Black hole

Strange objects at the center of the Milky Way Astrophysics

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

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

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…
When a black hole is simply too big Astrophysics

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…
A black-hole Sun: planets could also form around black holes Space

A black-hole Sun: planets could also form around black holes

What does a builder of worlds need to form planets? A protoplanetary disk made out of a suitable material in which differences in density can develop, and an object at the center of the system that acts as a common center of gravity and uses its force of attraction to prevent the cloud of material from floating off into infinity. Until now it had been assumed that these conditions were met primarily by stars. But apparently much more exotic planetary systems are also conceivable, as Japanese researchers have now described in a study. The scientists took a closer look…
New NASA simulations: what it’s like around a black hole Space

New NASA simulations: what it’s like around a black hole

A black hole grows by being fed from a so-called accretion disk that supplies it with fresh matter. This disk is made up of plasma, ionized gas that orbits in continuous spirals around the black hole at high speeds. This plasma is constantly heated by internal collisions. To an observer, however, an accretion disk won’t look like a classic disk (like, for example, Saturn’s rings). This is because a black hole generates such an unbelievably large force of gravity that radiation from the rear part of the disk becomes distorted as it moves toward the observer. Now, researchers at…
A radio view into a black hole’s backyard Astrophysics

A radio view into a black hole’s backyard

By definition, black holes themselves remain shut off from direct observation. But astronomers have been able to precisely image the sphere of influence of a black hole – the area in which its gravity is the dominant force. In the case of a supermassive black hole in the interior of a galaxy, this area can be up to 500 light-years across. For comparison, the closest star to the Sun is a good four light-years away. This imaging was done by the Atacama Large Millimeter/submillimeter Array (ALMA) in the Atacama desert of Chile. NGC 3258, a giant elliptical galaxy about…
How to look inside a black hole Astrophysics

How to look inside a black hole

When mass is so strongly concentrated that not even light can escape its gravitational field, physicists call this phenomenon a black hole. In reality, however, the name doesn’t quite fit its true physical nature. This is because some radiation, so-called Hawking radiation, is indeed emitted from a black hole. In addition, black holes set their surroundings in so much turmoil that in no way do they remain invisible: the matter falling into the hole forms an accretion disk around it, there are all kinds of swirling, turbulent magnetic fields – there’s little reason to fear falling into a black…