Is it possible for a planet far greater in size then our sun in other solar systems/galaxies etc...?

Answer 1

A planet can only get about 1 &1/2 times bigger than the diameter of Jupiter, and then it starts to shrink as you add more mass.

And if you just keep adding mass, eventually the core (already blazing hot in Jupiter) will be hot enough due to the crush of gravity to cause the (planemo?) to glow in the infrared.

Continue to add mass... and you get stronger infrared (a brown dwarf) at above 13 Jupiter masses, add more and it will fuse deuterium (easy to burn), keep adding more mass, it starts to burn Lithium and above 80 Jupiter masses it turns into a full fledged main sequence star ("M") buring regular hydrogen and the radiation pressure will make it swell out.

Answer 2

A planet larger than our sun? Doubtful. To begin with, were one to assemble a gas giant of solar mass out of hydrogen, what would happen next is that under the pressure at the core, nuclear fusion would spontaneously occur, and the thing would turn into a star. That's what sets the upper cap on the possible size of a gas giant: above a certain size (about 12-13 Jupiter masses), fusion can be sustained and what you get isn't a planet.

http://www.astro.umd.edu/~mpound/ophb11/OphB11_MNRAS.pdf

If the object is big enough to fuse deuterium (an isotope of hydrogen with one proton and one neutron) but not to fuse regular hydrogen (protium, lightest isotope, no neutrons), fusion will occur in the object for maybe a few tens of millions of years, until the deuterium is used up. This object, larger than a planet but smaller than a true star, is a brown dwarf. The largest of these is still much smaller than our sun. Above 0.08 solar masses, hydrogen fusion becomes sustainable, and what you get is a star.

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit2/starform.html

The natural question to ask at this point is "what if the planet is made out of something out of hydrogen". Couldn't it be assembled out of something that needs a greater mass to attain fusion (eg.carbon, which can't fuse in a star the same size as our sun) or which can't be used to generate energy through fusion at all (eg. iron)? Were such a planet assembled miraculously, it perhaps could exist for a while, but nature would almost certainly never create it.

Consider the deep gravitational well such a huge mass would create, and the temperatures on it, so much lower than on the surface of a star. Consider the nebula out of which this vast planet is condensing, which, due to the abundance of hydrogen in the universe, is almost certainly going to be hydrogen rich. Jupiter, at about 1/1000 of the mass of this object, is more than heavy enough to hold onto hydrogen. This body would be sucking it up like a vacuum cleaner, until a star formed around the unfortunate and soon to be incinerated planet. Anything that would be so quickly unstable in the environment in which it would have arisen could never have formed in the first place.

So the answer to your question is almost certainly no - it is to be doubted that such a planet exists anywhere in the universe.

Answer 3

This is a theoretical possibility, provided their sun is proportionately larger. We cannot fathom any planet larger than our sun because that is the boundary of our thinking just as a frog in small pond cannot understand the size of an ocean.

Again we are using a very small yard stick to postulate what should and what should not or could not exist.

Answer 4

A planet has to orbit the sun, so no. There are several objects far greater than our sun, beatlguese for example.

Answer 5

A planet of one solar mass would light up and be a star.

Answer 6

Good answer stargazer but I wonder if it could be done if it were composed of heavier elements then make up the sun. Clearly if it got too much larger then the sun it would start to bun heavier elements but I think it could be theoretically much bigger than the sun.

Answer 7

no
very unlikely
planets bigger than that will collapse due to their weight
they will ignite a thermonuclear reaction and causes 'planetary supernova' and besides if the planets got bigger, it will spin out of the way of the solar system

Answer 8

It is very unlikely, such a huge mass will be compressed by gravity to pressures and temperatures which will induce nuclear fusion and hence star formation.

Answer 9

I don't know if it's possible or not. So far, the largest extrasolar planet discovered has been about one fiftieth the mass of our sun.

Answer 10

what makes u think it is impossible.it is very much possible.