Summer started in Australia and New Zealand on December 1, and the nights are most definitely getting shorter. Both countries use the meteorological definitions of the seasons. Other countries use the astronomical definitions which relate to equinoxes and solstices.
Key points this month are not to miss out on the Geminids Meteor Shower and checking out 3 bright planets in the evening sky throughout the month and add Venus in towards Christmas.
December is well known to those interested in the night sky due to the solstice, which this year comes at 8:48am AEDT Thursday December 22nd.
Virtually every culture has celebrated the solstice as a seasonal “turning point. in the North it is a sign that brighter, longer days lie ahead and for the South that the nights will start to get longer.
Wurdi Youang is a stone arrangement site in Wathaurong country in Victoria dates back some 11,000 years ago. The stones were positioned to track the winter and summer solstice with three stones pointing to the summer equinox. Various research over the years has removed the possibility that this formation could have been caused by nature but rather that it portrays a culture that was well-attuned to the timings of the cosmos and could utilize its movements to aid tribal living.
This month is also known for the annual Geminid meteor shower, which peaks on Saturday, December 14th. Ordinarily astronomers can count on the Geminids to give us a pretty good show, maybe one meteor per minute from a really dark location. But this year the Moon is quite bright rising around midnight and setting 10am next day, so its light will wash out the faintest Geminids but it is still worth going out to check in the early hours of December 13/14. You could see up to 120 meteors an hour in a dark sky.
During summer the bright centre of the Milky Way is mostly below the western horizon by now This means we need to look to the south and east to see the cool stuff during the short warm summer evenings.
This is the time to check out the constellation of Orion – also known to us down under as ‘The Saucepan’ with its striking patterns of stars it makes for easy stargazing.
The Pleiades, Taurus, Orion, and his hunting dogs Canis Major and Canis Minor make their welcome return to the evening skies, spawning all manner of mythological tales. Sirius reminds us that it is the brightest star in the night sky, as it marks the collar of Canis Major, the ‘big dog’, while Orion has to negotiate with Taurus, the Bull, if he ever wants to make it with the Seven Sisters by Greek and roman mythology.
In many cultures the Pleiades are seen as seven sisters being pursued, usually by a man or beast. With indigenous Australian’s this is no different. The Warlpiri tribe of central Australia, see the the group of stars as the Napaljarri sisters from one skin group being chased by the Jakamarra man from a different skin group trying to take a wife, forbidden by tribal law.
In many other Australian indigenous cultures, the Pleiades are a group of young girls, and are often associated with sacred women’s ceremonies and stories. The Pleiades are also important as an element of Aboriginal calendars and astronomy, and for several groups their first rising at dawn marks the start of winter.
Western commonalities like The Pleiades don’t stop there. While the indigenous folks look for meaning between the stars in the dark, western cultures look for it in the stars themselves. We do share a common comfort that the stars above us are our loved ones watching peacefully over us.
Venus, Saturn and Jupiter continue their impressive nightly display lined up in the western evening sky.
Since Daylight Saving is in place in New South Wales, Victoria, South Australia, Tasmania, the Australian Capital Territory and Norfolk Island, all times this Month are in AEDT (Australian Eastern Daylight Time).
The Moon this Month
(All times are in Australian Eastern Daylight Time)
First Quarter was at 1 am on the 1st
Full Moon will be on the 8th at 2pm
In the 12th at 10am Moon at apogee (furthest from Earth at 405,869 km)
Last Quarter will be at 7pm on the 16th
New Moon will be at 8pm on the 23rd.
On the 24th at 6pm the Moon will be at perigee (closest to Earth at 358,270 km)
First Quarter will be on the 30th at 11am
The ancient Celts celebrated the summer and winter solstice as the time when the day length started to change. The December solstice occurs at 08:48 AEDT on December 22. At this time the South Pole of the earth will be tilted toward the Sun. The Sun will have reached its southernmost position in the sky and will be directly over the Tropic of Capricorn at 23.44 degrees south latitude. This is the first day of winter (winter solstice) in the Northern Hemisphere and the first day of astronomical summer (summer solstice) in some countries in the Southern Hemisphere
If you have been able to regularly watch the sunrise or sunset (a bit difficult of late in the eastern states with all the rain and cloud) you may have noticed that it rises and sets in a different place each day relative to the horizon. Due to a combination of the Earth’s tilt and orbit, over the course of a year the place against the horizon where the Sun rises and sets moves north, and then south, and back again, and the days where it reaches its maximum and turns around are the solstices. The word ‘solstice’ comes from ancient Latin – sol: sun, sistere: stand still.
On 22 December the Sun has reached its most northern location. Following this, it will then appear to move south a little more each day. It can be a fun little project over the next few months to make a note of where the Sun sets. You don’t have to do it every day, but try it maybe once a week, note where the Sun has set against the horizon and watch it move week after week. You should catch the last of its northern motion before the turning point on the 21st and the subsequent southern motion.
The December solstice is also the day of the year with the most amount of daylight for those in the southern hemisphere, and from here on out the days will get shorter. Note that this doesn’t mean that sunset will be earlier – in fact, it’s still getting later as summer progresses, but the later sunrises each day will start to shave time off the length of the day, making this a maximum length day.
