Do all plantets in a system have a sun near them?

[iamscuzzo]

I was thinking about time and how we use the sun as a way to measure time and all that. Then I thought about what if other planets didnt have a sun, how would time be measured? This is just something I was pondering but the real question here is:

Do all planets that are out there, how are they structured? For example, do all the planets out there, are they always in a system like ours where it has a sun and then X amount of planets are orbiting it? Or are there planets out there just by themselves with no sun around them or even no other planets nearby?

..... Ok I just did some wikipedia searching, and I just found out that what defines a planet is a "celestial" object which orbits a sun....so now I guess the question is that are there celestial objects out there that are no orbiting a sun? And are these objects that dont orbit a sun, are they considered totally different from earth and other solar system planets? Are they "dead" or full of gas.....

[01101001]

Welcome to BAUT Forum.


Then I thought about what if other planets didnt have a sun, how would time be measured?

There are very likely planet-sized bodies not near a star, perhaps ejected from their birth systems. They -- I guess "they" would be the inhabitants, but I'm not sure I see any reason to assume there are inhabitants on these bodies -- hypothetically could measure time by the rotation of their world, if they could see, as the different galaxies nearby move through the sky while the body rotates. Or they could note time by any other cyclic process, like a swinging pendulum, or simple body-process cycles such as eating or sleeping or circulating fluids. If the inhabitants became technologically advanced, they'd build clocks.


Do all planets that are out there, how are they structured? For example, do all the planets out there, are they always in a system like ours where it has a sun and then X amount of planets are orbiting it? Or are there planets out there just by themselves with no sun around them or even no other planets nearby?

Interesting planets that we can find probably have nearby stars. Rogue planets drifting through space would be very hard to detect and might have very little to offer, other than being a big lump of matter. Their circumstances won't be discovered for a very long time.


so now I guess the question is that are there celestial objects out there that are no orbiting a sun? [...] Are they "dead" or full of gas.....

They probably exist and they probably come in all the varieties as planets around stars. Their odds of being lifeless are probably greater because they are lacking the advantage of a convenient energy source. They would likely be cold and dark at their surface. Below, though, there may still be sources of thermal energy like Earth's deep-sea vents, and chemical energy.

See Wikipedia: Rogue planet (http://en.wikipedia.org/wiki/Rogue_planet)


Contents
1 Retention of heat in interstellar space
2 Proplyds of planetars?
3 Interstellar planets in popular culture
4 References
5 See also
6 External links