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Insider Insights: Articles

This 'corrugated' view of the Milky Way just made our home galaxy a LOT bigger

The corrugated Milky Way,


By Scott Sutherland
Meteorologist/Science Writer
@ScottWx_TWN
Monday, March 16, 2015, 11:10 AM

The Milky Way is a pretty big place to live, right? Estimates have put it at around 100,000-120,000 light years across, with Earth located about two-thirds of the way out from the centre, and it's home to some 300 billion stars (give or take a 100 billion). That's big!

Well, not big enough, it seems. Based on some of the latest research, those estimates are actually way off!

According to an international team of scientists, after sorting and sifting through galactic data from the Sloan Digital Sky Survey, they figured out that the Milky Way is actually 50 per cent larger than we thought.

How did all the extra 'space' get missed? Apparently, it was hidden from us by the shape of the galaxy, which appears to be corrugated, like a cardboard box.


The rippled contours of the Milky Way. Credit: RPI

"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 Professor Heidi Newberg, who teaches physics and astronomy at the Rensselaer School of Science in New York State. "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."

Situated here on Earth, looking out towards the edge of the galaxy, we see the number of stars drop off abruptly about 50,000 light years from the galactic centre. This was assumed to be the edge of the galaxy, and beyond that, about 15,000 light years further out from the edge, there was a ring of stars detected, called the 'Monoceros Ring'. This ring, which we can see because it 'bulges' above the galactic disk, was not considered to be actually part of the galactic disk itself, but instead was thought to be a streamer of stars that the Milky Way ripped from a nearby neighbour galaxy.

"We thought it was a tidal debris stream - a dwarf galaxy that came in and spread itself out in this big ring. For 15 years, there’s been a controversy in the field where half the astronomers think it’s a tidal stream and half the astronomers think its something in the disk. I was in the stream camp,” Newberg said in a statement. 

"What I was trying to do was find more evidence that it was streams. It took a very long time to get this result, partly because I had to change my whole way of thinking. It now looks to me like it’s part of the disk."

One way of thinking about this is to imagine being on the ocean when the waves are very high, or standing in hilly terrain. The next rise in the waves or the hills blocks the view of what's beyond.

In the same way, the next rise in the galactic structure is blocking our view of what's beyond, which apparently is a significant portion of the galactic disk.

Based on the distance of the Monoceros Ring, the diameter of the Milky Way increases from 100,000-120,000 light years to somewhere around 150,000-180,000 light years across, and Earth goes through a major change in galactic real estate, moving from two-thirds of the way out to right about in the middle between the core and the edge.

Furthermore, as Yan Xu, lead author of the study and a scientist at the National Astronomical Observatories of China, explained, "it may well be that there are more ripples further out which we have not yet seen."

Finding more rings could mean that our galaxy is even larger than this latest estimate, possibly even rivaling our neighbour, Andromeda.

Source: RPI News | RPI News | Research article on arXiv.org (free pdf)

RELATED VIDEO: Professor Heidi Newberg gives a public talk, explaining these incredible new findings


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