Space

Astronomers believe that star formation can be slowed or stopped by various factors, all of which deprive the galaxy of the gas needed to form new stars.
“Internal factors, such as a supermassive black hole or feedback from star formation, can push gas out of the galaxy, rapidly suppressing star formation. On the other hand, gas can be consumed very quickly, and if it does not flow from the galaxy’s neighbourhood in a timely manner, it will also lead to its death,” the authors of the discovery explained.

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When galaxies collide and merge, several processes happen in parallel: each one carries with it its own reservoir of hydrogen gas; when they merge, these clouds destabilise and many new stars form within them.
“Of course, interacting galaxies already have their own stars, and when they merge, they blend together. In the long run, such ‘families’ will form part of the stellar population of the newly formed galaxy. Once the merger is complete, it may seem hopeless to determine which predecessor galaxy the particular star streams belonged to, but there are actually some ways to trace their lineage,” the study authors explained.

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To date, astronomers have managed to obtain images of just two black holes: in the Milky Way and in the galaxy Messier 87. And, although they differ significantly in mass and size, the data indicate that they are remarkably similar, which has led scientists to wonder if they have things in common beyond appearance. To test this, the Event Horizon Telescope Project team studied Sagittarius A* in polarised light. Previous similar studies of the supermassive black hole in the Messier 87 galaxy showed that the magnetic fields around it allowed it to eject powerful jets of matter into its environment.

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Pluto’s “heart”, also known as “Tombaugh Regio”, is filled with nitrogen ice, which reflects more light than its surroundings. In addition, this region is “depressed” into the dwarf planet’s surface by an average of three kilometres.
“The elongated shape of the structure strongly suggests that the collision was not direct, but most likely at an acute angle. We recreated many such events by varying both the composition of the objects and the force, velocity and angle of impact,” the study authors explained.

According to the modelling, given that Pluto is very cold, the rocky fragments of the 730-kilometre-long impactor did not melt, but remained solid, despite releasing large amounts of heat on impact. And thanks to the angle, about 30 degrees, and the low speed of impact, they did not sink into the dwarf planet’s core, but remained relatively intact close to the surface, with the ice brought in quickly filling the resulting basin.

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The discovered black hole was labelled Gaia BH3. Its discovery was made possible by the presence of its companion star, whose observations allowed not only to identify and accurately determine the mass of the black hole, but also to test some theoretical predictions.
“Stars in pairs tend to have similar compositions, which means that the companion of the detected black hole contains important clues about its progenitor,” the study authors noted.

Beyond the Milky Way, not a few equally massive stellar-mass black holes have been discovered. Theoretical predictions suggest that they may be formed by the collapse of stars with very few elements heavier than hydrogen and helium in their chemical composition. These so-called metal-poor stars are thought to lose less mass during their lifetime and therefore have more material left over after they die to form large black holes.

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