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

(ORDO NEWS) — Using data from the Gaia space telescope, a team of scientists led by researchers from Lund University in Sweden has shown that large parts of the Milky Way’s outer disk are vibrating.

The ripples are caused by a dwarf galaxy currently visible in the constellation Sagittarius. She made the Milky Way vibrate by passing it hundreds of millions of years ago.

The Milky Way contains between 100 and 400 billion stars. Astronomers believe that our galaxy was born 13.6 billion years ago, emerging from a cloud of gas composed of hydrogen and helium. For billions of years, the gas accumulated in a spinning disk where stars, including our Sun, formed.

Scientists have published the results of their study of stars in the outer regions of the galactic disk of the Milky Way in the journal Monthly Notices of the Royal Astronomical Society.

“We can see that these stars are oscillating and moving up and down at different speeds. The passing dwarf galaxy Sagittarius has caused waves in our Milky Way galaxy, a bit like throwing a rock into a pond,” explains Paul Macmillan, lead researcher.

Using data from the Gaia telescope, the research team was able to study a much larger area of ​​the Milky Way’s disk than previously possible.

By measuring how strong the ripples are in different parts of the disk, the researchers began to piece together a complex puzzle that provides clues to the history of Sagittarius and the orbit around our home galaxy.

“At the moment, Sagittarius is slowly being torn apart, but 1-2 billion years ago it was significantly larger, probably around 20% of the mass of the Milky Way disk,” says Paul McMillan.

The researchers were surprised at how much of the Milky Way they were able to study using the Gaia data. To date, the telescope, which has been operating since 2013, has measured the movement of about two billion stars across the sky.

“With this new discovery, we can study the Milky Way in the same way that geologists infer the structure of the Earth from the seismic waves that travel through it. This type of “galactic seismology” will tell us a lot about our home galaxy and its evolution,” concluded Paul Macmillan.

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