Astrophysics

In the early universe, a hydrogen diet made black holes fat Astrophysics
Jan 13 2020

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…
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Three giant black holes at the center of one galaxy Astrophysics
Dec 18 2019

Three giant black holes at the center of one galaxy

At the center of any galaxy that wants to be taken seriously, a mysterious giant is lurking – a supermassive black hole, often with a mass of millions to billions of solar masses. The center of our Milky Way has a gravitational monster, Sagittarius A*, which has sucked up the mass of more than four million stars the size of our Sun. But in terms of the universe, that’s almost nothing. Astronomers have now identified three supermassive black holes in the irregular galaxy NGC 6240 as reported by the University of Göttingen. NGC 6240 is about 330 million light-years…
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Hot and cold: an ice giant orbiting a white dwarf Astrophysics
Dec 16 2019

Hot and cold: an ice giant orbiting a white dwarf

In a few billion years, when our Sun has exhausted its supply of fuel, it will first turn into a red giant and then collapse to form a white dwarf. Some planets of our Solar System will probably survive this time (if they’re not flung out into deep space). Astronomers know this will happen – theoretically. But until now, nobody had ever found a white dwarf with a planet in orbit around it. So, it’s understandable why researchers are so excited about the discovery of WDJ0914+1914, which is located in the constellation Cancer about 1500 light-years away. “It was one…
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When a black hole is simply too big Astrophysics
Dec 14 2019

When a black hole is simply too big

One of the distinguishing features of black holes is that they are hard to see. Astronomers looking for them sometimes have luck, but at the cost a star: when a ravenous black hole tears off and devours stellar material from an orbiting star, the resulting accretion disk emits radiation that can be measured. Almost all known black holes have been discovered this way. But it seems logical that those aren’t the only ones out there. Black holes are formed when heavy stars die. And many of these giant stars die alone, without a companion that a resulting black hole…
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How exoplanets develop in multiple-star systems Astrophysics
Dec 12 2019

How exoplanets develop in multiple-star systems

In the novel, “The Three-Body Problem,” a civilization that developed in a system with three stars plays an important role. This situation has dramatic consequences for the civilization’s planet, which I don’t want to spoil for you. I was reminded of the novel when I read a press release of research work at the University of Jena. Dr. Markus Mugrauer, an astrophysicist there, examined 1300 known star systems with exoplanets to determine how many stars there were within these systems. To do this, he used the most up-to-date version of the data from the ESA Gaia Mission. A clever approach…
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Fascinating images from the beginning of the universe Astrophysics
Nov 22 2019

Fascinating images from the beginning of the universe

Next to theory and experiments, simulations are one of the most important tools used in research today. Occasionally, scientists develop theories that cannot be tested using today’s practice or technology. Here, a simulation might then be able to point the theoretical physicist where he or she needs to look. Other times, it might happen that there are two different theories that could be suitable for describing reality. If simulations are built based on both theories, their results can sometimes separate the significant from the useless. And sometimes it also happens that there isn’t any theory yet, only data from…
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How much energy can we borrow from a vacuum? Astrophysics
Nov 5 2019

How much energy can we borrow from a vacuum?

Negative energy doesn’t exist; that’s what we learned in school. If it did, then there’d also have to be negative mass – and thus a repulsive gravitational force, because energy and mass are directly linked with each other, as Einstein showed in his theory of relativity. At the micro-level, however, that’s not true (and that’s one of the reasons why physicists are still having a lot of fun trying to unite relativity and quantum theory). In extremely small areas, it is possible for energy to fall below zero for a short time, so that we are essentially borrowing energy…
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How a universe made out of fuzzy dark matter might look Astrophysics
Nov 3 2019

How a universe made out of fuzzy dark matter might look

The exact composition of 84 percent of all the matter in the universe is unknown. That is the portion, called dark matter, which neither emits radiation nor interacts with conventional matter that we already know of in any other way than through gravity. Cosmologists believe they can use the standard model of the universe, Lambda-CDM, to get to the bottom of dark matter. This model assumes that dark matter is “cold” (cold dark matter - CDM). In physics, “cold” means that something is moving slowly. So-called “WIMPs” (weakly interacting massive particles) would have to be previously unknown particles, heavier…
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