Talk:Hippocamp (moon)

Semi-major axis value
According to Kepler's Third Law, the ratio of the cube of the semi-major axis to the square of the orbital period for Neptune's moons should be constant. Using the values for semi-major axis and orbital period for Galatea, Larissa and Proteus from the table in Moons of Neptune gives ratio values of 1.29203e+15, 1.29160e+15 and 1.29344e+15 km3d-2, respectively. The same calculation using the semi-major axis and period values for S/2004 N 1 from the Sky & Telescope reference gives a ratio of 1.33149e+15. Assuming the values from the table are not systematically in error, one of the values from Sky & Telescope must be a little off. Since period is what is measured directly, I calculated a value for the semi-major axis of S/2004 N 1 based on the Sky & Telescope period value and the average ratio value for Galatea, Larissa and Proteus from the table. WolfmanSF (talk) 04:06, 16 July 2013 (UTC)


 * I just chatted with Dr. Showalter. He says that because Neptune is oblate, Kepler's laws do not apply precisely.  More precise calculations are required involving gravitational moments.  He confirms that the published numbers in Sky&Tel and IAU Circular are correct.


 * I understand that phone calls are not "sources" for Wikipedia. But I do think it better for us to go with the published values once they have been confirmed as correct. JavautilRandom (talk) 22:23, 16 July 2013 (UTC)


 * Thanks for checking that out. In that case, the values given in the JPL web site, the source of the data I used, must be systematically in error, perhaps due to incorrectly assuming the validity of the third law in calculating the semi-major axes. WolfmanSF (talk) 23:37, 16 July 2013 (UTC)


 * Mail from Dr Showalter to me. He wants to make sure that the Wikipedia page is accurate!


 * The relationship between mean motion n and semimajor axis a is a function of the gravity field of the central planet. That gravity involves higher gravitational moments when the planet is oblate, as are all the gas giants. The gravity field expansion is typically described in terms of moments J2, J4, .... There are other moments as well but they tend to vanish due to symmetry.


 * The latest and most accurate values of the gravity moments of the outer planets are found here.


 * The relationship between n and a is found here accurate to J4.


 * JavautilRandom (talk) 03:25, 17 July 2013 (UTC)

Name
Can someone explain why this is S/2004 N 1 and not S/2013 N 1 ? IIRC, this is supposed to be by year of discovery, not by year someone archived a photograph but didn't discover anything. Same as how asteroids can have prediscovery photographs, by the codename isn't based on any of those. -- 76.65.128.222 (talk) 07:17, 17 July 2013 (UTC)


 * No, it is the year when the data was obtained, not the year when the data was analysed. For another example, see S/1986 U 10, discovered in 1999 in Voyager images from 1986. Or S/1981 S 13, discovered in 1990 in Voyager images from 1981. There is a note to that effect in Provisional designation in astronomy but not in Astronomical naming conventions. Perhaps this should be noted in the article?  — Preceding unsigned comment added by 82.132.218.209 (talk) 09:56, 17 July 2013 (UTC)
 * Yes, please, i didnt know that, and asked my self the same question! Please, can you add it in article? -- WhiteWriterspeaks 17:06, 17 July 2013 (UTC)
 * Added a note explaining the name.JavautilRandom (talk) 18:35, 17 July 2013 (UTC)
 * The same is true for minor planets, including the asteroids, BTW: for example, Eris received the temporary designation "2003 UB313", despite having been discovered in January 2005, because it was discovered in images from 21 October 2003. (Perhaps this isn't the best example, because it's not clear if asteroid and minor planet are synonymous, or if the former only refers to minor planets in the inner Solar System; and you did mention "asteroids" explicitly.) Double sharp (talk) 13:35, 12 June 2014 (UTC)

Synchronous orbit and resonances
Hello. The article has just had added this: "Proteus and S/2004 N 1 have drifted away from Larissa since then because the former two are outside a synchronous orbit (and are being tidally accelerated) while Larissa is within one." Apart from their being no citation for this, I was puzzled by "a" synchronous orbit. Is ther enot only one synchronous orbit for a body of any given mass/gravitational field? I wondered if this sentence would make more sense if it read "Proteus and S/2004 N 1 have drifted away from Larissa since then because the former two are outside Neptune's synchronous orbit (and are being tidally accelerated) while Larissa is within the planet's synchronous orbit and is being decelerated." or similar. hamiltonstone (talk) 12:02, 18 July 2013 (UTC)


 * Hello. You are absolutely correct. While there is only one synchronous orbit per body, the phrase "a synchronous orbit" can be/is used because there are different types of synchronous orbits for different bodies, (for example, a Geosynchronous orbit or a Heliosynchronous orbit).  Reatlas  (talk)  12:55, 18 July 2013 (UTC)


 * Yes, but the only relevant body here is Neptune, so it looks odd to mention "a synchronous orbit" when Neptune only has one synchronous orbit (which would be called a poseidosynchronous orbit, I guess?). I see, though, that the sentence in question has been changed to say "Neptune-synchronous orbit" instead of just "a synchronous orbit". Double sharp (talk) 13:47, 12 June 2014 (UTC)

Discoverers
One the cited JPL planetary satellite discovery circumstances page, the discoverers of S/2004 N 1 are listed as "M.R. Showalter, I. de Pater, J.J. Lissauer, R.S. French", and this is reflected in the infobox. Only Showalter however is named in lede and the body text. There needs to be an explanation of the role of the co-discovers, but I'm not sure where to find it. Ideas? hamiltonstone (talk) 23:20, 18 July 2013 (UTC)
 * It appears that Mark was the individual who first spotted the new world, but that a supporting cast of coworkers and/or collaborators helped him do this. The exact contributions made by the supporting cast may not be publicly available now - or ever. WolfmanSF (talk) 07:48, 19 July 2013 (UTC)
 * It's traditional that the person who first sees the moon gets top billing, but that the project collaborators are included in the IAU Circular. JavautilRandom (talk) 21:18, 19 July 2013 (UTC)

Period error?
This says the orbital period is 0.9362 days, while looking at JPL Ephemeris data, the period looks close to 0.95 days! Can anyone check a better source? The S&T article says period as 22h 28.1m, which is indeed 0.9362 days. 0.95 days is 22h48m. Tom Ruen (talk) 21:58, 14 April 2018 (UTC)
 * Ah, this NASA source says 0.95 days! Tom Ruen (talk) 23:29, 14 April 2018 (UTC)

Name
The moon has officially been named Hippocamp. Source: https://www.sciencenews.org/article/neptune-smallest-moon-may-be-chip-another-moon — Preceding unsigned comment added by 72.231.228.215 (talk) 18:08, 20 February 2019 (UTC)

Planetary Satellite Physical Parameters
You have removed the density from the article, which was based on the 2015 version of this source. It seems like Hippocamp has been removed from that table completely in the latest (2020) update, which would render the source useless. Is there an archived version of the table somewhere? The oldest version of the site that I can find with the Wayback Machine dates to September 2021. It is already based on the M. Brozović (2020) "Update of the inner Neptunian satellite orbits — NEP097", which apparently does not include Hippocamp. We'd need the version as it was before late 2020. Otherwise the source, and anything that it is used for, has to be replaced. Renerpho (talk) 17:18, 26 April 2022 (UTC)
 * I believe you're looking for this one on the old URL. N rco0e   (talk · contribs)   22:50, 26 April 2022 (UTC)