|In the 1940's and 1950's one of the problems that astronomers worked
on was whether the spiral arms of galaxies curved in the direction of
a galaxy's rotation- or followed it. In order to figure it out, astronomers needed to know which arms where in the foreground and which parts of the galaxy
were on the "backside." This would be determined by the dust lanes in the
galaxy (which block the light of things behind them). The rotation of a galaxy
would be determined by the spectra of its stars. In this example, there is
little question as to what is in the foreground- the prominent dust lane
divides the disk and bulge dramatically. The rotation of the galaxy is also
easy to determine. However, figuring out which way the arms spiral in a nearly
edge-on galaxy requires some detective work. The ends of the galaxy show
a bit of spiral structure (especially the left side in this image) and give
astronomers that vital clue to solving this typical problem.
Famous astronomers such as Hubble and Vaucouleurs worked on these projects
to further our understanding of the cosmic frontier.
NGC 678 is more
than 120 million light years away. Note that the gravitational influence of
NGC 678 has distorted its nearby elliptical neighbor- NGC 680.
|L R G B color production was used to create this image.||
Minimum credit line: Richard and Leslie Maynard/Adam Block/NOAO/AURA/NSF
BACK to main Best of AOP page.
Return to NOAO Home Page