December: Many sights to delight on a summer night

The Helix Nebula – also known as NGC 7293 or Caldwell 63 – is a planetary nebula located 650 light-years away in the constellation Aquarius. This object is one of the closest to Earth of all the bright planetary nebulae. Photo: MPAS member Nik Axaris

If you are observing the sky with binoculars, there is a great deal to see looking south this month. NGC 3114 and NGC 2516 are both prominent open clusters worth observing in Carina in the southeast. The Eta Carina Nebula, or NGC 3372, is a bright diffuse nebula visible through binoculars or a small telescope. The bright open cluster IC 2602, or the Southern Pleiades, is a great binocular object. Also look out for the Small Magellanic Cloud in Tucana and the Large Magellanic Cloud sitting on the border of the constellations Mensa and Dorado. A small telescope will show star clusters and bright patches of nebulosity within it.

Mars’s orbit around the sun will carry it to its closest point to Earth – its perigee – on December 1. Since the size and brightness of Mars in the night sky both increase when it is close to us, the days around its perigee represent the best time to observe it. Mars will reach perigee around the time when it passes Earth in its orbit. At this time, the sun, Earth and Mars lie in a straight line, with Earth in the middle. Consequently, on December 8 Mars appears almost exactly opposite the sun in the sky – a configuration called opposition, when Mars reaches its highest point in the sky at midnight and is visible for much of the night.

This month we have the Geminids meteor shower on the night of December 14-15. The shower owes its name to the constellation Gemini because the meteors seem to emerge from this constellation in the sky. Unlike most other meteor showers, the Geminids are not associated with a comet but with an asteroid called 3200 Phaethon. As Earth passes through a massive trail of dusty debris shed by the weird, rocky object, the dust and grit burn up as they run into Earth’s atmosphere in a flurry of shooting stars. The asteroid takes about 1.4 years to orbit the sun.

By Nerida Langcake
This article appeared in the December 2022 issue of the Mornington Peninsula Magazine.