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Astronomers have found a connection between the shape of galaxies and their age

25.04.2018
Science, Space

Scientists for the first time managed to prove that with age, galaxies become more spherical.
This is stated in a study published in Nature Astronomy.

Studying stars, astronomers can learn about how galaxies evolve. For example, the average age of the luminaries makes it possible to understand when the system began to form, and the movements of the stars indicate past collisions with other galaxies. Thanks to the data of new spectroscopic surveys, astronomers can explore galaxies of different epochs and find new patterns.

The group, led by Jesse van de Sande from the Sydney Institute of Astronomy, used the images from the SAMI Galaxy Survey survey to study 843 galaxies. The researchers evaluated the ellipticity of galaxies (that is, how much "round" or flattened), analyzing the motions of stars in them. In such galaxies as the Milky Way, stars usually move in an orderly manner, like cars on a race track, while in more spherical galaxies with low ellipticity the stars move more chaotically, like a swarm of bees. In addition, astronomers collected data on the average age of objects, based on the characteristics of the radiation of light.

It turned out that young galaxies are more elliptical, and the stars in them move along more ordered orbits. When galaxies grow older, the trajectories of stars in them change, because of what they take a more "rounded" shape. Earlier such a dependence was found only for the "extreme" cases - the youngest and oldest galaxies born when the universe was 3 billion years old - but now scientists have shown it for objects of intermediate epochs. It is not clear whether galaxies really are born flat and eventually "inflate", or the revealed dependence has a different nature.

Recently, scientists have estimated at what speed the Milky Way grows - theoretical calculations show that it is 500 meters per second. However, this is not due to changes in the movements of the stars, but to the birth of new luminaries on the outskirts.

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