Black hole

Photo of Black hole: Astro-Sensation will be presented in a few hours

This graph shows a star that is swallowed by a black hole, leaving behind a red tail of X-rays.

Never has a black hole been seen directly. A research team wanted to change that with eight radio telescopes. Now they have announced first results. The science world is in a state of excitement because the first photo of a black hole is expected.

Astronomers around the world are waiting eagerly for the first picture of a black hole. The mass monsters are like phantoms of the universe. So far, their existence could only be proved by detours. No telescope could take a black hole directly. A few years ago, an international research team set about making the first recording with a worldwide telescope network.

On Wednesday afternoon at 3 pm, the project called Event Horizon Telescope wanted to present a "groundbreaking result" at six simultaneous press conferences around the world. It is nothing less than a review of the general theory of relativity Albert Einstein. The most important questions and answers at a glance.

What is the event Horizon Telescope?

The EHT is not just a single instrument. Rather, the project is a composite of eight giant radio telescopes spread across the globe - from Hawaii to Arizona, Spain , Mexico and Chile to the South Pole. The German Max Planck Institute is also involved in the project. This combination of telescopes forms a virtual radio observatory with an effective diameter of 12,000 kilometers - the diameter of the earth.

What is expected?

Two years ago, astronomers at the EHT focused on two particular heavyweights: the black hole at the center of our home galaxy, the Milky Way. It is called Sagittarius A * (short Sag A *) . On the other hand, the much larger one in the center of the elliptical giant galaxy Messier 87 (M87) . Now that a "groundbreaking result" has been announced, many experts suspect that at least one of the recordings has actually been successful.

X-ray: NASA/umass/D.Wang et al., IR: NASA / STScI The Bils shows the supermassive black hole Sagittarius A * (Sgr A *) in the center of the Milky Way.

How big are these objects?

Sag A * is approximately 26,000 light-years away from our solar system and has a diameter of approximately 44 million kilometers. That sounds huge, but from Earth's perspective it's just the size of a golf ball on the moon . On the other hand, in the much further away galaxy M87 lurks a gravity monster of 1500 times the size. One of these two black holes will be seen on the expected image for Wednesday.

what is a black hole?

Black holes are one of the predictions of general relativity that Albert Einstein set up about a century ago. In them, the mass of several to several billion suns is compressed to a point. Due to the immense gravitation not even light can escape from the direct environment, hence the name. Black holes, for example, can occur when burned out giant stars collapse under their own weight.

What is inside?

At the center of the black hole, all of its mass concentrates in a single point of infinite density and infinite gravitational field. Physicists speak of a singularity. Limited are black holes from the so-called event horizon, which gave the EHT project its name. Anything inside the event horizon can not escape the black hole - that would require an infinite amount of energy.

How can a picture of a black hole look like?

A black hole itself is also invisible to the best telescopes. Drawings based on general relativity often show a black circle with a bright ring. The inside of this ring marks the so-called event horizon, in English "event horizon", which gave the project its name. He is the place around a black hole from which light can escape. You only photograph the bright ring around the black hole.

Why does the event horizon shine?

Many black holes are getting new matter. But this matter does not fall directly into the black hole. Instead, it collects on an ever faster rotating disk - much like water in a whirlpool flows out of the bathtub. In this so-called accretion disk, matter heats up to millions of degrees by mutual friction and lights up brightly before it disappears forever in the throat of the gravity monster.

ESO, ESA / Hubble, M.

Why is it so hard to scan?

Although black holes have unimaginable mass, but are very small. For example, a black hole with the mass of our earth would only be as big as a cherry. In addition, the black holes are very far away: the center of the Milky Way is 26,000 light-years, M87 is even 55 million light-years away. A light year is the distance the light travels in a year. And these two candidates still have the biggest event horizons seen from Earth. However, you can not build a telescope that can detect details of the event horizon at this distance.

Why should the Event Horizon Telescope be able to do it?

The researchers combined eight radio telescopes on four continents. This creates a virtual super telescope whose diameter is as big as the earth. This virtual event, Horizon Telescope, achieves a sharpness of detail that could be used to read a newspaper in New York from Berlin .

Why do astronomers use radio telescopes?

Radio waves are just like visible light electromagnetic waves, they have only a much larger wavelength. Their advantage is that they are not so much swallowed by gas and dust. The black holes are usually surrounded by large amounts of gas and dust, so that the event horizon can be spotted only with radio waves.

What brings astronomers a picture of a black hole?

On the one hand, astronomers want to clarify whether the environment of a black hole actually looks as expected. If it does not, it could indicate a departure from physical theory. On the other hand, such observations allow a test of the theory of relativity under the most extreme gravitational conditions that exist in the universe. In addition, many questions about the black holes are not yet clear, such as how the matter swirls exactly in the throat.

Why in some black holes a part of this matter is thrown out again in a sharply focused beam before reaching the event horizon. Such insights also affect the image astrophysicists currently have of our universe.

What does this have to do with Einstein?

The EHT project is considered the largest test run so far for the general relativity theory of Albert Einstein. So far, all predictions of the theory have been confirmed in the context of black holes - in the most impressive way by the first observation of so-called gravitational waves in 2015, which were created in the collision of two black holes.

However, these two black holes were tiny compared to the massive gravity monsters now studied. Whether the results of their exploration are consistent with the theory of relativity will now be proved.