Neutron stars in collision

This image of the Crab Nebula was taken by NASA's Hubble Space Telescope.

This image of the Crab Nebula was taken by NASA’s Hubble Space Telescope.

For more than a thousand years, alchemists tried to make gold from other metals. Carl Sagan’s brilliant book The Demon-Haunted World was subtitled Science as a candle in the dark. Interestingly, science has just explained how gold was made. The explanation is more amazing than anything the alchemists dreamed of.

For millions of years after the Big Bang, 13.8 billion years ago, gold did not exist. Neither did carbon, oxygen, or any elements except the simplest, mostly hydrogen and helium. Eons passed. Denser regions of gas contracted by gravity, became hot, and stars were born. Some stars exploded a billion years later, making briefly “new stars” or supernovae.

Chinese astronomers recorded one in 1054. In that explosion, half the star blew out and can still be seen as the Crab Nebula. The rest was squeezed down to a 20-kilometer-diameter (about 12 miles) “neutron star” spinning 30 times a second, so dense that a teaspoonful would weigh about 5 billion tons.

In 1967, radio pulses from the Crab Nebula were discovered by a young astronomer, Jocelyn Bell Burnell. Her boss, Anthony Hewish, was awarded the 1974 Nobel Prize for the discovery. The object was called a pulsar. Two years later it was found to be also emitting light flashes. Bell Burnell recounted that in the 1950s another woman, looking at the Crab Nebula through a public telescope at the University of Chicago, said a star was flashing. The professional said she was mistaken, that it was due to atmospheric twinkling. But she was a qualified pilot and knew better. No one believed her.

More pulsars were discovered, some in pairs orbiting around each other. In 1981 one such “binary pulsar” was seen to be losing energy, with the orbital period changing precisely as expected by radiating gravitational waves.

The observation of gravitational waves, ripples in space-time, from two massive black holes crashing together was awarded this year’s Nobel Prize. In October, the same team announced the observation of gravity waves from two neutron stars colliding. Other astronomers detected a burst of gamma rays and a flash of light, with an expanding cloud of “debris.” Astronomers estimate that the debris contains around 20 Earth masses of gold, and even more platinum.

Probably nearly all the gold in your wedding ring was made in neutron star collisions, and spread in space before Earth was formed about 5 billion years ago. Until now nobody knew that! Talk about a candle in the dark!

This is a version of an article that originally appeared in Positively Naperville.