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The human being often is arrogant, by believing to know everything. In reality the mysteries of the universe are still countless and even when we think to have found the answer to all the questions, there arrives something to overturn our certainties. Like the thing that we believed that all the galaxies have a black hole in their middle. Here you have arriving Abell 2261, a galaxy without the black hole to bring down all of our certainties. Let’s discover together the strange case of Abell, the galaxy without the black hole.
Black holes and galaxies
It’s been now years that scientists and astronomers found an almost absolute evidence. Which is that in the middle of all the big galaxies there is a bòack hole which keeps together all the galaxy, thanks to its incredible gravity.
Usually the black holes are formed after the collapse of a single star and they are much smaller than the ones that we find in the center of the galaxies. They are called Supermassive, to distinguish them from the normal black holes.
We don’t know exactly how the supermassives were born and how they ended up in the middle of the galaxies. We think they are very ancient, ancestral, objects, that are there since the dawn of the universe. Probably they are the consequence of the collapse of the very first stars. We think, infact, that the very first stars born in the primordial Universe were very big.
Being these black holes ancestrals, they had a lot of time to further grow their mass. The supermassives, infact, catched all the surrounder matter. In some cases two galaxies collided and their two supermassives melted in one, becoming even bigger.
Abell 2261, the galaxy without the black hole
Let’s now come back to the galaxy of which we were talking about. Abell 2261 is a massive cluster of galaxies, about 3 billion of light years away from the Earth. To rule the group of galaxies there is Abell A2261-BCG.
It is a giant elliptic, the biggest known one. Therefore, right Abell A2261-BCG has the largest core ever observed (up to 10.000 light years).
Inside it there might be a supermassive black hole, one of the biggest ever found in the known universe. A black hole that might be at least 10 billions of solar masses. Just think that the black hole of the Milky Way is only 4 billions of solar masses. However there is nothing there.
Looking for the black hole
We have to say that, surely, it isn’t an easy research. It’s about to look for something which is invisible and that doesn’t emit any kind of radation.
However the other black holes have been always found. Even if the object itself is invisible, it leave some clues. The stars around the black hole, infact, move very fast attracted by an unmatchable gravity.
In the 2012 they thought to find the supermassive in the middle of the galaxy Abel A2261-BCG, and so they pointed the super telescope Hubble right on that direction, but nothing.
In the middle of the galaxy the core was expanded, but no black hole. Therefore, in its middle there wasn’t the maximum cluster of stars as normally. The maximum concentration of stars was instead moved of about 2000 light years.
Therefore, the middle of the galaxy wasn’t visibly as the ones of the other galaxies, which means brighter. The lightness, unlike to increase, dropped.
Further researches about Abell 2261
The astronomers wanted to discover something about the strange phenomena of the galaxy without the black hole, and so the researches went on. They so did two new observations on the middle of the galaxy. One with the radio waves and one with the X rays.
With the first one they tried to understand the behaviour of the celestial bodies close to the core. Infact, if there was a black hole on its middle, they had to move to a speed very close to the light speed, before to be catched by it, but nothing. They, though, find some very light radio emissions, 50 million of years old. It was like there was a black hole there once, but then it disappeared.
While the second one found something in the core of the massive galaxy: a strange cluster of matter, that they found out, though, that was two mini galaxies catched by the bigger one.
What’s happened to the black hole?
The scientists so have come to a conclusion. The galaxy Abell A2261-BCG is the result of a collision between two galaxies. For this reason the core is very large and always for this reason the maximum concentration of stars isn’t in its middle.
But so what’s happened to the black hole? According to the scientists from this conclusion two scenarios open. The first one is that the supermassive black hole is there, but that it’s possible to see because it already ate everything that was around it and, so, there isn’t any object that runs at the light speed around it.
The second one is that the black hole was expelled outside the galaxy after the collision. In both cases it will be impossible to find it and the one of the galaxy without the black hole will remain a mystery.
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