Far out cosmology: influences of large magellanic cloud (Introduction)

by David Turell , Sunday, May 14, 2023, 22:32 (557 days ago) @ David Turell

Our neighboring galaxy influences us:

https://www.sciencealert.com/the-large-magellanic-cloud-shapes-the-milky-way-in-ways-we...

"Our galaxy's largest nearby companion is the Large Magellanic Cloud (LMC), a dwarf galaxy visible to the naked eye in the Southern Hemisphere.

"In recent years, new theoretical research and better observational capabilities have taught astronomers a great deal about our (not-so-little) neighbor.

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"Weighing in at 10-20 percent the mass of our own galaxy, the LMC is worth taking seriously. Astronomers believe that it's on its first orbit around the Milky Way.

"Before that orbit began, it was a spiral galaxy in its own right. Interacting with the Milky Way distorted its spiral arms, though it still features a strong central bar as evidence of its previous structure.

"The Milky Way, too, was changed by the interaction. The stars and stellar streams nearest to the LMC had their orbits deflected, for example, and there were larger, structural changes to the Milky Way too.

"Because the Milky Way isn't rigid, but rather made up of stars, dust, gas, and rock in varying densities, parts of the galaxy closer to the LMC were affected more than distant parts.

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"The fact that it's difficult doesn't mean astronomers are giving up. The LMC's size and proximity mean that its perturbations on our home galaxy ought to be quite significant. But how to find them?

"The answer may lie, in part, in the most recent Gaia data, which showed a peculiar 'striped' pattern in the position and velocity of stars in the Milky Way's galactic halo. The halo is a spherical region that encircles the galactic disk and contains stars at a much lower density than the more populous disk does.

"These stripe patterns are believed to be the traces left behind by long-dead galaxies that merged with the Milky Way in the ancient past, like the hypothesized Gaia-Enceladus galaxy.

When the LMC passed near to the Milky Way in the more recent past, it should have left distortions in those stripes, and that's what astronomers like Vasiliev are hoping to find.

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"As for the future of the Milky Way and the LMC, they are, ultimately, on a collision course. The LMC will merge with the Milky Way in a few billion years, delivering more mass and metallicity to the Milky Way's halo.

"Of course, this dramatic event will be only a precursor to the even larger merger in store for the Milky Way, as the Andromeda Galaxy will, at that point, be on its final approach toward us.

"If there is a moral to this story, it's that no galaxy is an island. The Milky Way's neighbors are helping to shape its past, present, and future, and astronomers are making an effort to take those effects into account as they study of our home galaxy."

Comment: although a large somewhat isolated galaxy we are influenced by our neighbors. It is important to see how.