- The Sun -
An ordinary, garden-variety star with exactly one unique characteristic: it is in the middle of our system of planets. This close proximity has two important implications: the Sun is the only star that we can study in detail (others are simply point sources, even with the world's most sophisticated telescopes); the Sun is also responsible for all life on Earth. It is a G2 V-type star, composed mostly of Hydrogen (90%) and Helium (10%), with trace amounts of other elements, and has an apparent magnitude of -26.6.
It is has a mass of 1.99 x 1030 kilograms (1.99 nonillion kg or 1 Solar Mass);
It is on average, 150 x 106 kilometers away from us (150 million km or 1 Astronomical Unit = 1 AU);
It has a diameter of 1.39 x 106 km (1.39 million km or 1 Solar Diameter);
It has a luminosity of 390 x 1024 Watts (390 septillion Watts or 1 Solar Luminosity).