Far out cosmology: The Milk Way satellite galaxies plane (Introduction)

by David Turell , Monday, December 19, 2022, 17:06 (703 days ago) @ David Turell

A puzzle no more. Its plan is explained:

https://phys.org/news/2022-12-cosmological-enigma-milky-satellite-galaxies.html

"Astronomers say they have solved an outstanding problem that challenged our understanding of how the universe evolved—the spatial distribution of faint satellite galaxies orbiting the Milky Way.

"These satellite galaxies exhibit a bizarre alignment—they seem to lie on an enormous thin rotating plane—called the "plane of satellites."

"This seemingly unlikely arrangement had puzzled astronomers for over 50 years, leading many to question the validity of the standard cosmological model that seeks to explain how the universe came to look as it does today.

"Now, new research jointly led by the Universities of Durham, U.K., and Helsinki, Finland, has found that the plane of satellites is a cosmological quirk which will dissolve over time in the same way that star constellations also change.

***

"The Milky Way's satellites seem to be arranged in an implausibly thin plane piercing through the galaxy and, oddly, they are also circling in a coherent and long-lived disk.

"There is no known physical mechanism that would make satellites planes. Instead, it was thought that satellite galaxies should be arranged in a roughly round configuration tracing the dark matter.

"Since the plane of satellites was discovered in the 1970s, astronomers have tried without success to find similar structures in realistic supercomputer simulations that track the evolution of the universe from the Big Bang to the present day.

***

"However, this latest research saw astronomers use new data from the European Space Agency's Gaia space observatory. Gaia is charting a six-dimensional map of the Milky Way, providing precise positions and motion measurements for about one billion stars in our galaxy (about 1% of the total), and its companion systems.

"These data allowed scientists to project the orbits of the satellite galaxies into the past and future and see the plane form and dissolve in a few hundred million years—a mere blink of an eye in cosmic time.

***

"They realized that previous studies based on simulations had been misled by failing to consider the distances of satellites from the center of the Galaxy, which made the virtual satellite systems appear much rounder than the real one.

"Taking this into account, they found several virtual Milky Ways which boast a plane of satellite galaxies very similar to the one seen through telescopes.

"The researchers say this removes one of the main objections to the validity of the standard model of cosmology and means that the concept of dark matter remains the cornerstone of our understanding of the universe.

***

"'But thanks to the amazing data from the Gaia satellite and the laws of physics, we now know that the plane is just a chance alignment, a matter of being in the right place at the right time, just as the constellations of stars in the sky.

"'Come back in a billion years, and the plane will have disintegrated, as will today's constellations.

"'We have been able to remove one of the main outstanding challenges to the cold dark matter theory. It continues to provide a remarkably faithful description of the evolution of our universe.'"

Comment: the faint galaxy satellite group feeds the Milky Way and makes it grow as our galaxy's gravity pulls them in.