The Sun (Sol).
The giver of life here on Earth- without it, we would perish. The Sun provides enough heat and light to sustain life, however it is also so destructive that it can easily destroy life as well.
Located 150 million kilometres (93 million miles), the Sun is thousands of times closer to us than the other stars we see in the night sky, and therefore, it looks much bigger. In fact, it only takes light a mere 8 minutes to reach us on Earth, whilst the next closest star to us- Proxima Centauri, lies 4.243 light YEARS away. And that is the very closest star to us.
Whilst considered a yellow dwarf star, the Sun is still large enough to fit 1.3 million copies of Earth inside it's radius. However, apart from the relatively close distance to Earth, the Sun is really just an average star, and Earth just so happens to lie within the "Goldilocks Zone"- a region of space that is not too hot and not too cold, but more so just the right temperature to sustain life. Almost every star could potentially have planets just like Earth orbiting around Goldilocks Zones.
It has been burning for 4.5 billion years, and will continue to burn for another 5 or so billion years, before swelling 20 per cent brighter and 20 per cent hotter than it's current size to become a Red Giant (an elderly star). The radius of the Sun at this point will extend past the current orbit of Earth, hence the planet will ultimately become vaporised. Over billions of years, the core of the Sun will cool and the star will become a White Dwarf star, before eventually settling down to become a Black Dwarf star.
On the Spectral scale, the sun is classified as a G2 V type star, one of billions of stars out there. A G2 star is the second hottest of the yellow G class of stars, with a surface temperature of 5,800K (kelvins). V represents a main sequence dwarf star, which is common for stars of this class.
The components of the sun are made of gas- predominantly hydrogen and helium. There is no hard surface on the Sun. In the core of the Sun, the process of nuclear fusion is taking place, where hydrogen fuses to form helium, which in turn, produces heat and light to sustain life on Earth. Every second, the Sun produces as much energy as 1 trillion megaton bombs! In fact, the temperature at the core of the Sun is greater than 15 million degrees Kelvin.
The immense size of the sun produces a gravitational warp so strong that all of the planets of the solar system are held in orbit around the star.
So the next time you look up at the gently glowing orb in the daytime sky, remember that nuclear reactions of particles deep in the core of the Sun are providing that very light and warmth we here on Earth depend on every day.
-EJ
Source: http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun
Image Credit: Extreme Ultraviolet Imaging Telescope (EIT) Taken 14th September, 1999
