Unit of power in the SI unit system. 1 Watt = 1 Joule per second.
A very dense star with a mass below 1.4 solar masses that is no longer burning nuclear fuel. The Sun will one day evolve into a white dwarf with a diameter of 10 000 km.
Periodic comet which orbits the Sun once every 5.45 years. Discovered in 1948 at the Lick Observatory, California, by Carl A. Wirtanen. It is a so-called `Jupiter-type' comet, whose orbit is strongly influenced by that planet. Perihelion is at 159 million km (1.06 AU) from the Sun, i.e. just outside the orbit of the Earth. Aphelion is at a distance of about 768 million km (5.13 AU), near the orbit of Jupiter. Target of ESA's Rosetta mission, which will go into orbit around the nucleus and deploy a lander on its surface.