Is the Milky Way special, or is it at least in a special place in the universe? An international team of astronomers has found that the answer to this question is yes, in a way it hasn’t been appreciated before. A new study shows that the Milky Way is larger than its “cosmic wall,” something not yet seen in other galaxies. The new research has been published in Monthly Notices of the Royal Astronomical Society.
The cosmic wall is a flattened arrangement of galaxies around other galaxies, marked by particularly empty regions called “voids” on either side of them. These voids seem to crush the galaxies together into a pancake-like shape to make the flat arrangement. This wall environment, in this case called the local sheet, influences the way the Milky Way and nearby galaxies It rotates around its axes, in a more orderly manner than if we were in a random place in the universe, without a wall.
Normally, galaxies tend to be much smaller than this so-called wall. The Milky Way was found to be surprisingly massive compared to its cosmic wall, which is a rare cosmic event.
The new findings are based on a recent computer simulation, which is part of the IllustrisTNG project. The team simulated the size of a universe roughly a billion light-years across containing millions of galaxies. Only a handful – about a millionth of all the galaxies in the simulation – were as “special” as the Milky Way, that is, both are embedded in a cosmic wall like the Local Plate, and both are as massive as our own.
According to the team, it may be necessary to take into account the special environment around the Milky Way when running simulations, to avoid the so-called “Copernican bias” in drawing scientific inferences from the galaxies around us. This bias, which describes the successive removal of our own status in the nearly 500 years since Copernicus lowered the Earth from the center of the universe, may come from the assumption that we live somewhere exactly in the middle of the universe. To simulate observations, astronomers sometimes assume that any point in a simulation like IllustrisTNG is as good as any other, but the team’s results suggest that it may be important to use precise locations to make such measurements.
“So the Milky Way is special in a way,” said research leader Miguel Aragon. “Earth is obviously very special, it is the only home of life that we know of. But it is not the center of the universe, or even the solar system. And the sun is just an ordinary star among the billions in the Milky Way. Even our galaxy seems to be just something else. spiral galaxy Among billions of others in visible universe. ”
“The Milky Way has no special mass or type. There are a lot of spiral galaxies that are almost like it,” said Joe Silk, another researcher. “But it is rare to take into account the surroundings. If you could easily see the nearest dozen large galaxies in the sky, you would see that they are almost all on a ring, embedded in the local plate. This is a little bit special in itself. What we discovered recently is The walls of other galaxies in the universe such as the Local Plate rarely seem to have a massive galaxy like the Milky Way.”
“You may have to travel half a billion light years From the Milky Way, many past galaxies, to find another cosmic wall with a galaxy like ours,” Aragon said, “that is a few hundred times farther away from the nearest large galaxy around us, Andromeda. ”
“You have to be careful, though, when choosing which real estate is considered ‘special,'” said Nerink, another member of the team. This, then we will definitely be the only galaxy in the observed galaxy being like this. But we think this ‘too big for its wall’ property is physically meaningful and relevant enough to be watched really special.”
MA Aragon-Calvo et al, An unusual plate system for the Milky Way: implications for rotation strength and alignment, Monthly Notices of the Royal Astronomical Society: Letters (2022). DOI: 10.1093/mnrasl/slac161
Royal Astronomical Society
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