/sci/ - Science & Math

No.

I don't think it's possible for a planet to have more mass than a sun.
I think to obtain such a mass would pretty much mean the "planet" would have to become a sun.

Suns are stars. Stars not within a galaxy are fixed.

>>2429762
i agree, unless there is some crazy phenomena that we don't know or understand yet it should be impossible for a star to orbit a planet.

>>2429752
i think technicly if the planet had much more size and gravitational pull it would, but the planet would be so dense i think it collapse on itself before such a thing could happen with our sun. Maybe if it was very small new born sun/ Big planet

For a star to orbit a planet, the planet would need be massive enough for the star to be significantly effected by the gravitational field of said planet. A planet this massive would undergo nuclear fusion, becoming a star.
Basically, it would be a binary system, though it is possible that a planet of extremely heavy elements could be massive enough to gravitationally hold a star and not undergo nuclear fusion.

Not to be extremely picky about everything ever but stars and planets orbit around a shared axis between the two due to the fact that both exert a gravitational force on one another. Is it possible for a star and planet to share an axis that is over half the length between the two near the planet? Maybe. It would mean that a planet is more massive than a star but less dense, which is hard to imagine, a brown dwarf might get close in the case of an extremely large gas giant.

I believe a planet is defined by it being an object of a certain shape orbiting a clear path around a star.

For a star to orbit a planet, a very very very massive star would need to have a very very massive planet orbiting it and then that planet having the smallest possible star orbiting it.

The problem is if a planet is bigger than even the smallest of stars then it should be a star itself no matter what it is made out of. Th heavier, less fusable elements would produce ridiculously high pressures that might due odd stuff like fuse electrons and neutrons. It might simply be qualified as a black dwarf or a neutron star.

You would have to be a astrophysicist and have to know the the size of the smallest stars, the size of the biggest stars, the stability of such a system, and the know the sort of nuclear reactions that might be caused within the core of such a massive planet to answer this question properly.

Regardless of whether is possible or not, I can tell you with 99.9% certainty that such a system would not occur naturally.

>>2429777
dude wat
I'm pretty sure that stars aren't "fixed" and that relatively few stars are to be found between galaxies.

Depends on what you mean by "orbits." In two-body systems, the bodies orbit a barycenter at their center of mass, so you could say they orbit each other.

This is all semantics, however. The answer to the question you asked is no. The definition of a star is the presence of nuclear fusion in its core, which is mass-dependent. As hydrogen is so abundant, the only bodies that can have such mass are mainly hydrogen, so they begin fusion and become stars themselves. There are stars which orbit other stars.

Theoretically, though, if a rocky planet with very little hydrogen in its composition and a star-like mass existed, its composition would render fusion impossible. Such a thing is impossible, however, because there is simply too much hydrogen everywhere.

>>2429805
>I can tell you with 99.9% certainty that such a system would not occur naturally.
I would say that is a bit of a stretch. The universe is uncomprehensivly massive, so somewhere, sometime, something like this (the massive, heavy-element planet idea) happened.
But yes, it is certainly a rare occurance.

no, for a planet to have a star orbitting it, the planet would have to be atleast a fraction of a percent larger than the star, or to be a super massive planet just on the edge of becoming a star but not quite, and having it orbit a small star, while then having an incredibly bare minimum sized star orbit said planet like a moon.

still, i'd bet against it, a planet massive enough to hold a star would in itself become a star.

Its impossible, because "planets" that reach a certain mass 'become' stars, as the gravitational forces cause so much friction inside the planet that it 'spontaneously' combusts. Thus it is impossible for a sun to orbit a planet because it would require the planets mass to exceed that of a star, which isn't possible, as the mass of the planet has obviously passed the minimum mass necessary to create a star.

>>2429821
I'm sticking to my guns. I believe it is practically impossible. There isn't any reason to consider the chance. It's a trivial system that even if it does exist it is in some distant corner of the galaxy and will only be stable for a few million years before breaking apart and never occurring again.

In a two-body system bound by a central force, like gravity, all bodies will orbit the center of mass of the system. A stable orbit must be an ellipse, which may or may not precess. One foci of the ellipse will be the center of mass. Taken loosely, we can assume the sun to be a star whose mass ranges anywhere along the main sequence -- .10 to 40 solar masses.

