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."
Fascinating!
Assuming, of course, that one were properly tuned in to detect the characteristic radio emissions from the lunar newspaper.....
The purported location of the Star Wars scene?
You can learn that at the local grocery store...
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Not unique, just more unusual than we'd thought. There are several barred spirals visible in this "Hubble Deep Field" image. And that's just a little tiny piece of the universe as seen from out in the galactic boonies of one the Milky Way Galaxy's spiral arms.
In addition, I think barred galaxies are believed to be temporary in the life of spiral galaxies, with the bar dissipating over time.
I've always been interested in galaxies. I see them as beautiful island universes within the universe.
About 3 weeks ago, I took image below of the Whirlpool M-51 Galaxy, in the Constellation Canes Venatici.
There is some dispute as to how distant this Galaxy actually is. I have read ranges from 23 million to 37 million light years away.
This digital image below was a set of 15 exposures at 50 seconds each, and stacked or combined into one image. I performed minimal processing to reveal additional data in the image. Given the conditions, and some new changes to the camera, I was pretty happy with it.
Couldn't have been. That was in a galaxy far, far away.
People think they know something about the universe, yet we don’t even know what our own galaxy looks like.
bump
Excellent! Good job! Not quite the Hubble image, but I bet you didn’t get to spend billions of $ on your equipment, either!
We’re not hosting an intergalactic kegger down here.
True... must’ve been some other barred galaxy.
Sweet.
Given my puny budget, it seemed like billions. lol... Actually it took my about 7 years to get to this point, collecting items as I went along, buying used, trading up, trying to keep up with technology etc. Thanks.
From another article with a lot more detail.
The galactic image that stuck, Benjamin said, was one with the four spiral arms, now called Norma, Scutum-Centaurus, Sagittarius and Perseus. Our sun lies near a small, partial arm called the Orion Arm, or Orion Spur, located between the Sagittarius and Perseus arms.
Using a star-counting method, Benjamin and his colleagues noticed an increase in the number of stars in the direction of the Scutum-Centaurus Arm, but not in the direction of the Sagittarius and Norma arms. (The fourth arm, Perseus, wraps around the outer portion of our galaxy and cannot be seen in the new Spitzer images.) The two major arms, according to these findings, are the Scutum-Centaurus and Perseus arms.
The findings confirm an earlier observation by a team of astronomers, making a strong case that the Milky Way has two major spiral arms, a common structure for galaxies with bars. These major arms have the greatest densities of both young, bright stars and older, so-called red-giant stars.
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