Talk:Deneb

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
WikiProject Astronomy / Astronomical objects  (Rated C-class, Top-importance)
WikiProject icon Deneb is within the scope of WikiProject Astronomy, which collaborates on articles related to Astronomy on Wikipedia.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 Top  This article has been rated as Top-importance on the project's importance scale.
Taskforce icon
This article is supported by WikiProject Astronomical objects, which collaborates on articles related to astronomical objects.
 

Arabic[edit]

I suggest that the Arabic meaning of Deneb, and the associated mythology, be added to this article.

Blue Giant[edit]

I got to this page by following a link from the Blue Giant article. Shouldn't the Deneb article mention that Deneb is a Blue Giant? This would seem to be important information.

If Deneb is a spectral class of A (not O or B), then it may be confusing to call it a Blue Giant, especially along with the reference that it is a short-lived star. O and B are Blue Giants, A is more a White Giant with a blue tinge. Blue Giants, if my understanding is correct, is a term used for O and B classes, not A classes. If my understanding is correct, the text referencing Deneb as a Blue Giant should probably be clarified. Tesseract501 June 6 2006.

Absolute magnitude estimate[edit]

Why is the value -8.73 given to two decimal places, while later in the text both distance and luminosity are uncertain by a factor of four? (which is almost two magnitudes). Wouldn't it be better to say "about -8.5" and leave it there? Alfio 12:14, 21 August 2006 (UTC)

I've changed the page. Alfio 22:30, 2 September 2006 (UTC)
Thanks to Hevron for changing the value for absolute magnitude in the article to match that in the Starbox sidebar, -6.95. This value would seem to be derived from the data in the 2008 Apellániz et al. article (reference 3) which gives the parallax of Deneb as 2.29 mas, but with an uncertainty of more than 10% (±0.32). This parallax value may be used to calculate a “most likely” absolute magnitude value of -6.95, but it seems appropriate to round this off to 2 significant figures, i.e. -7.0, to reflect the considerable uncertainty in distance. The value has been tweaked in both the Starbox sidebar and the main text, and the text has been reworded slightly to put somewhat more emphasis on the rather large uncertainty band of both distance and absolute magnitude. Piperh (talk) 00:15, 23 August 2010 (UTC)
(Belatedly) This 2009 paper by Schiller gives the luminosity as a whopping 196,000 and absolute magnitude of -8.38 (!) - but doesn't give light year distance in it. Would gel with a further distance and doesn't hipparcos have one somewhere of 3000 light years? Anyway, might be good to lay all the evidence out. Casliber (talk · contribs) 20:38, 30 June 2012 (UTC)
The star is far enough away that the extinction may be pretty significant. I just added a sentence to that article about extinction reducing the magnitude by around 1.8 magnitudes per kiloparsec (in the V band) for stars near the galactic plane, which this star is. In this case though, the paper linked by Casliber only gives an AV of 0.11, so obviously YMMV. Regards, RJH (talk) 21:18, 30 June 2012 (UTC)
The paper gives a distance of 802 parsecs. I have included this in the article. You can add light years too if you want. Lithopsian (talk) 23:55, 30 June 2012 (UTC)
Dang, I missed that - I did scan the article for mention of light years....great. Casliber (talk · contribs) 23:59, 30 June 2012 (UTC)
Chesneau et al (2010:p. 9) point out that the van Leeuwen (2007) value for distance is considerably smaller at 432 ± 61 pc, which results in a luminosity of 55,100 L. You might want to just list both values. Regards, RJH (talk) 21:14, 3 July 2012 (UTC)
The Schiller paper lists within it previous attempts to examine Deneb's size, distance and luminosity. I think the best approach is to read, digest and then regurgitate them in an orderly fashion on the page as I am sure they will be quite fascinating (maybe not to the detail of Betelgeuse but still a fairly interesting and long tale). I am warming to the idea of donig it myself, but am not crash-hot on the physics. If anyone is keen for a collaboration, I am - on the farthest first magnitude star....Casliber (talk · contribs) 00:47, 4 July 2012 (UTC)
Yes, it's probably worth expanding the current paragraph on the topic. Thanks. Regards, RJH (talk) 17:24, 4 July 2012 (UTC)

