2020
January
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Galaxy group from the epoch of reionization discovered

The universe has a 13.8 billion year long history behind it. Astronomers have already found lots of evidence to support the current model, but the more evidence there is for a theory, the better. To observe the formation of the universe, astronomers use actual time machines – their telescopes. The farther an object is away from us, the longer its light takes to reach us, and thus the farther back in time the light we are now seeing was created.

An international research group has now succeeded in observing the most distant galaxy group to date. “EGS77” is a trio of galaxies that existed at a time when the universe was only 680 million years old, which corresponds to 5 percent of the universe’s current age. Even more exciting for the astronomers, however, was the realization that EGS77 was still in the midst of an important process, namely the epoch of reionization. During this era, the universe first began to become transparent, like we know it today.

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Strange objects at the center of the Milky Way

Sometimes they behave like a cloud of gas and then they’ll start behaving again almost like an ordinary star: the so-called “G-objects,” which astronomers describe in an article in the scientific journal Nature, are hard to fit into any single category. Six of these objects have already been identified by researchers. They were all found in the direct vicinity of the center of our Milky Way – orbiting the supermassive black hole, Sagittarius A*.

This point of commonality probably also contributes to their strange behavior. G1 to G6 have orbits that lead them around the black hole once every 100 to 1000 years. Whenever they get close to the black hole, they are stretched like chewing gum by its gravity, and then they apparently contract again as they move farther away.

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Hubble detects small clumps of dark matter

Dark matter holds galaxies together and gives the visible universe its structure. Even though it makes up about five-sixths of all the mass in the cosmos, to date nobody has been able to figure out what it’s made of. On the other hand, there have been some indications about what dark matter is not made of, but researchers still need to determine if dark matter is hot, cold, or possibly even fuzzy, with the temperature designation here referring to the speed at which the particles of dark matter are moving.

NASA’s Hubble telescope has now pushed the probabilities a little closer toward cold dark matter, which is also what the standard cosmological model (Lambda CDM) assumes. Using the Hubble, researchers were able to detect much smaller clumps of dark matter than was previously possible. If dark matter existed only in large clumps, which is what had to be assumed before based on observations, scientists had to come up with an explanation for the lack of smaller concentrations. This explanation was warm dark matter with quickly moving particles that would not stay together very long in small clumps. However, since these small clumps have now been detected in some sense, warm dark matter is no longer needed.

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Is the universe repelled by itself?

Does the universe repel itself? That is roughly the idea that researchers from the Immanuel Kant Baltic Federal University in Kaliningrad, Russia proposed in a recent paper. Their paper refers to the Casimir effect, which involves a quantum-physics phenomenon that was predicted and also later confirmed by the Dutch scientist Hendrik Casimir. The Casimir effect causes two conductive plates arranged in parallel in a vacuum to be attracted to each other by a force.

The idea that it might be responsible for previously unexplainable phenomena like dark energy is not completely novel. In general, it predicts that hard, fixed boundaries might lead to effects that produce certain forces, not only forces that attract, but also repel. The Russian researchers have now transferred the effect to a holographic model of the universe.

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In the early universe, a hydrogen diet made black holes fat

Only a billion years after the big bang, there were already galaxies whose centers harbored supermassive black holes several billion times the mass of our Sun. Astronomers know this from observations of far distant quasars and active galaxies. But how were the black holes able to grow so large so quickly? The problem seemed even more complicated, because earlier observations with ALMA, the Atacama Large Millimeter/Submillimeter Array, had shown a lot of dust and gas in these early galaxies, which promoted rapid star formation. However, if a lot of stars were created, there would have been little left over to feed a black hole.

The solution: the young giants were fed from huge reserves of cold hydrogen gas. This finding was discovered by astronomers using the European Southern Observatory’s Very Large Telescope.

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