Talk:Rigel

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Season location[edit]

At what time of the year is Rigel most visible? I'm trying to locate it around the earth at the spring, summer, winter or fall position

In which hemisphere? :) I imagine it makes a difference? I only know that, in the northwestern United States, we see Rigel most clearly from October to April. Don't know if that's specific enough for you. It also depends on whether you want when Rigel is at its peak at midnight, or whether you want it earlier in the evening. Jwrosenzweig 19:49, 10 Mar 2004 (UTC)
Hemisphere in this case (N/S) doesn't matter. Rigel is in the night sky during the winter, as you say. It's in the southern celestial hemisphere, but very near the celestial equator, meaning that it is visible from the entire southern hemisphere of the Earth and all but the highest latitude Arctic regions of the northern hemisphere. -- Decumanus 19:53, 10 Mar 2004 (UTC)
Hemisphere does matter when the question is asking in terms of the seasons. Winter in the northern hemisphere translates to summer in the southern. --seav 19:14, 29 Aug 2004 (UTC)
How high does it get from Glasgow (Scotland)? I don't think Orion rises very high in the sky.81.107.126.114 14:17, 24 August 2007 (UTC)
I was gonna say :P It's summer right now and Rigel is bright and high... SpitValve 08:23, 9 January 2006 (UTC)

Giant - Dwarf[edit]

The article says Rigel is a super giant;

I suspect the dwarf category was added because the companions of Rigel are main sequence. I have deleted that category though, just to keep things clear as Rigel is usually understood to be the main star.--Kalsermar 19:32, 4 December 2005 (UTC)

what the hell -- unsigned

In this case, should we split off Rigel B as a separate aticle? -- CaptainMike 17:41, 19 April 2007 (UTC)

Celestia[edit]

Excuse me, but what a junk Celestia imagery. :-p It's not even an "artists" rendition as it claims, unless a software is now an artist. :-p

Anyway, my point is, wouldn't it be better to have real images than just Celestia things? Keep in mind that Celestia use about 5 textures for all documented stars it supports in our galaxy. Sure, a real picture can't be quite as up close, but still... It'd at least depict Rigel. -- Northgrove 16:52, 26 April 2007 (UTC)

Right, the current image is pretty useless as it is not informative. In addition, it is wrong because B supergiant stars like Rigel don't have sunspots. A size comparison might be handy.— JyriL talk 17:14, 26 April 2007 (UTC)

Radius and diameter[edit]

I don't get it. On Rigel's page it says its 70 solar radii. Yet the list of largest stars has the units in diameter. This list has Rigel on it listed as 70 sun diameters. So is it a simple mistake?

No mistake, but what is exactly the problem? 70 radii means the radius is 70 times the radius of our sun. 70 diameters means 70 times the diameter of our sun. Both things are equivalent.--CWitte 14:53, 9 October 2007 (UTC)
The problem is the back-and-forth. Rigel's radius and diameter are 70 times that of the Sun, yes, but we should adopt a consistent rule across articles to avoid this minor confusion. Radius or diameter? You choose. 68Kustom (talk) 02:03, 18 February 2008 (UTC)
I think radius is standard in astronomical texts. ... said: Rursus (bork²) 16:24, 24 June 2009 (UTC)
why does NASA say that "Rigel is much larger at 78 solar radii" here http://www.nasa.gov/worldbook/star_worldbook.html —Preceding unsigned comment added by 68.115.186.143 (talk) 17:11, 4 December 2008 (UTC)

Well first of all, you can calculate the radius of a star based on b-v (color index) and the absolute magnitude as shown in http://cas.sdss.org/dr6/en/proj/advanced/hr/radius1.asp The steps are: 1) based on the b-v (color index) you can find out the temperature of the star 2) using the temperature of the star and the absolute magnitude of the star you can calculate the star radius as shown in the link

The downside is that I calculated Rigel's temperature using those formulas and it isn't 11.000 K, i got 9076.59347 K and that led to its radius of 85.9568577517187 solar radii. Raydekk (talk) 16:48, 22 February 2009 (UTC)

