How has Andromeda’s dwarf galaxies formed? The Hubble telescope finds more questions than answers

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Dozens of dwarf galaxies that swarming around the Andromeda galaxy like bees were caught by the Hubble world space telescope in front of the camera, which took more than a thousand organs on earth to get a full family portrait of Andromedas Hellen satellites.

The 36 dwarf galaxies vary in their properties, and many show puzzling organs that have not yet been able to explain conventional theories. The solutions to these secrets could give a lot about how they Andromeda Galaxy – This is the closest big spiral galaxy For us, which were removed and developed around 2.5 million light years.

“We find that a lot of diversity must be explained in the Andromeda satellite system,” said Daniel Weisz from the University of California in Berkeley. “The way things come together is very important to understand the history of this galaxy.”

The concept of dwarf galaxies that float around larger galaxies is expected by models from Galaxy formation Based on the standard model of cosmologyWhat A shows a universe Filled with so -called “cold” dark matter. “In this scenario, galaxies are assembled in a structure of the dark matter, the gravity of which takes on small lumps of normal matter – also known as the dwarf galaxies – and it combines them. This is known as a hierarchical formation.

As such, the family of dwarf galaxies, which swear around in a larger galaxy like the Andromeda galaxy, can tell a lot about the formation history of the larger galaxy.

This new one Hubble world space telescope The picture is only half of a planned project to examine the movements of Andromeda’s dwarfs. In five years Hubble or the James Webb Space Telescope Collect more data to create a different image like this. By comparing the two pictures, astronomers can see how the dwarf galaxies have moved. Backtracking can then rewind the time and let the dwarf galaxies run backwards to see where the areas came from billions of years ago and to understand how this affected their relationship with Andromeda.

However, some of Andromeda’s dwarf galaxies are particularly puzzling. Dwarf galaxies around the Milky WayFor example, either billions of years ago stopped to form stars, or have recently started to form them again after they have entered the sphere of influence of our galaxy, in which gravitational elements stirring pockets of the water in order to reinforce the process of the star birthday.

However, it seems that some of Andromeda’s dwarf galaxies have never stopped forming stars, and that this continues to do this in all cosmic history at a slow speed.

“The star formation was really continued until many later times, which would not expect for these dwarf galaxies,” said Alessandro Savino from the University of California, Berkeley, who led the study in Andromeda’s satellites, said in a explanation. “This does not appear in computer simulations. Nobody knows what to make of it so far.”

A note comes how close these dwarf galaxies are to their parent galaxy. “It is a clear indication of how a small galaxy growth is disturbed by the influence of a massive galaxy like Andromeda,” said Savino.

Another special feature is how the organs of some dwarfs are arranged, with half of them surrounding the Andromeda galaxy at the same level and all in the same direction.

“It’s strange,” said Weisz. According to the standard model, the dwarf galaxies should approach the halo of the dark matter – within which a large galaxy grows from all perspectives – and therefore swarming around on random lanes. To ensure that the galaxies are all in the same level and move in the same direction.

“It was actually a total surprise to find the satellites in this configuration, and we still don’t fully understand why they appear like this,” said Weisz.

Although the standard model of galaxy formation with dark matter haloes has difficulty explaining why half of Andromeda’s dwarf satellite galaxies are at this level, the phenomenon is actually a prediction of an alternative theory of gravity, modified Newtonian dynamics or actually moonThis tries to replace the dark matter by optimizing the focus at low accelerations.

In the moon scenario, the Milky Way and the Andromeda galaxies had experienced a close encounter about 8 billion years ago. The proximity of the Andromeda galaxy to the Milky Way would have torn material out of our galaxy to implement the Andromeda galaxy in the same orbital level and form the dwarf galaxies there, a bit like moons that form around a planet. However, another team of astronomers has previously controversial This is that the plane is only a random alignment. Nevertheless, the new Hubble observations can suggest something else.

So while it is still possible that a solution can be found under the standard model paradigm, the confirmation that this level of satellite galaxies is present is seen as a significant victory in the eyes of moon theoretics.

In both cases, the observations emphasize the fact that our Milky Way and the Andromeda galaxy have experienced significantly different stories. Implement studies on our own Galaxy growth that it has been a fairly quiet place in the past 10 billion years in the past 10 billion years and has no large mergers with medium or large galaxies, while Andromeda galaxy shows that they have experienced a significant merger with another galaxy in the past billions. This is supported by others The youngest Hubble observations This has shown 100 million stars in Andromeda galaxy. This merger could have contributed to the fact that the environment in the vicinity of Andromeda is more dynamic and Andromeda is imposed itself (it is twice as massive as our Milky Way and has more satellite galaxies).

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This questions how wise it is to use our own galaxy as a template for other galaxies.

“There is always a tendency to use what we understand in our own galaxy in order to extrapolate more galaxies in the universe,” said Weisz.

The evidence grows that galaxies can be very different, with different properties and stories, and how your satellite family has developed can be a sign that something is different. “Our work has shown that galaxies with a small mass in other ecosystems have followed different evolutionary paths than what we know from the Milky Way satellite galaxies,” concluded Weisz.

It seems that the lion and tiger wildly differ wildly in the Galaxy Zoo than we imagined.

The new results were published on January 28th in The astrophysical journal.