Talk:Vega/Archive 1

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Magnitude

Perhaps someone should include Vega being the 0 point of absolute magnitude? I'm too lazy to do it myself ;) Ilγαηερ (Tαlκ) 05:35, 29 Aug 2004 (UTC)

Vega in the Foundation series

In the Foundation novels by Isaac Asimov, Vega is the central system of the Galactic Empire, and in which lies the planet Trantor.

Since when has Vega been in/near the center of the Galaxy? --Jyril 20:43, Apr 4, 2005 (UTC)
That's not what Asimov's novels say. They simply place it at the center of the Galactic Empire, which would not necessarily cover the entire galaxy. Even if it did, however, its political center would not necessarily have to be its "physical center," any more than the political and economic centers of the United States have to be in, say, Kansas. 4.243.146.153 18:55, 6 January 2007 (UTC)
The original novels were explicit in that Trantor lies near the center of the Galaxy. A later novel mentions that it is actually somewhat further out (as the center would be inhospitable, a fact that was not know in the 1940s). Of course, the name may have nothing to do with the star itself (as opposed to Arcturus sector, which includes the Sun and obviously refers to Alpha Boötis).--JyriL talk 19:38, 6 January 2007 (UTC)
Vega is mentioned in the Foundation series, but is explicitly shown in that series to be distant from Trantor and Terminus. The most prominent mention of Vega is as the source for "Vegan tobacco", the Foundation equivalent of Cuban tobacco, and thus prized for its quality. -- B.D.Mills  (T, C) 03:15, 22 April 2008 (UTC)

Vega b

Is there any consensus on whether the possible planet orbiting Vega should have its own section? Since it's still unconfirmed, I think it fits well in the protoplanetary disk paragraph, but apparently 71.98.197.91 disagrees. By the way, can anyone confirm the name Vega b? I've only found one other site that mentions it, and no press releases that do. Lusanaherandraton 05:56, 29 July 2005 (UTC)

Okay, I contacted Dr. Holland, who led the JAC team, and he cleared some things up, directing me to a relevant article. I've incorporated this into the proplyd paragraph and made that into its own section. Apparently the name "Vega b" isn't current in astronomy. Lusanaherandraton 04:53, 31 July 2005 (UTC)


Picture

I added the picture. — Hurricane Devon (Talk) 01:06, 31 October 2005 (UTC)

You mean David Hardy's artwork is not copyrighted? Even if it was in a press release [1] doesn't make it copyright free, since it was not a NASA press release. Remember that every image is copyrighted unless explicitly mentioned otherwise. --Jyril 08:02, 31 October 2005 (UTC)

Rapid rotation

Vega has a fast rotation [2]. It rotates every 12 hours. because of this it's pollar temp. is 17,900°F, while it's equatoral temp. is 13,800°F.
Hurricane Devon ( Talk ) 01:48, 11 January 2006 (UTC)

See also [3]. That quotes 12.5 hours for the rotation.

Stellar evolution model for Vega

This is for the benefit of an editor who is apparently insisting that Vega will not become a red giant.

The standard stellar evolution models are the Geneva Grids. The relevant grid for this case is grid I with Z=0.020 (similar to solar metallicity). The relevant table to use is table14 from this list, which corresponds to a 2.5 solar mass star with solar metallicity. To obtain the full table, set "maximum entries per table" on the query form to unlimited.

The table contains values for log10(temperature) and log10(luminosity) as the model star ages. Here's some of the relevant data (with logarithms converted to values):

Row Age (106 y) Temperature (K) Luminosity (sun=1)
7 479 8851 60.5
28 643 4886 66.7
51 757 3926 902
  • Row 7 describes a star which is similar to Vega as we observe it today.
  • Row 28 describes a star quite similar to the two components of the binary yellow giant Capella. The lower temperature means the star has expanded significantly to maintain a similar luminosity.
  • Row 51 describes a star similar to the bright K-class red giant Alphard.

Thus the star goes through the yellow giant stage and ends up as a red giant. Hope that clears things up. Chaos syndrome 15:43, 14 April 2006 (UTC)

turkish music group

VEGA

Really sorry about this

Unfortunately it looks like a large portion of the material in this article under the "Possible planetary system" heading is a copyright violation of SolStation. I'm going to revert the article back to the last version before the copyright material was added, per WP:CP. Unfortunately this was added quite a while back - the last version before the addition of the copyright material was on the 4 April. Chaos syndrome 18:01, 25 July 2006 (UTC)

Age

The page contains inconsistent info: Vega's current age is about 0.5 billion years. ... ... due to the star's relatively young age of about 200 million years.

