• Mel Hulbert

What’s in the Sky - December 2020

Moon Phase:

Last Quarter 8th

New Moon 15th

First Quarter 22nd

Full Moon 30th


Summer Solstice: 21st


Planets:

Evening Sky

Jupiter & Saturn are in the western sky after sunset and start the month in the constellation of Sagittarius. Mid-month they move into Capricornus.

Mars is high in the northern sky after sunset in the constellation of Pisces.

Morning Sky

Venus is low in the eastern sky just before sunrise in the constellation Libra. The brilliantly shining planet will then move into the constellation Scorpius just after mid-month and then a few days later into Ophiuchus.


Worth a Look:

13th: The waning crescent Moon and Venus are side-by-side in the early morning twilight. May make for some interesting widefield images.

17th: In the western sky after sunset the 3-day old waxing crescent Moon joins Jupiter and Saturn in the western sky after sunset. Jupiter and Saturn are 0.5 degrees apart and from Jupiter to the Moon’s northern cusp is 0.3 degrees. This should make for some lovely widefield images and definitely worth a look!

21st: Jupiter and Saturn are at their closest, a mere 0.1 degrees apart. It is a rare opportunity to see both planets in the same field of view through a telescope, with both planets only meeting in the sky (as seen from Earth) every 18 to 20 years. Definitely worth a look through a telescope or binoculars. Great opportunity for telescopic and widefield imagers alike!


Meteor Showers:

13th-14th: The Geminids are one of the best annual meteor showers. While most meteors showers originate from the debris left by comets, the Geminids are unusual in that they originate from 3200 Phaethon, an asteroid (or possible “rock-comet”) [1]. When the Earth passes through the trail of particles left by 3200 Phaethon, we see lots of meteors appearing to come from the one area of the sky. This is called the radiant and each shower is named after the constellation or bright star near which the radiant appears. In this case it’s the constellation of Gemini and the radiant is near the bright star Castor, one of the twins heads.

The best time to observe any meteor shower is after midnight, usually a few hours before dawn and in dark skies away from city lights if possible. The Geminids are active from the 4th to the 17th of December, with the peak on the morning of the 14th here in Australia. Predictions suggestion an hourly rate of 150 meteors, though keep in mind that this is a prediction and that activity can vary from year to year. With New Moon on the 15th, the early morning hours will be free from moonlight – perfect observing conditions! The Geminids often produce bright, medium speed (35km/s) and provides a good opportunity for both visual observers and widefield imagers. It will take patience and a wide angle lens with short continuous exposures to capture a meteor or two!


You can download a star map for December here.

Clear Skies!


References:

[1] NASA Science, Solar System Exploration, In Depth. (2019, December 19). Retrieved November 22, 2020, from https://solarsystem.nasa.gov/asteroids-comets-and-meteors/meteors-and-meteorites/geminids/in-depth/

Dawes G., Northfield P., Wallace K. (2019). Astronomy 2020 Australia, Quasar Publishing.

Lomb, N. (2019). 2020 Australasian sky guide. Ultimo, NSW: Museum of Applied Arts and Sciences Media.