Ancient Chinese Astronomy: New insights from old information

New insights from old information

British astronomer Richard Stephenson, who taught himself ancient Chinese and is now a leading expert on the astronomy of the Far East, has looked into the “guest star” of AD 185. He identifies the Southern Gate as the two bright stars Alpha Centauri and Beta Centauri. And he concludes that the guest star was so brilliant that it had to be a nearby supernova – the most violent kind of stellar explosion.

Led by the Chinese results, Stephenson has pinpointed where the explosion occurred. And here astronomers studying X-rays from the Cosmos with the orbiting Chandra Observatory have located the incandescent fireball still expanding from the 2000-year-old explosion.

“One of the key things is that you have a definite date,” Stephenson explains, “so you know precisely how long the remnant has been evolving.”

The Chinese observations can also indicate how bright the supernova was. “In the case of a supernova seen in AD 1006,” Stephenson continues, “the Chinese said it was so bright that you could see things on the ground by its light.”

These ancient observations really come into their own with the supernova spotted in July AD 1054. A star exploded in the constellation we know as Taurus, shining so brilliantly it was visible in daylight for 23 days.

Today, in this location we find the twisted wreck of the long-dead star: the Crab Nebula. It’s powered by a collapsed core of the old star, which lurks at the centre of the nebula as a pulsar – a super-dense ball of neutrons only 25 km across, spinning around 30 times a second.

Astronomers and physicists are short in understanding how neutron stars change as they grow older. With the Crab Pulsar, the Chinese observations provide a unique piece of information: the pulsar’s age. We know that it was born exactly 953 years ago.

The Chandra Observatory has also pinpointed pulsars within supernova remnants that - according to Stephenson - are the fireballs from stars the Chinese saw explode in AD 386 and 1181.

Sometimes, the imperial astronomers were treated not to a guest star, but to a “broom star” – a fuzzy object that crawled across the sky, sweeping the sky with its tail. In 240 BC, they set down the world’s first record of the celestial visitor we now know as Halley’s Comet.

In AD 530, the Chinese recorded Halley’s Comet with more precision: “On 1 September, it was one degree to the northwest of Xiatai [a star in Ursa Major].” These early fixes on the comet’s orbit meant that European mission controllers could predict its 1986 apparition with greater accuracy, enabling them to send the Giotto spacecraft through the comet’s heart with unerring precision.

Could Chinese Astronomers predict eclipses of the sun and moon? - Read on to find out....