Astrophysics

How do you weigh a particle that you don’t even know exists? Astrophysics
Feb 27 2022

How do you weigh a particle that you don’t even know exists?

Dark matter accounts for 85 percent of the mass content of the universe. Researchers call it "dark" because we don't notice anything about it - except for its gravity. However, it can be detected quite well. Without dark matter, galaxies would move differently than they demonstrably do, and the universe would have a different structure. The physicists need the Dumkle materie thus, in order to explain the cosmos. Too bad that they still do not know what it consists of. There are candidates for it: MACHOs (massive compact halo objects), for example, WIMPs (weakly interacting massive particles) and even invisible…
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How warm was the universe 880 million years after the Big Bang? Astrophysics
Feb 3 2022

How warm was the universe 880 million years after the Big Bang?

13.8 billion years ago, the universe was hotter than hot. Then it expanded and cooled down - to 2.725 Kelvin today, the temperature of the cosmic background radiation. From the moment the cosmic background radiation was released until today, the universe has expanded by a factor of about 1100. The cosmic background radiation, which originally had a temperature of about 3000 Kelvin and whose thermal radiation thus looked at that time as similar as the light of a halogen lamp, cooled down by the same factor. Of course, the entire universe was never equally warm everywhere. This makes it…
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Is there a highest temperature? Astrophysics
Jan 27 2022

Is there a highest temperature?

It cannot get colder than -273.15 degrees Celsius (0 Kelvin, -459,67 Fahrenheit). The reason physics gives for this is that temperature is a measure of the kinetic energy of particles, i.e. it tells us something about how fast they are moving. When all motion stops, we have reached the minimum of the temperature scale, which by definition is 0. But is there also a highest temperature? One could assume that, because there is not only a minimum speed (0), but also a maximum speed (the speed of light c). But then it is not so simple, because the energy…
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X(3872): A mysterious particle from the early days of the universe Astrophysics
Jan 26 2022

X(3872): A mysterious particle from the early days of the universe

At the very beginning of the universe, it was still very, very hot. At that time, matter did not consist of the particles we know today, such as protons or neutrons. If it becomes too hot for these particles (generally called hadrons), they start to boil and decompose into their components, like water becomes steam. For this it must be at least 1.7 trillion Kelvin (3 trillion Fahrenheit) hot, the so-called Hagedorn temperature. The particles which then float in the soup, the plasma, are on the one hand quarks, on the other hand gluons. The gluons are normally the…
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How a false vacuum could lead to the destruction of the universe Astrophysics
Jan 21 2022

How a false vacuum could lead to the destruction of the universe

When physicists at CERN discovered the Higgs boson in 2012 with the help of the Large Hadron Collider, they not only confirmed the last important building block of the Standard Model of elementary particle physics, which explains how particles acquire their mass (through the Higgs field, through which they move as through a viscous mass). In the process, they also measured the weight of the Higgs particle, which is 125GeV (giga-electron volts). And this is not just a number: It means that our universe is very likely in a metastable state, i.e. a state that is stable only at…
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How many black holes are there in the universe? Astrophysics
Jan 19 2022

How many black holes are there in the universe?

A lot. If a star is heavy enough (i.e., it is still at least 2.5 solar masses after its supernova), then it continues to collapse until a black hole forms. Such stellar-sized black holes have been forming for quite some time, and more and more are forming. How many are there already? This intriguing question has been addressed by Alex Sicilia, a PhD student under the supervision of Prof. Andrea Lapi and Dr. Lumen Boco of Italy's Scuola Internazionale Superiore di Studi Avanzati. In a first paper just published in the Astrophysical Journal, the authors studied the demography of…
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What does a black hole look like from the inside? Astrophysics
Jan 11 2022

What does a black hole look like from the inside?

A black hole is an amazing phenomenon. It is invisible because it does not even allow light to escape. Nevertheless, it can be imaged. It concentrates mass in a very small part of space - so small that the conventional laws of physics lose their meaning. Nevertheless, physicists are getting closer and closer to its secrets. One of them is what a black hole looks like inside. Black, it is clear, is not there. Quite the opposite. Inside, all the mass and energy that cannot escape the event horizon are concentrated. If one could see in a black hole,…
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Why we don’t stick to the ground with our bellies – or why our earth is not a super earth Astrophysics
Jan 9 2022

Why we don’t stick to the ground with our bellies – or why our earth is not a super earth

During the search for exoplanets astronomers notice again and again that our solar system seems to be clearly out of the way. There are neither "hot Jupiters" (gas giants in the proximity of the central star) nor super earths (rock worlds with more than three times earth mass). At first it was thought that this could be due to the way of searching. The techniques used work particularly well with celestial bodies that are very large and orbit close to their star. In the meantime, however, the list of exoplanets is clearly in four digits, and super-Earths are still…
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