lets see what we got here, the biggest planet of our Solar System into which all other planets would fit with space to spare. It is Jupiter, named after Roman god of gods or Zeus in Greece mythology.
It is nine times wider than Earth but its mass is 1300 times larger. It is the fastest spinning planet, one day on Jupiter is 10 hours long which makes him 6% less like a circle. Mean distance from Sun is 800,000,000 km or 5.2 AU.
Jupiter is the closest gas giant, which means that he has no surface only thicker and thicker poisonous clouds with various gases. Darker parts are called zones and lighter belts, both of them are rotating in opposite directions. This process is powered by the internal heat of planet (Jupiter loses heat more than he receives) and by fast rotation.
On the picture you can see The Great Red Spot, it is on left of southern hemisphere. That is storm which lasts for decades but now we know that it is shrinking and eventually it will disappear. But for now it is stronger than any storms we ever hope to have on Earth with winds of over 500 km.
When we would dive beneath its deadly atmosphere we would appear in ocean of metallic hydrogen (hydrogen atoms that are sharing their electrons which makes them act as metal). Underneath we are not really sure but there can be solid core of metals and/or rocks.
While Jupiter is really large it is not even close to becoming star, it would have to be 12 times more massive. There exists a theory that Jupiter helps Earth by changing the pathway of comets and other stuff in space but on the other hand it could work in the same opposite way, but still we are not dead yet.
Juno (Hera) spacecraft is right now heading towards Jupiter. In the half of 2016 it will arrive and for 15 months it will collect the most accurate data that we ever had because of its close orbit.
For now there is 65 known moons orbiting Jupiter and I will definitely mention some of them in the future.