Wonders of the Universe

MAPPING THE NIGHT SKY

The moment you leave a city and experience a truly dark night sky, it becomes obvious why our ancestors spent a great deal of time looking up at the stars. They are a bewildering array; a patterned silver canopy self-evidently not devoid of meaning or purpose. For thousands of years ancient astronomers endeavoured to capture and catalogue every light; to observe, log and name as many of these distant suns (for we now know their true nature) as they could. The oldest-known record of a star chart may be over thirty thousand years old. A carved ivory mammoth’s tusk, discovered in Germany in the late 1970s, appears to be imprinted with a pattern that resembles the constellation of stars we now call Orion. In France, cave paintings have been discovered which reveal that humans were mapping the night skies tens of thousands of years before the great civilisations of antiquity began to slowly explore the Universe in more detail.

This celestial map shows a more detailed, highly illustrated view of the constellations according to Dutch cartographer Frederik de Wit in the seventeenth century.

For thousands of years ancient astronomers endeavoured to capture and catalogue every light; to observe, log and name as many of these distant suns (for we now know their true nature) as they could.

The Egyptians were one of the first ancient cultures to not only map the night sky but to name some of the stars they observed. They called the North Star the ‘star that cannot perish’, and they also recorded the names of constellations. The Sumerians and Babylonians went a step further by writing down these early names and patterns and creating astronomical catalogues that listed and grouped stars in ever-increasing complexity. Greek, Chinese and Islamic astronomers all continued to build ever more complex systems of classification, with many stars today still being referred to by their original Arabic names.

To the ancients, the stellar backdrop had a deceptive permanence that no doubt motivated them to record and mythologise the patterns they saw. But in AD 185, for the first time in recorded history, a particular type of fleeting addition to the lights in the night sky was observed and documented. Understanding the nature of this rare and spectacular phenomenon eventually led us beyond merely naming the stars and enabled us to tell the story of their births and deaths.

In AD 185, Chinese astronomers witnessed a brightness in the sky comparable to that of Mars, and this remained for eight months. This phenomena was the first recorded occurrence of a supernova explosion, but it was not until late 2006 that the remains of this cosmic event were identified. This picture, taken by the Chandra X-ray Observatory, shows an object now known as RCW 86. The image shows low-, medium-and high-energy X-rays in red, green and blue respectively. It was the study of the distribution of X-rays with energy, combined with measuring the remnant’s size, that enabled scientists to conclude that RCW 86 was created by the explosion of a massive star around 8,000 light years away.

NASA

In late 2006, the remains of the cosmic event of AD 185 that illuminated the skies and minds of Chinese astronomers almost two thousand years ago was identified. The picture above, taken by the Chandra X-ray Observatory, is that of the object known as RCW 86. This object is thought to be the still-glowing remains of one of the most powerful events in our universe – a supernova explosion.

Supernovae are the final act in the lives of massive stars, colossal explosions in which a single star can shine as brightly as a billion suns. If RCW 86 is the remains of the AD 185 supernova, then the ‘guest star’ described by the Chinese astronomers that glowed brightly in the skies for eight months before fading from view was around 8,000 light years away – a quite colossal distance for something to shine so brightly in our skies. The ancient astronomers didn’t know it at the time, of course, but they had documented the first clear evidence that the stars must all eventually die