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Searching for the super supernova

A supernova is a powerful explosion at the end of the life of many stars. All massive stars with an initial mass greater than eight solar masses will eventually be torn apart by a supernova, but that fate also awaits smaller stars that are unlucky enough, after their actual end as a white dwarf, to accrete more material from a partner star, with which they form a binary system. Without supernovae, there would be no life, because it’s the only way heavy elements can be spread around the cosmos.

On the whole, this process is understood. Particularly energetic supernovae, however, still attract the attention of astronomers, because some of them are still hiding a few secrets. One of these is pair-instability supernovae, which can involve stars that are greater than 64 solar masses and are particularly poor in elements heavier than helium, or stars greater than 140 solar masses, if these are normal main-series stars of the current generation. These supernovae tear apart the star completely, there’s not even a black hole left – thus, they also produce a lot of energy. The term “pair instability” comes from the fact that, in these stars, temperature (billions of degrees) and density are so high that photons from gamma radiation produced by fusion are transformed into electron-positron pairs. This, however, reduces the radiation pressure, and the star collapses on itself like air being let out of a balloon.

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Einstein was right – and Sagittarius A* is a giant black hole

Physical theories have one downside that physicists are very aware of: they cannot be proven true for always. Instead, they can be considered correct just until someone can demonstrate that they’re wrong. That applies to Einstein’s theories too. His General Theory of Relativity, however, has been amazingly robust so far. Einstein himself proposed three tests for his revolutionary theory, which wasn’t based on experimental findings, but on an almost philosophical line of thinking.

His first test concerned the orbit on which the planet Mercury moved around the Sun. Its point closest to the sun (perihelion) changes in a very specific way, which should be able to be accurately calculated using the General Theory of Relativity. This test confirmed the theory’s predictions back in 1916. The other tests had to wait longer, because technology had to make enough progress to be able to perform them – or because the processes the tests were measuring were rather slow. For example, astronomers had to track the orbit of a star around the black hole, Sagittarius A*, at the heart of the Milky Way for more than 25 years to be able to verify the perihelion precession predicted by the General Theory of Relativity.

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Kepler-1649c: an Earth twin with a short-tempered host star

The Kepler telescope has already been shut down, but astronomers are still finding new exoplanets in its data. Kepler-1649c, which is 300 light-years from Earth, is one of these recently discovered treasures. The planet was overlooked by the first, automated search through the data. The rocky planet has one very intriguing characteristic: it is the most Earth-like exoplanet discovered to date.

Kepler-1649c is only 1.06 times larger than Earth. Its host star supplies it with about three-quarters of the energy that the Earth receives from the Sun. That means that water, if it exists there, would be liquid on its surface. One unlucky thing is that Kepler-1649c orbits around a red dwarf (and once every 19.5 Earth days). These dwarf stars are known for the bad habit of regularly plunging their planets into devastating outbursts of radiation, flares, which likely blow any atmosphere or water into space. Depending on the frequency of these events, the chances for life on Kepler-1649c could be severely reduced.

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Dark matter: on the trail of the Zʹ boson

Almost 1000 physicists from 26 countries have committed themselves to one collective task: using the Belle-2 experiment to search for signs of a new model of physics, a model that might explain, among other things, dark matter. This phenomenon, whose existence has been observed many times already, has stubbornly refused to be explained using the current standard model of physics. In the Belle-2 experiment, researchers collide electrons with their antiparticles, positrons (identical mass, but opposite charge), in the SuperKEKB accelerator in Tsukuba, Japan.

They hope to use these collisions to find traces of a new elementary particle, the Zʹ boson (pronounced: zee prime). The Zʹ boson is not included in the standard model. It would be used, however, if extensions to the theory of the electroweak interaction (which unifies the electromagnetic and weak interactions) prove to be correct. Or worded a little differently: if the Zʹ boson is found, that would be an important indication that we’re on the right path with the proposed extensions to the standard model.

