Could a Planet Gain Mass and Ignite as a Star?

[ThomasFuhlery]

So I heard a theory once that a planet, gaining mass through collisions, could over time become a feelble star (if it gained about 10x the mass of jupiter), through adding kinetic energy and pressure, etc., and that this would create nuclear ignition.

My question is this: If somehow we could fabricate a way to add mass to a planet that was this size, would it be possible to instigate nuclear ignition over a relatively short period of time? (nevermind how we would add the mass). Also, would the fuel (hydrogen, etc.) be found naturally in the planet, or would it be scarce and immediately collapse, or what?

 

[Entropy]

would it be possible to instigate nuclear ignition over a relatively short period of time? (nevermind how we would add the mass). Also, would the fuel (hydrogen, etc.) be found naturally in the planet, or would it be scarce and immediately collapse, or what?

Yes. A planet, like Jupiter, is already mostly hydrogen and helium, just like the sun. If you could simply add more mass in the form of additional hydrogen, then yes it would ignite and become a star.

 

[russ_watters]

I'm not sure I see the point, here - the OP is pretty much redundant: you stated that if mass is added to a planet it could become a star and then asked if a planet could become a star if mass is added...

Is the question regarding what form the "mass" would have to be? Obviously, it would have to be hydrogen - but since hydrogen is by far the most plentiful in the universe, that's probably what it would be anyway.

 

[Soul Surfer]

The more important point is just adding more mass to a body creates a great deal of heat which comes from either the adiabatic compression of the gas or the collision energy of the body striking the surface if you drop things on it. The final point is that it is not all that easy to add mass to a body because you have to get rid of the angular momentum or it just whips round in a tight orbit and shoots off.

Young sun type stars are much brighter while they are cooling down before they join the main sequence and even eventual brown dwarfs will get very hot and bright for a while if they form fast enough