Nasa researchers simulate the evolution of galaxies using computer models. In a wild dance first small and then ever larger star systems collide, until the fast rotating wheels of the present develop. Image: © F. Governato and T. Quinn (Univ. Of Washington), A. Brooks (Univ. Of Wisconsin, Madison), and J. Wadsley (McMaster Univ.).
Reading aloud Most galaxies today look similar to the Milky Way: they are ordered spirals, wheels of fire made of billions of stars. So far, astronomers have assumed that such star clusters completed their development about eight billion years ago and since then can show their current appearance. But now a study by researchers around Susan Kassin shows that galaxies like the Milky Way galaxy were a lot more chaotic a few billion years ago than they are today. "Galaxies are like young adults, " she says. ? Many of them had an exciting youth. But now they are calmer and more mature. In their study, the researchers studied 544 galaxies of different ages using the Keck telescope in Hawaii to visualize the movements inside them. They focused on galaxies whose blue color indicates that new stars are being born there.

The researchers found that the farther away they are, the more chaotic, disordered movements occur in galaxies. The rotational speed, however, increased in closer galaxies. The most massive galaxies showed the highest degree of order.

"Most galaxies in the neighborhood of the Milky Way, where new stars are formed, form rotating disks, like the Milky Way itself or the Andromeda Galaxy, " Kassin says. "Such disk-shaped galaxies are well organized. There is a defined plane in which the galaxy lies, and most stars and clouds of gas rotate in the same direction around the center. Only a few stars do not move in circular orbits around the galactic center.

But eight billion years ago, things looked quite different, Kassin and her colleagues noted to their surprise. At that time, stars and gas clouds were still criss-crossing in many galaxies. Only gradually did the familiar order come to an end. The Milky Way was probably a much more chaotic place around the time the solar system was born. display

Earlier studies on the evolution of galaxies excluded messy representatives from the outset. So the researchers falsely came to the impression that the development of the Star Islands had been completed long ago. But in reality there are still clashes between small and large galaxies, though not as common as they were a few billion years ago. After two systems are merged, there is usually an explosion of new star births. Then it takes another billions of years, until the order gets through again.

Susan Kassin (Nasa Goddard Space Flight Center, Greenbelt, Maryland) et al .: The Astrophysical Journal, Vol. 758, No. 2 doi: 10.1088 / 0004-637X / 758/2/106 © science.de - Ute Kehse

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