Talk:Astronomical system of units

Merge other mass articles with this one?

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section.

With "concerns" about the stubbyness of some mass articles, should the Solar mass article be merged into this?

Should other mass articles; Jupiter mass, Earth mass, Lunar mass be merged into this article?

This could be done under a heading "Other units used in Astronomy". HarryAlffa (talk) 11:32, 21 September 2009 (UTC)

Solar mass

The following is a closed discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the proposal was no merge

• Oppose I think there is enough out there that it can be kept as a standalone article. 76.66.196.139 (talk) 06:06, 22 September 2009 (UTC)
• Oppose If there's one "astronomical mass" article that should remain independent, it's this one. The solar mass effectively serves as the standard for all the other masses. Physchim62 (talk) 08:33, 22 September 2009 (UTC)
• Oppose This is quite a commonly used mass and the standard for stellar masses in addition to masses of black holes and galaxies. There are enough users who would want to know about solar mass with out the extra 'baggage' of other less commonly used masses. From the stand of precedence all other standard units have their own separate pages. TStein (talk) 15:40, 22 September 2009 (UTC)
• Oppose This one is fine by itself. There's a clear distinction in astronomy between the units used at stellar scales and those used at planetary scales. Iridia (talk) 00:21, 23 September 2009 (UTC)
• Oppose (weakly) based on all of the above. -- Kheider (talk) 09:02, 23 September 2009 (UTC)

The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Jupiter mass

• Oppose I think there is enough out there that it can be kept as a standalone article. 76.66.196.139 (talk) 06:06, 22 September 2009 (UTC)
• Support merge into an article on planetary mass. Physchim62 (talk) 08:33, 22 September 2009 (UTC)
• Oppose: It is used enough for the description of planets to keep as a separate article. Physchim62's idea would work as well. I would prefer both the standalone Jupiter mass and the planetary mass.TStein (talk) 15:46, 22 September 2009 (UTC)
• Support Physchim62's suggestion, which I also mooted at Talk:Jupiter. Iridia (talk) 00:34, 23 September 2009 (UTC)
• Neutral I am not really sure since this is almost an inclusionist/deletionist debate. -- Kheider (talk) 09:02, 23 September 2009 (UTC)

Earth mass

• Neutral 76.66.196.139 (talk) 06:06, 22 September 2009 (UTC)
• Support merge into an article on planetary mass. Physchim62 (talk) 08:33, 22 September 2009 (UTC)
• Support Physchim62's suggestion. I am not an astronomer but it does not seem useful enough of a unit to keep on its own. TStein (talk) 15:46, 22 September 2009 (UTC)
• Support Physchim62's suggestion: measurements of extrasolar planetary systems have a clear set of units, and this is one of them. Iridia (talk) 00:34, 23 September 2009 (UTC)
• Neutral I think usage of this will increase over the next few years as we discovery more Earth-like exoplanets. -- Kheider (talk) 09:02, 23 September 2009 (UTC)

Lunar mass

• Support though the article currently says it is about the IAU defined units... perhaps two articles are in order, one for the IAU units, and one for other units... 76.66.196.139 (talk) 06:06, 22 September 2009 (UTC)
• Support merge into an article on planetary mass. Physchim62 (talk) 08:33, 22 September 2009 (UTC)
• Support Physchim62's suggestion. I am not an astronomer but it does not seem useful enough of a unit to keep on its own. TStein (talk) 15:46, 22 September 2009 (UTC)
• Delete This isn't used. The article already has a delete note on its talk page from two years ago. Iridia (talk) 00:23, 23 September 2009 (UTC)
• Merge/Delete The only time I have defined something compared to our moon is the Pluto infobox at 0.178 moon, and even then I didn't wiki-link to anything. Perhaps just merge lunar mass to Earth mass. -- Kheider (talk) 09:02, 23 September 2009 (UTC)

Discussion

I would prefer a separate article on planetary mass rather than merging them here: they are empirical quantities rather than a system of units. Physchim62 (talk) 08:33, 22 September 2009 (UTC)

Sounds good to me.TStein (talk) 15:46, 22 September 2009 (UTC)

Is the mass of Jupiter an IAU standard? I didn't see it listed in the referenced document.—RJH (talk) 16:50, 22 September 2009 (UTC)

The mass of Jupiter is not a standard. The best estimates come from it being an adjusted parameter in solar system ephemerides, in which the unit of mass is the solar mass. You can also create separate "Jovian" ephemerides, but I think the accuracy of these is much less that the ones based on the solar system as a whole. Physchim62 (talk) 19:39, 22 September 2009 (UTC)

Alright, we have Physchim62 and TStein at this page, and at Talk:Jupiter we have Kheider and myself in clear support of a merged planetary mass article, to merge Jupiter mass and Earth mass. I would say this is probably sufficient consensus: are there any other suggestions, or any objections? Iridia (talk) 00:34, 23 September 2009 (UTC)

What I suggest is that I create Planetary mass – I say me simply because I happen to know my way around the sources to a certain extent – but without explicitly merging the other articles. Then we can have another couple of days of discussion as to where things go before taking the plunge. Merging is relatively easy, but demerging afterwards is more difficult, so I don't think we need to be in a rush. There's enough material to create an article on planetary mass from scratch, even if we end up never doing any merges, and I can get a first version out this afternoon (European time). Physchim62 (talk) 11:54, 23 September 2009 (UTC)

Comment shouldn't it be planet-based mass units? (or similar) 76.66.197.30 (talk) 04:57, 24 September 2009 (UTC)

It took me a bit longer than I thought, but planetary mass is now up and open for improvement! Physchim62 (talk) 13:00, 26 September 2009 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Digit?

