Talk:Poles of astronomical bodies

IAU definition

Does the definition used by the IAU change with the Earth's precession? Also, is there any plan to extend it to other solar systems? Wnt (talk) 19:36, 1 June 2008 (UTC)

No, see invariable plane (which is used in the definition). It is very similar to the plane of the ecliptic, which is affected by precession, but stays very similar to the invariable plane. --91.32.79.168 (talk) 16:37, 8 April 2010 (UTC)

Galactic poles

This article could probably use some discussion and explanation of the galactic coordinate system which uses the IAU definition of north and south galactic poles, of course. I've sometimes wondered about the right-hand rule with regard to rotation (the Milky Way is upside down in this regard, as is the Earth with regard to its own magnetic field), and I'm sure people who research the galactic magnetic field have their own questions. arkuat (talk) 10:47, 13 June 2008 (UTC)

Retrograde ?

I've removed the statement that the milky way revolves with retrograde motion. This dosn't make any sense. Whichever way a system revolves is the direct motion for that system. An object within a system can be retrograde if it is orbiting or rotating in the opposite direction to the system. Zbayz (talk) 10:47, 18 August 2009 (UTC)

Mercury

Along with the near/far/leading/trailing poles of synchronous satellites, we could mention the 'hot poles' of Mercury: the points on the equator where the Sun is at zenith at alternate perihelia. If memory serves, the points where the equator crosses the terminator at perihelion are called the 'warm poles'. — But I don't know offhand of a specific source that uses these terms. —Tamfang (talk) 17:59, 30 November 2010 (UTC)

leading pole

best defined as the point most removed from the plane formed by the north-south and near-far axes, on the leading side

Why not the easternmost point on the limb as seen from the primary? —Tamfang (talk) 18:03, 30 November 2010 (UTC)

Presumably for satellites in retrograde orbits, revolving opposite to the primary's rotation. — Joe Kress (talk) 06:43, 1 December 2010 (UTC)

Har har. Leading point on the limb, then. —Tamfang (talk) 22:07, 1 December 2010 (UTC)

Well, the limb is not exactly a great circle, so that is not a good way to define the pole. --Lasunncty (talk) 17:32, 2 December 2010 (UTC)

The Moon

Article needs the RA and Dec of the poles of the Moon, or an explanation of why that is not possible. 94.30.84.71 (talk) 23:21, 21 February 2011 (UTC)

The moon's polar axis direction is stable and defineable, as confirmed here: [1]. It looks very close to the ecliptic axis of the earth's orbit as shown here Ecliptic_north_pole. Tom Ruen (talk) 02:16, 22 February 2011 (UTC)

That page doesn't look reliable to me. Compare Orbit of the Moon#Inclination: "...the rotation axis of the Moon precesses with the same rate as its orbital plane, but is 180° out of phase." —Tamfang (talk) 09:07, 22 February 2011 (UTC)

The section you linked says Thus, although the rotation axis of the Moon is not fixed with respect to the stars, the angle between the ecliptic and the lunar equator is always 1.543°, so the moon's axis is very close to the ecliptic as I said. Tom Ruen (talk) 20:27, 22 February 2011 (UTC)

I added the coordinates of the Moon's poles from the "2009 rotational elements" cited in the article. The table currently ignores any changes due to precession or other reasons from the J2000 (ICRF) coordinates. — Joe Kress (talk) 22:19, 22 February 2011 (UTC)

I removed the coordinates of the Moon's poles. The reason being that the data given is unlikely to be correct. The quoted source show that the RA of the pole is: 269°9949 + 0.0031T − 3°8787 sin E1 +... And at time T=d=0, E1=125°045. Same thing for the other angles. The location of the pole must be computed rather than lifted from the formula.109.9.32.61 (talk) 17:22, 10 December 2011 (UTC)

• The lunar pole precesses with a period of 18.6 years, so coordinates for the pole won't be exact except for one particular date. However, the precession is small-- it precesses around in a circle of about 1.5° radius on the celestial sphere, so if we give a figure, the actual pole direction will be no more than 3° off. Skepticalgiraffe (talk) 20:24, 2 May 2018 (UTC)

leading & trailing poles, again

Other synchronously-rotating objects, such as Pluto and some asteroids with large asteroid moons, can also be described as having "near" and "far" poles - though "leading" and "trailing" may not be as significant in these cases.

Why not? —Tamfang (talk) 18:56, 11 October 2011 (UTC)

leading & trailing poles, still more

I am unable to understand what the leading and trailing poles are from the definition ( "a single unmoving point which is furthest along Io's orbit"). I think additional text or maybe a figure would help. 109.9.32.61 (talk) 13:52, 10 December 2011 (UTC)

The leading-trailing axis is tangent to the orbit, at least if the orbit is circular. --Lasunncty (talk) 10:16, 12 December 2011 (UTC)

I see. Actually, the text makes a mention of "leading and trailing hemispheres", which makes things a lot clearer than the "unmoving point" definition. What's unmoving ? After all, the zenith of every point on Earth is also an unmoving point, yet leading poles have something more.109.9.29.228 (talk) 22:16, 26 December 2011 (UTC)

Uranus

Since it is only speculation that a collision caused the difference in the directionality of Uranus' poles vs the other planets, I suggest that the sentence "Venus rotates in the opposite direction to the other planets, and Uranus has been knocked on its side and rotates almost perpendicular to the rest of the solar system." be changed to "Venus rotates in the opposite direction to the other planets, and Uranus rotates almost perpendicular to the rest of the solar system." This seems like plenty of information, and it avoids stating speculation as fact. — Preceding unsigned comment added by Incentative (talk • contribs) 18:44, 29 March 2012 (UTC)

Sounds good to me! --Lasunncty (talk) 16:02, 31 March 2012 (UTC)

Magnetic poles

It says in the article: "The direction of the field determines whether the pole is a magnetic north or south pole, exactly as on Earth". Is this really true? The North magnetic pole on Earth is actually a South pole, it is called the North magnetic pole by convention because the North pole of a compass needle points to it (hence it must be a South pole), see Earth's_magnetic_field#Dipolar_approximation. Aarghdvaark (talk) 01:56, 7 June 2013 (UTC)

Pluto pole positions

The polar constellations given for Pluto do not match the coordinates given. The given coordinates for the positive pole lie in Hydra; of the negative pole in Delphinus. There is an error somewhere. Oikofuge (talk) 22:21, 2 October 2022 (UTC)

Good catch! There were a few others that needed correction as well. --Lasunncty (talk) 09:23, 3 October 2022 (UTC)