Talk:Orbital pole
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Too confusing
[edit]An orbital pole is either end of an imaginary line running through the center of an orbit perpendicular to the orbital plane, projected onto the celestial sphere. Say what? And what's the point of the picture? If there's anything in there, it's completely lost when resized to a thumbnail. More importantly, what's the purpose of making this measurement? I hope this this isn't astrology or something. Ewlyahoocom 12:00, 6 April 2006 (UTC)
Not astrology and awesome, but ...
[edit]It only recently occurred to me that there is a center to the circle described by the ecliptic.
Some thoughts: (but I'm not feeling up to editing the article right now): 1) I think the initial line An orbital pole is either end of an imaginary line running through the center of an orbit perpendicular to the orbital plane, projected onto the celestial sphere. is fine. This is the definition, and anyone who wishes to do so can follow the link to the definition of "celestial sphere".
2) Ok... what we want to say is essentially [And YES, I know that much of what I'm about to say is IMPRECISE and/or not 100% accurate... that's why I'm not posting it into the article... but MAKING it PRECISE strikes me as a pain, so maybe someone else would care to tackle the task]: "There are two circles which are normally drawn on maps of the Earth's (night) sky: The ecliptic and the celestial equator. The 'center' (in reality the term 'center' is incorrect. The correct term should be 'pole') of the [celestial equator] is the North Celestial Pole (or in the Southern Hemisphere, the South Celestial Pole). The centers/poles of the [ecliptic] are the orbitals poles of the Earth (also known as the Ecliptic Poles). Any object (such as a planet or satellite) which has an orbit also has its own 'orbital poles'.
3) Note: all of this is rendered a little more complicated by the fact that none of the planets orbits in a perfect circle. So the "center" of a planet's orbit should essentially be the point equidistant from (i.e. "right in the middle of") the two foci of the orbit. The orbital poles are located on the line that passes through THAT point and is perpendicular to the plane of the planet's orbit.
4) A copy/link of the picture located here (which does include labels for the North and South Ecliptic Poles): https://wiki.riteme.site/wiki/Ecliptic#/media/File:Earths_orbit_and_ecliptic.PNG would probably be helpful.
5) I think the graphic of the various planetary orbital poles is very interesting and useful. A discussion (preferably with reference links) of the way the poles are clustered and what they may suggest about the angular momentum of the proto-solar system / early solar nebula would be VERY interesting. I'm pretty sure such an article could be found. (Looks like the planetary nebula was rotating a bit out of alignment with the mass that became the Sun... I wonder why that would be. Odd. (hmmm... L = mr x v ... maybe the Keiper belt should be considered... low mass, but big r... *muttering* (I apologize for going off on a bit of a tangent here, but a link to an outside article discussing this would strike me as very worthwhile.)
Okay. Now it's time for smarter people than me to actually IMPROVE the article. These are just suggestions. TheScatteredMan (talk) 19:41, 23 May 2017 (UTC)
Snapshot of orbital poles
[edit]The diagram can be recreated as follows.
Go to https://ssd.jpl.nasa.gov/horizons.cgi
To obtain the rotational pole coordinates, set:
INPUT: Ephemeris Type [change] : OBSERVER Target Body [change] : Sun [Sol] [10] Observer Location [change] : Geocentric [500] Time Span [change] : Start=2000-01-01, Stop=2000-01-02, Step=1 d Table Settings [change] : QUANTITIES=32 Display/Output [change] : default (formatted HTML)
You will obtain the values, then change the Target Body and repeat for each planet. 10 is the Sun, 199 is Mercury, 299 Venus, 399 earth, 499 Mars, 599 Jupiter, 699 Saturn, 799 Uranus, 899 Neptune (999 is Pluto, if you care). Earth's rotational pole in equatorial coordinates is by definition at declination +90°, right ascension irrelevant.
