Posted on 06/04/2008 2:31:50 PM PDT by neverdem
Fresh look.
Recent surveys of the Milky Way show it contains a prominent central bar feature (bottom), distinguishing it from other galaxies of the classic spiral variety (top).
Credit: (top) NASA/Spitzer Space telescope (bottom) NASA/JPL-Caltech/R. Hurt (SSC/Caltech)
By Phil Berardelli
ScienceNOW Daily News
03 June 2008
Forget what you thought the Milky Way looked like. The galaxy is far from the simple and elegant spiral-armed structure so often portrayed. New observations, presented today at the 212th meeting of the American Astronomical Society in St. Louis, Missouri, reveal, among other things, that the Milky Way is missing two of the four spiral arms it was thought to have. The findings should force a significant rethinking about how the Milky Way evolved and how its stars formed.
Mapping the Milky Way is extremely difficult. William Herschel first tried it in 1765 by counting stars with his small optical telescope. But even with improved modern instruments, astronomers have faced several challenges. For starters, our solar system sits on the Milky Way's outskirts, along a branch of one of the spiral arms, so there isn't a panoramic view of the main structure. In addition, our vantage point is obscured by many stars and large clouds of interstellar dust.
Now two teams have pierced that veil with unprecedented clarity. One team used the Spitzer Space Telescope, which can see through dust, to chart the positions and orbital speeds of more than 110 million stars. They discovered a big surprise: Two of the galaxy's four spiral arms are actually just small side-branches. On the other hand, the central bar of the galaxy turns out to be nearly twice as big as previously thought, Spitzer team member Robert Benjamin of the University of Wisconsin, Madison, said at a teleconference today.
Meanwhile, another team probed the galaxy with the Very Long Baseline Array, which comprises a telescope of such power that you could use it to read a newspaper on the moon. They have learned that many young stars in the spiral arms orbit the galactic center slower than calculations suggest. Analyses of their motions reveal what happened: The stars were born when gravity compressed interstellar gas clouds. The new stars got kicked out of the circular orbit of their parent clouds and into more elliptical paths.
"The new data give a much, much better picture of what's going on," says theoretical astrophysicist Avi Loeb, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, who was not involved in the survey. So theorists should be able to improve their models of the Milky Way significantly and "perhaps gain a better understanding of how galaxies of its type are organized."
Well, they have a very good idea of what the structure looks like now.
Up until several centuries ago, we didn't even know what the planet we're all riding on looked like, if it was flat, spherical etc. It takes time, much thought and considerable research.
As well you should have been. It's a great image.
Of course it's hard to determine the shape and size of something that you are *inside*, especially when parts of it are obscured by dust (from your point of view) or "glare". Add to that the inability to directly measure distances, and it's amazing that we can get even close. Of course it helps that nearby Galaxies offer a peak at similar structures to help guide our examination of our own Galaxy.
My cell phone camera ain’t near as good as yours!
Thanks. It’s not a real easy endevor to obtain these shots, but it’s fascinating when after processing, the image comes alive. Advances in computers, digital imaging and processing of these images are truly fantastic.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.
