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Re: Mass of Jupiter



-----Original Message-----
From: phys-l@lists.nau.edu: Forum for Physics Educators
[mailto:PHYS-L@lists.nau.edu]On Behalf Of Paul O. Johnson
Sent: Monday, January 29, 2001 9:52 PM
To: PHYS-L@lists.nau.edu
Subject: Re: Mass of Jupiter


The mass of any satellite orbiting a central object (M) is proportional to
the cube of the orbital radius (r) and is inversely proportional to the
square of the orbital period (T). The relationship is
M = 4(pi)*2 r*3/G T*2
where G is the universal gravitational constant.
This is derived by equating the centripetal and gravitational
forces acting
on the satellite
So the mass of any planet can be calculated from measured values of its
average distance from the sun and its orbital period.

In your equation M is the mass of the central object (strictly M is the sum
of the masses of the two bodies). By measuring the distance and period of a
planet you can find the mass of the *sun*.

For planets like Venus which don't have any satellites, you can calculate an
approximate value for the mass by measuring their perturbations on the
orbits of nearby planets. Much more accurate values have been computed from
the orbits of spacecraft passing by.


Tore Ottinsen
Hellerud high school
Oslo, Norway
http://www.ottisoft.com
Orbit Xplorer - The educational orbit simulator