May 23, 2011
A galaxy's central bar may look like a solid structure, but it’s really a dense region that affects the galaxy as it rotates around the core. Gas near the galaxy’s center moves at faster speeds than that farther out. This, combined with density waves, helps create the bar. Astronomy: Roen Kelly, after Daisuke Namekata, et al.
Bars are also density waves that rotate around the disk with a speed different from the rotation speed of individual stars, much like the waves that create the spiral structure of these galaxies. Gravitational instabilities in the centers of galaxies, or gravitational disturbances from nearby galaxies, can cause density waves. As the waves rotate around the galaxy, they hold their shape like the blades of a fan.
You are currently not logged in. This article is only available to Astronomy magazine subscribers.
Already a subscriber to Astronomy magazine?
If you are already a subscriber to Astronomy magazine you must log into your account to view this article. If you do not have an account you will
need to regsiter for one. Registration is FREE and only takes a couple minutes.
Non-subscribers, Subscribe TODAY and save!
Get instant access to subscriber content on Astronomy.com!
- Access our interactive Atlas of the Stars
- Get full access to StarDome PLUS
- Columnist articles
- Search and view our equipment review archive
- Receive full access to our Ask Astro answers
- BONUS web extras not included in the magazine
- Much more!