Newly-Discovered Arm of Milky Way Gives Warped Structure

eldavojohn writes "Researchers are now suggesting that a newly-discovered arm of the Milky Way Galaxy gives it a warped structure. Accumulated evidence leads them to claim that an 18-kpc-long arm exists on the other side of the galaxy and this arm traverses some 50 degrees across our sky as an extension of the Scutum-Centaurus Arm (which is one of the two major arms of our galaxy, the other being the Perseus Arm that we can see much more clearly). The researchers conclude that this extension of the Scutum-Centaurus Arm is partially obscured behind the middle of our galaxy because our galaxy is warped 'like the cap from a freshly-opened beer bottle.'"

Looks a lot like NGC 1365

[digitaldc]

This barred-spiral structure makes the Milky Way look a lot like NGC 1365.
Here is what it might look like:
http://en.wikipedia.org/wiki/File:Phot-08a-99-hires.jpg [wikipedia.org]

Re:Who decided?

[decipher_saint]

The word "arm" conveys several meanings, one of which is branch or division.

Re:3-dimensional accetion disk?

[popoutman]

In an accretion disk the majority of matter is a small amount of interaction with other matter in the disk before it ends up close to or past the event horizon, and matter accretes from outside the disk to end up in the disk.
In a galaxy, the vast majority of the matter in orbit is extremely unlikely to end up anywhere near the galaxy centre, and matter does not accrete in any significant volume (excluding galaxy mergers and collisions).
Of course, both a genuine accretion disk and a galaxy are effects of matter in a gravity well....