Milky Way Galaxy in which we’re living is an Abnormal Galaxy

Astrophysicists very often use the Milky Way as a standard for researching how galaxies form and evolve. Since we’re residing inside it, astrophysicists can study it in detail employing advanced telescopes. By probing it in different wavelengths, astrophysicists and astronomers can understand its stellar population, its gas dynamics, and its other characteristics in significantly more detail than faraway galaxies.

But new research that scrutinizes 101 of the Milky Way’s kin demonstrates how it differs from them. One authoritative way to understand things is to compare and contrast them with others in their category, a method we learn in school. Surveys are an effective tool to compare and contrast things, and astral surveys have contributed a massive amount of foundational data towards the effort. The Two Micron All Sky Survey (2MASS), the Sloan Digital Sky Survey (SDSS), and the ESA’s Gaia mission are all prominent examples.

The Satellites Around Galactic Analogs (SAGA) Survey is yet another, and its third data release features in three fresh studies. The studies are all based on 101 galaxies comparable in mass to the Milky Way, and each study deals with a different aspect of comparing those galaxies to our Milky Way.

• The SAGA Survey. III. (A Census of 101 Satellite Systems around Milky Way–mass Galaxies)
• The SAGA Survey. IV. (The Star Formation Properties of 101 Satellite Systems around Milky Way–mass Galaxies)
• The SAGA Survey. V. (Modeling Satellite Systems around Milky Way–Mass Galaxies with Updated UniverseMachine)

Research shows that galaxies form inside colossal haloes of dark matter, the elusive material that doesn’t interact with light. 85% of the Cosmos’s matter is enigmatic dark matter, while only 15% is normal or baryonic matter, the type that builds up planets, stars, and galaxies. Though we are not able to see these massive haloes, astrophysicists can observe their effects. Their gravity draws normal matter together to fashion galaxies and stars.

SAGA is focused at understanding how dark matter haloes work. It studies low-mass satellite galaxies around galaxies comparable in mass to the Milky Way. These satellites can be arrested and drawn into the dark matter haloes of larger galaxies. SAGA has found several hundred of these satellite galaxies revolving around 101 Milky Way-mass galaxies.

“The Milky Way has been an incredible physics laboratory, including for the physics of galaxy formation and the physics of dark matter,” said Risa Wechsler (the Humanities and Sciences Professor and professor of physics in the School of Humanities and Sciences). “But the Milky Way is only one system and may not be typical of how other galaxies formed. That’s why it’s critical to find similar galaxies and compare them.” Wechsler is co-founder of the SAGA Survey.

The comparison between the Milky Way and the 101 others bared some noteworthy differences. “Our results show that we cannot constrain models of galaxy formation just to the Milky Way,” said Wechsler “We have to look at that full distribution of similar galaxies across the universe.”