The majestic Andromeda galaxy is located 2.5 million light years away and looks like a faint spindle-shaped object at the angle of a full moon. What backyard observers don’t see is that nearly thirty small satellite galaxies surround the Andromeda galaxy, like bees around the hive.
These satellite galaxies represent NASA’s Hubble Space Telescope being studied in unprecedented detail, representing a carnival “ecosystem” of the Milky Way. This ambitious Hubble Treasury Program uses observations from more than 1,000 Hubble tracks. Hubble’s optical stability, clarity and efficiency make this ambitious investigation possible. This work includes building an accurate 3D map, buzzing the galaxies of all dwarves, and reconstructing the efficiency of their formation of new stars over the nearly 14 billion years of the universe’s lifetime.
In a study published in the Journal of Astrophysics, Hubble revealed a distinct ecosystem from the satellite galaxies surrounding our Milky Way. This provides forensic clues about how our Milky Way and Andromeda’s galaxy have developed differently over billions of years. Our Milky Way is relatively calm. But it seems Andromeda’s history is more dynamic, which could be affected by a major merger with another large galaxy billions of years ago. This encounter, and twice the size of Andromeda, is our Milky Way that explains its rich and diverse dwarf galaxy population.
It is very challenging to investigate the entire satellite system of the Milky Way in such a comprehensive way because we are embedded in the Milky Way. It is also impossible to complete for other large galaxies because they are too far away to study small satellite galaxies in detail. The closest galaxy with a mass similar to the Milky Way outside Andromeda is M81, nearly 12 million light-years.
This bird’s eye’s view of Andromeda’s satellite systems allows us to decipher what drives the evolution of these small galaxies. “We see that the duration of satellites that can continue to form new stars does depend on their size and distance from Andromeda galaxies,” said lead author Alessandro Savino, University of California, Berkeley. “This clearly shows how small-million-mid-mountain growth is affected by huge galaxies like Andromeda.”
“Everything scattered in the Andromeda system is very asymmetric and perturbing. It seems that something important happened not long ago. “There is always a tendency to use what we understand in our own galaxy to infer more generally into other galaxies in the universe. We have been worried that we are applying more widely to other galaxies with the Milky Way. Or is there more diversity among external galaxies? Do they have similar properties? Our work shows that low-mass galaxies in other ecosystems follow different evolutionary paths than they know from the Galaxy satellite galaxies. ”
For example, half of Andromeda satellite galaxies appear to be confined to planes, and they all travel in the same direction. “It’s weird. It’s actually a surprising thing to find satellites in that configuration, and we still don’t fully understand why they appear in this way,” Weisz said.
Andromeda’s brightest companion, the Milky Way, is Messier 32 (M32). It’s a compact elliptical galaxy that may just be the remnant core of a larger galaxy that collided with Andromeda billions of years ago. It continues along the orbit after gravity strips the gas and some stars. The Galaxy M32 contains older stars, but there is evidence that it had a series of stars formed billions of years ago. Apart from M32, there seems to be no unique dwarf galaxy in Andromeda that appears as the Milky Way. They set up most of the stars early on, but did not stop there. They form stars at very low speeds over a longer period of time.
“The formation of stars does continue until later, and that’s not what you expect from these dwarf galaxies at all,” Savino continued. “This isn’t in computer simulations. So far, no one knows what to do.”
“We do find that there is a lot of diversity that needs to be explained in the Andromeda satellite system,” Weisz added. “Things come together are very important in understanding the history of the galaxy.”
Hubble provided the first component image, where astronomers measured the motion of dwarf galaxies. Within five years, Hubble or NASA’s James Webb Space Telescope will be able to obtain a second set of observations, allowing astronomers to dynamically rebuild all 36 dwarfs’ galaxies, which will help astronomers reversal the movement of the entire Andromeda ecosystem over the past few years.
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