Talk:Milky Way

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[edit] bad math in "size"

under the "size" section there appears to be some dubious math going on: "100,000 light years in diameter, and about 1,000 light years thick" but "if it were reduced to 130 km (80 mi) in diameter, the Solar System would be a mere 2 mm (0.08 inches) in width." these do not agree.... Rootneg2 (talk) 10:16, 18 February 2008 (UTC)

These do agree. Ratio of diameter of solar system to diameter of Milky Way is about 0.00156 ly to 100000ly equaling 1.6e-8, and ratio of 0.002m to 130000m is also 1.6e-8. I base the diameter of the solar system on Pluto's aphelion. 71.33.130.248 (talk) 11:24, 20 February 2008 (UTC)
also, the 1000 lightyear thickness may be quite wrong! the source quoted and linked merely states "this is the value". no explanation on data or methodology given.
a value around 6000 to 12000 ly seems more probable. the following link has info on data/methodology: http://www.usyd.edu.au/news/84.html?newsstoryid=2163 but even here it's not clear if they're talking about the bulge's or the disk's thickness. more detail needed. --Tobyvoss (talk) 08:57, 20 February 2008 (UTC)
This whole comparison seems arbitrary and not very helpful (why 130km to 2mm, rather than, say, 65km to 1mm?). If you're going to make size analogies then you have to use things that people can easily imagine - very few people have a mental picture of what 130km looks like compared to 2mm. Cosmo0 (talk) 14:10, 23 February 2008 (UTC)

[edit] USydney size clarifications

The article should state the fact that the 1000LY (avg)/12000LY (core) thickness measurements do not include halo objects. These halo objects are often included in diametric measurements. 65.166.89.2 (talk) 17:26, 20 February 2008 (UTC)

[edit] Thickness/U Sydney Press Release problems

I discussed some of the problems with this article on this slashdot thread

99.235.196.247 (talk) 13:04, 21 February 2008 (UTC)

There seems to have been a lot of misinterpretation of this result by Wikipedia editors. As you say in the linked thread, it refers to the gas disk and not the stellar disk and so doesn't replace the earlier value of 1,000 light years, which is for the stars and is well-established. Both values are averages. I've tried to clean up the confusion in the article, making the difference between the 2 estimates more clear, but it's far from perfect. Although the recent research is unpublished, I've left it in since the size section previously lacked any mention of the different components of the disk. Cosmo0 (talk) 14:04, 23 February 2008 (UTC)

[edit] 'Size' paragraph information not in line with 'Magellanic Clouds' article?

"The Galactic Halo extends outward, but is limited in size by the orbits of the two Milky Way satellites, the Large and the Small Magellanic Clouds, whose perigalacticon is at ~180,000 light-years.[12]"

This point doesn't seem to be corresponding with;

"Once they (The Magellanic Clouds) were thought to be orbiting our Milky Way galaxy. However, new research seems to indicate that this is not the case.[1][2]"

Quoted from the http://en.wikipedia.org/wiki/Magellanic_Clouds article.

Perhaps this point should be reviewed. Keep up the good work here! —Preceding unsigned comment added by 83.161.18.155 (talk) 21:17, 25 February 2008 (UTC)

[edit] Velocity

How about the velocity of the Milky Way from the "center" of the Big Bang? RobertM525 (talk) 08:19, 1 March 2008 (UTC)

The Big Bang had no center, since by definition it happened everywhere. The velocity of the Milky Way can, however, be measured relative to the rest frame of the CMB, which is the remnant of the Big Bang. The value is given in Milky Way#Velocity. Cosmo0 (talk) 11:21, 1 March 2008 (UTC)

So... everything isn't radiating out from a central point? I thought that was the whole principle behind the big crunch thing... Guess not... RobertM525 (talk) 09:49, 2 March 2008 (UTC)

[edit] Panorama

Jdrewitt (talk · contribs) feels like shrinking the panorama. I feel this is a bad idea and hurts the article.

