Also, just adding to what Nigel said: the spiral arms are not so much the result of spin as a region with a high density of stars most likely due to density waves; density waves could have a number of causes, for example, an interaction with a nearby companion galaxy (which is quite likely for M51).

But whatever; they’re pretty!

@19 Nigel: Why, half a WITCH of course!!!

I don’t believe there’s such a thing as a dumb question.

What’s the difference between a duck?

L.

Please [#5 Ian] offer him and his team a very big thankyou from me. Love the WISE work! One of my favourite missions and very much appreciated.

Incidentally, I watched the launch of WISE – over the internet on NASA-TVwhich was one of the first one’s I viewed like that so remember it well and have followed it closely since. I’m still hoping the WISE data will lead to a nearby brown dwarf or two turning up perhaps even one closer than Proxima Centauri. Don’t suppose you can give us here any hints or scoops at all can you?

@11. Joel :

@ Egaeus (6) – NGC 6822, aka Barnard’s Galaxy, is an awkward one. First, it’s a very small galaxy. It definitely has a central bar, and there is what appears to be a small and vague single arm, more obvious in visible light. .. [SNIP] .. It’s usually classed as a barred irregular, but that’s an odd sort of group on the edges of spirals. It’s also very, very similar in appearance to the Large Magellanic Cloud, which may have originally been more spirally before getting distorted by the Milky Way. NGC 6822 is part of the local group, but I’m not sure how close it is to any other larger Galaxies which may or may not have affected it.

Informative comment – thanks.

The LMC definitely has spiral structure of sorts in my book & looks like a barred spiral albeit a small & disrupted one to me.

@2. PS :

I have two questions about these pics from a minimally educated though highly inquisitive mind:

1) The spiral shapes are due to a “spin” and we believe that the spin is generated by super massive black holes in the center of these galaxies. Correct? So my question is, how visible is the spin in these views? That is, how long would it take for one of these to complete a rotation? Obviously the further out, the longer the duration, but how observable is it?

Are you asking here can we detect the rotation of these galaxies? Not in our lifetimes I think given the timescales involved.

2) In layman’s terms, how would you describe the reasons why two spirals would look so dramatically different? For example 628 vs 1398. Not the direction of the spin, but why one looks so “clean” while the other looks more scattered. Does it relate to how long it’s been spinning? The positioning of the matter when it was caught up in the spin?

Almost all galaxies have their own unique appearances and various factors create them incl. formation history ie. how the ga scloud that formed its first stars fell together, subsequent gravitational encounters with other galaxies, mergers and the intergalactic environment around them esp. for those in dense clusters and superclusters.

These are probably questions that would have been answered in a 6th grade science class, but I was too foolish then to know what I was missing when I goofed off in that class.

Heck, we’re all human and as such fallible beings – and we all have to start somewhere. Curiousity is good as is further reading on subjects you’re curious about – I’d recommend almost anything by Tim Ferris, Carl Sagan and Isaac Asimov – and never be afraid to ask and seek information. I don’t believe there’s such a thing as a dumb question. (Well, okay maybe very, very rarely! )

Remember : Some of us like answering questions too!

http://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies

&

http://apod.nasa.gov/apod/ap110421.html

Arp 273 on A.P.O.D.

&

http://apod.nasa.gov/apod/ap110226.html

Shell galaxies in Pisces, again via APOD for just a handful of rather different looking not-so-spiral “spiral” galaxies.