Talk:Mu Arae

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Good article Mu Arae has been listed as one of the Natural sciences good articles under the good article criteria. If you can improve it further, please do. If it no longer meets these criteria, you can delist it, or ask for a reassessment.
September 16, 2006 Good article nominee Listed
WikiProject Astronomy This article is within the scope of WikiProject Astronomy, which collaborates on articles related to astronomy, and WikiProject Astronomical Objects, which collaborates on articles related to astronomical objects.
Good article GA This article has been rated as GA-Class on the assessment scale.

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"...its age is estimated at approximately 6000 million years."

Why not just say "approximately 6 billion years"?

Because billion means both thousand million (short scale) and million million (long scale). Thousand million is unambiguous.--JyriL talk 16:51, 22 August 2006 (UTC)
Yes, but the universe itself is only around 14,000,000,000 years old, so there's no real ambiguity. 6,000,000,000,000 years would make it older than the whole universe!  :-) Besides which, long scale is falling out of use in English-speaking nations anyways Nik42 (talk) 23:34, 7 June 2008 (UTC)

Contents

[edit] Planet designations

There are now two systems for the designations of the planets in this system.

  • Pepe et al. (2006) designate the planets (in order of increasing orbital period) as c,d,b,e - this breaks with the previously-used designations for the three-planet system, the reasoning is explained in the paper.
  • Gozdziewski et al. (2006) designate the planets (in order of increasing orbital period) as d,e,b,c - this is consistent with the previously-used designations.

The Extrasolar Planets Encyclopaedia is going with the Gozdziewski system (as is this article at the time of writing). Not sure what the best policy for this article would be, maybe use headings 9-day planet, 310-day planet, etc. and then in the text state the designations under the two different nomenclature systems. Chaos syndrome 20:35, 29 August 2006 (UTC)

Ok, having looked at it, I think the best policy is to go with the Gozdziewski system (to avoid confusion with the previous system), until it becomes clear which system gets adopted in follow-up papers. If it looks like the Pepe et al. system is used, we'll have to shuffle a few articles around, but so be it. Chaos syndrome 21:56, 10 September 2006 (UTC)

[edit] Orbit images

  • I've uploaded a system orbits image that helps to identify the planet positions. I think that we should keep the present designations for now.Ricnun 03:23, 30 August 2006 (UTC)
    • My main criticism of those images is the colour schemes are very dark, and SVG would be a better way of handling this kind of data. I've already made SVG images for the 47 Ursae Majoris, 16 Cygni B and 55 Cancri inner system, I'll try and get one done for Mu Arae at the weekend. Chaos syndrome 15:42, 30 August 2006 (UTC)
      • OK, no problem here. I just wanted to provide some reference in order to avoid confusion with the planet names and to provide some updated reference. Yes, your images for those systems are great! Ricnun 17:21, 30 August 2006 (UTC)

[edit] Trojan points

I've flagged the statement on the possibility of Earthlike worlds in Trojan points, since it is not clear whether the Trojan points of planet "b" would actually be stable, particularly with a 2:1 resonance going on with planet "e". If a study of the stability of the Trojan points in this system for the four-planet configuration can be found, we shouldn't say there could be planets in the Trojan points. Chaos syndrome 19:18, 12 September 2006 (UTC)

Ok, I've done a few simulations using a gravity simulator of planets in the Trojan points of planet "b" and they suggest that interactions with the 310-day planet perturb the Earthlike world out of the Trojan point and then it ends up getting kicked around all over the place. While this would constitute original research and thus shouldn't go into the article, I think this is good grounds for getting rid of the uncited statement about Trojan planets from the article. Chaos syndrome 21:03, 13 September 2006 (UTC)


