The Milky Way Is Gaining New Stars From A Collision That Hasn’t Even Occurred Yet
“This is the first direct evidence of new stars forming from any galactic stream associated with the Magellanic Clouds, and it appears to have occurred from a stream of gas that’s already passed through the galactic plane. It’s eminently conceivable that it was that very event – when this gas ejected from the Magellanic Clouds passed through the Milky Way’s disk – was what triggered the formation of the new stars we’re seeing today.
When you take all of this information together, it leads to a remarkable conclusion that changes the way we think our local galactic neighborhood is evolving. New gas is already being funneled into the Milky way from satellite galaxies that are still nearly 200,000 light-years away. This gas, low in heavy element abundance but cool in temperature, provides about 95% of the cold gas suitable for the formation of new Milky Way stars. These nearby galaxies haven’t even encountered us yet, and we’re already forming new stars because of them.”
In another few hundred million years, the two Magellanic Clouds, located a little less than 200,000 light-years away, will collide with and begin merging with our Milky Way. But already, over 100 million years ago, a fraction of the gas from these clouds came into our galaxy and formed stars! 94,000 light-years away, in the halo of the Milky Way, these stars are unlike anything else seen in our galaxy before.
Here’s how the Milky Way has gained stars from a collision that hasn’t even occurred yet, and what it means for our galaxy’s future!
This Is How The Milky Way Is Eating Our Galactic Neighbors
“New star formation is triggered by mutual gravitational interactions combined with the Milky Way’s tug.
The gas within these galaxies gets shunted into new clusters, including the local group’s largest star-forming region: 30 Doradus.
But these gravitational interactions also strip the gas away from these dwarfs, where the Milky Way will devour it.
The largest gas stream seems to connect both galaxies, but which cloud it originated from was a mystery.
Until, that is, scientists led by Andrew Fox looked at the absorption effects of this gas from background quasar light.”
While the visible Universe extends for tens of billions of light years, our local group of galaxies extends for only a few million. Around our own Milky Way are a handful of dwarf galaxies, including two bright ones: the Large and Small Magellanic Clouds. These two galaxies contain large numbers of young stars, show evidence of hot, glowing gas, and are destined to be devoured by our Milky Way in cosmically short order. But until that happens, they’re engaged in a cosmic tug-of-war with one another, battling to expel the gas from each other and capture it for themselves. Because the Milky Way is nearby, the expelled gas is getting stretched and drawn into our own galaxy, but which cloud, the Large or the Small, did it arise from?
Owing to new work by a Hubble team led by Andrew Fox, we finally know it’s the Small Magellanic Cloud. Here’s how, and here’s what it means for science.