On this date in 1719 The Aurora Borealis (Northern Lights) appeared for the first time to New Englanders, USA. 10 facts about the Aurora Borealis:
The name was coined by Galileo in the 17th century. He named the phenomenon after Aurora, the Roman goddess of dawn and Boreas, the Greek god of the north wind. The Aurora Australis which occurs in the southern hemisphere is named for the Greek god of the south wind, Auster.
Galileo wasn’t the first to observe an aurora by any means. Cro-Magnon cave paintings in Spain dating to 30,000 BC feature them. The oldest known written record of the aurora was in a Chinese legend written around 2600 BC.
So what causes it? Charged particles being emitted by the Sun and hitting the Earth’s atmosphere and magnetic field. "Coronal mass ejections", when the sun ejects more particles than usual is when you get the most impressive auras. Dr Affelia Wibisono, from the Royal Observatory in Greenwich describes it as “a big sneeze by the Sun."
Auroras are colourful. The different colours which can be seen are due to the different gases in the atmosphere. Green lights are caused by Oxygen and the Purples, Blues and Pinks by nitrogen. When particles hit oxygen at very high altitudes, however, it produces a Red glow.
The lowest part of an aurora is usually about 50 miles (80 km) above the Earth's surface. The highest part could be 150 miles (800km) above the Earth. This means that Astronauts on the International Space Station sometimes fly right through it.
Northern Lights are seen most often in regions close to the North Pole such as Scandinavia, Greenland, Alaska, Canada and Russia, but occasionally further south – they have been seen as far south as the Caribbean. The Southern lights are commonly seen across Antarctica and sometimes in the south of Australia and New Zealand. The northern hemisphere is more densely populated which is why you tend to hear more about the Aurora Borealis than the Aurora Australis.
The best time to spot auroras is around the equinoxes (March-April and September-October), because there are more magnetic storms then. The brightest auroras tend to be around 11pm to midnight local time.
It’s not just a light show, either. The auroras make sounds as well. People have reported hearing hissing, snapping or popping sounds. This happens when negative charges are released after being trapped in the inversion layer, a part of the atmosphere where temperature increases with altitude, rather than decreases.
Since it’s caused by what’s happening on the sun, it stands to reason that the other planets in the solar system get them, too, although they’d look different in terms of colours because the atmospheres are made up of different gases. The Hubble Space Telescope, and the Cassini and Galileo spacecraft have allowed us to see auroras on Jupiter, Saturn, Uranus and Neptune.
Ancient peoples came up with their own explanations of what those lights in the sky meant. These include: a giant Arctic fox running across the sky making sparks with its tail; the gods burning torches; the spirits of the dead giving guidance, messages or warnings, or dancing, or playing football in the sky with a walrus skull.
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