What’s In December’s Skies

By Matt Woods

Planets:

All the planets are visible in the evening sky in December. Mercury and Venus start December in the constellation of Ophiuchus (The Serpent-Bearer) and move into the constellation of Sagittarius (The Archer) in the first full week of the month, and that’s where they’ll be for the rest of the month. Mars can be found in the constellation of Taurus (The Bull) during December. On the 8th of December, it’ll be at opposition, so it’s a great time to go out with a telescope and look at Mars.

Jupiter can be found throughout the night in between the constellations of Cetus (The Sea Monster) and Pisces (The Fish). Saturn can be found in the evening sky in the constellation of Capricornus (The Sea-Goat) and its sets in the evening. Uranus can be found in between the constellations of Aries (The Ram), Cetus, and Taurus. Neptune is near Jupiter again in December. It can be located, in between the constellations of Pisces, Cetus, and Aquarius (The Water Bearer).

Mercury, Venus, Jupiter, Saturn, and Neptune on the 15/12/22 at 08:00 pm. Image Credit: Stellarium Mars, and Uranus on the 15/12/22 at 10:00 pm. Image Credit: Stellarium

Mercury’s greatest elongation in the East on the evening of 21/12/2022. Image Credit: Stellarium

The Geminids Meteor Shower:

The Geminids are THE meteor shower to see in the southern hemisphere and on the night of the 14th/15th of December, they’ll reach their peak. The shower is active for just over two weeks from the 4th of December to the 20th of December. You should be able to see 50 meteors per hour in dark locations around Western Australia, and the best time to see them is around 2:30 am (AWST). The Moon will be around the last quarter phase, so we’ll be dealing with some light pollution in the second half of the night from 11:17 pm (AWST) onwards.

The meteor shower appears to come from the Gemini constellation with the streaks being caused by tiny dust particulars and meteors hitting our atmosphere at tremendous speed and burning up due to the friction. The Geminids were first discovered in 1862 and they occur because The Earth is travelling through the left-over material from the tail of the asteroid 3200 Phaethon, this asteroid is considered a rock comet which is an asteroid that shares some of the characteristics with a comet including a comet tail and it has surface jets. The Gemini Constellation after which the meteor shower is named appears in our sky around 10:00 pm so it’s best to go out and watch for them after midnight when Gemini is higher in the sky as the shower gets better throughout the night.

Geminids Meteor Shower on the 15/12/22 at 02:00 am. Image Credit: Stellarium 2012 Geminids taken from Perth Observatory. Image Credit & Copyright: Roger Groom

The December Solstice:

The December Solstice occurs on Tuesday the 22nd of December at 5:47 am (AWST). This marks the beginning of astronomical summer for the southern hemisphere and the start of winter for the northern hemisphere. This is an exact moment when the Sun’s declination equals 23.5 degrees south as seen from the Earth. The line of latitude where the Sun passes directly overhead during the December solstice is known as the Tropic of Capricorn, although in modern times, the Sun is in the astronomical constellation of Sagittarius in mid-December, thanks to precession.

In the 21st century, the December solstice will occur on the 21st and the 22nd of December until 2043 and will start occasionally occurring on the 20th of December in 2080.

Equinoxes and Solstices. Image Credit & Copyright: timeanddate.com

The December solstice means the southern rotational pole of the Earth is tipped towards the Sun and will now begin its long apparent journey northward again until June. The wobble of Earth’s axis known as the Precession of the Equinoxes takes about 26,000 years to complete one ’wobble.’ Live out an average 72-year life span, and the equinoctial points will have moved one degree (about twice the diameter of a Full Moon).

Celestial Wonder To Look At This Month:

The Rosette Nebula:

The Rosette Nebula (NGC 2244) is an HII nebula located near one end of a giant molecular cloud in the constellation of Monoceros (The Unicorn) region of the Milky Way Galaxy. It also has an open cluster with these 2500 young stars being formed from the nebula’s matter. It’s hard to see the Rosette visually, even in large telescopes, the nebula is an excellent photographic target, and the cluster is a superb sight

The cluster and nebula lie 5,000 light-years from Earth, and it measures roughly 130 light-years in diameter. The radiation from the young stars excites the atoms in the nebula, causing them to emit radiation like a neon sign and this produces the emission nebula we see. The mass of the nebula is estimated to be around 10,000 solar masses. Most of the ongoing star-formation activity is occurring in the dense molecular cloud to the South East of the bubble.

On the 16th of April 2019, the Oklahoma Legislature passed HB1292 making the Rosette Nebula the official state astronomical object. Oklahoma Governor Kevin Stitt signed it into law on the 22nd of April 2019.

The Rosette Nebula on the 15/12/22 at 09:00 pm. Image Credit: Stellarium

NGC 2244

The Rosette Nebula

Image Credit & Copyright: Antonio Ferretti & Attilio Bruzzone