Talk:Galaxy morphological classification

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[edit] "S" means lenticular ...

I'm not really an expert on the subject, but I'm gonna go out on a limb and say that "S" is short for 'spiral', not 'lenticular'. - Che Nuevara: Join the Revolution 20:53, 25 April 2006 (UTC)

That's true, S does mean Spiral. However E9, S0, SA0, SB0, SAB0 mean "lenticular". Lenticulars are spirals without arms, more or less. 132.205.93.90 18:58, 24 May 2006 (UTC)


Sites should be merged. Same exact topic, and many users would benefit from consolidation of info. for research purposes.----sjenkins

[edit] Andromeda Galaxy classification?

Quote from this article: "The Milky Way Galaxy is now believed to be an SBb galaxy; previously, it was thought to be Sb like its giant companion, the Andromeda Galaxy." I'm not an astronomer... but the Andromeda Galaxy is described as a barred spiral galaxy in its Wikipedia article so wouldn't that make the Andromeda Galaxy an SBb and not an Sb? 65.31.132.187 07:23, 22 August 2006 (UTC)

The Andromeda Galaxy is apparently a complicated case. The galaxy contains a bar that was only identified recently (in an article currently only in preprint form), but most people would think that it is unbarred. References to it in this article should possibly be removed. GeorgeJBendo 21:17, 15 November 2006 (UTC)

[edit] Morphology not just for galaxies

The term morphology in astronomy is used to describe the shape of any object, though it's usually used for a point source surrounded by extended emission. It is particularly important in the description of planetary and protoplanetary nebulae and dust ejections around other stars like Eta Carinae. Anyone have any idea where to get refs for this, though? --Keflavich 21:30, 12 May 2007 (UTC)

While morphology may be relevant in other parts of astronomy, this is an article about galaxy morphology. I suggest creating another article about morphology in other objects and linking to it from this page in the "See also" section.
(I also did not understand the comment about how morphology is usually applied to point sources with extended emission. I usually see the term "morphology" applied to galaxies, but I may be biased because I am an extragalactic astronomer.) Dr. Submillimeter 07:32, 14 May 2007 (UTC)

[edit] Wholesale rewrite

As soon as I am finished with the revision of the list of NGC objects, I would like to revise this article. Among other things, I would like to:

  • Streamline the discussion on the Hubble classification system.
  • De-emphasize the division between barred and unbarred spiral galaxies in the section on the Hubble classification system. Except for the bar, the two types of galaxies are actually very similar.
  • Greatly expand the section on the de Vaucouleurs classification system.
  • Add images of galaxies to illustrate the vaious morphologies.
  • Add inline citations.

Does anyone have any comments before I start on this? Dr. Submillimeter 15:01, 7 June 2007 (UTC)

I think the Hubble sequence deserves it's own page since it's the most well-known morphological scheme. The de Vaucouleurs system can be included under that or on a separate page. It would be nice to see a paragraph on the pros and cons of the Hubble scheme (I have some notes on that but I'll wait until you've completed the rewrite and maybe add them in if needed). Apart from that I agree that it needs trimming down a bit, especially the detailed stuff about galaxy properties which belongs elsewhere. Cosmo0 23:12, 15 June 2007 (UTC)
Having separate pages for each scheme would be appropriate, but general overviews here would still be appropriate. (What are the pros and cons of the Hubble scheme? Is this something to do with perspective effects?) Dr. Submillimeter 08:22, 16 June 2007 (UTC)
I was thinking firstly of the fact that it relies on subjective judgements of observers (rather than a quantitative criterion such as spectral lines or concentration-asymmetry indices). There have been studies that show an average scatter of ~1 Hubble type between different observers' classifications of the same set of galaxies. Also the difficulty of reliably classifying edge-on, faint or distant galaxies (both because of the small number of pixels in an image of a distant galaxy and the fact that high-redshift galaxies don;t appear to follow the same Hubble sequence). But on the plus side, Hubble type correlates well with many physical paramters (Roberts & Haynes 1994). I was only thinking of a single short paragraph on this (and the same for the other schemes). Cosmo0 14:43, 16 June 2007 (UTC)
Actually, I think a longer discussion would be warranted, and it would be applicable to virtually any morphological classification scheme (Hubble, de Vaucouleurs, etc.). I also wanted to use a lot of the material from Roberts & Haynes (and the Kennicutt ARA&A article) in this article. Dr. Submillimeter 17:09, 16 June 2007 (UTC)
Since you seem to be still busy with other things, and I have time on my hands, I'm going to take a stab at this. I intend to make a separate page for the Hubble sequence, because I think it merits it. Cosmo0 12:41, 15 September 2007 (UTC)
OK, I've done that. I (almost) completely re-wrote the Hubble sequence stuff and moved it to it's own page, with a summary on this page. If anyone objects strongly to that then we can move it back to this page. I also added a few references and images for the different types. I removed the tables of galaxy properties because I mostly don't think they're relevant, but I left them as comments on this page so they can easily be re-added without undoing the rest of the changes.
Comments? Suggestions?
Cosmo0 15:04, 15 September 2007 (UTC)

[edit] Possible Mislabel of Galaxies

A minor note: the galaxy types given for the elliptical galaxy examples differ quite drastically from those given by the respective individual galaxy articles. For example, in this article, M49 is labeled as an E4 galaxy, but in the M49 article, the classification is given as E2/S0. Philolexica

This page is poorly referenced compared to the articles on individual galaxies. I hope to fix it once I take care of a few other things on Wikipedia. Dr. Submillimeter 08:38, 21 June 2007 (UTC)