Lifetime of Earth: Planet vs Sun

[mersecske]

What is the liftime of a solid planet compared to the life of its sun?

 

[Nik_2213]

IIRC, unless it is subject to a mega-collision, or spirals into sun due tidal drag, the next 'planet killer' is the star's red-giant phase. The Sun will then shrink to a white dwarf. Loss of mass may cause an orbit shift, but not cast planet into deep space. If the star is somewhat larger than our Sun, it will go supernova, which may zap the planet. If planet survives that, it should just orbit the stellar remnant until heat-death...

 

[mersecske]

I mean, let's assume that we see a star on the sky (we don't know its color).
And we suppose that planets are around that star, if it is possible.
But what is the possibility that planets are around that star at this moment?
So the sun isn't to young or old?

b) And what is the same probability for any star in the galaxy,
independent of the fact that we can see or not?

 

[Nabeshin]

suppose that planets are around that star

what is the possibility that planets are around that star

What? This makes no sense, and I really don't know what you're asking.

A planet can exist indefinitely -- there are no forces which will ever cause it to dissipate or otherwise disrupt itself.