In praise of … supernovae | Editorial

You wouldn’t want one for a close neighbour – at their fiercest, they can be five billion times brighter than the sun – but supernovae, briefly capable of outshining an entire galaxy, have in the past 400 years lit up our universe. Tycho’s nova or new star, recorded in 1573, was the first direct evidence that the heavens were not immutable. Kepler’s supernova in 1604 was visible even by daylight. Both served as beacons to signal the scientific revolution. The latest candidate for supernova celebrity – provisionally called PTF 11kly – is blazing in the Pinwheel galaxy, 21m light years away: it has already earned its place in history, if only because astronomers caught the explosion within hours of its commencement, and are now fiercely measuring every stage of its bright but brief convulsion. This is a Type 1a supernova, and such puzzling celestial fireworks have served as “standard candles” to measure the rate at which the universe is expanding: if you know exactly how bright such a star ought to be, you can make a good guess, from its dimness, at its distance. Supernovae are, so far, science‘s best explanation for the heavy elements: everything from helium to iron is known to have been forged from hydrogen in the thermonuclear furnaces of ordinary stars. But gold, lead or uranium require something much fiercer, and supernovae are the best candidates for such alchemy. If so, we owe these fiery monsters everything, including the fabric of the planet from which we observe them.

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