0
$\begingroup$

It's relatively easy to find tables for Earth aphelion and perihelion dates and times, such as this one:

http://www.astropixels.com/ephemeris/perap2001.html

But what about the other planets in the solar system? Are there tables or lists of aphelion and perihelion dates for them too? I checked Wikipedia, but it only lists perihelion distances and not dates, so it is insufficient.

Update:

This is the error I get on the SPICE web interface.

enter image description here

$\endgroup$
  • $\begingroup$ astronomy.stackexchange.com/questions/13488 may help $\endgroup$ – barrycarter Oct 7 '18 at 18:11
  • $\begingroup$ Thanks. I tried the SPICE web interface (wgc.jpl.nasa.gov:8443/webgeocalc/#NewCalculation), but I got an error when for instance studying Jupiter: "Insufficient ephemeris data has been loaded to compute the state of 599 (JUPITER) relative to 10 (SUN) at the ephemeris epoch 2200 FEB 21 00:01:04.183." Since the outer planets orbit so so slowly, I need a wider range of samples. $\endgroup$ – posfan12 Oct 8 '18 at 21:39
  • $\begingroup$ To use SPICE, you have to download SPICE kernels: naif.jpl.nasa.gov/pub/naif/generic_kernels/spk -- the README files should explain which kernels you need/want. I use DE431 myself, but it's a bit on the large side. However, this should've worked on the website as well. Could you screenshot what you tried? 2200 is well within SPICE's range. $\endgroup$ – barrycarter Oct 8 '18 at 21:42
  • $\begingroup$ There is a web interface too (wgc.jpl.nasa.gov:8443/webgeocalc/#NewCalculation) which is where I got the error. $\endgroup$ – posfan12 Oct 8 '18 at 21:42
  • $\begingroup$ My mistake-- I know of the web interface, just didn't read what you wrote carefully. Also try HORIZONS if you just need data. $\endgroup$ – barrycarter Oct 8 '18 at 21:43
2
$\begingroup$

(too long for a comment, this answers why barycenter data is available for a much longer time span than planet center data)

When NASA computes planetary positions, they treat each planet and its moons as a single point mass (the barycenter of the planet and its moons). They compute these positions +-15000 years from now.

For most planet systems, the barycenter is very close to the planet center (Mars' planet barycenter is only a few inches from Mars' system barycenter because Phobos and Deimos have such little mass-- for the moonless Mercury and Venus, the system barycenters and the planet barycenters are the same).

They then compute the locations of the moons and the planet's center itself. These calculations are done for a much shorter period of time.

Therefore, you can compute the location of the barycenter of Jupiter and its moons for +-15000 years, but the actual barycenter of Jupiter itself for a much shorter period of time, even though Jupiter is massive enough that its own barycenter is very close to the barycenter of Jupiter and its moons.

$\endgroup$
1
$\begingroup$

If you search for "Astronomical Ephemeris" you will find plenty of resources. For example: http://astropixels.com/skycal/skycalmain.html

$\endgroup$
  • $\begingroup$ I looked at the site you linked to, as well as this one: eclipse.gsfc.nasa.gov/TYPE/ephemeris.html. You have to know the dates beforehand to use them as far as I can see. $\endgroup$ – posfan12 Oct 8 '18 at 4:21
  • $\begingroup$ Also, JPL HORIZONS only shows one value (the closest time in the future) per ephemeris, not a table listing several values spread across decades, centuries, etc. $\endgroup$ – posfan12 Oct 8 '18 at 4:39
  • $\begingroup$ @postfan12 - please make question more specific. $\endgroup$ – Dr Chuck Oct 8 '18 at 6:10

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.