Distance in Light Years[edit]

Why is the distance given here thousands of light years different from the one in List_of_stars_in_Cygnus and List_of_brightest_stars? Xorthan (talk) 17:52, 3 December 2008 (UTC)

To add to Xorthan's comment above, the Hipparcos star catalogue cited in the article claims a distance of 3,229ly [1], as does the Stellarium planisphere software. Clackpot (talk) 18:07, 31 May 2010 (UTC)

"Distance 802+66pc" seems to be a mistake. Possibly, plus or minus should be used. — Preceding unsigned comment added by 78.105.0.33 (talk) 13:56, 6 September 2012 (UTC)

The distance listed is way off if you try to calculate it using the parallax equation (distance = 1 / parallax). It should be closer to 430 pc. A quick Google search supported this. I have no idea where the 802 figure comes from, but it's not even close to being correct. — Preceding unsigned comment added by 209.106.183.195 (talk) 13:37, 3 October 2013 (UTC)

The distance of 802pc is not derived from the parallax. It has an inline reference that you could read if you are really interested in the details of where that number came from. Or if that is too much work, just read the article. The biggest section discusses distance estimates and the inconsistencies between them. Lithopsian (talk) 15:22, 3 October 2013 (UTC)

Comparison[edit]

Estimates for Deneb's radius range from 200 to 300 times that of the Sun. This is the approximate size of the Sun (right) relative to Deneb.

Unless someone can provide a reference for the ~250 solar radii figure, this image (which uses this number) should not go in the article as it is potentially-misleading. The Kaler reference uses ~110 solar radii, so I've updated the article to use that. Icalanise (talk) 17:52, 25 July 2011 (UTC)

Rank among stars[edit]

The article states that "Even assuming the lowest estimates of distance and luminosity, Deneb is the brightest and most distant of the first magnitude stars." This is a bit misleading, since "first magnitude stars" (technically, those between 0.51 and 1.50 apparent magnitude) is a bit obscure and even lowest estimates of its distance place it closer than δ CMa, which is has an apparent magnitude of 1.83. AldaronT/C 22:45, 15 October 2012 (UTC)

That line struck me too, I would guess the intended meaning is that Deneb is 1)the most distant of any of the really bright stars we can see with the naked eye - this is certainly true, it easily outstrips the other major stars -. and 2) the star with the highest absolute (real) luminosity among the first-magnitude stars, and perhaps of all stars with an apparent magnitude brigther than 1.50. With the second one here, we're talking of two different kinds of magnitude. Many of the best visible stars, such as Sirius and Vega, are potent to us because they are close, but Deneb is at least 1.200 light years away, perhaps twice as far, and is still one of the brightest, seen from earth.83.254.151.33 (talk) 00:50, 28 August 2013 (UTC)

surface gravity (log g)[edit]

In the table of properties of deneb, what's the "log g" all about?65.130.253.244 (talk) 04:37, 15 March 2014 (UTC)

g is gravity. log(g) is the logarithm of g, an easier number to use because g itself varies over such a wide range. Supergiants tend to have low surface gravity because of their large extended atmospheres. Or if you like they have large extended atmospheres because of their low surface gravity ;) Lithopsian (talk) 20:40, 15 March 2014 (UTC)

@Lithopsian what is Earth's log g? hi (talk) 16:59, 2 May 2015 (UTC)

Surface gravity. Wikipedia is your friend. Lithopsian (talk) 20:34, 2 May 2015 (UTC)

External links modified[edit]

Hello fellow Wikipedians,

I have just modified one external link on Deneb. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at {{Sourcecheck}}).

YesY An editor has reviewed this edit and fixed any errors that were found.

  • If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
  • If you found an error with any archives or the URLs themselves, you can fix them with this tool.


Cheers.—InternetArchiveBot (Report bug) 23:09, 10 December 2016 (UTC)