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Donald Wilgus
Posted: Mon Dec 22, 2003 1:41 am
Guest
If one takes the "Northern View" of the orbits of the planets (around the
Sun), are all the focus points biased to one side. Or is this not a valid
question??

Cheers,
Don W
Odysseus
Posted: Mon Dec 22, 2003 3:59 am
Guest
Donald Wilgus wrote:
Quote:

If one takes the "Northern View" of the orbits of the planets (around the
Sun), are all the focus points biased to one side. Or is this not a valid
question??

If you're asking about the orientation of the major axes of the planets'

orbits, or the positions of the foci not occupied by the sun, they're
quite scattered. Moreover they all precess slowly over time (at rates on
the order of a degree per millennium). In the Planetary Fact Sheets
indexed at

<http://nssdc.gsfc.nasa.gov/planetary/planetfact.html>

look for the J2000 Orbital Elements table for each planet; its 'empty
focus' will be in the opposite direction from the listed "longitude of
perihelion". For example Jupiter's perihelion is at about 15° ecliptic
longitude, so the major axis of its orbit runs from there through both
foci towards 195°; the figure for Uranus is nearly opposite, its major
axis running from about 171° to 351°.

--
Odysseus
Donald Wilgus
Posted: Mon Dec 22, 2003 1:23 pm
Guest
"Odysseus" <odysseus1479-at@yahoo-dot.ca> wrote in message
news:3FE6B276.2DC5D29C@yahoo-dot.ca...
Quote:
Donald Wilgus wrote:

If one takes the "Northern View" of the orbits of the planets (around
the
Sun), are all the focus points biased to one side. Or is this not a
valid
question??

If you're asking about the orientation of the major axes of the planets'
orbits, or the positions of the foci not occupied by the sun, they're
quite scattered. Moreover they all precess slowly over time (at rates on
the order of a degree per millennium). In the Planetary Fact Sheets
indexed at

http://nssdc.gsfc.nasa.gov/planetary/planetfact.html

look for the J2000 Orbital Elements table for each planet; its 'empty
focus' will be in the opposite direction from the listed "longitude of
perihelion". For example Jupiter's perihelion is at about 15° ecliptic
longitude, so the major axis of its orbit runs from there through both
foci towards 195°; the figure for Uranus is nearly opposite, its major
axis running from about 171° to 351°.

--
Odysseus


Thanks for the link. So with all of this there is no chance that the
respective distance ordering of the planets from the Sun is ever changed?
It would be very nice if there was a top level view / Java script of the
precession of these major axes.

Don W
Odysseus
Posted: Mon Dec 22, 2003 7:48 pm
Guest
Donald Wilgus wrote:
Quote:

Thanks for the link. So with all of this there is no chance that the
respective distance ordering of the planets from the Sun is ever changed?
It would be very nice if there was a top level view / Java script of the
precession of these major axes.

Precession can't make any difference to the distance order of any of the

major planets; with the exception of Pluto the eccentricities of their
orbits are all much too small. The ratio of a planet's aphelion distance
to that of its perihelion is typically just a few percent over unity,
while the ratio between the average orbital radius (semimajor axis) of
one planet to the next in sequence is generally at least 3/2. Sorry, I
don't know of any site that shows the precession of the orbits graphically.

--
Odysseus
 
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