The Milky Way galaxy, as we know it, is about 100,000 light years across. It contains, depending on which estimate you use, anywhere from 100 to 400 billion stars.

Now, new research suggests that it is actually 50 percent bigger than that and possibly more. The research was led by Heidi Newberg, professor of physics, applied physics, and astronomy in the Rensselaer School of Science and Yan Xu, a scientist at the National Astronomical Observatories of China.

In a paper published in the Astrophysics Journal says that the galactic disk is made of several concentric ripples, which disguise its true size.

“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. 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,” said Newberg in a statement.

In 2002 data from the Sloan Digital Sky Survey was used to establish the presence of a bulging ring of stars beyond the plane of the milky way. The new research demonstrates that the rings are part of the milky way and not outside of it as previously thought.

“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. 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,” said Xu.

The researchers believe that a dwarf galaxy, dark matter lump or some other object may have passed through the galaxy at some point, setting off ripples.

“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. 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,“ said Newberg.

The new research follows an earlier, 2002, study by Newborn that establishes an over-density of stars, or “Monoceros Ring” at the edge of the milky way where it bulges above the galactic plane. Newborn reports that, at that time, she noticed second area that had an over density of stars but didn’t have the data to investigate further at that time.

“I wanted to figure out what that other over-density was. These stars had previously been considered disk stars, but the stars don’t match the density distribution you would expect for disk stars, so I thought ‘well, maybe this could be another ring, or a highly disrupted dwarf galaxy,” said Newberg.

Next, the team is interested in seeing if the distributed gases found in the Milky Way matches the rippling pattern that has been observed in stars.

“In the gas, we have seen a couple of perturbations, these vertical oscillations, in the outer part of the galaxy,” astronomer Leo Blitz, with the University of California, Berkeley, told Discovery News.

Discovery also reports that a potential intruder galaxy, which could have been responsible for the galactic ripples, may have already been found and that publication of that research is still pending.