retrograde motion?

This is a homework question I am not sure about.

A large planet (jupiter mass) is orbiting a sun like star 100 light
years away from the earth. The star is easily visible with binoculars.
From the earth we should see the planets orbit edge on ( from the
side) using newtons law of gravity and his three laws of motion, esp
3rd, what sort of motion of the star should we see?

I guess it it seen in retrograde motion, because the star is not
orbiting around the planet, therefore the planet does not appear, hmmm
no, maybe it is a parallax?
help please?

wrote in message
...
This is a homework question I am not sure about.

A large planet (jupiter mass) is orbiting a sun like star 100 light
years away from the earth. The star is easily visible with binoculars.
From the earth we should see the planets orbit edge on ( from the
side) using newtons law of gravity and his three laws of motion, esp
3rd, what sort of motion of the star should we see?

I guess it it seen in retrograde motion, because the star is not
orbiting around the planet, therefore the planet does not appear, hmmm
no, maybe it is a parallax?
help please?

Consider the relative masses of the planet and star and how exactly that
would determine the motion of the planet and the star relative to each
other. Bear in mind they have told you that Newton's 3rd Law is significant,
so think along those lines initially.

You should already have some idea as to what we can measurements we can make
from analysing the star's light; and thus come up with at least 1 meaningful
observation as a result of the relative motion of the star and planet as
seen edge on from the earth.

It may be simpler to consider a circular orbit initially, but will probably
get more credit if you can describe how the observations would change if the
orbit was elliptical.

Read closely what you have available about orbits.

wrote in message
...
This is a homework question I am not sure about.

A large planet (jupiter mass) is orbiting a sun like star 100 light
years away from the earth. The star is easily visible with binoculars.
From the earth we should see the planets orbit edge on ( from the
side) using newtons law of gravity and his three laws of motion, esp
3rd, what sort of motion of the star should we see?

I guess it it seen in retrograde motion, because the star is not
orbiting around the planet, therefore the planet does not appear, hmmm
no, maybe it is a parallax?
help please?

You are guessing; in a sense the star IS orbiting around the planet, like
this:
http://www.androcles01.pwp.blueyonde...barycentre.gif
The star and the planet orbit a common barycentre. It is this tiny motion
of the star that enables astronomers to detect planets, which are too small
to be seen. Even our own local giant planets, Saturn and Jupiter, are so
far away (about a light-hour) that they appear as a point of light without
a telescope, so you have no chance of seeing them 100 light years away.