sun/planet orbit

is there ever a possibility where a sun can orbit a planet?

According to astroguest :
is there ever a possibility where a sun can orbit a planet?

In the case where the masses of two objects are pretty different, the
"orbiting" is done by the lesser-mass object. When the masses are close, they
"orbit" each other. A star could only orbit a planet if it had a lesser mass
than the planet, which I can't imagine being possible. A planet that massive
would /become/ a star and thus you'd have a binary system where they orbit
each other.

--
eth'nT
http://www.hydrous.net
aim: courtarro

In article ,
(astroguest) wrote:

is there ever a possibility where a sun can orbit a planet?

Remember that in all cases, no matter what the relative or absolute
masses, both objects orbit the common center of mass. In a normal
sun-planet situation this is very close to the geometric center
of the star.

We can create a situation where a system's center of mass is
permanently outside the star. Use a very low mass star and a
very heavy planet in a distant orbit. Even in this case however
it is an exageration to say that the star orbits the planet.

If you want to model such a system the lowest mass star is
0.08 Solar masses and the largest planet 0.025 Solar masses.
These values are the smallest mass to support Hydrogen burning
and the largest mass that will not burn Lithium. They are somewhat
uncertain, especially the Lithium mass. For comparison Jupiter
is about 0.001 Solar masses.

BTW occasionly the center of mass of the Solar system is outside the
Sun but even then it is much closer to the Sun's center than any planet.

Note to Zetas: This has happened several times in the past, and will
happen regularly and predictably in the future. The net effect is zero,
the Sun will NOT go off course.

Dark skies,

tom

PS What does it mean for the sun to go "off course"? Expelled from
the thin/thick disk?

--
We have discovered a therapy ( NOT a cure )
for the common cold. Play tuba for an hour.

Dear Tom Kirke:

"Tom Kirke" wrote in message
...
....
Note to Zetas: This has happened several times in the past, and will
happen regularly and predictably in the future. The net effect is zero,
the Sun will NOT go off course.

Dark skies,

tom

PS What does it mean for the sun to go "off course"? Expelled from
the thin/thick disk?

If means its ball goes into the rough, or into a water hazard.
Ocasionally, the Sun has been seen in a nearby bar/pub, which gives rise to
the question of whether the Sun went off course on purpose. Perhaps for
cheaper drinks... ;}

David A. Smith

is there ever a possibility where a sun can orbit a planet?

The Sun does orbit every planet and vice versa. Bodies orbit
around each other, not just one around the other. The star is so
massive that it's movement is very slight compared to the planets.
That's how we detect planets around other stars, by watching for
their 'wobbling' as they orbit around each other.

That's my simple explanation, anyway.
Paul.

In article ,
Tom Kirke wrote:
[...]

BTW occasionly the center of mass of the Solar system is outside the
Sun but even then it is much closer to the Sun's center than any planet.

Only "occasionally"? A BOTE calculation suggests that the centre of mass
of the Sun + Jupiter system lies at 1.07 solar radii from the center of
the Sun. That would seem to imply "usually" rather than "occasionally".

Chris Thompson
Email: cet1 [at] cam.ac.uk