I noticed that too. Googling "How old is the star Vega?" led me to http://outreach.jach.hawaii.edu/pressroom/1998_vega/ which lists the age of the star as 350 million years. I'll make some appropriate edits. RobertAustin 13:15, 23 September 2006 (UTC)
Also, this sounds awkward: "Vega will pass through a class M red giant stage before condensing down to become a white dwarf." The term 'condensing down' is inaccurate and unwieldy, and the red-giant description could be worded better, if everyone agrees. 68Kustom (talk) 04:42, 4 February 2008 (UTC)
Yes I agree.—RJH (talk) 20:24, 4 February 2008 (UTC)

Vega's Arabic name

I think the phrase نسر الواقع an-nasr al-wāqi' means 'swooping eagle' not 'swooping vulture'. I saw 'falling eagle' in the alternative names section, so I didnt edit it myself..

64.131.215.7 20:39, 26 September 2006 (UTC)

That's right. nasr means eagle only (which is a vulture anyway, but that has another word...) and waqi' means falling, fallen or swooping. I'll do the required work. And add the Arabic name to the "Alternative Names" sections, so that it is not lost in the text in case someone is quoting that particular section, or doing a copy-paste. Orionist 01:08, 10 October 2006 (UTC)

Non-standard jargon: "Luminous" vs "powerful"

The article uses the word "powerful" where astronomers would use the more precise term "luminous". I would suggest a global replacement of the word powerful to make the language more in keeping with standard practice. --24.108.2.150 19:47, 18 December 2006 (UTC)

J.F. Nash, others

It is my understanding that during a psychotic episode, John Nash felt Vega, or some inhabitant of that system, was communicating with him. It is also my understanding that other outstanding people have had similar experiences, i.e., some feeling of communication from Vega. I'm not an alien conspiracy "theorist," but this story is interesting, I'll see what I can dig up and perhaps add some new section. MotherFunctor 06:36, 17 May 2007 (UTC)

can't find any sources for this, probably an information error. MotherFunctor 07:12, 20 May 2007 (UTC)
Do you mean John F. Nash the schizophrenic co-winner of the Nobel prize in economics? Otherwise I think adding something of this nature would need some significant evidence of notability. — RJH (talk) 21:22, 29 October 2007 (UTC)

non-English names

I'm moving the following sentence here from the "Culture" section:

It is known as 织女星 (Zhìnǚxīng, the Star of the Weaver Girl) in Chinese, (See Qi Xi) and Vanand in Persian tradition.

Not only is it unreferenced but I also don't think that English wikipedia should serve as a dictionary of non-English object names. If either these names have some unique cultural context then that would be more useful information. Thanks. — RJH (talk) 23:11, 5 November 2007 (UTC)

I found some more information on Vanand, which has been added. — RJH (talk) 23:14, 15 November 2007 (UTC)

Good article nomination on hold

This article's Good Article promotion has been put on hold. During review, some issues were discovered that can be resolved without a major re-write. This is how the article, as of November 16, 2007, compares against the six good article criteria:

1. Well written?: Yes
2. Factually accurate?: Generally accurate, but see some points below.
3. Broad in coverage?: Yes
4. Neutral point of view?: No
5. Article stability? Stable
6. Images?: Ok

Please address these matters soon and then leave a note here showing how they have been resolved. After 48 hours the article should be reviewed again. If these issues are not addressed within 7 days, the article may be failed without further notice. Thank you for your work so far.— Ruslik 10:54, 16 November 2007 (UTC)

I have fixed one obvious error in the period of a planet in the habitable zone. However I noticed that the luminosity used for this calculation (37 Solar from [6]) is actually the full luminosity of Vega (a different value ~35 Solar can be found in Table 1 of ref [4]). Planets, if they exist, orbit in the equtorial plane. Therefore the size of the habitable zone is actually smaller because equtorial luminosity is weaker (I think around 30 solar). So I think that the values for the habitable zone should be recalculated. Ruslik 10:54, 16 November 2007 (UTC)

Good catches. Okay I found a suitable reference and have updated the formulae. But I'm unclear why you think the text doesn't have a neutral point of view. Thank you. — RJH (talk) 16:37, 16 November 2007 (UTC)
NPOV ? I did not mention it. The values in parentheses (I assume you meant this) are only for information. In addition, taking into account the precision of models, those two values for the full luminosity are in agreement. I also modified the statement about 20 % diffrence in luminosity because it was misleading. Now I am going to promote this article to GA. Ruslik (talk) 15:44, 17 November 2007 (UTC)
Thanks. In the itemized list above you had " Neutral point of view?: No", which I took to be an issue with PoV. But I'll just assume you meant it wasn't a problem. — RJH (talk) 17:07, 19 November 2007 (UTC)
I meant no problem.Ruslik (talk) 17:49, 19 November 2007 (UTC)
Thank you. — RJH (talk) 18:05, 19 November 2007 (UTC)

