Talk:Van Maanen 2

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van Maanen 2[edit]

It bugs me very much that the first star in van Maanen's list of two stars is called van Maanen 2. Controlled by SIMBAD – it's correct, oddly enough. Said: Rursus ☻ 18:15, 24 June 2008 (UTC)[reply]

But this site lists this wd star as van Maanen 1, so someone got the numbers the other way. Said: Rursus ☻ 18:19, 24 June 2008 (UTC)[reply]

Yes it is a little odd. The name van Maanen 2 for this star dates back to at least 1943.[1] Regards, RJH (talk) 01:53, 17 March 2012 (UTC)[reply]

Radial velocity[edit]

[2] follows the letter of the law, but is false. It is legal, but evil. If one is so concerned with sources, then search a good source for the radial velocity. It is a crying shame to claim +6 ± 15 km/s in one place, 60 km/s in another, and cite some silly approach-predicting paper with stupid calculations, given such mess and uncertainty on the radial velocity. Incnis Mrsi (talk) 15:55, 9 August 2012 (UTC)[reply]

The 60 km/s is not the radial velocity; it includes the transverse components of motion as well. Hence there is no contradiction unless the radial velocity is larger than 60. It looks like the radial velocity used in García-Sánchez et al (2001) is based on Greenstein and Trimble (1967). Makarov (2004) assumes a radial velocity of –38 km/s, which is well outside the margin of error used in the García-Sánchez paper. You most likely have a point, but we should pull the sentence altogether rather than speculating. The derogatory nature of your remarks seems unnecessary. Regards, RJH (talk) 16:18, 9 August 2012 (UTC)[reply]

Yes, I made a mistake. I calculated the transverse component, it gives namely 60 km/s. We have figures: 1.237 ″/yr for right ascension and 2.709 ″/yr for declension. Since r.a. is almost 0 and its cosine is about 1, we can neglect the difference between spherical and Cartesian coordinates and apply Pythagoras' theorem, so we have about 2.978 ″/yr of angular transverse motion. Let us multiply it to 4.3 parsecs… we have 12.805 AU/yr. There are 1,915,628,000 km in 12.805 AU and 31,556,926 s in a tropical year, so the transverse velocity component is 60.7 km/s. Incnis Mrsi (talk) 18:59, 9 August 2012 (UTC)[reply]

Yes, the radial velocity determinations are all over the map. Of the papers I looked at, the Aannestad et al (1993) seems to give the best accounting of the radial velocity with respect to the Sun. They list –38 km/s, the same value later assumed by Makarov (2004). So I'd say we should probably go with that. It's at odds with the value assumed by García-Sánchez et al (2001), so that should be yanked until a newer source becomes available. We may as well pull the space velocity information as well since Sion et al (2009) didn't clarify what value they used. Will that resolve the concern? Regards, RJH (talk) 01:07, 10 August 2012 (UTC)[reply]

This new paper from 2021 https://www.aanda.org/articles/aa/full_html/2021/08/aa41344-21/aa41344-21.html provides explanation of how the 263 km s^-1 value came to be, and suggests it is a poor quality data. It also provides a much better number of −11.74 ± 7.11 km s^-1, so I think we should go with this value instead. AstroChara (talk) 15:29, 11 March 2023 (UTC)[reply]

That makes sense. The paper has a good discussion of the issue, and it might even be worth a few sentences in the article. Praemonitus (talk) 18:00, 11 March 2023 (UTC)[reply]

Mass[edit]

The article once claims that is mass is 68% of the Sun mass and 1.1% of the radius. Later, it claims that it is 63% of the Sun mass and 1% of the radius. Which mass is the correct one?— Preceding unsigned comment added by 177.18.205.246 (talk • contribs) 2014-07-20T01:03:49

Addressed. Praemonitus (talk) 18:24, 26 February 2016 (UTC)[reply]

Distance[edit]

The distance table lists (consistently) a 13.3-14.4 ly distance), while the text claims 12.4 ly. Something is not right. — Preceding unsigned comment added by 24.138.49.198 (talk) 01:37, 21 May 2015 (UTC)[reply]

Addressed. Praemonitus (talk) 18:24, 26 February 2016 (UTC)[reply]

Pronunciation[edit]

Found an astronomy web page to cite, but no confidence in it. Could be how the author thinks it should be pronounced rather than how ppl actually say it. Not just "van-MAN-inz"? Anyone know for sure? — kwami (talk) 07:37, 28 April 2019 (UTC)[reply]

Ref of 650 Rsol during the red giant phase[edit]

I wasn't able to find a ref for the 650 solar radii estimate during the red giant phase of Van Maanen 2, I did however find an estimate of 1,000 Rsol in the paper. Nussun05 (talk) 13:30, 1 August 2020 (UTC)[reply]

Thanks. It was originally 1,000, then was changed to 650 by this edit. Possible OR? Praemonitus (talk) 02:23, 8 September 2020 (UTC)[reply]