h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Possibly the most important point about clusters is that they provide an important basis for estimating cosmological distances since the internal difference of distance between different stars in a cluster is almost neglible by comparison of the distances of the intergalactic objects the clusters are associated with, on which account the differences in brightness of individual stars can be treated as intrinsic rather than as a consequence of distance.

There's also an unusual point in orbital dynamics with globular clusters.

All the individual stars in the cluster are in orbit around the center of gravity of the cluster, rather than any discrete object, in orbits more or less randomly distributed with respect to any hypothetical plane of the ecliptic.

The system as a whole has no appreciable rotation.

Entry: Yawn - the Top Ten Most Unexciting Things in the Galaxy - A87832155
Author: Galaxy Babe - eclectic editor - U128652

Icy - yes, this was your suggestion I took up but I wrote that up for the Post. I then tweaked the title for Peer Review of my much-expanded article to cross "Y" off my list of entries still-to-write I've added your link to the references tag as "yawn" isn't mentioned anywhere in the Entry other than the title

mvp - thank you, I'm always pleased when someone gets my in-jokes and little digs I'm afraid I have to disagree with you about clusters. But I have been spoiled by the awesome photos at APOD (eg http://apod.nasa.gov/apod/ap140608.html)

ITIWBS - I read somewhere that globular clusters are possible remnants of smaller galaxies that have been gobbled up by larger ones, and as they seem to have much older stars than their parent galaxy this seems to make sense to me. When I joined Galaxy Zoo I found a galaxy which had a halo of globular clusters orbiting the galaxy, it was stunning, I used it as my avatar from then on. I probably lost the image in my last computer transfer but I'll try and find it on the 'net.

GB

Globular clusters newly formed after galactic collisions and close passes are often veru irregular.

One that's got a strongly spherical distribution of stars is usually a comparatively old one, at least a few million years since it was torn from its parent galaxy.

While classifying galaxies in Galaxy Zoo, I found a spiral with a central supermassive blackhole and an axial jet, but I lost it again and have never managed to find the e-mail I sent to the Galaxy Zoo project - they were looking for black holes.

I also found a galaxy with jets when they were looking for black holes. I uploaded it to the forum at the time (2007). I got an email some time ago (March 2012) telling me it was chosen as outstanding image of the day at the forum (though I was long gone from there).

I did save some images which I thought were outstanding to F41297?thread=4372799 but I don't have time to go through them all I'm afraid. The links take you to the SDSS finder tool page but don't do anything else, the page will reload with the image I saved. My black hole is in there somewhere, along with the polar ring galaxy I'm trying to locate.

Here's a jet from a merger (which I didn't find at GZ, it was uploaded by a newbie): http://cas.sdss.org/astro/en/tools/chart/chart.asp?ra=226.42431&dec=5.09507&scale=0.09903

I found the polar ring galaxy which I used as my avatar at GZ: http://cas.sdss.org/astro/en/tools/chart/chart.asp?ra=222.81&dec=35.542

That's lovely, GB!

WHy is that called a polar ring galaxy? What's polar about it?

I'm amused by the fact that the things in GB's entry are so boring that nobody is talking about them. We're talking about much more interesting things.



Most polar ring galaxies consist of a spiral galaxy, which is a flat disc, and a ring whose axis is at 90° to the axis of the galaxy, so that the ring crosses the 'pole' of the galaxy.

In this case, it is a similar sort of ring, but it is around an elliptical galaxy which doesn't have any obvious pole. The mechanism for creating the ring is the same in either case, so I presume they use the same name for both, even though in this case it is not strictly polar.

I admit I was shocked when I saw that categorised as a "polar ring galaxy" by the Zookeepers when I uploaded it to the GZ forum. It's not what I had thought, I thought I had discovered an ancient elliptical galaxy which had coalesced after a merger or several mergers, and all that was left was cores/lumps of stars like globular clusters of the originals, but considering how far away that galaxy must be it's doubtful we'd see them even if they are orbiting the elliptical at an extreme distance, rather like maypole dancers. The Maypole galaxy has a nice ring to it, and I've never found it anywhere else.

GB

I enjoyed this Entry

I particularly like The Eridanus Supervoid section

Sorry I don't agree GB's entries form a solid foundation of knowledge which can expanded by people like me with an interest. They need no discussion as they are complete.
With the aid of a star chart or a star finder app on a tablet they are excellent guides.

Boring no!

Your Guide Entry has just been picked from Peer Review by one of our Scouts, and is now heading off into the Editorial Process, which ends with publication in the Edited Guide. We've moved this Review Conversation out of Peer Review and to the entry itself.

If you'd like to know what happens now, check out the page on 'What Happens after your Entry has been Recommended?' at EditedGuide-Process. We hope this explains everything.

Thanks for contributing to the Edited Guide!

Well done GB - how many letters have you got left?

<BB<

Brava!

Thank you very much!

Now if I could just find that piece of paper I had the letters written on, I could answer that question

The letters I still have to do are: I, K, Q and X. The planets I still have to write something about are Mercury and Uranus.

Have you thought of writing about the planet IX in the Dune universe, and maybe also the Klingon homeworld Kronos, also spelt Qo'noS?

<BB<

They wouldn't count as astronomy entries though, would they?

Well done