Habitable planet

Reluctantly I had to remove the following text from the article because I don't have a good reference for the equatorial luminosity of Vega:

The habitable zone around this star is the distance at which the energy flux from the Vega is comparable to the output of the Sun as received at Earth. Along its equatorial plane Vega is about 30 times the luminosity of the Sun, so the habitable zone for this star is centered at a radius of about 5.5 AU.[1] The orbital period for a hypothetical planet at that distance would be 8.9 years.[2]

The 30 times solar looks like a good first-order approximation by Ruslik, but I think we need a paper so it can satisfy FA criteria. Hopefully when a suitable reference becomes available, this can be re-inserted. — RJH (talk) 18:05, 19 November 2007 (UTC)

Unsourced early classification

An anonymous editor inserted some text into the page stating that Vega was probably B8V in its eariest years. Unfortunately this was unsourced, so I am unclear how this was obtained. It is also vague about the time period involved. Did this mean pre-main sequence? Is so, was this a classification on a Hayashi track? If possible I'd like to have this clarified with a reference before it is re-inserted into the article. Sorry for the difficulty.—RJH (talk) 22:11, 16 December 2007 (UTC)

Vega NOT pole star during Egyptian/Assyrian times!

The article mentions that: "Vega was the pole star when the Egyptians used it to orient their temples at Abydos and Luxor. […] The Assyrians named this pole star Dayan-same" however, it is clear from what the previous paragraphs mention and the articles about Luxor, Abydos, and the Assyrian civilization, that Vega was no longer pole star at this time (previous paragraph: "around 12,000 BCE the pole was pointed only five degrees away from Vega").

This should be corrected somehow. However, I do not have time right now, and would like to see someone more knowledgeable about Egyptology and Assyriology (? is that the word ?) than me set the facts straight.

CielProfond, 07:39 UT, 2007-12-28 —Preceding comment was added at 08:39, 28 December 2007 (UTC)

The James Francis and Katherinus Hewitt (1894) reference states that, "...the astronomical observation of the temple sites show that at Abydos and Luxor, which all Egyptologists regard as at least as old as Annu, there was a still older cult, as the star worshipped at these places was α Lyræ or Vega, which was the pole star from about 8000 to 10,000 B.C." Of course that may be an outdated perspective since they got the date range wrong.—RJH (talk) 18:24, 1 January 2008 (UTC)

Pole Star

This sentence needs clarification and expansion:

Through precession, the pole will again pass near Vega around 14,000 CE. It is the brightest of the successive pole stars.

This apparently ignores the situation in the southern sky. Canopus passes within 10 degrees of the SCP during the precession cycle, and Canopus is brighter than Vega. Although 10 degrees is not a particularly close passage, one must ask, where does one draw the line between "pole star" and just another star with a high declination? Some sources allow Canopus as a pole star, others may disallow Vega. -- B.D.Mills  (T, C) 19:53, 30 January 2008 (UTC)

I added the word "northern" to remove the ambiguity. Thanks for pointing out the concern. As for your question, it seems fairly arbitrary and might just be a function of the star's magnitude and people's opinions. Brighter stars may get more slack in their role as pole stars.—RJH (talk) 22:35, 30 January 2008 (UTC)

Artists' impressions of O-B-A stars

I see artists' impressions of OBA stars in the articles and, while the images are pretty, I wonder if the depictions are correct. The depicted limb darkening resembles that of the Sun, where the limb photosphere is cooler (redder) and dimmer than the central disk. In hot OBA stars, though, the central disk photosphere would be even BRIGHTER blue-white than the limb. Right? And that pesky gravity darkening in rapidly-rotating oblate stars only adds to the fun. Anyone wanna take a crack at creating an 'adjusted' image? How do you depict brilliant blue-white fading to bright white-blue?

