Star

A Star was ball of gas composed of hydrogen and helium which existed throughout the universe, as well as many paralell worlds. They often supported planets, keeping them able to support life, stars that did this were known as Suns.

History
Ever since the Big Bang the stars had thrived throughout this universe, and many others. They existed from the earliest days of the universe up until the universes older days.

Billions of stars existed, The Doctor was said to have known all of their names. Stars could often be seen from the night sky, and in one case, from the daytime sky.

Gallifrey had twin suns, supporting it.

There were 14 stars in the Rexel planetery configuration, home to a race called The Carrionites.

The planet Earth had a singular son, Sol and several other planets- Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto and Mondas.

In 10,000 BC the sun was thought of as "Orb", which brought light to Earth, keeping the cavemen warm. Orb not appearing in the skies during the winter led the cavemen to become in desperate need of fire.

Arcan was a sun, in the Arcan solar system, far away from the Sol system. It had six planets in it, and was home to two races, the Arcateenian's, and The Oblivioners.

In Pete's World (a paralell universe), the stars were "going out", one by one, dissapearing, and the same event occured in all other universes, this was due to the testing of the Reality Bomb. Davros had intended to destroy all realities, except for the Dalek Empire and himself, if this had happened, it would have involved every star becoming dust, then atoms, then non-existant by cancelling out the electrical field binding them together.

The Dream Lord created two dream realities, in which The Doctor, Amy and Rory were placed. One of which featured a Cold star. This caused the TARDIS to become in a frozen state. The Doctor said that such a thing could exist in the real world for all he knew, but Amy believed the science of it was "all wrong". This was proven true when the Cold star reality turned out to be a false one.

In the 42nd century, The Doctor and Martha arrived in a cargo ship, in the Torajji System, where they encountered a living sun, The Torajji Sun was a living organism, determined to kill the crew of The S.S. Pentallian due to them feeding off it's energy. ]]which pocessed crew members, due to particles of it being used by the spaceship as fuel, The Torajji Sun was damaged because of this, but the sun particles were returned to it, fixing all the damage.

Once, when the TARDIS exploded it caused every star to supernova at every moment in history, causing none of them to ever exist, and to keep the Earth alive, the Sun was replaced by a burning TARDIS. In this version of the universe stars never existed, except The Sun, although stories of stars were still spread, there has even been Star Cult's. Richard Dawkins was part of a Star Cult.

In the year 5000,000,000 The Sun exploded after becoming a large red giant, destroying The Earth in the process.

Other stars
There were other stars throughout the universe, these included Montoon which had at least two planets in orbit, one of which was visited by K9 Mark I, Mortain, Qqaba, Iota Ophiuchi, Population III star, Izjol, Proxima Centauri (the second closest star to Earth), The Black Sun and the Folflower system.

Death
When stars died, they did several things. Some became black holes and sucked in all matter nearby. Some expanded into red giants and destroyed nearby planets in a supernova. Others would shrink into white dwarves.