Imagine the 100 billion stars in the Milky Way as a flat, calm pool of water. Now, imagine someone dropping a stone the size of 400 million suns into that water. Calm shattered. Wave after wave of energy ripples across the surface of the galaxy, wrestling and bouncing off its stars in a chaotic dance that takes eons to subside.
Astronomers think that something like this may have already happened — not just once, but many times over the past several billion years.
In a new paper published on September 15 in Monthly Notices of the Royal Astronomical Societyresearchers explain how a small galaxy is nearby – the Sagittarius dwarf galaxy – It looks like it has crashed through Milky Way On at least two separate occasions, causing stars all over galaxy Oscillates mysteriously at different speeds.
Using data from the European Space Agency’s Gaia space observatory, the researchers compared the motions of more than 20 million stars located throughout the Milky Way, but especially in the outer regions of the galactic disk. The data revealed a mysterious ripple, or shake, that looked like stars jostling across the galaxy.
“We can see that these stars are oscillating and moving up and down at different speeds,” said study author Paul Macmillan, an astronomer at Lund University in Sweden. He said in a translated statement.
Through a process the researchers equated with “galactic seismology,” the team modeled a wave pattern that could explain the strange ripple effect that causes the Milky Way’s stars to spiral out of control. They concluded that the ripples were likely released hundreds of millions of years ago, when the Sagittarius dwarf galaxy last passed through our galaxy — “a bit like when a stone fell into a pond,” MacMillan said. It’s possible, the researchers added, that a second collision, even before that, had previously occurred between the two galaxies.
Previous studies (Opens in a new tab) They suggested that an ancient collision with Sagittarius may have created ripples in the center of the Milky Way, but this new research is the first to show that these ripples extended all the way to the edge of the galactic disk, turbulent stars every step of the way. The researchers write that this new research should help piece together the long and violent history of our galaxy and its smaller neighbour.
Today, the Sagittarius dwarf galaxy is estimated to be about 400 times the mass of the galaxy a land‘s the sun Just a shrimp compared to the Milky Way’s estimated mass of 1.5 trillion suns. Scientists believe that Sagittarius was much larger, but it lost up to 20% of its mass in our galaxy after repeated collisions over the past several billion years.
It is possible that these collisions changed the shape and size of our galaxy as well; A 2011 study suggested that the spiral arm of the Milky Way is present result of two collisions With the Sagittarius dwarf galaxy. Another study of Gaia data released in 2020 indicated a cosmic collision between our galaxy and Sagittarius Baby boom triggered of new stars in the Milky Way each time the two galaxies meet.
Originally published on Live Science.