This weekend’s night sky (20 - 21 September 2014) As we head towards the spring equinox on the 23rd of September we see a rapid change in our daylight hours, with our days getting longer and our nights shorter. Equinox means “equal night” because we have the same number of hours of daylight and the same number of hours of darkness. Mercury is moving towards its greatest eastern elongation from the Sun on 22nd, so now is a good time to look out for this elusive planet close to the western skyline at dusk. On Saturday, Mercury will make a close pairing with the bright star Spica in the constellation of Virgo. Spica is the 15th brightest star in the night sky, located around 260 light years away. It is in fact a close binary star, with the two components orbiting each other every 4 days. The pair is so close that they can’t even be split by a telescope. The main star is a blue giant, around 10 times more massive than the Sun. The Moon continues to wane as we move towards new moon next week, and will be rising after 3:30am this weekend. This means we have the possibility of dark, moonless evenings to observe fainter objects in the sky. Stretching between Fomalhaut in the east and Altair in the north is a long string of stars that forms the zodiac constellation of Aquarius, the water bearer. There are a number of deep sky objects in this constellation that are worth hunting down: M2 is a lovely globular cluster, nearby to 3rd magnitude star Beta Aquarii. With a magnitude of 6.3, M2 is a difficult naked eye object, so a good challenge for those with clear dark skies and good eyesight. It is easily visible in binoculars as a hazy star and with a 20cm telescope a few individual stars can be resolved. To the southwest of Delta Aquarii is NGC 7293, the Helix Nebula, one of the largest and closest bright planetary nebulae to our solar system at 700 ly away. The Helix nebula spans around 2 and a half light years in diameter, covering an area of the sky equivalent to half the size of the Full Moon.
Posted on: Fri, 19 Sep 2014 02:55:13 +0000
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