[edit] GA review

  • Opening paragraph: Contains somewhat unweildy, information-loaded sentences. Might be more readable with a pause. "second star in which a fourth planet was discovered" takes a couple readings to understand.
  • Distance and visibility: Reasonably good, but it might be better to give light years (a term more familiar to the non-specialist) before parsecs. It may be useful to copy the diagram (with a descriptive caption) from the parallax article to quickly explain how it works, but use your own judgement on this.
  • Stellar characteristics: The chromospheric activity section isn't all that clear as to how this is measured and how it is relevant. However, this is more a fault of the chromosphere article, which lacks useful information that would help explain yours. Can this be written to be easier for a non-specialist with reasonable ease? Likewise, the Stellar types article fails to help understand what G3IV-V is. Since neither is a fault of your article, this should not hurt your GA status, but it would be useful in the longer term to edit these supporting articles to make them a better reference for articles like this one.
  • The paragraph "Measurements of the star's ultraviolet flux suggest that the circumstellar habitable zone as defined by the ability of a planet to support liquid water at its surface does not overlap with the habitable zone as defined by the amount of ultraviolet radiation received. This may mean that any potentially habitable planets may not receive enough ultraviolet to trigger the formation of biomolecules.[5]" works in rather convoluted manner to an easy-to-understand conclusion. Much better is the "Habitability" section's description.
  • Diagram of planetary system: "Mu Arae d" is a slightly awkward term to use when the nomenclature isn't finalised. It might be best to use a more generic term like "9-day-orbit planet"
  • Nomenclature: A section dealing on esoteric naming conventions is an odd place for the first mention of the planet's year-lengths. Perhaps move the section "Discovery" to before it.
  • Discovery: The fact that Mu Arae was the first star in which a hot Neptune was discovered ought to be in the article's first paragraph.
  • System structure: The phrase "evaporated remnant of a gas giant" is rather unclear.

This is a difficult article for a non-specialist such as myself to read. Nonetheless, I feel I did understand most of it. Whilst I'm largely inclined to give GA-status now, one more revision could make it definately GA, and, as such, I'm going to briefly hold off. Leave a message on my talk page when you're ready. Adam Cuerden talk 06:39, 15 September 2006 (UTC)

[edit] GA re-review

Going by the 6 GA criteria:

1. Thanks to the latest edits, the article is now much clearer, and even enjoyable to read, and so now passes the "well-written and easily comprehensible to a non-specialist criteria."

2. It is, as far as I can tell, well-referenced and cited. Very informative.

3. It is, as far as a non-astronomer can tell, broad in its coverage.

4. Point of view remains completely missing.

5. it seems reasonably stable, ignoring, of course, the preparations for GA status.

6. Has a nice selection of images. The one comparing its solar system to ours is particularly useful.


As such, I think it has passed GA! Congrats! Adam Cuerden talk 16:56, 16 September 2006 (UTC)

[edit] Adding new stuff to the star table

You should start adding galactic and ecliptic coordinates to every star articles under the astrometry. You should also add galactic year (Mya), space velocity (km/s) (relative space velocity to other stars (km/s)), eccentricity (e), and inclination (i) around the galaxy under the new starbox: galactic characteristics in between astrometry and physical characteristics/Visual binary. Also add angular diameter in arcseconds under astrometry. In every star articles with the right ascension, you should add degrees (°), minutes ('), seconds(") just under the time with no parenthesis up to 180° using positive and negative values east and west of the prime meridian (0°) (meridian of the First point of Aries), just like declination using positive/negative values for north and south of the equator, but only up to 90°. Positive values for east of the prime meridian (eastern hemisphere), and negative values for west of the prime meridian (western hemisphere) When it is exactly 0° or 180°, you do not put any sign infront of it. When is positive, you must put the plus sign infront of it and of course minus sign when it is negative. You should add all of these to make the starbox more complex. Cosmium 19:46, 30 December 2006 (UTC)

Most stars don't have a known galactic orbit. But you're right: those who have, should have the orbital parameters listed (including possible membership of a stream or moving group). Geneva-Copenhagen survey catalog[1] has a large list of calculated orbits of nearby Sun-like stars which could be used here. Measured apparent diameter might be useful, but on the other hand the same information is much easier to understand as solar radii. I don't see why right ascension should be shown as degrees, nor why galactic coordinates should be shown. Those who need that information use the original databases, or calculate the values by themselves. They don't need Wikipedia for that. Finally, starboxes are not meant to be complex, quite opposite: they are to make searching data more easier. Too much less relevant data is counterproductive.--JyriL talk 01:13, 31 December 2006 (UTC)