Welcome to the August night sky. This month we get a rare opportunity to spot the elusive planet Mercury low on the western horizon just after sunset from the beginning of the month.
We are aided in this endeavour by the two bright planets Venus and Jupiter that will also be low in the western sky during the early evening.
On the fourth of this month, Mercury will be seen just above the thin crescent Moon with Venus about 10 degrees to the right and Jupiter about 10 degrees to the left.
On the evening of August 18, the gas giant planet Jupiter will be seen just above Mercury, with Venus still to the right of the pair, and on August 27 both Venus and Jupiter will move very close to each other and will appear to be almost one object shining brightly just above the western horizon at sunset.
As the sky becomes fully dark, looking in the direction south, the planets Saturn and Mars are still in the constellation of Scorpius and on the night of the 11th the first quarter Moon is close to the pair.
The famous Perseid meteor shower will happen on the night of the 12th and into the morning of the 13th. This shower is dust left over from the tail of comet Swift-Tuttle that last passed Earth in 1992.
This comet is 26 kilometres in diameter and has the distinction of being the largest known object to pass close to us. The next time we will have a close encounter with this massive comet will be in 2126 when it will miss the Earth by 14 million miles on August 5.
The speed of this comet relative to the Earth is about 60 kilometres per second and although there is no danger of an impact, at least for the next few thousand years, if it did collide with us the energy release would be much more than the impact that probably wiped out the dinosaurs 65 million years ago, so it would cause a mass extinction event that would end most life on this planet.
The moon is new on August 2, first quarter on the 10th, full on the 18th and last quarter on August 25.
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 July Sky Map click on the pdf link below