Sky Matters: Soak in the wonders of the night sky this December
This is the month for the king of constellations, majestic Orion, the Hunter. It is visible throughout the night, rising due east about 8pm, with the three bright stars in its belt providing a barely miss-able landmark. Orion can be seen even from urban areas, where light pollution makes other constellations hard to pick out.
To the top left of Orion’s belt is a bright, reddish star called Betelgeuse, a mammoth star nearing the end of its lifetime and which has swelled up to be so huge that it would engulf the Earth if placed where our Sun is.
To the bottom right is a young star, Rigel, which has a blueish-white colour. Sporting a mass 18 times that of our Sun, a temperature twice as high as our Sun’s and a brightness that is some 40,000 times brighter than our Sun, Rigel is a truly impressive star.
Yet Rigel is only 8 million years old — our Sun is 4.5 billion years old — and will last about as long again before it likely blows itself apart in a so-called supernova.
Now that WILL be worth heading outside to see. In fact so bright will an exploding Rigel be that night-time will almost rival daytime for days to weeks.
Hanging from the belt of Orion is his sword, marked by a vertical line of faint stars. To see these better, look slightly to either side, rather than staring straight at them. This “averted vision” trick can be used whenever you are looking at something faint.
A pair of binoculars will reveal an even better view, a wispy cloud-like structure in which the faint stars appear to float. This is a stellar nursery-ground and the wispy clouds, or nebulae, are the feedstock for stars which are being born right now.
The light from those causes the nebula to glow. Another stellar nursery can be seen to the top right of Orion, a group of stars called the Pleiades, or Seven Sisters.
December hosts the shortest day of the year, the Winter Solstice. This year it occurs on the 21st when the day is 7 hours, 45 minutes and 38 seconds long (sunrise to sunset). The second-shortest day is December 20, three seconds longer! The latest sunrise of the year is January 1, at 8:41am, while the earliest sunset is on December 12 at 16:43.
Keep an eye out for the Geminid meteor shower which peaks on the night of 13th and morning of 14th. The full moon of 14th, which is the third supermoon of 2016, will make it difficult to see all but the brightest meteors.
Nevertheless, the Geminids have traditionally produced many bright meteors, and given their unpredictable nature you could be very lucky!
Meteors are best seen with the unaided eye and can appear anywhere in the sky.
Jupiter is a beautiful morning object all month long, almost due south at 7am. You really can’t miss it.
DID YOU KNOW?
The largest diamond ever found is actually a star in the constellation Centaurus, called a white dwarf. BPM 37093 (or “Lucy” as it is affectionately called) would equal a diamond of 10 billion trillion trillion carats.
