LS Thomas wrote:Hello,
I was wondering if you could be more specifc about the location of the bar. For example, does it point from the 2 o'clock to the 8 o'clock position on the photo? This might be a bit more helpful that "it's huge".
Thx
Photo: ESO
Think of it like this. This galaxy is NGC 1232. NGC 1232 either has no bar or a very short bar.
You can see that the yellow center of NGC 1232 is relatively round. You can also see that the spiral arms start right at the edge of the round center.
In NGC 1672, you can see that there is a round center. This round center is surrounded by an elongated "S"-shaped brown dust structure. This dust structure is not a spiral arm, but rather it is part of the bar.
Where do the spiral arms of NGC 1672 start? I'd say that the lower spiral arm parallels the shape of the "S"-shaped dust structure which surrounds the center, but the arm starts some distance below the end of that dusty "S". The lower arm has a long, dark dust lane running along its inside, and it is peppered with pink star formation regions and blue stars. Can you see it?
As for the upper arm, there is a similar elegantly curving dust lane peppered with pink and blue star formation near the upper right corner of the picture. I think that is the beginning of the upper arm.
If you click on
this link, you'll come to a (large) picture by the space telescope GALEX which traces the hot ultraviolet stars of NGC 1672. (Note that the orientation of the GALEX image and the Hubble image are not the same.) In the GALEX image you can see the oval bar structure quite well, as well as the small round yellow center. You can see that the arms don't start at the small yellow center, but a considerable distance away from it. Note that you can see a set of large, faint outer arms too, which are not seen in visual light.
Ann