Wikipedia:Peer review/Barnard's Star/archive1

Barnard's star

I feel this one is ready for peer review. I realize it's not exceptionally long, but it is comprehensive, with every paper I could find introduced. It is absent pics, unfortunately, because I can't find a damn thing. I would like some eager volunteer to look at the abstracts and see that I am representing the details properly (I'm a numbers dummy). Particularly, I'd like an explanatory note for "msin i", but I'm not confident I'll represent it properly. Here is one explanation. Any other comments appreciated. Marskell 16:52, 5 October 2006 (UTC)[reply]

Why no more on the process of Van de Kamp's "discovery" of an extrasolar planet? This could give it a tad more length, plus it's interesting (the group all independently measuring the plates and averaging their results). Oh well... very good article, in my first glance. --198.185.18.207 18:50, 5 October 2006 (UTC)[reply]

I had worried in that section about straying too far from the subject itself and not using summary style. However, an extra sentence won't hurt. I'll look back at the source. Do agree it's interesting—the planet controversy is the colour that raises up what might be a dry list of numbers. Marskell 20:28, 5 October 2006 (UTC)[reply]

Anon, where exactly are you reading/interpreting "the group all independently measuring the plates and averaging their results"? Marskell 21:38, 5 October 2006 (UTC)[reply]

Well, I read it elsewhere, but you can see it in a source you already have: [1]. --198.185.18.207 21:51, 5 October 2006 (UTC)[reply]

Ah yes, thank you. I hadn't looked at that one in a while, as the George Bell piece seemed the more comprehensive. Marskell 21:58, 5 October 2006 (UTC)[reply]

Yes it looks good. I could only find a few minor issues:

Suggested links: celestial equator, effective temperature
- Done.
"...received more attention than any M dwarf star given...": you probaby meant "...any other M dwarf star...".
- Done.
Could you double-check the 34.6/10000 value? I think it is an order of magnitude too high.
- Does (3.46)×10^-3 = 34.6/10000? Yes, really, I'm a numbers dummy, so I need everything written out real nice: ten to the negative three equals 0.001 (right?) or 1/1000. I realize the value for this "bolometric" luminosity is an order of magnitude higher than visual luminosity, but I understood the latter as only referring to the visual spectrum (thus it makes sense that there is a large difference, as B's Star likely emits largely in radio). Here is the source.
  - Probably my bad. Thanks. — RJH (talk)
The text lists a temperature of 3134, but the infobox lists 3,000. Perhaps you could clarify the reason for the difference in the text?
- I haven't touched the infobox yet. Numbers in the body are often more precise because I'm going right to papers. I believe the infobox is from SIMBAD like other stars I've looked at; but then I don't totally get it, because SIMBAD doesn't actually seem to list that much info, unless I'm missing something. Anyhow, if I change one number in the infobox I'll have to cite everything, so I'm saving that for last. I'll post when I do.
There should be a space in "m sin i" with m and i in italics to indicate they are variables. You should probably also indicate that m is the planetary mass and i is the orbital inclination. Possible reference: "Kepler’s Laws, Newton’s Laws, and the Search for New Planets"[2]
- I'll look at the PDF and post again. This has driven me nuts—more than anything, for proving how inept I am at digesting mathematical formulas.
I would suggest adding Professor Kaler's article[3] to the external links.
- Kaler is an interesting source I'd never seen. I just put it in the external links and will work a reference into the body so that it's more obvious. I'm a little uncertain though, as he doesn't list his own sources. There's the radial velocity bit above, and he also simply says 10% metallicity, with no range provided. I haven't seen anything that has nailed it down so (apparently) easily.
Finally I would suggest nominating this on the good article candidates list.
- My feelings on GA are clear on the talk page (technically, it's already a GA). I don't have much time for that process, but I won't protest again if someone else posts the tag. I would like to take this to FA. Though, obviously, I need some help... Marskell 23:10, 6 October 2006 (UTC)[reply]

Thanks. — RJH (talk) 15:22, 6 October 2006 (UTC)[reply]

Updates.

Added a brief sentence about averaging plates, per anon.

Added Kaler to the body (the angular diameter of the full moon bit, which I thought a good way to render the speed understandable).

"“Msini”, represents the mass of the planet times the sine of the angle of inclination of its orbit, and hence provides the minimum mass for the planet." I've literally done a cut and paste of this from the PDF you've helpfully provided RJH, and put it in as a note. You'll have to explain it to me like I'm a two year-old, but that may take to long. Marskell 13:07, 7 October 2006 (UTC)[reply]

I'll give it a shot, and hope I'm not just blowing smoke. The M sin i value is what we know from radial velocity measurements, but we don't know the value of i. However sin i is always between 1 and -1, and its absolute value is between 1 and zero. So M sin i is less than or equal to M, and represents the minimum value of the planet's mass. (I.e. only if i were exactly 90° would M sin i equal M. Otherwise it is less than M.) — RJH (talk)

"sin i is always between 1 and -1, and its absolute value is between 1 and zero" makes this much more understandable. I just want it to be clear in the note that the formula determines a relative value, so that people don't walk away thinking "oh, they've refined it all the way down to 7.5 Earths". Marskell 15:37, 9 October 2006 (UTC)[reply]

I believe the resulting net velocity relative to the Sun would be about 140 km/s. (Square root of the sum of squares of velocities.) Professor Kaler gets 139 km/sec.
- SIMBAD lists it as 106.8 (see next) as does this. But I'm scratching my head over the sum of squares of velocities, so perhaps you can enlighten further.
  - The proper motion gives the traverse (sideways) velocity. The radial velocity is the motion along the line of sight. So the two velocity components are like the sides of a right triangle with the hypotenuse giving the total velocity. The total velocity comes from the Pythagorean theorem:

v={\sqrt {(90)^{2}+(106.8)^{2}}}=139.7

D'oh. I was simply mixing up radial velocity and proper motion, I think. Marskell 15:37, 9 October 2006 (UTC)[reply]

Wait a minute: proper motion is simply listed in degrees of arc, yes? So it has a proper motion of 10"3. Would the above value actually be its true motion (or "peculiar velocity"[4])?

Some searching tells me they are distinct terms. I have listed the above body as "true velocity" in the article, and thrown your formula in for good measure. Marskell 16:07, 9 October 2006 (UTC)[reply]

Yes, "transverse velocity" would probably be a better term when speaking of the estimated traverse motion in units of km/sec.[5] :-) — RJH (talk) 16:27, 11 October 2006 (UTC)[reply]

Now I'm thinking the term we need is space velocity. A diagram here seems to explain it. Marskell 17:29, 11 October 2006 (UTC)[reply]