Other opinions? Dragons flight (talk) 19:36, 22 April 2008 (UTC)

The original size of the thumb at 700px is unacceptable. Wikipedia pages look different on different machines. Read: Wikipedia:Manual of Style#Images, specifically: "Some users need to configure their systems to display large text; forced large thumbnails can leave little width for text, making reading difficult". The new gallery format is much more satisfactory and improves the article considerably. It also includes both panorama's instead of just one. Jdrewitt (talk) 19:48, 22 April 2008 (UTC)
We have panoramic images on many pages, e.g. {{wide image}}. By ensuring no other text occupies the same horizontal space you eliminate the crowding concern. And, yes, panaromas are informative and useful to the general reader. In my opinion, shrinking this image (even in the gallery) substantially detracts from the purpose of the section, i.e. to describe the appearance of the galaxy. Dragons flight (talk) 20:08, 22 April 2008 (UTC)
The user can click on the image in the gallery and see the image in whatever resolution they wish. However, for the purposes of making the article 'look' good, the new format is more satisfactory and is a vast improvement considering the issues I have highlighted with the previous format. However, the opinion of other users who are neutral to this dispute would be greatly appreciated. Jdrewitt (talk) 20:13, 22 April 2008 (UTC)
I've looked at the two versions (specifically this one and this one) and, personally, I think it looked fine as it was originally. That said, I don't have any particular objection to the current layout either, but if I had to choose between them I'd pick the former (I'm just referring to the one image here, not to the other changes that have been made). Cosmo0 (talk) 22:09, 22 April 2008 (UTC)
I disagree, particularly as the former layout, not only makes things look wierd, but also demotes a former featured picture , as shown below
Former featured picture
Former featured picture
to the sidelines. Jdrewitt (talk) 07:52, 23 April 2008 (UTC)


[edit] Historic Herschel graphic

The image shown of Herschel's illustration of the Milky Way is flipped 180 degrees on the horizontal axis. The original PhilTrans paper (which is sitting in front of me on my desk) has the bifurcated arms on the left, not the right. I've made a note to that effect in the text describing it. Sorry to not actually just flip it; I'm new to Wikipedia. Thanks. —Preceding unsigned comment added by 216.31.151.2 (talk) 20:44, 28 April 2008 (UTC)

[edit] Speed Relative to the Universe

The infobox lists speed relative to the Universe. That's meaningless. Does anyone know what this speed is actually in reference to?—David618 t Fiziker t 20:34, 15 May 2008 (UTC)(old username)

The speed relative to the universe is the anisotropy of the background microwave radiation caused by local movements of the Earth around the solar system, the solar system in the Milky Way galaxy, and the Milky Way in the universe. The microwave radiation is slightly blueshifted in the direction we are moving and slightly redshifted in the direction we are moving away from. The former two motions are well known from other calculations and so can be calculated, and removed from the anisoltropy. Any residual blue and red shifts then are due to the Milky Way's own motion in the cosmos. Hope this helps. John D. Croft (talk) 23:42, 15 May 2008 (UTC)

Well, that suggests that the number isn't "meaningless", but it hardly explains to Wikipedia's readers what it does mean. Motion cannot conventionally be defined without being relative to something else, and "the cosmos" isn't adequately and specifically described in a way to make this comprehensible to most other than astrophysicists (assuming even they all agree, which I'm not sure is true given the apparent recency of some of the data and theories on this aspect of cosmic anisotropy). I also suspect that this may be the only galaxy article for which we have such a number, which further begs the question of what it really means to a general audience. In short, I'm not sure there's a point to including this number in an infobox, as if it's a standard, general measurement with no questions over its meaning or derivation. It sounds more like something that needs significant explanation, far more in fact than one can find at Cosmic microwave background radiation#Velocity relative to CMB anisotropy or in the first paragraph at Anisotropy#Physics. ~ Jeff Q (talk) 01:26, 16 May 2008 (UTC)
This should be taken out of the infobox and properly explained in the main part of the article. I might get around to looking up the information in the coming week, but if John D. Croft or anyone who already knows what this means can do it, it would be good. —Fiziker t 14:57, 16 May 2008 (UTC)
There's already an explanation in the text. I've changed the title in the info box, to make it more clear what the number refers to, and linked it to Cosmic microwave background. I also updated the value in the infobox to agree with the one given in the text, which is correct according to the paper cited (the original citation was to an encyclopedia, which is where the 'relative to the universe' language seems to have come from). Cosmo0 (talk) 20:52, 16 May 2008 (UTC)
Thanks, Cosmo0. Stupid of me not to have noticed the explanation in this article after the trouble I went to to review the other pertinent articles. I'm still not sure this number belongs in the infobox, but at least the label is more specific and has a reference cited. I wonder if it might not be better to direct the inbox label link to the paragraph in this article, which is a more direct explanation, but also has links to those relevant articles. I've added a span-id tag to that paragraph (linking to Milky Way#cmb) in case we decide to do this. ~ Jeff Q (talk) 23:03, 16 May 2008 (UTC)