OUTPUT: Date__(UT)__HR:MN N.Pole-RA N.Pole-DC ******************************************* Target Body [change] : Sun [Sol] [10] 2000-Jan-01 00:00 286.13000 63.87000 Target Body [change] : Mercury [199] 2000-Jan-01 00:00 281.00970 61.41430 Target Body [change] : Venus [299] 2000-Jan-01 00:00 272.76000 67.16000 Target Body [change] : Earth [399] 2000-Jan-01 00:00 0.00000 90.00000 Target Body [change] : Mars [499] 2000-Jan-01 00:00 317.68143 52.88650 Target Body [change] : Jupiter [599] 2000-Jan-01 00:00 268.05720 64.49581 Target Body [change] : Saturn [699] 2000-Jan-01 00:00 40.58900 83.53700 Target Body [change] : Uranus [799] 2000-Jan-01 00:00 257.31100 -15.17500 Target Body [change] : Neptune [899] 2000-Jan-01 00:00 299.33373 42.95036
Now switch to this:
Ephemeris Type [change] : ELEMENTS Target Body [change] : Neptune [899] Center [change] : Sun (body center) [500@10] Time Span [change] : Start=2000-01-01, Stop=2000-01-02, Step=1 d Table Settings [change] : reference plane=FRAME Display/Output [change] : default (formatted HTML)
Where we picked: Coordinate systm: Earth Mean Equator and Equinox of Reference Epoch
This will give us two values: IN Inclination w.r.t XY-plane, i (degrees) OM Longitude of Ascending Node, OMEGA, (degrees)
The RA and DEC of the orbital pole will be DEC = 90° - IN RA = OM - 90°
Target Body [change] : Mercury [199] IN= 2.855225598038233E+01 OM= 1.098794759075666E+01 Target Body [change] : Venus [299] IN= 2.443305162681789E+01 OM= 8.007372118303223E+00 Target Body [change] : Earth [399] IN= 2.343903457134406E+01 OM= 1.852352676284691E-04 Target Body [change] : Mars [499] IN= 2.467709030069997E+01 OM= 3.373683487612662E+00 Target Body [change] : Jupiter [599] IN= 2.323522450646089E+01 OM= 3.253264882911588E+00 Target Body [change] : Saturn [699] IN= 2.254953826354944E+01 OM= 5.941172633991222E+00 Target Body [change] : Uranus [799] IN= 2.366368752370749E+01 OM= 1.849664887569509E+00 Target Body [change] : Neptune [899] IN= 2.229498390977143E+01 OM= 3.488137262861999E+00
After a little massage, we have:
| Object | Rotational pole | Orbital pole | ||
|---|---|---|---|---|
| RA | DEC | RA | DEC | |
| Sun | 286.13 | 63.87 | n/a | n/a |
| Mercury | 281.0097 | 61.4143 | 280.9879 | 61.4477 |
| Venus | 272.76 | 67.16 | 278.0074 | 65.5669 |
| Earth | 0 | 90 | 270.0002 | 66.5610 |
| Mars | 317.6814 | 52.8865 | 273.3737 | 65.3229 |
| Jupiter | 268.0572 | 64.4958 | 273.2533 | 66.7648 |
| Saturn | 40.589 | 83.537 | 275.9412 | 67.4505 |
| Uranus | 257.311 | -15.175 | 271.8497 | 66.3363 |
| Neptune | 299.3337 | 42.9504 | 273.4881 | 67.7050 |
Urhixidur (talk) 20:20, 2 March 2018 (UTC)
Dunno what to say, but as the table on the page now shows, the above was somehow wrong. Jupiter, Saturn and Neptune have their orbital poles in Camelopardalis, further than originally shown. Can someone generate the correct image? I don't have the means right now. Urhixidur (talk) 14:09, 21 July 2019 (UTC)
- Looks like you were right the first time, when you wrote here in March 2018. Actually the table in the article was pretty good, except for the Right Ascension column, and the image that was derived from it.
- I looked at the website you referenced when converting from ecliptic to equatorial, and the calculator there is a poor mess. The site mentions pitfalls when converting between coordinate systems, and falls right into all of them, they use tangent inappropriately, and don't track signs when using atan. They don't even use atan2! Never use that calculator, and I would say anything unconfirmed from that site is probably suspect. There isn't much for online converters, I found this one, which is clunky to deal with (no decimal input!) but at least does the calculation right. I ran my own conversion from a spreadsheet.
- I have changed the table and updated the numbers, adding Ceres and Pluto for variety. I also reverted the image to the previous one, it was more accurate (unsure how accurate, but way better than the "corrected" one).Vickas54 (talk) 06:42, 1 September 2020 (UTC)