I see no mention is this article of the digit, from Classical times until (very?) recently one-twelfth of the apparent diameter of the sun or moon and used, I believe, in measurement of eclipses. Has this been replaced by some other unit, or simply forgotten? Justlettersandnumbers (talk) 17:10, 26 August 2011 (UTC)

Length

Are Lunar radius, Earth radius, Jupiter radius and Solar radius notable enough to be worth mentioning in this article? These units appear in popular science articles as well as in scientific papers. --Artman40 (talk) 13:00, 23 June 2014 (UTC)

Third party references

I note that this article has no third party references at all. I think the concept of the article is useful, but it's misleading and uncited to say that the IAU (1976) System of Constants (a specific document) is the generic "astronomical system of units". This article covers a number of units which are used for convenience in astronomy, all of which are recognized by standards bodies and common usage as real units. Putting that in one article is helpful, but framing it as a single, coherent system of units is a little misleading, I think. —Alex (Ashill | talk | contribs) 23:24, 13 July 2015 (UTC)

Agreed. The article title and the phrase should be changed, as they are misrepresenting the concept covered. —Quondum 01:39, 14 July 2015 (UTC)

Yes, agreed. The IAU 1976 system was just a set of generally accepted values. It was never intended to be a "system of measurement" as described here, i.e. like the SI system. The article is more than a little misleading. Beside all that, the 1976 system is long ago superseded at this point in time. Lastly, I for one have never heard of an "Astronomical system of units". It seems to have been invented for this article. A casual search yields one hit - this article. Tfr000 (talk) 01:14, 23 November 2015 (UTC)

New definition of the astronomical unit of length

The astronomical unit of length is now precisely defined as exactly 149 597 870 700 m and no longer rely upon the estimation of other parameters.

Have a look at resolution B2 of this document.

-- Pylade (talk) 08:03, 24 July 2015 (UTC)

disputed

Ok, I added a disputed tag to the article. See the comments above at Third party references. We need to change the name and some of the text of the article. Tfr000 (talk) 21:48, 23 November 2015 (UTC)

IAU1976 Note the difference - here it is system of constants, not system of units. Otherwise, the article is accurate. Tfr000 (talk) 23:34, 25 November 2015 (UTC)

III.

RECOMMENDATIONS TO IAU GENERAL ASSEMBLY, 1976

RECOMMENDATION 1:

IAU (1976) SYSTEM OF ASTRONOMICAL CONSTANTS

It is recommended that the following list of constants shall be adopted as the "IAU (1976) System of Astronomical Constants".

Units

The units metre (m), kilogram (kg) and second(s) are the units of length, mass and time in the International System of Units (SI). The astronomical unit of time is a time interval of one day (D) of 86400 seconds. An interval of 36525 days is one Julian century. The astronomical unit of mass is the mass of the Sun (S). The astronomical unit of length is that length (A) for-which the Gaussian gravitational constant (k) takes the value 0.017 202 098 95 when the units of measurement are the astronomical units of length, mass and time. The dimensions of k² are those of the constant of gravitation (G), i.e., L³M^-1T^-2. The term "unit distance" is also used for the length A.

In researching gaussian gravitational constant, I went through a lot of the back story of this article as well. The astronomical system of constants did not come into existence in 1976 — something like 1895 is close, and of course many of the actual constants have been known since antiquity, although not officially organized or standardized. See some of the references I attached to that article, particularly [Clemence, G. M. (1965). "The System of Astronomical Constants". Annual Review of Astronomy and Astrophysics. 3: 93. Bibcode:1965ARA&A...3...93C.]. There have been several efforts to make it more internally consistent, 1976 being one of them. However, it is an ongoing effort to measure naturally-occurring things more accurately, not an establishment of a measurement system like SI. Evidence of this is the recent abandonment of the Gaussian constant as a way of defining the astronomical unit. Now that we know the a.u. in meters pretty well, we no longer have a need to do it that indirect way. This isn't what you do with a system like SI. Tfr000 (talk) 13:28, 3 January 2016 (UTC)

So we seem to have at least two articles on approximately the same subject, this one and astronomical constant. Both contain IAU definitions mixed together with random other stuff, like light-years and redshift, which have nothing to do with the IAU system of constants. Probably what is needed here is a separation into two articles: one for general discussion of any and all units used in astronomy from whatever source, and another for the strict IAU system, which is supposed to be a consistent system and hence can't have random stuff added or removed from it. I noticed that astronomical constant has a list of IAU constants and then gives other sources for the information... big no-no. Plugging in other values of the constants from other sources destroys the integrity of a "system". Tfr000 (talk) 13:51, 3 January 2016 (UTC)