The WAVE

[Mari]

Mysterious ripples in the Milky Way were caused by a passing dwarf galaxy

Lund University. Our cosmic home, the Milky Way, contains between 100 and 400 billion stars. Astronomers believe that the galaxy was born 13.6 billion years ago, emerging from a rotating cloud of gas composed of hydrogen and helium. Over billions of years, the gas then collected in a rotating...

www.lunduniversity.lu.se

Published 23 September 2022

Illustration: NASA JPL-Caltech R. Hurt (SSC Caltech)

Using data from the Gaia space telescope, a team led by researchers at Lund University in Sweden has shown that large parts of the Milky Way's outer disk vibrate.

The article explains this phenomenon as:

"The ripples are caused by a dwarf galaxy, now seen in the constellation Sagittarius, that shook our galaxy as it passed by hundreds of millions of years ago."

“We can see that these stars wobble and move up and down at different speeds. When the dwarf galaxy Sagittarius passed the Milky Way, it created wave motions in our galaxy, a little bit like when a stone is dropped into a pond”, Paul McMillan, the astronomy researcher at Lund Observatory who led the study, explains.

By using data from the European space telescope Gaia, the research team was able to study a much larger area of the Milky Way's disk than was previously possible. By measuring how strong the ripples are in different parts of the disc, the researchers have begun to piece together a complex puzzle, providing clues about Sagittarius' history and orbit around our home galaxy.

The study is here: disturbed outer Milky Way disc