the time the first animals evolved on Earth. That's the travel time it took for the particle to get from the distant, unnamed galaxy (cataloged as 2MASX J20570298+1412165) in the constellation of The Dolphin to Earth. It occurred as a result of "AT2019dsg." This is what astronomers call an event in which a star was ripped apart…

Premature birth? The most distant quasar raises questions

Astrophysics

Jan 13 2021

Premature birth? The most distant quasar raises questions

Astronomers have discovered the most distant quasar yet. The monstrous celestial object called J0313-1806, which existed 670 million years after the Big Bang, shines thousands of times brighter than the Milky Way and is powered by another extreme, the earliest supermassive black hole, more than 1.6 billion times the mass of the Sun. This fully formed distant quasar with a redshift of z = 7.64, formed more than 13 billion years ago, is also the earliest quasar discovered to date, giving astronomers a glimpse of how massive galaxies formed in the early universe. Quasars, powered by the feeding orgies…

Were the first black holes born in the form of baby universes?

Astrophysics

Dec 30 2020

Were the first black holes born in the form of baby universes?

Shortly after the Big Bang, the universe was still impenetrable. Its density was so high that a variation of only 50 percent - a coffee bean in a cake batter - would have been enough to produce a black hole immediately. The density was at least variable enough to let grow whole galaxies from the differences later. However, there seem to have been no "coffee beans" at that time - this is revealed today by the rather uniform cosmic background radiation. Nevertheless, so-called promordial black holes could have been formed at that time, just on other ways. They could…

Massive black hole turns star in solar size into spaghetti

Astrophysics

Oct 25 2020

Massive black hole turns star in solar size into spaghetti

About 215 million years ago the fate of a star was fulfilled: It was swallowed by a black hole with a million solar masses. The death struggle dragged on for a whole month. Meanwhile, the dying star was bidding farewell, a high-energy flare that emitted enough energy in the X-ray range alone to accelerate the Earth to one percent of the speed of light. This flare, called AT2019qiz and registered on Earth in 2019, was a gift to terrestrial astronomers. It is the first star death of this kind that was discovered so close to the Earth (although 215…