Sun isn't actually planet but star. Really big ball made of gases. Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%). Sun is the biggest object in our Solar System. It's 99.86% of the total mass of the Solar System.
... wikipedia is really grat if you have questions like that ;)
The sun is not a planet. If it was, it would be the biggest planet but it's not. Jupiter is the largest planet in our solar system. Jupiter is bigger than all the other planets put together.
Increasing the pressure on a reaction involving reacting gases increases the rate of reaction. Changing the pressure on a reaction which involves only solids or liquids has no effect on the rate.
