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Astronomers Map the Peanut in the Center of the Milky Way Galaxy (Video)

First Posted: Sep 12, 2013 09:07 AM EDT
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The center of the Milky Way is difficult to see. After all, Earth resides within this galaxy, so it's hard for scientists to get a perspective from outside of it. Now, though, astronomers have used data from ESO (European Southern Observatory) telescopes to make the best three-dimensional map yet of the central parts of the Milky Way. It turns out that the inner regions, surprisingly, look a bit like a peanut.

The galactic bulge is one of the most important and massive parts of the galaxy. This central cloud of about 10,000 million stars spans thousands of light-years. While it is huge, though, its structure and origin aren't very well understood. That's mainly because from our vantage point within the galactic disk, the view of the galactic bulge is obscured by dense clouds of gas and dust. This means that researchers can only see the bulge by observing longer wavelength light, such as infrared radiation.

That's not to say that scientists have been unable to at least see some of the galactic bulge. The 2Mass infrared sky survey hinted that the bulge had a mysterious X-shaped structure. In order to get a closer look at the shape, though, scientists employed observations from several of ESO's telescopes.

Two groups of scientists were involved in examining the central bulge. The first group employed the VVV near-infrared survey from the VISTA telescope in Chile. This new survey can pick up stars that are thirty times fainter than previous bulge surveys. In all, the scientists identified 22 million stars belonging to a class of red giants whose well-known properties allow their distances to be calculated.

The second team actually compared images taken eleven years apart with the MPG/ESO 2.2-meter telescope. They managed to measure the tiny shifts due to the motions of the bulge stars across the sky. These were then combined with measurements of the motions of the same stars toward or away from the Earth in order to map out the motions of more than 400 stars in three dimensions.

"We find that the inner region of our Galaxy has the shape of a peanut in its shell from the side, and of a highly elongated bar from above," said Ortwin Gerhard, co-author of the new paper, in a news release. "It is the first time that we can see this clearly in our own Milky Way, and simulations in our group and by others show that this shape is characteristic of a barred galaxy that started out as a pure disk of stars."

In fact, the latest findings reveal that the Milky Way probably did originate as a pure disk that eventually formed a flat bar billions of years ago. The inner part of this then buckled to form the three-dimensional peanut shape. The research reveals a little bit more about galaxy evolution and shows new insight into how our own galaxy managed to form.

The two studies are published in Monthly Notices of the Royal Astronomical Society and Astronomy & Astrophysics.

Want to get a better view of the Milky Way? Check out the video below, courtesy of the ESO.

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