Let's make thing worse: Is Jupiter Considered a Planet???

[weixing]

Hi,
A lots of disagreement and argument after Pluto had been demote from "Planet" status... Let's make thing worse : may be they should consider promote the mighty Jupiter to whatever except a planet??

Many of us may know that Jupiter actually didn't orbit around the Sun (it may appear so). The Sun and Jupiter (same with the rest of object in the solar system) actually revolve, or spin, around the very center of the mass between them... this point is called "barycenter". To consider orbit around the Sun, this point need to be inside the Sun surface. So let's take a look and check does this happen to the Sun and Jupiter "relationship"??

The Formula
r1 = a x [m2 / (m1 + m2)]

r1: the mean distance from the center of the first body.
a: the mean distance between the two bodies.
m1: the mass of first body.
m2: the mass of the second body.

The Left Conrner: Our Star, The Sun
Mass: 1.988435E+30 kg
Mean Radius of Sun: 696,000 km

The Right Conrner: The Mighty Jupiter
Mass: 1.899E+27 kg
Mean Distance From Sun: 778,412,027 km

The Result
The distance to the barycenter of Sun and Jupiter from the center of Sun:
r1 = 778,412,027 x [1.899E+27 / (1.988435E+30 + 1.899E+27)] = 742,692 km
which is 742,692 - 696,000 = 46,692 km outside the surface of Sun. This mean that both Sun and Jupiter are orbiting around a point outside the surface of the Sun... so strictly speaking, Jupiter does not obrit around the Sun.

So does Jupiter still consider a planet since it didn't actually obrit around the Sun?? Hee hee

Have a nice day.

[gwenyi]

hmmm.. interesting point raised. haha

[philip]

Jupiter does orbit round the sun but due to it mass the barycenter point was formed.

[alvinsclee]

It's all relative.

With reference to a 'fixed' point in universe, the barycentre between the Sun and Jupiter can be calculated. But with reference to either body, the other is simply orbiting around the datum point. Strictly speaking, since the universe is expanding, is there a true fixed point for reference?

Makes me wonder if we were to use the mass of black holes to calculate the barycentre... where is it between 2 black holes? Note that black holes are so dense that their mass can be considered as very near infinity!

[weixing]

Hi,

Jupiter does orbit round the sun but due to it mass the barycenter point was formed.

Jupiter and Sun are actually orbiting around their barycenter (same with other object in the Solar System). If the barycenter is in the Sun itself, the object will look like it is orbiting around the Sun. Because of this, the Sun will wobble a bit.

This is how astronomer find giant planets or any object that is massive and cannot be seen directly near other stars... If they detect that a star is wobbling, they know that there must be something quite massive near the stars.

With reference to a 'fixed' point in universe, the barycentre between the Sun and Jupiter can be calculated.

The reference point is Jupiter and the Sun.

Anyway, I was just "finding chicken bone in chicken egg yolk"... having some fun... ha ha ha

Have a nice day.

[Tachyon]

Like WX said, ALL objects orbit each other. The only difference is how far away the barycenter is from the gravitational center of the individual masses. As more and more objects are discovered, we will have a range of objects orbiting the star with barycenters varying from within the star to outside of the star (30-40%?). How do we set the limit then?

[rlow]

This barycenter is a fundemental gravitional property that applies to all objects with mass, including Earth too! Send this to IAU and they will think we are 'goondu'. This barycenter is a resultant point that constantly varies depending on the relative varying positions and masses of all objects, whether planets, moons, asteroids or comets etc.

[ALPiNe]

Many of us may know that Jupiter actually didn't orbit around the Sun (it may appear so). The Sun and Jupiter (same with the rest of object in the solar system) actually revolve, or spin, around the very center of the mass between them... this point is called "barycenter".

So does Jupiter still consider a planet since it didn't actually obrit around the Sun?? Hee hee

Yes I know, but you are contradicting yourself.

Like WX said, ALL objects orbit each other

Wrong. Weixing didn’t say that too. ALL objects, including Earth, are actually orbiting their centre of mass called the barycentre and not each other.

The only difference is how far away the barycenter is from the gravitational center of the individual masses

It’s not so much about the barycentre, but more on the mass of the two objects in orbit. We can take Earth and throw it right into Pluto’s orbit, but its barycentre will still remain within the Sun’s surface. Consider this scenario, if we were to blow up Earth to several billion times its own mass such that it becomes larger than the Sun, the barycentre will shift towards Earth instead and the Sun will ‘appear to orbit’ around Earth. To visualize how mass can have an impact, look at the animation in the following link:

http://en.wikipedia.org/wiki/Barycentre#Barycenter

This barycenter is a fundemental gravitional property that applies to all objects with mass, including Earth too! Send this to IAU and they will think we are 'goondu'.

Yeap, you are right..


Cheers,
- ALPiNe
.- .-.. .--. .. -. .

[weixing]

Hi,

Yes I know, but you are contradicting yourself.

Hmm.... did I???

Have a nice day.

[ALPiNe]

;)