Posted on 08/16/2005 7:04:45 PM PDT by LibWhacker
The Milky Way is not a perfect spiral galaxy but instead sports a long bar through its centre, according to new infrared observations from NASA's Spitzer Space Telescope.
Galaxies come in a wide variety of shapes usually thought to be produced by gravitational interactions with nearby objects. Some spiral galaxies look like pinwheels, with their arms curving out from a central bulge, while others have a straight bar at their centres.
Radio telescopes detected gas that hinted at a bar at the heart of the Milky Way in the late 1980s. A decade later, observations with the near infrared survey 2MASS bolstered the case for a bar, but dust in the centre of the galaxy obscured the observations.
Now, astronomers have used Spitzer to peer through that dust at slightly longer wavelengths, observing 30 million stars in the galactic plane in the region around the centre of the galaxy.
They found that the central bar was much longer than previous observations had suggested - reaching about half the distance between the galaxy's centre and our Sun. The bar is estimated to stretch a total of about 27,000 light years from end to end.
"It is a major component of our galaxy and has basically remained hidden until now," says team member Ed Churchwell, an astronomer at the University of Wisconsin in Madison, US. "The fact that it's large means it's going to have a major effect on the dynamics of the inner part of our galaxy."
Bar food
Stars in the spiral arms circle the galaxy in roughly circular orbits. But the old, red stars in the bar appear to be on more elliptical paths that take them more directly towards and away from the galaxy's core, where a colossal black hole is thought to lurk.
"This bar probably does carry matter into the centre of the galaxy and feeds the black hole," Churchwell told New Scientist.
But it is still not clear what the discovery reveals about the Milky Way's past. "I don't think anybody really fully understands how bars are formed," says Churchwell. "What we do know is that it appears there are so many barred galaxies they must be rather stable. Astronomers have to come up with some kind of model that can explain the stability of these structures."
The team will publish its results in an upcoming issue of Astrophysical Journal Letters and has requested more time on Spitzer to study the innermost part of the Milky Way.
I'd like a rum and coke.
Well, there are two explanations I've seen for why about 1/3 of the spiral galaxies are barred spirals. One is that it's due to gravitational interactions with neighboring galaxies, and the other is that they are the result of a galaxy formed by the collision and merger of two smaller galaxies. In the case of the Milky Way, this finding would seem to give more credibility to the latter, because the Milky Way isn't really near enough to any galaxies sizable enough that they should have such a dramatic gravitational effect (the Andromeda isn't big enough, I don't think). Also, the Milky Way is an especially large galaxy which gives additional merit to the idea that it formed out of the merger of two elliptical galaxies.
If there are additional hypotheses for explaining barred spirals, then this should help us sort out what is the most likely correct explanation. So, in general, the significance is that it furthers our understanding of how the universe works and it provides some insight into the nature of our own galaxy and its history.
There's also just the spectacle and grandeur of it all. =)
How on earth do we appear to be alone?? LOL
The nice thing about threads like this is that you can have wisecracks and serious comments side-by-side... And none of them seem out of place and all of them are welcome. :-)
We appear to be alone. In other words, there is no sign of life out there. The situation could change, but that's how it is right now.
You just have to go with the flow and laugh at the funny comments, roll your eyes at the lame ones (mine mostly) and read with interest the informed ones. I don't mind it much since threads like this one never attract that much attention anyway. Now, those threads that have 30,000+ comments are all but unreadable! :-)
We cannot see well enough to tell one way or the other. In order for us to appear to be alone, we must see the universe in such a way that it appears no one else exists. We cannot see but an infinitesimal fraction of the universe that well. At most, we appear not to have identified anyone else.
It's a little hard to find a place to take that picture from.
Where did you think a picture like that of the Milky Way would be taken from? Maybe the lessor or great Magellanic clouds?
But here are a couple of "photos" of barred spiral galaxies.
M83 Galaxy in the constellation Hydra is classified as an SBa type Galaxy. It is also known as NGC 5236. It is sometimes called the "Southern Pinwheel"
Barred Spiral Galaxy NGC 1300
Big, beautiful, barred spiral galaxy NGC 1300 lies some 70 million light-years away on the banks of the constellation Eridanus.
Standing in the middle of the Sahara you could believe you were the only human on the planet, too. Of course you'd be wrong, but perspective is everything-galactically speaking.
So far, we appear to be alone. There is nothing in the Hubble volume that has presented itself as being the work of any form of life that we can see.
If you're offered a "Black Hole", decline. Similarly anything made of Dark Matter, which seems to wind these spirals tighter than the visible mass can account for. No one has much of clue what sort of stuff it might be, so better safe than (very) sorry.
About how many stars are there in our galaxy?
And it's a glorious sight. I need to get out town more often, although I can see it kinda sorta from the central Texas Town I live in. I'll bet it's awesome from the President's Ranch near Crawford.
Well, as I see things, any given galaxy probably has at most two civilizations in it anyhow. One is the first civilization that decides to destroy all other civilizations and succeeds. The other is any civilization that hasn't been around long enough to be discovered by the first civilization. Since our galaxy is old and big, we almost surely have a civilization-destroying civilization out there - and it's by definition paranoid and hiding itself. Since we've only been transmitting to the galaxy for barely 100 years, it almost certainly hasn't figured out we're here yet. But it's only a matter of time!
I was going to write that, too (binary nature to that core structure), but realized it wasn't funny and so...pause...
The humor on this thread is pretty astute, I'm thinking that a discussion about what surely appears to be a (very) long ago collision of two galaxies to form our (now combined) galaxy is only funny if I can think something up...sorry, can't. Maybe a bunny with a pancake on it's head at the center, dunno.
Hard to say. It could lead to a better understanding of galaxy formation. It could help determine what the heck "dark matter" might be. And it's impossible to predict what that might lead to.
No kidding. The arrow is 3.8 pixels above and to the right of the actual location of our sun. ;^)
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