Astronomers discovered a less bright dwarf galaxy on the outskirts of Andromeda, the closest galactic neighbor of the Milky Way, located about three million light years. Their peculiarities open new questions about star formation.
“This discovery entails more questions than answers,” says Marcos Arias, a researcher at the American University of Michigan and principal author of the study that includes Tuesday Astrophysical Journal Letters magazine.
The Milky Way houses dozens of these satellite galaxies. They are different from the central and much smaller galaxy, but they are close enough to be trapped by their gravity.
“They are completely functional galaxies, but they have a millionth part of the size of the Milky Way. It is like having a perfectly functional human being of the size of a grain of rice, ”explains another of the authors, Eric Bell, an astronomy professor at the University of Michigan in a statement from this university.
In the last two decades astronomers had technologies sensitive enough to discover most known satellites of the Milky Way. And these satellites have meant a key source of information on tiny galaxies.
“In the past, this type of galaxies could only be discovered around a system, the Milky Way. Now, we can also observe galaxies around Andromeda, ”explains Bell.
To find the new galaxy, which has been called Andromeda XXXV, Arias examined previous visualizations of Andromeda to make a list with the most interesting areas and, subsequently, observe those close points with the Hubble Space Telescope.
This is how the finding of Andromeda XXXV was reached. It is not the first satellite galaxy in Andromeda that is located, so it is called XXXV and not Andromeda I, but they were previously discovered were so large and brilliant, that they had not questioned, as if it has done this, what has been learned from the Milky Way.
The tiny size of Andromeda XXXV makes researchers rethink issues such as how long the galaxies of forming stars are capable.
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Galaxies have a certain limit to stop forming stars
The most striking difference between the satellites of the Milky Way and those of Andromeda lies in when they stopped forming stars.
“Most of the Milky Way satellites have very old star populations. They stopped forming stars about 10,000 million years ago, ”explains Arias.
However, with the discovery of Andromeda XXXV, researchers have seen that similar satellites in Andromeda can form stars until around 6,000 million years ago.
The researchers explain that a galaxy, whether it is huge and tiny, needs to have a gas reserve available to condense in stars. When that gas disappears, the star formation stops.
Astronomers consider whether this end is due to the fact that the gas supply of a galaxy is exhausted on its own or that is absorbed by the host galaxy.
In the case of the satellites of the Milky Way, its anterior blackout coincides with the first option, in the Andromeda Satellite Galaxies, given that the star formation lasts longer, it seems that it is the second.
Organizations such as NASA plan to launch missions capable of discovering more satellite galaxies in the coming years, which will help to know the evolution of the universe better.
With EFE information
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