Eh, we should prefer using sourced radii measured or computed outside. ... said: Rursus (bork²) 16:27, 24 June 2009 (UTC)

image[edit]

What can be seen on the "artist's impression" image? Why is it "viewed from 1AU" and how should it look like e.g. from 2AU or from 7 ly? I just see a white circle, some spots and nothing else. Maybe one should put a small sun inside the picture to have a comparision at least, --CWitte 08:21, 9 October 2007 (UTC)

I don't see the point of this image either. Rigel is white, blurry, seems to have sunspots or something, and it's so big it doesn't fit into the frame of the picture. / edg 01:09, 15 March 2008 (UTC)

i wonder who named it —Preceding unsigned comment added by 204.193.212.203 (talk) 03:57, 8 October 2008 (UTC)

I just ran across this image two years later again. Still I wonder... Isn't File:Rigel_sun_comparision.png better?--CWitte (talk) 08:49, 27 June 2009 (UTC)

Deneb?[edit]

The article says "the nearest more powerful star is Deneb" but I could swear that Zeta Puppis is both closer than Deneb and more powerful than Rigel. Wayne Hardman (talk) 12:57, 9 January 2009 (UTC)

It seems the latest analysis might agree with you on the closeness, but I cannot figure out the accepted, most recent, bolometric luminosity of Deneb to be sure that Deneb is more powerful than Rigel. Can an expert check these? Meanwhile I have added this to the Zeta Puppis article:
2008 reductions of Hipparcos raw data claim a more accurate distance of 335 parsecs (1092 light years) +/- 4%, and for Deneb, 475 pc +/- 20%.[1]
-84user (talk) 14:43, 9 January 2009 (UTC)
I went ahead and corrected the sentence after checking a few sources to make sure Zeta Pup was both more luminous than Rigel and closer than Deneb - To the best of our knowledge, it is although uncertainties in Deneb's distance are quite large. Wayne Hardman (talk) 00:04, 30 January 2009 (UTC)
I notice that this change has caused some disagreement between this article and the article on Zeta Puppis. I agree that Zeta Puppis is closer than Deneb according to the latest data, but what about the luminosity? The infobox in the Zeta Puppis article lists its absolute magnitude as -5.96, less than that of Rigel's which is listed as -6.7. Hence, Zeta Puppis is not "more powerful than Rigel". Is this inconsistency because Zeta Puppis' absolute magnitude has not yet been corrected for the new distance measurement? One other thing, why say "Zeta Puppis out in Vela"? Surely Zeta Puppis is located in Puppis (though it may have origins in Vela)? Sisterdetestai (talk) 13:45, 7 February 2009 (UTC)
I believe Zeta Pup. abs mag should be greater, the magnitude in the star box hasn't been corrected for its new distance. If I get chance, I'll look it up. Thanks for the heads up! Wayne Hardman (talk) 17:12, 7 February 2009 (UTC)
I've restored Deneb in the sentence. Zeta Pup. has been edited also to reflect its new, closer, distance and lower luminosity. Zeta Pup. *is* still more powerful than Rigel going on the figures in this article (66,000L vs 360,000L) but I'm not confident the bolometric for Rigel is accurate. I may be reverting this edit if it is. Wayne Hardman (talk) 23:34, 7 February 2009 (UTC)
I'm sufficiently convinced that the sentence was inaccurate and that Naos is both more powerful than Rigel and closer than Deneb. This issue should be closed now. Wayne Hardman (talk) 22:22, 3 April 2009 (UTC)

Something I don't get: what about Betelgeuse? More powerful and even closer than Rigel? Talking about "powerful" you should consider bolometric luminosity, shouldn't you? Comparing absolute magnitude MV is kind of odd (anthropocentric...).--CWitte (talk) 15:42, 27 June 2009 (UTC)

Fact request[edit]

I found the text "jumk.de does not cite its sources, so please replace with better source when one found", in the article, as regards to the radius 62 — I just agree, and think it deserves a talk note too. ... said: Rursus (bork²) 16:32, 24 June 2009 (UTC)

It got a new source. NASA should be a little more reliable, I think. ... said: Rursus (bork²) 16:48, 24 June 2009 (UTC)

Size and Mass[edit]

This page says, and I quote:

Rigel is a blue supergiant, at 17 solar masses, shining with approximately 40,000 times the luminosity of the Sun.[5]

The "Blue Supergiant" Page says:

"The best known example is Rigel, the brightest star in the constellation of Orion. Its mass is about 20 times that of the Sun, and its luminosity is more than 60,000 times greater."