Planets are typically many orders of magnetude smaller in mass than even the lightest star, but assuming you could build a super-planet that wouldn't collapse under its own weight, or become a black hole, there's nothing that prevents the center of mass of the system to lie very near to the planet, rather than nearing the star, as it typically does.

There is a logical contradiction.

A sun must be large enough to have at one point undergone hydrogen fusion at it's core, so suns have more mass than planets.

In order for a sun to orbit a planet the planet must have more mass than the sun.

While mass is important, to determine if the star will orbit the object, so is density. If the volume is great enough, even a large amount of mass can be distributed enough to prevent nuclear fusion from starting. I'm not sure if it occurs in nature, but perhaps a fairly dense nebula could have a small star orbiting it for awhile. The definition of "planet" then comes into question, as there wouldn't be a big different between this nebula and a jovian planet's composition, though the size, possibly the shape, and certainly whether or not it orbits a star would be different. At some point, the cloud might be called a protostar, not quite a star and not quite a nebula, doesn't that throw a wrench in your defenitions!?

>With a mass only 93 times that of Jupiter, AB Doradus C, a companion to AB Doradus A, is the smallest known star undergoing nuclear fusion in its core.

>Brown dwarfs occupy the mass range between that of large gas giant planets and the lowest-mass stars; this upper limit is between 75 and 80 Jupiter masses.

The only way this shit would work was if a Red Dwarf was paired with a brown dwarf and even then the actual star would always have more mass. So no, there is no way a single star and single planet system could have their semantic roles reversed.

>>2429937
A fairly dense nebulae is a far cry from a planet. Even a gas giant.

>>2429957
Why is that? They can both be made of gas. They can both be roughly sphereical (consider planetary nebulae), though in this case the nebula would over time probably become a disk. The main difference is the scale, and that one does not orbit a star.

>>2429974
Well, I guess because one is a planetary nebulae and will eventually collapse into a planet and the other, with more mass than the star, would collapse into another, larger star like you said. And at any rate, this is above and beyond what OP was thinking about, so I think in answer to his simple minded question, it would be a resounding no.

>>2429991
The OP asked if was possible to orbit, not orbit he did not specify how long for.
Also
>planetary nebula
>will eventually collapse into a planet
Yeah, that's my cue to back up, turn around, and leave the discussion.

some of you are forgetting the functionality of a solar system.

When a star forms all of the elements in the area are pulled towards the center to create the star. The LEFTOVERS make the planets and everything else.

The star would get the majority of the elements, especially hydrogen, which would mean it would have the only chance to get fusion reactions in its core.

The only way a planet would have the gravity to make a sun orbit it, is if it had a fusion core, but then that would change it from being a planet.

Yes there are small probabilities of this happening because of how big the universe is. but those chances are so small its not even worth debating over.

It's like a freak accident, you don't expect someone to go through a jet engine and survive its improbable, yet its happened.

If it happened it would be an anomaly and may not even last very long.

wtf is wrong with you all the sun orbits our planet everyday it's why we have day time and night time...

>>2430067
0/10

If any significantly dense object in space (gaseous/nebulous body, planet, etc) reaches a mass of approximately 1.193352x10^29 kg it will become a star, as this is the point where the gravitational forces can ignite nuclear reaction.

Therefore it is impossible to have a star orbit a planet because lower mass objects always orbit higher mass objects. For a sun to orbit a planet, the mass of the planet must exceed the mass of the orbiting sun which is obviously above the minimum mass necessary to initiate fusion through gravity.

So NO, a star cannot orbit a planet, it is impossible.

>>2430600
It's just a matter of perspective, you doofus.

But what if there was a planet so huge that a star orbitted it.

>>2430616
read
>>2430600

If the planet was almost wholly Iron and if a brown dorf can be called a star. Then, sure.

Though they would almost certainly rotate around a barycenter outside the hunk of iron.

If you added mass to the 'planet', you would of course get the center of orbit inside it, but then you risk it collapsing into degenerate matter. Which would make it a star.

In any system, bodies orbit the point of centre of mass of said system, so each body orbits eachother equally when divided by mass of that body. Theoretically, the sun is orbiting us, just we have negligible effect on it, because we are so small, and the centre of mass of the solar system is pretty much in the centre of the sun anyway, because planets on the other side cancel our effect on it out pretty much.