Star Chart for Western Sky in August 2012
Star Chart for Eastern Sky in August 2012
This month it’s time to turn our gaze to constellations that, while not so well known, still contain as many treasures as the more famous parts of the southern sky.The constellation of Boötes is not widely known in the Southern Hemisphere but can be easily picked out by spotting the reddish orange Arcturus in the northwest after sunset. Arcturus (Greek for ‘guardian of the bears’) is the fourth brightest star in the sky and named Ruawãhia in Te Reo Mâori.
Arcturus is near the top of Boötes as seen from the Southern Hemisphere. The constellation name also comes from Greek and means a herdsman, or plowman. When low in the sky as in August, the star often appears to twinkle between red and green as the air near the horizon refracts the orange light, sparking reports of UFOs.
North of Scorpius and Sagittarius, try to make out Ophiuchus, the serpent bearer. This constellation lies across the path of the Sun (the ecliptic), effectively making it the 13th sign of the zodiac. There are five stars bright enough to be seen with the naked eye in reasonable conditions, with the brightest, Rasalhague, relatively nearby at 47 light-years.
Seven globular clusters can be found in Ophiuchus. M10 and M12 are both worth looking for with good binoculars.
Aquila (the Eagle), just to the east of Ophiuchus, has been mentioned in texts from as early as the 4th century BC. Altair is the brightest star in the group; a striking white star located only 16 light-years away, one of the Sun’s closest neighbours. Starting at Altair it is quite easy to pick out a bright triangle, adding Vega in Lyra and Deneb in Cygnus. In the Southern Hemisphere this is often referred to as ‘the Winter Triangle’ - but as ‘the Summer Triangle’ in the Northern Hemisphere.
This is also the best time of year to spot Delphinus (the dolphin), which has bright stars that form a distinctive asterism to the northeast.
The two brightest stars of this constellation, Sualocin (otherwise known as Alpha Delphini) and Rotanev (Beta Delphini), are some of the most interesting in the sky.
They don’t derive from Greek mythology or Arabic tradition, but rather, are someone’s name spelt backwards! It is thought they date from a star catalogue published at the Palermo Observatory, Italy in 1814. Nicolaus Venator is the Latinized version of the name of the assistant director of that observatory at the time, Niccolò Cacciatore.
Saturn continues its run of the evening sky this month, as does Mars – but look out for them together later in the month as they become increasingly close, and then form a beautiful partnership with the Moon on the evening of 22 August.
There are also two exceptionally bright predictions for the crossing of the International Space Station this month (5 and 23 August); although both will happen very early in the morning.