Back in 2002, astronomical data from the Sloan Digital Sky Survey showed a bulging ring of stars beyond the known plane of the Milky Way.
Researchers led by Rensselaer Polytechnic Institute Professor Heidi Jo Newberg took another look at this 2002 data.
“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 Heidi Newberg, professor of physics, applied physics, and astronomy in the Rensselaer School of Science. “As it radiates outward from the sun, we see at least four ripples in the disk of the Milky Way. While we can only look at part of the galaxy with this data, we assume that this pattern is going to be found throughout the disk.”
The new research shows the bulging ring of stars is actually part of the Milky Way Galaxy. We thought the Milky Way’s width was 100,000 light years. This new research extends it to as much as 150,000 light years.
“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,” said Yan Xu, a scientists at the National Astronomical Observatories of China and lead author of the paper. “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.”
A press release explains what the researchers found:
When they revisited the data, they found four anomalies: one north of the galactic plane at 2 kilo-parsecs (kpc) from the sun, one south of the plane at 4-6 kpc, a third to the north at 8-10 kpc, and evidence of a fourth to the south 12-16 kpc from the sun. The Monoceros Ring is associated with the third ripple. The researchers further found that the oscillations appear to line up with the locations of the galaxy’s spiral arms.
What could produce this rippling effect? According to Newberg, maybe a dwarf galaxy. The findings support recent research of a theoretical dwarf galaxy or dark matter lump passing through our galaxy, which would produce a similar rippling effect.
“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,” said Newberg. “If a dwarf galaxy goes 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. If you view this in the context of other research that’s emerged in the past two to three years, you start to see a picture is forming.”
Research on the theoretical dwarf galaxy is still awaiting publication.