I once asked a professional astronomer how limb darkening in OBA stars would look. He paused, then replied, "I have no idea." Guess we'll have to wait until someone orbits Regulus . . . 68Kustom (talk) 02:19, 18 February 2008 (UTC)

Yes well you can blame me for this image. =) I understood that there is some limb darkening, so I hinted at that by radially reducing the color saturation. If you could actually see the star up close the luminosity would so saturate your eye's receptors that it would look like a white disk. You would need a heavy filter to observe any limb darkening. (As an example, there's an illustration on this page that shows the limb darkening of the Sun: http://solar-center.stanford.edu/art/explainlyle.html .) Through a suitable filter, the center of the star should be more saturated than the limb, so the color would be less visible at the core. I did apply a heavier gradient along the poles, and used scientific colors to match the temperatures. (Unfortunately that isn't readily apparent; you have to look a little closely.) So the colors are close to accurate, and any adjustment thereof would be a skew toward artistic bias. But, in the end, the illustration is just an artistic representation to show the dimensions and hint at the coloration.—RJH (talk) 16:38, 18 February 2008 (UTC)
P.S. Perhaps what we really need is somebody to write a software program that will produce a correct rendering of the stellar apparence, given a set of parameters (temperature distribution, rotation, &c.)? That might make for an interesting open source project...—RJH (talk) 16:47, 18 February 2008 (UTC)

A little confused

In "Infrared excess" there is written:

"...and came from within an angular radius of 10 arcseconds (10″) centered on the star. At the measured distance of Vega, this corresponded to an actual radius of 80 astronomical units (AU),..."

and then:

"In addition, there is a hole in the center of the disk with a radius of no less than 80 AU.[3]"

Do the Disk have a diameter of 80 AE or ist the hole in the middle as large as 80 AE(!!!) and the dust ring is around that 80AE? --FrancescoA (talk) 16:03, 26 February 2008 (UTC)

Compare the cited Harper et al (1984):808 with Dent et al (2000):707. They are two different observations at different wavelengths. The second is a more refined estimate.—RJH (talk) 18:53, 26 February 2008 (UTC)

Luminosity vs. Absolute Magnitude

The absolute visual magnitude given for this star is +0.58.

How can the star's Luminosity be only 37x that of the sun, if it's absolute magnitude is 0.58? That should correspond to a visual Luminosity of about 50x the solar value, and (given its color) a bolometric Luminosity that's even higher. Is the 37x Solar value the Luminosity after correcting for our pole-on view of the star's rotation disk?

--Rogermw (talk) 01:22, 9 July 2008 (UTC)

Yes. Ruslik (talk) 07:53, 9 July 2008 (UTC)

Error in the article.

Vega can not be the "the second brightest star in the northern celestial hemisphere, after Arcturus.". This is because in the article about Arcturus the claim is that Arcturus is "the third brightest star in the night sky, with a visual magnitude of −0.05, after Sirius and Canopus". It looks like that Vega is the third brightest star on the North, after Sirius and Arcturus. bspasov@yahoo.com —Preceding unsigned comment added by 98.119.172.128 (talk) 19:22, 1 February 2009 (UTC)

Thanks but you might want to look a little closer. Sirius is at a negative declination and thus is not in the northern hemisphere. Both statements are correct.—RJH (talk) 20:35, 2 February 2009 (UTC)

Absolute magnitude X Apparent magnityde

Vega#Rotation:

The 'Apparent luminosity' statement would mean that the star seen in the sky would be 57x more bright than our own sun as seen from Earth.

Details Luminosity 37 ± 3[4] L☉

(This is absolute luminosity)

I changed 'apparent' -> 'apparent absolute', though I'm not sure it makes much sense.

189.62.195.228 (talk) 20:15, 11 February 2009 (UTC)

Saying "apparent absolute" seems confusing to me. Perhaps it would suffice to do away with "apparent" or "apparent absolute" altogether, since we're comparing apples to apples.—RJH (talk) 00:03, 12 February 2009 (UTC)

Absolute magnitude

I am not sure that calculation of absolute magnitude from apparent magnitude and parallax is correct, because the star is not spherical. --Anton Gutsunaev (talk) 19:27, 26 April 2009 (UTC)

Curious, is there a standardized definition of absolute magnitude that requires it to be as viewed from the stellar equator? I'm not sure how useful that would be, since in many cases the inclination of a star is not known exactly.—RJH (talk) 18:55, 27 April 2009 (UTC)

    where rAU is the mean radius of the habitable zone in AU and Lequator is the luminosity of the star along the equator as compared to the Sun.

    • ^ The solution for the orbital period of a small body is given by:

    where P is the orbital period, M is the mass of the central body, a is the length of the orbit's semi-major axis, and G is the gravitational constant. See formula 3.9 at:

    Braeunig, Robert A. (2007). "Orbital Mechanics". Rocket and Space Technology. Retrieved 2007-11-02. 

    It follows that for a hypothetical, relatively small planet in orbit around Vega:

    giving an orbital period of 8.9 Earth years.