Planets in December
This month’s fun fact about the planets:
Venus is the second planet from the Sun and is Earth’s closest planetary neighbour. It’s one of the four inner rocky planets, and it’s often called Earth’s twin because it’s similar in size and density. These are not identical twins, however – there are radical differences between the two worlds.
Venus has a thick, toxic atmosphere filled with carbon dioxide and it’s perpetually shrouded in thick, yellowish clouds of sulfuric acid that trap heat, causing a runaway greenhouse effect. It’s the hottest planet in our solar system, even though Mercury is closer to the Sun.
Another big difference from Earth – Venus rotates on its axis backward, compared to most of the other planets in the solar system. This means that, on Venus, the Sun rises in the west and sets in the east, opposite to what we experience on Earth.
Venus was the first planet to be explored by a spacecraft – NASA’s Mariner 2 successfully flew by and scanned the cloud-covered world on December 14, 1962.
Mercury is visible the entire month in the western twilight sky. Venus is never too far from Mercury during the month – closest at less than 2° on the 28th to 30th. On the 24th these planets have a impressive encounter with the Moon.
In either conjunction, if you have trouble seeing the planet in the bright sky, try looking for brilliant Venus in binoculars, tis elusive little one will be in the same field. Mercury reaches its greatest elongation of 20° east of the Sun on the 22nd.
Venus appears just a few degrees above the horizon in the western evening dusk, early in the month. The best viewing time is toward the end of December, after it gains a little altitude. Christmas Eve has a pleasant view in store when the very thin crescent Moon (1-day old) is 4° to the left of Venus low in the early twilight sky. Mercury is to the upper right of Venus a similar distance, with all three fitting in a 7° circle – binoculars will help. Venus and Mercury have a close encounter on the 28th to 30th when they appear less than 2° apart.
The Earth is at Solstice on the 22nd, when the days are longest. On this day, the Sun is at most southerly position with a declination of – 23.5°.
Mars rises in the early eastern evening sky in Taurus. Coming to opposition on the 8th, its closest approach to our planet occurs on the 1st. The timing of opposition and closest approach can vary by up to two weeks due to the orbits of Mars and Earth being eccentric and inclined to each other. Its northerly declination of +25° puts it low in the sky form mid-latitude Australians skies, favouring Northern Hemisphere observers- but that’s okay, as it’s always high in the sky south of the equator during the best oppositions.
The Red Planet can be a delight for the casual or serious observer at any time. Being the only planet where amateurs can observe surface detail makes it more Earth-like than all the others. Due to this relatively unfavourable opposition, visual observers will need good optics, steady seeing, and patience to bring out the best of Mars.
Jupiter stands out brilliantly in the north-western sky at the end of evening twilight this month. The gas giant has two visits by the Moon, on the 2nd by the 9-day old waxing gibbous Moon, and on the 29th by the 7-day old waxing crescent Moon – the last is the closest, only 1° from the lunar limb around 11pm AEDT.
Saturn, in Capricornus, is visible in the early western evening sky, setting around 11pm mid-month. Although not really close, the 4-day old waxing crescent Moon to Saturn’s south (left), makes a pleasant summer evening view on the 26th.
Uranus, now past opposition, is in the northern evening sky at the end of astronomical twilight in Aries, transiting the meridian around 9pm mid-month.
Neptune, in Aquarius, comes to the end of five months in retrograde motion on the 4th and appears in the early north-western evening sky at the end of astronomical dusk.
A casual observer may watch the sky at night and see 3 to 5 sporadic meteors per hour. However, on some nights, this number may increase markedly, and on projecting the paths of the meteors back, we find that many appear to radiate from a tiny area in the sky. This point or place is termed the radiant of the meteor shower.
Geminid Meteor Shower
The Geminids visible from December 4th to December 20th are considered to be one of the most spectacular meteor shows of the year, with the possibility of seeing around 120 meteors per hour at its peak, which is on December 13 or 14, depending on your time zone. The waxing gibbous Moon will be a hindrance until after 2 am but from then until dawn the sky will be Moon free.This is the one major shower that provides good activity prior to midnight as the constellation of Gemini is well placed from midnight onward. The Geminids are often bright and intensely coloured. Due to their medium-slow velocity, persistent trains are not usually seen. These meteors are also seen in the southern hemisphere, but only during the middle of the night and at a reduced rate.
The shower owes its name to the constellation Gemini because the meteors seem to emerge from this constellation in the sky. Whereas most meteor showers are associated with comets this one is associated with an asteroid 3200 Phaethon.
The Phoenicids is a southern shower discovered in 1956 during its only known major outburst with rates of around 100 plus. Since then, there have been three minor bursts and some significant activity in 2014; therefore, a shower to keep an eye on, just in case. They are active from November 28 to December 9, with maxima around the 2nd after dusk and before dawn on the 3rd. The Phoenicids’ radiant culminates at dusk, so early evening viewing should provide the best activity. There will be lunar interference all night as it is the day after Full Moon.
The Puppid-Velids are a vast, complex system of southern showers active during November and December. Each radiant is so close that visual observation cannot easily separate them. They are active from December 1-15 and could produce a zenith hourly rate of 10 around the evening of the 7th and morning of the 8th. The Full Moon around the peak this year will spoil any chance of observation.
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