[edit] Map needed

It would be good to put in a map of the sky that shows the "path" of the Milky Way. I looked all over Wikipedia and couldn't find any decent map of the whole sky or a map showing the Milky Way. Eric Kvaalen (talk) 23:23, 29 May 2008 (UTC)

[edit] Two arms or four?

News item: New observations have indicated that the Milky Way might better be divided into two arms rather than four.

http://news.yahoo.com/s/space/20080603/sc_space/newimagesmilkywaylosestwoarms

-- Powers T 20:32, 3 June 2008 (UTC)

SPACE.com has a great illustration showing the new thinking: http://a52.g.akamaitech.net/f/52/827/1d/www.space.com/images/080603-galaxy-arms-02.jpg There has apparently been some merging, splitting, and deleting done with some of the arms and their names. --24.11.104.84 (talk) 21:41, 3 June 2008 (UTC)

Just to round out the coverage: http://www.msnbc.msn.com/id/24951910/ MSNBC's version. (I'd offer to be bold, but looking at that neatly done section, with its spiffy chart and image, makes me very wary...) umrguy42 02:34, 4 June 2008 (UTC)

Unfortunately, I don't have a nice reference handy, but people have known for some time that there are a number of "issues" with the classic four arm configuration. One of which is that it isn't very stable. In contrast to a two arm system, a four arm patterns are predicted to dynamically degenerate into either two-arm systems or multi-arm messes on time scale that are astronomically short (a few billion years), so if the Milky Ways does have four arms then it would have to have been excited during a relatively "recent" epoch. The other problem is that if you look out at the sky, the other four arm galaxies we see (and they are rare) tend to have arms clustered in pairs rather than laid out in a uniform pinwheel. While it was always possible that the Milky Way is simply an unusual galaxy, it does seem more natural to think that we haven't yet gotten the shape right. Dragons flight (talk) 02:59, 4 June 2008 (UTC)
Indeed... so, how can we fix the article? :) umrguy42 03:15, 4 June 2008 (UTC)
The article doesn't really go into detail about the arms, so I think a slight reworking of the "spiral arms" section is all that's needed. We'll need to keep the old configuration up for the time being, but mention the new configuration as well. I would also suggest reworking the graph to point out that the "Orion arm" isn't a full spiral arm but just a spur off one of the big ones. We might want to include this new image too. Personally, I think it looks nicer than the old one.Serendipodous 09:57, 4 June 2008 (UTC)
Is that image done under contract to NASA, and thus PD? (*hoping*) Powers T 12:32, 4 June 2008 (UTC)
As far as I can tell, yes. It's from a NASA press release. Serendipodous 12:45, 4 June 2008 (UTC)
I've proposed replacing the old Milky Way artist's conception with this new one at Wikipedia Talk:WikiProject Astronomy#New image of Galaxy. The discussion should be in one place, wherever that is, and I've already posted messages in a few places pointing to the project talk. Indeed, the new image is far better scientifically; I'll let others make aesthetic judgements. ;)
I'll work on the spiral arms section when I get a chance. (I am at the same institution as the folks who did this work, so I've heard a lot about it.) ASHill (talk | contribs) 14:37, 4 June 2008 (UTC)

[edit] ebay

Um... Anybody notice that The Milky Way has been put up for auction on eBay? SHould this be mentioned within the article? 71.97.240.153 (talk) 04:52, 4 June 2008 (UTC)

I'd say no, it's not really relevant. Serendipodous 09:51, 4 June 2008 (UTC)