Astrophysics

What are time crystals? Astrophysics

What are time crystals?

Ice crystals are more orderly than flowing water - right? Wrong. There is a so-called translational symmetry in the liquid. That is, no matter where we look in the stream, it always looks the same. However, when the water freezes, its molecules arrange themselves in a fixed lattice. Now, if we look at a particular spot, there is either a molecule there (if we are lucky) - or not (if we caught the interstices of the crystal). The translational symmetry of the system is broken, the physicist says, in terms of spatial coordinates. Moreover, crystals are normally in the…
Black holes determine the evolution of the universe Astrophysics

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…
A planet at maximum fluffiness Astrophysics

A planet at maximum fluffiness

It's not often that the word "fluffy" appears in a press release about a new astronomical discovery. It refers to the exoplanet WASP-127b, which orbits a star a good 500 light-years from Earth that is slightly larger than the Sun. An international team of astronomers has now not only detected clouds there, but also measured their height with unprecedented precision. WASP-127b is a so-called "hot Saturn" - a giant planet with a similar mass to Saturn, but unlike our (cold) Saturn, it orbits very close to its sun. During one orbit around its star, WASP-127b therefore receives 600 times more radiation…
A huge hole in space Astrophysics

A huge hole in space

About 500 to 1000 light-years from Earth, two large masses of cold cosmic matter are concentrated in space. "Cold" because they are matter in molecular form. The Perseus and Taurus molecular clouds each contain so much mass that at least 10,000 suns could form from them. Nevertheless, they are almost invisible in their entire extent, because they do not glow. The situation is different in the infrared. Heat radiation arises here, because an area concentrates more and more and gives birth to new stars. Between these two clouds, however, there is no normal interstellar matter. Rather, astronomers have now…
Let there be light: How to generate photons from nothing Astrophysics

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…
Sharpest radio image of the Andromeda galaxy achieved Astrophysics

Sharpest radio image of the Andromeda galaxy achieved

The Andromeda Galaxy is the closest spiral galaxy to the Milky Way - but still 2.5 million light-years away. Details are therefore difficult to discern. This makes it all the more important to observe our future home (Andromeda will merge with the Milky Way in a few billion years) in all possible wavelengths. Each region of the spectrum reveals different secrets. Such an image has now been obtained with unprecedented accuracy at the microwave frequency of 6.6 GHz by physicist Sofia Fatigoni of the University of British Columbia, together with colleagues from the Sapienza University of Rome and the…
Atomic nucleus swallows electrons: New supernova type found Astrophysics

Atomic nucleus swallows electrons: New supernova type found

At the end of its life, stars, if they are only heavy enough, perish in a gigantic firework, a supernova. Up to now, one knew roughly two ways to get there. A core-collapse supernova occurs when a massive star - one with more than 10 times the mass of the Sun - runs out of nuclear fuel and its iron core collapses, creating a black hole or neutron star. On the other hand, if a white dwarf - a low-mass star at the end of its lifetime - captures so much mass from a companion that it becomes unstable,…
The birth of supermassive black holes from dark matter – and their growth Astrophysics

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…