August night sky – 10pm

By Clive Jackson [email protected]

Clive Jackson is the Director of the Astronomical Observatory of Tavira (Sitio do Malhão, Tavira) and the Camera Obscura (next to the Castle in Tavira), specialising in education and public outreach.

Welcome to the August night sky.  Soon after sunset, low on the western horizon, we get our last chance this year to see the ringed planet Saturn.

This planet is at the moment in the constellation of Virgo and has been close to a star called Porrima for a few months now. This star is fainter than Saturn but, slightly to the left of Saturn, you can see Spica, which is the brightest star in Virgo constellation and much more brilliant than Porrima.

Through any telescope, Spica is a brilliant white point of light but it is in reality a close binary star whose two components orbit each other every four Earth days. Together they shine more than 13,000 times brighter than the Sun and they are around 260 light years away. The crescent Moon was located below Porrima on the night of the 3rd and below Spica on the night of August 4.

At the beginning of the month, around midnight, the gas giant planet Jupiter can be seen rising over in the northeast and, by the end of the month, Jupiter rises two hours earlier.

The last quarter Moon will be close to this planet on the 19th, and Jupiter will be in the constellation of Aries and spends an average of one year in each constellation of the Zodiac due to its 12 year orbit of the Sun and there being 12 zodiacal constellations.

Tomorrow (Saturday), the Asteroid Vesta is at opposition in the constellation of Capricorn. This 530km wide object was discovered in 1807 and is presently being visited by the NASA probe Dawn that will stay in orbit for a year before moving on to another asteroid called Ceres.

It is possible to see Vesta with binoculars as a small faint star like point; it’s currently 114 million miles away.

August is well known for the Perseid meteor shower that traditionally happens on the night of the 12th, but this year the bright moon will make it difficult to see any but only the most luminous meteors.

High overhead on dark August nights is the constellation of Cygnus the Swan. This constellation is sometimes called the Northern Cross and its long axis points in the direction of the southern horizon. Over towards the northeastern horizon by midnight can be seen rising the star cluster called the Pleiades or the Seven Sisters. This is a sure sign that summer is coming to an end and winter is on its way.

The Moon is first quarter on the 6th, full on the 13th, last quarter on the 21st and new again on August 29.

Clive Jackson can be contacted on Tel 281 322 527, fax 281 321 754 or email [email protected] Alternatively, please visit www.cdepa.pt