Astrophysics

Is there a highest temperature? Astrophysics

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

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

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…
How many black holes are there in the universe? Astrophysics

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…
What does a black hole look like from the inside? Astrophysics

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

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…
The death throes of red supergiants Astrophysics

The death throes of red supergiants

For the first time, astronomers have imaged the dramatic end of a red supergiant's life in real time. They observed the rapid self-destruction of a massive star located 120 million light-years from Earth in the galaxy NGC 5731 and its final death throes before collapsing into a type II supernova. Led by researchers at Northwestern University and the University of California, Berkeley (UC Berkeley), the team observed the red supergiant during its last 130 days before its fatal detonation. The discovery, published in the Astrophysical Journal, contradicts previous ideas about how red supergiants evolve just before they explode. Previous observations…
In the ultraviolet the sky never turns black Astrophysics

In the ultraviolet the sky never turns black

The universe is permeated by a universal light. Don't worry, it's not getting esoteric here, and I'm not talking about the cosmic microwave background. It is about a completely different part of the spectrum, on the other side, the ultraviolet range. The so-called Lyman-alpha ultraviolet background was first discovered in the 1960s; its existence was confirmed in 1971. It is formed when light particles of a certain frequency (an excitation frequency of hydrogen) are scattered by neutral hydrogen atoms. Such photons emanate from the Sun in large numbers in the solar system. The light particles are invisible to the eye…