Mysterious ripples in the Milky Way due to a dwarf galaxy: study

Using data from the Gaia space telescope, a team has shown that large parts of the Milky Way’s outer disk are vibrating. The ripples are caused by a dwarf galaxy, now seen in the constellation Sagittarius, which jolted our galaxy as it passed hundreds of millions of years ago.

Our cosmic home, the Milky Way, contains between 100 and 400 billion stars. Astronomers believe the galaxy was born 13.6 billion years ago, emerging from a spinning cloud of gas made up of hydrogen and helium. Over billions of years, the gas then accumulated in a spinning disk where stars, like our sun, formed.

In a new study published in Monthly Notices of the Royal Astronomical Society, the research team present their findings on stars in the outer regions of the galactic disk.

“We can see that these stars are wobbling and going up and down at different speeds. When the Sagittarius dwarf galaxy passed the Milky Way, it created wave motions in our galaxy, much like when a stone falls into a pond,” Paul said. McMillan, the astronomy researcher at Lund Observatory who led the study, explains.

Using data from Europe’s Gaia space telescope, the research team was able to study a much larger area of ​​the Milky Way’s disk than before. By measuring the strength of the ripples in different parts of the disk, researchers began to piece together a complex puzzle, providing clues to the history and orbit of Sagittarius around our home galaxy.

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

The researchers were surprised at how much of the Milky Way they could study using data from Gaia. To date, the telescope, which has been in operation since 2013, has measured the movement across the sky of around two billion stars and the movement towards or away from us of 33 million.

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