Astronomy Picture of the Day 06-07-03

Astronomy Picture of the Day ^ | 06-07-03 | Astronomy Picture of the Day

[ThinkPlease]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2003 June 7

Warped Spiral Galaxy ESO 510-13
Credit:

Hubble Heritage Team (STScI / AURA),

C. Conselice (U. Wisconsin / STScI)

et al.,

NASA

Explanation: How did spiral galaxy ESO 510-13 get bent out of shape? The disks of many spirals are thin and flat, but not solid. Spiral disks are loose conglomerations of billions of stars and diffuse gas all gravitationally orbiting a galaxy center. A flat disk is thought to be created by sticky collisions of large gas clouds early in the galaxy's formation.

Warped disks are not uncommon, though, and even our own Milky Way Galaxy is thought to have a small warp.

The causes of spiral warps are still being investigated, but some warps are thought to result from interactions or even collisions between galaxies.

ESO 510-13 is about 150 million light years away and about 100,000 light years across.

[ThinkPlease]

I had to backtrack a day because warped galaxies are so near and dear to my heart. My first research experience was using Fortran code on Sun Sparcstation IPC to attempt to determine that the perceived warp in the disk of our own galaxy may have been caused by the Magellanic Clouds (two smaller dwarf galaxies visible only in the Southern Hemisphere). Our research (collaborated by others since) showed that indeed the gravitational effects of the two smaller galaxies had an effect on our larger galaxies, especially at the fringe, where the effect is most noticeable, but that it wasn't enough to cause all of the observed warping.

Here is an image showing the amount of warp in our own Galaxy's disk:

So, for example, the galaxy is about 100,000 light years across, with the earth being about 26,000 or so light years from the center. Starting at just outside the Earth's distance, the disk begins to flare, so that at the time you get to the edge of the visible disk at 50,000 light years, you are almost 15,000 light years above the disk, and looking across it. In the opposite direction, the flare exists, but not as impressive. It curves up to about 3200 light years at the edge of the visible disk, but then data by radio telescopes show that the disk curves back DOWN to the plane of the galaxy at almost 65,000 light years from the center. Voila! A galaxy squished like an old sombrero!