Expert: Tom Whiting - 12/20/2006

Question
Tom,
Many thanks for that great reply.  It will keep me going for a while. To explain, I'm a photo artist working with pendulum patterns.  I recently created a program for simulating some of the patterns and am exploring similarities to spiral galaxies.

The crude image in my last question was of a two armed spiral galaxy, not barred.  I have a clearer, but still curde, image below.

http://www.usuff.com/spiral_galaxy_rough_simulation_21Dec2006.htm

When I come around to photographing them, I'll be on the lookout for any similarity to real DSOs.

I appreciate spiral galaxies in the infinite of space are created by an entirely different process to that of earth bound pendulum patterns.  As an artist, however, I'd want to "talk up" my creations, but without losing sight of the science.  (I took a 101 Astronomy course at UMass at Amherst with Prof Skrutje in 1992 - each class amazed me more than the last class as I learnt more about our stunning Universe over 13 weeks.)

Just for interest, I've read that a swinging pendulum observes one of Kepler's three law of motions.  So there is some link between pendulums and astronomy!

I'll keep you informed if I come across anything interesting.

Cheers,
Usuff


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The text above is a follow-up to ...

-----Question-----
Hello Tom,
I'm looking for a picture of a spiral galaxy that looks like the image at this page :-

http://www.usuff.com/is_there_a_spiral_galaxy_similar_to_this.htm

If you have the name or designation of such a galaxy, I'll look up NASA's website to see if there is an image of it.

Thanks!
Regards,
Usuff
-----Answer-----
Hi Usuff,
The hardest part of your "diagram" is trying to determine
whether or not there is a horizontal "bar" of "star stuff"
through the center, before the spiral arms break off and do
their turning.  In other words, are you (we) looking for a
barred spiral galaxy....classified as SBc....or just a grand design
straight 2-armed spiral galaxy....classified as just an Sc?

Personally, I can't get a distinguishable bar in your diagram,
so I'm going with the "grand design" Sc spirals, as opposed to "Barred Spirals".

Ok, check out 2 Messier Galaxies, M-74 in Pisces and
M-100 in Virgo, and see what you think....the picture is at
http://antwrp.gsfc.nasa.gov/apod/ap030524.html
and to get to M-100, just punch on the link "grand design)
below the photograph.
Unfortunately I don't have a pictorial atlas of Galaxies, because galaxies are not my main DSO (Deep Sky Object)
of interest, but rather planetary nebulae and globular clusters.
So I'm going strictly on memory, but I do remember a fine
picture of NGC 2997 in the Southern hemisphere very similar
to your diagram.  Although it's not perfect...but I guess nothing in nature is super-perfect.  But at least I've given you
a start.  Oh, also google or punch up M-83 in Hydra.

Oh, and if you think that there is a central "bar" of star-stuff,
then check out these grand design SBc....2-armed barred
spirals; NGC's 175,  1300, 1365, and 1073.

Also, as a last resort, you can go to the website called
"astronomy picture of the Day....nicknamed APOD,
and go through their archives.
Hope I've been of some help,
and good luck with your research,
Clear Skies,
Tom Whiting
Erie, PA

PS...Oh, hey,  check out the famous whirlpool galaxy, M-51...
that means Messier 51 but google will know what you mean...
A near perfect Sc spiral, but unfortunately it may have too
many appendaged arms to satisfy your "purely" 2-arm classification.

FOLLOW UP:
And if you don't like any of those, try M-99 in Coma
Berenices....very fine Sc Spiral galaxy.....Cheers.

ADDITIONAL FOLLOW UP:
Wish I knew what we were trying to do, here...your diagram
appears to be computer generated.
But just a couple of facts about spiral galaxies...they aren't
what they seem, or look like.  They do not rotate like a solid
wheel...it's differential rotation. Also, they appear that all the
stars are in the arms, and there is no stars inbetween in the
dark lanes....Not True.  The arms simply are delineating where
the recent burst of star formation occurred, so the arm stars
are the hot, big, blue white stars outlining the arms...there are
plenty of solar size and red dwarf size members in the dark
lanes that do not photograph because they aren't bright
like the blue white giants in the arms themselves. The burst
of star formation is thought to be caused by spiral density
waves traveling throughout the galaxy...the shock waves
hits the dust and gas, triggering another round of new,
bright star formation.  Thus the arms, to survive, have to
be "fed and nourished" by the density waves.  That's why
you rarely find a galaxy arm that has spiraled greater than
one turn around the galaxy.....over long periods of time, the
arms fade, and re-form with a new round of star formation.
Hope this explains in part, how spiral galaxies work in the
very long run.  Just thought you'd like to know.
Clear Skies,
tom

Answer
Hi Usuff,
Thanks for the update and for satisfying my curiosity about
your art patterns.  In fact, the one you just forwarded sure
reminds me of the spiral density waves that first create the
arms of a spiral galaxy.
Hey, I just thought that maybe some of our club members may
be interested in your art work, as some of them get into painting too.
So feel free to contact me directly at
bwhiting@velocity.net
so we don't have to bother with allexperts website.
Thanks again,
Clear Skies,
Tom Whiting
Erie, PA