Space

The Sun and everything gravitationally bound to it: eight planets, their moons, dwarf planets such as Pluto, and countless smaller bodies including asteroids and comets. The Sun's gravity holds the whole system together and keeps the planets in elliptical orbits described by Kepler's laws of planetary motion.

A massive, luminous sphere of plasma held together by its own gravity, generating energy in its core through nuclear fusion — mainly the fusion of hydrogen into helium. Stars form from collapsing clouds of gas and dust, shine for millions to billions of years depending on their mass, and eventually exhaust their nuclear fuel, ending their lives as white dwarfs, neutron stars, or black holes depending on their initial mass.