These pages appear to be in contradiction.--131.215.7.219 (talk) 05:34, 15 April 2010 (UTC)

There appear to be contradictions on this page also. The physical properties section states that Rigel is about 24 solar masses, while the radius is 71 solar radii. That would appear to indicate a volume and thus mass relative to the sun at least 1.5 million times greater (4/3*pi*r^3), unless the density of Rigel B is extremely (vanishingly) low.Plantsurfer (talk) 01:25, 16 March 2012 (UTC)

Rigel is in the supergiant stage, which means the outer atmosphere has expanded significantly compared to when it was a main sequence star. Yes the density of Rigel's outer envelope is very low; most of the mass is likely concentrated near the core. Consider the surface gravity (log g) of Rigel: 1.75; this is equal to a gravitational force of 56 cm/s2, or 0.057 g's.
As for the value discrepancy, the values on this page are reliably sourced; the values on the Blue Supergiant page are not. That isn't to say that the estimates on the latter page are wrong. Most likely the two estimates are based on estimates made at different points in time, from observations made with differing instruments, different models or methods and different estimates of the star's distance. Radii based on direct interferometric measurements (as on this article) may be more accurate than those derived from stellar models, assuming you have a good distance estimate. &c. Also it's usually best to go with a recent source rather than a dated reference, when there is a choice in the matter. Regards, RJH (talk) 02:51, 16 March 2012 (UTC)

In popular culture?[edit]

Just sitting here watching an old Star Trek episode (Wolf in the Fold), and the Rigel system features prominently in the episode, as well as other episodes in other Star Trek series. Does it warrant a mention? I assume "Rigel IV" would be the fourth planet in the fictitious Rigel system? Note: I'm not a "Trekkie", just thought maybe it belonged? Ebrockway (talk) 04:56, 13 May 2012 (UTC)

Okay, I found this page "Rigel in fiction" and maybe that could be somehow linked? Yeah, I know I'm conversing with myself! Ebrockway (talk) 05:07, 13 May 2012 (UTC)
It is listed in the See Also section at the bottom of the page. Personally I'd make a summary of that article and put it in this one but have not had the time. Casliber (talk · contribs) 13:09, 13 May 2012 (UTC)
Ah, personally I'd prefer that you didn't. "Object in fiction" articles are notorious trivia attractors that are often difficult to summarize concisely, in the form recommended by WP:SS. They end up just drawing useless trivia to astronomy articles. Thanks. Regards, RJH (talk) 14:38, 13 May 2012 (UTC)

Spectral type[edit]

Simbad lists B8Iab:. The reference it gives for this also quotes B8Iab:, but that is simply copied from another paper: http://www.aavso.org/files/webpublications/ejaavso/v31n1/11.pdf That "original" reference gives the spectral type as B8Iae. I;m not sure if someone made a typo or whether they are simply taking liberties. Incidentally, the current value in the starbox cites the paper that Simbad cites, but gives a spectral type that omits the colon, so that should probably be changed anyway. The reverted edit actually gave the correct value from the paper (via Simbad).

As to the value we should show, there is no doubt that it is B8 because it is defined to be B8. There is little doubt about the I. The spectrum does have some emission, but it is largely emission wings on absorption lines and not very strong. Plenty of authors simply quote Ia. — Preceding unsigned comment added by Lithopsian (talkcontribs) 17:18, 3 August 2012 (UTC)

Moravveji et al (2012) is a pretty up-to-date summary/study of the star. They list B8 Ia, so why don't we use that? Regards, RJH (talk) 18:47, 3 August 2012 (UTC)