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The Sun as a lens: A new method for taking high-resolution photographs of exoplanets

The universe is damn large and, in comparison, everything that exists inside it is extremely small. Sometimes, astronomers are lucky and get some help in their observations of, for example, an individual star in a far-away galaxy: help delivered by the gravity of other massive objects, which refract and amplify the light of even-more distant objects like a lens. The effect is called a gravitational lens.

This effect, however, has one big disadvantage: we can’t intentionally create a gravitational lens for any object we want. To be able to use this effect to view a certain object, there must already be a massive object in our direct line of sight. And with the enormous distances in the universe, that is extremely unlikely, unfortunately.

What to do? We do already have one massive object in our Solar System – the Sun. We can’t move the Sun around, of course, but we can change the line of sight we use for observations by placing a telescope not on the Earth, but instead on a spaceship. We could then send the spaceship to a position where the effect of a solar gravitational lens would be visible. And voilà, we get a high-resolution image of an unbelievably far-distant object.

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Can the special theory of relativity explain the strangeness of quantum physics?

Physics has had a problem for some time. Its basic theories, the General and Special Theories of Relativity and theories of quantum physics, have proven correct in many cases. But they don’t fit together – in extreme cases, like in black holes or the big bang, where you would need to use both relativity and quantum physics, the math doesn’t work out. Quantum physics appears to be the more fundamental theory, so scientists have assumed that the theory of relativity would need to be modified to quantum relativity.

But that might not have to be the case. Dr. Andrzej Dragan from the Physics Department at the University of Warsaw (FUW) and Prof. Artur Ekert from the University of Oxford have presented an argument in a paper that leads to a different result. The strange phenomena of quantum mechanics can apparently be explained within the framework of the Special Theory of Relativity. All you need to do is take a certain, rather unorthodox step.

Albert Einstein based the Special Theory of Relativity on two postulates. The first is known as the Galilean principle of relativity and states that the physics is the same in any inertial system (i.e., a system that is either at rest or in uniform, straight-line motion). The second postulate requires a constant speed of light in any reference system.

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50,000 solar masses – and that’s just a midsize black hole

Astronomers have been looking for medium-sized black holes for a long time. You’ve probably heard about the giant black holes at the center of galaxies and those that start with the mass of one star as a result of a supernova. But as small black holes, like from a supernova, gradually grown into giants, they must pass through intermediate stages sometime. The only problem is that these midsize black holes are not very easy to find.

The Hubble Space Telescope has now delivered some important evidence that such black holes actually exist. In 2006, the Chandra and XMM-Newton X-ray observatories detected radiation outbursts in the X-ray range, which were designated X-ray source 3XMM J215022.4−055108. Researchers conjectured that they might have been produced when a star was torn apart by a compact, massive object – something like a black hole. What was really interesting, however, was that the X-ray radiation wasn’t coming from the center of our galaxy, giving the researchers hope that they might have found a medium-sized black hole.

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Axions to the rescue?

The neutron is, as suggested by its name, electrically neutral. Nevertheless, it still contains electrical charges. More specifically, it is made up of one up quark (charge: 2/3 of an electron charge e) and two down quarks (charge: -1/3 e each). In total, 2/3 + 2*(-1/3) equals exactly 0. But the neutron is not one-dimensional. It has a diameter of at least 1.7 * 10-15 meters, and when three components have to be spread out over any distance, even with an overall zero charge, some difference in charge should still be detectable. Calculations from theory say that a neutron should have an electrical dipole moment of 10-16 e*cm.

In reality, however, absolutely no dipole moment can be detected. If it does exist, it must be less than 10-25 e*cm, which is a difference of nine orders of magnitude, a huge discrepancy. One solution would be the existence of a previously only hypothetical, extremely lightweight particle, the axion. Huge quantities of these tiny particles, billions of times lighter than an electron, might then be roaming around our universe unnoticed. This is because axions normally do not interact with normal matter.

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