Welcome to the November night sky. The gas giant planet Jupiter is now lost below the western horizon at sunset. The ringed planet Saturn is also getting low in the southwest as night falls, and the crescent Moon will be alongside this planet on the night of the 11th. The red planet Mars is still shining quite brightly high in the south, and the first quarter Moon will be close to Mars on the night of the 15th.
Looking over towards the east in the early evenings, we can see the constellation of Orion the Hunter as it rises. In the northern hemisphere, Orion is a winter constellation and as it is on the Equator of the sky, it’s visible from any place on the planet during the hours of darkness.
The most well-known meteor shower in November is the Leonids. They have their origin from the short period comet Tempel Tuttle. This comet has a 33-year orbit and when the Earth crosses this orbit every year in November, on the 17th, we have a resulting meteor shower.
Every 33 years, this shower has the potential to be much stronger as the dust from the nucleus of Temple Tuttle will be much denser due to the recent passing of the comet. There is now no danger of Tempel Tuttle hitting the Earth, but in the year 1366 it came within two million miles of us. This is very close in astronomical terms and is one of the closest known approaches of a comet to the Earth.
Impacts from comets can be much more destructive than the asteroid impacts as they are faster, and the energy depends on the square of the speed. This means that for equal mass a comet going three times faster than an asteroid would have nine times the impact energy.
There is a theory that a comet of similar size to Tempel Tuttle hit the Earth about 12900 years ago and put our planet back into an ice age for a thousand years; then the parent comet of the Taurid meteor shower broke up and hit the northern hemisphere ice sheet that covered most of North America at the time.
The Moon is new on the 7th, first quarter on the 15th, full on the 23rd and last quarter on November 30.
By Clive Jackson
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Clive Jackson is the Director of the Camera Obscura (next to the Castle in Tavira), specialising in education and public outreach.
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To see the October Sky Map click on the pdf link below