See gallery: 鈥�Space superlatives: The universe鈥檚 extreme performers鈥�
Everyday units are far too small to cope tidily with the brilliance of the cosmos. Instead, astronomers use the sun, and its dazzling light output of 4 脳 1026 watts, as a standard lamp.
The sun is in fact an above-average star in terms of brightness, but some stellar show-offs outshine it by far. The most luminous example clearly visible to the naked eye is Epsilon Orionis, the middle star of Orion鈥檚 Belt. This blue supergiant is 1300 light years away and 400,000 times as bright as the sun. Much further away within our galaxy, or obscured by dust, are yet brighter stars such as the unstable Eta Carinae, which pumps out as much light as 5 million suns.
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In July 2010, astronomers found a new record breaker. R136a1 is a star in the Large Magellanic Cloud that is as bright as almost 9 million suns. With a mass estimated to be 250 times that of the sun, this freakish body is heavier than anyone thought possible, at least for a star made from the kind of chemical mixture available in the gas of the Milky Way and its neighbours. Could it be built from an almost pure source of hydrogen and helium gas that had somehow survived uncontaminated since the early days of the universe, or is there something wrong with our theories of stellar structure?
Some massive stars burn brighter still 鈥� but only for a few weeks and at the cost of their lives (see 鈥淲hat鈥檚 hot鈥�). A supernova called SN 2005ap, in a galaxy 4.7 billion light years away, qualifies as the brightest stellar explosion on record, peaking at about 100 billion suns.
Gamma-ray bursts emit even more energy than a supernova, and they can pack it into a matter of seconds rather than spreading it over several weeks. A burst can make even our solar unit seem absurdly feeble: its luminosity can equal more than 1018 suns.
If such explosions seem unsatisfyingly transient, then the brightest steady lights in the universe are quasars, in which a massive black hole feeds on a copious supply of stars and gas. As this doomed material spirals inwards it becomes white hot, and it can shine with the light of more than thirty trillion suns.
Read more: 鈥�Extreme universe: Eight cosmic record-breakers鈥�
