Every so often you get a reminder of how little we know about the universe: Rogue stars outside galaxies may be everywhere | Science/AAAS | News.
You’ve heard of rogue planets, floating through the universe untethered to any solar system. Now meet rogue stars, which drift through space with no galaxy to call home. A new study has come to the startling conclusion that as many as half of all stars in the universe may be rogue, having been ejected from their birthplaces by galaxy collisions or mergers.
The article goes on to discuss that this is just a possibility at this point. Not everyone is convinced.
“We’ll have to confirm, but they are hard to accommodate with the star model,” he says. Also, he points out, if there is a huge population of stars outside galaxies, we should see a noticeable number of supernovas occurring out in the middle of nowhere as those rogues stars die. “There are ways to test in the near term. It’ll be an enthusiastically pursued question,” Moseley says.
But if this does turn out to be true, what a revision to our view of the universe! All this time we’ve been thinking that the space between galaxies was this vast emptiness with only the occasional gas or dark matter particle, but now it may be filled (relatively speaking) with stars. (Yeah, I know “filled” is probably not the right word since even within galaxies there is an unimaginably vast emptiness between stars. But intergalactic emptiness would still seem a lot less empty than we had previously understood.)
So, in recent years, we’ve learned that there are billions of rogue planets between the stars, and now we may be headed toward learning that half of all stars are between galaxies. If nothing else, this should keep us humble about what we think we know about the universe.