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The Milky Way Galaxy is More Than 50 Percent Larger Than First Estimated

First Posted: Mar 12, 2015 07:40 AM EDT
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It turns out that the Milky Way galaxy is a bit larger than expected. After re-examining the data from the Sloan Digital Sky Survey, scientists have found that our galaxy is at least 50 percent larger than commonly estimated.

"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, one of the researchers, in a news release. "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."

In fact, the researchers found that the features previously identified as rings are actually part of the galactic disk, extending the known width of the Milky Way from 100,000 light-years across to 150,000 light-years. While astronomers observed that the number of Milky Way stars diminished rapidly about 50,000 light-years from the center, the apparent ring is actually a ripple in the disk. Scientists also estimate that there may be more ripples further out.

In all, the researchers found four anomalies when they revisited the data: one north of the galactic plane, one south of the galactic plane, a third to the north and evidence of a fourth to the south. The Monoceros Ring is associated with the third ripple. More specifically, the researchers found that further out, the oscillations appear to line up with the locations of the galaxy's spiral arms. The findings support other research, including a theoretical finding that a dwarf galaxy or dark matter lump passing through the Milky Way 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 Heidi Newberg, one of the researchers, in a news release. "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."

The findings reveal a bit more about our Milky Way galaxy and show that it's far larger than anyone at first suspected.

The findings are published in The Astrophysical Journal.

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