PARIS: Rings of stars thought to surround the Milky Way are actually part of it, according to new research, meaning the galaxy is bigger than previously believed.
The findings extend the known width of the Milky Way from 100,000 light-years across to 150,000 light-years, said Yan Xu, a scientist at the National Astronomical Observatories of China and former visiting scientist at Rensselaer who was the lead author of a paper detailing the discovery in Astrophysical Journal.
“Going into the research, astronomers had observed that the number of Milky Way stars diminishes rapidly about 50,000 light-years from the center of the galaxy, and then a ring of stars appears at about 60,000 light-years from the center,” Xu said. “What we see now is that this apparent ring is actually a ripple in the disk. And it may well be that there are more ripples further out which we have not yet seen.”
An international team led by Rensselaer Polytechnic Institute Professor Heidi Jo Newberg, came to this conclusion after revisiting astronomical data from the Sloan Digital Sky Survey and finding that the galactic disk of the Milky Way is actually contoured into several concentric ripples.
“In essence, what we found is that the disk of the Milky Way isn’t just a disk of stars in a flat plane — it’s corrugated,” said Newberg, a co-author of the paper. “It’s very similar to what would happen if you throw a pebble into still water — the waves will radiate out from the point of impact.”
But in this case, the pebble could be a dwarf galaxy passing through the disk. “It would gravitationally pull the disk up as it comes in, and pull the disk down as it goes through, and this will set up a wave pattern that propagates outward,” she explained. “As it radiates outward from the sun, we see at least four ripples in the disk of the Milky Way.”
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