FLPhotoCatcher wrote: ↑
Sat Jun 29, 2019 4:34 am
Beautiful galaxy! How similar to the Milky Way is it, ignoring the size difference? Is there a galaxy that better illustrates what the Milky Way looks like?
The renderings used to show what the Milky Way looks like always bother me since they are so fake looking - better to use a picture of a real galaxy, IMHO.
The way I see it, you can't ignore the size difference. Interestingly, vigorous star formation is more often found in small galaxies than in large ones. Of course, a much greater part of the galaxy can be involved in vigorous star formation if the galaxy is small than if it is big. Both galaxies can have the same absolute amount of star formation, but the small galaxy will be dominated by it, while the large galaxy will not. But I will say that M83 forms more stars in absolute terms than the Milky Way does, based on its appearance alone.
The galaxy is undergoing more rapid star formation than the Milky Way, especially in its central region.
A huge difference between M83 and the Mlky Way is that M83 has hosted six supernovas in the last 100 years, whereas the Milky Way, during the same time period and as far as we know, has not seen a single one. (Or at least not a single one that was observed while it light should have reached us.)
The morphological classifications of M83 and the Milky Way are also different.
The morphological classification of NGC 5236 in the De Vaucouleurs system is SAB(s)c, where the 'SAB' denotes a weak-barred spiral, '(s)' indicates a pure spiral structure with no ring, and 'c' means the spiral arms are loosely wound.
The 'c' in SAB(s)c makes M83 different from the Milky Way. The 'c' denotes a galaxy with loosely wound spiral arms, and such galaxies are often dominated by their spiral arms (well, compared with other spiral galaxies). In my opinion, the Milky Way is not dominated by its spiral arms, and its spiral arms are less loosely wound than those of M83, and the Milky Way has a (relatively and absolutely) larger and brighter bulge than M83 does.
M83 is a "blue" galaxy, with B-V colors of 0.66. No one has been able to measure the B-V of the Milky Way, but my guess is that it is at least 0.85. The difference may not sound like much, but in terms of galaxy colors, it's a big difference.
So what does our own galaxy look like? Sue me. I'm going to have a guess.
NGC 4394. A Milky Way face on twin?
Galaxy ESO 510-G13. An edge-on Milky Way twin?
NASA and the Hubble Heritage Team.
EDIT: Ooops! It turns out that NGC 4394 is a dwarf galaxy and a satellite of M85
. That's not a good Milky Way twin. But how about galaxy M58 in the Virgo Cluster? M58 appears to be about twice as larg and bright as the Milky Way and obviously much, much larger and brighter than NGC 4394, but their morphologies are similar. I think that the Milky Way looks something like this, although perhaps with a bit more loosely wound arms. Another possible twin is NGC 7773, but I wonder if the arms of NGC 7773 are not too freely flailing.
M58. A Milkky Way twin?
Photo: Adam Block/Mount Lemon Sky Center.
NGC 7773, a Milky Way twin? Photo: Hubble.