Find out what to go out and look at this month

Planets:

Mercury will join Venus, Jupiter and Saturn in the evening this month. Mercury will appear low in the South West in the constellation of Sagittarius (The Archer) during the last week of the month. Venus can also be found in the Western early evening sky in the constellation of Ophiuchus (The Serpent-Bear) at the start of the month and will quickly move into the constellation of Sagittarius (The Archer) during the first week of December and will remain in that constellation for the rest of the month. Mars will appear low in the early morning Eastern sky in the constellation of Libra (The Scales) late in the first week of December. It’ll move into the constellation of Scorpius (The Scorpion) in the middle of the month and then into the constellation of Ophiuchus (The Serpent-Bearer) for the last week.

Jupiter can be found in the high in the west during the evening in the constellation of Aquarius (The Water-Bear). At the beginning of the month, Jupiter will set at 00:07 am (AWST) and by the end of the month, Jupiter will set at 10:20 pm (AWST). Saturn can be found near Jupiter in the constellation of Capricornus (The Sea-Goat). At the beginning of the month, Saturn will set at 11:11 pm (AWST) and by the end of the month, Saturn will set at 09:22 pm (AWST).

Uranus can be found in the evening sky in the constellation of Aries (The Ram). At the beginning of December, Uranus will set at 03:38 am (AWST) and by the end of the month, it’ll set at 01:37 am (AWST). Neptune will be viewable as well in the evening between the constellation of Aquarius and the constellation of Pisces (The Fish). At the start of December, Neptune will set at 01:17 am (AWST) and by the end of the month, it’ll set at 11:16 pm (AWST).

Venus, Jupiter and Saturn on the 15/12/21 at 08:00 pm. Image Credit: Stellarium
Mars on the 15/12/21 at 04:00 am. Image Credit: Stellarium
Uranus and Neptune on the 15/12/21 at 09:00 pm. Image Credit: Stellarium

Conjunctions and Occultations:

Conjunctions involve object(s) in the Solar System and/or more distant objects, such as a star. It’s an apparent phenomenon in which multiple objects which aren’t close together appear close in the sky and it’s caused by the observer’s perspective. An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer.

  • 01/12/21 – Conjunction of the Moon and Spica (Where to look)
  • 06/12/21 – Alignment of the Moon, Venus, Jupiter and Saturn (Where to look)
  • 07/12/21 – Conjunction of the Moon and Venus (Where to look)
  • 08/12/21 – Conjunction of the Moon and Saturn (Where to look)
  • 09/12/21 – Conjunction of the Moon and Jupiter (Where to look)
  • 18/12/21 – Conjunction of the Mars and Acrab (Where to look)
  • 19/12/21 – Conjunction of the Moon and Elnath (Where to look)
  • 22/12/21 – Conjunction of the Moon, Castor and Pollux (Where to look)
  • 29/12/21 – Conjunction of Mercury and Venus (Where to look)
  • 30/12/21 – Conjunction of the Mars and Zubenelgenubi (Where to look)

Astronomical Events This Month:

Total Solar Eclipse:

On Saturday the 4th of December, the Moon will pass between the Earth and Sun and cause a Total solar Eclipse for a small region of Antarctica turning day into night for a few minutes. This Total Solar Eclipse, the last eclipse of 2021 will be viewable in Victoria and Tasmania as a Partial Solar Eclipse and will start at 07:34 pm (AEDT) in Hobart and at 07:53 pm (AEDT) in Melbourne. From Hobart, at its maximum, the eclipse covers 21% of the Sun, while from Melbourne it’ll cover only 7 per cent. From both cities, the eclipse ends at sunset and unfortunately, we’ll miss it here in Perth.

The moon partially obscures the sun during the total solar eclipse of Aug. 21, 2017. Image Credit: Bill Ingalls
December's Partial Solar Eclipse viewing map. Image Credit: timeanddate.com
Types of Solar Eclipses. Image Credit: timeanddate.com

WARNING: Please for the love of God don’t look directly at the Sun even during an Eclipse, You WILL lose your eyesight.

The Geminids Meteor Shower:

The Geminids are THE meteor shower to see in the southern hemisphere and on the night of the 14th and 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 and there is a great window to view the meteors without the Moon brightening the sky on Wednesday the 15th of December after 02:30 am. You should be able to see 30 to 50 meteors per hour in dark locations around Western Australia. If you’re in locations around the equator where the Gemini constellation is high in the sky, you should see up to 120 meteors per hour. 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.

When looking at Gemini try to look about 30 to 45 degrees left or right of the constellation. This is because the meteors aren’t necessarily coming from the Gemini constellation, but if you trace the meteor streaks that occur back to their radiant point it’s the Gemini constellation.

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 the 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 15/12/21 at 02:00 am. Image Credit: Stellarium
2012 Geminids taken from Perth Observatory. Image Credit: Perth Observatory volunteer Roger Groom
3220 Phaethon's Orbit the course of the Geminids meteor shower. Image Credit: Astronomy.com
Comet A1 Leonard:

Comet A1 Leonard (C/2021 A1 Leonard) an inbound long-period comet is brightening and might become 2021’s brightest comet in mid-December. The Astronomer Gregory Leonard, working at the Mount Lemmon Observatory near Tucson Arizona discovered the comet on the night of January the 3rd 2021. The first long-period comet of the year, the discovery was exactly one year to the day prior to perihelion. The comet at the time was 5 astronomical units away (about the distance of Jupiter from the Sun) and its brightness was mag +19 when he discovered it. Early indications had hinted that the comet might prove to be something special at the end of 2021.

The comet is on an 80,000-year retrograde orbit and unfortunately, this is its last orbit around the sun as it’s due to be ejected from the solar system after this perihelion passage where it’ll be 0.62 AU from the Sun and just inside Venus’s orbit on the 3rd of January 2022. The comet had reached its aphelion at a distance of 3,500 AU in the Oort Cloud about 35,000 years ago.

Current predictions have the comet reaching mag +4, and it’s looking like it could flirt with naked-eye brightness. The comet passes Earth at a distance of 34.9 million kilometres on the 12th of December (Mag +4.22). Our best chance to see it in Perth will be on the 16th and 17th of December as it arrives in the Southern Hemisphere’s sky and at the moment, it’s predicted to be Mag +4.38 on the 16th and Mag +4.5 on the 17th so it keeps to the predictions it should be a binocular comet at least. To see Comet Leonard on the 16th and 17th of December, you’ll need to look very low in the west below Venus (See map) after 8 pm and you’ll have 40 minutes to see it before it sets for the night.

Dave Dickson from Universe Today has noted that another intriguing effect may also come into play during the December apparition of the comet with the Sun-Earth-Comet phase-angle for the tail sitting at greater than 120 degrees from December 9th to December 22nd and reaching a maximum of 160 degrees on December 14th just after it passes closest to the Earth on December 12th. This sets up conditions ideal for a possible surge in brightness, adding the brightness of the tail to the coma of the comet itself.

Please Note: Cometary behaviour is difficult to predict by nature and the ability of comets to either disappoint or pleasantly surprise us, is one of many things that make them so interesting.

C/2021 A1 (Leonard). Image Credit: José J. Chambo
C/2021 A1 (Leonard) path in Perth's sky during December at 8:15 pm. Image Credit: Stellarium
C/2021 A1 (Leonard) position in the Solar System on the 16/12/21. Image Credit: astro.vanbuitenen.nl
The December Solstice:
The Earth's position around the Sun at Solstices and Equinoxes. Image credit: Almanac.com

The December Solstice occurs on Tuesday the 21st of December at 11:58 pm (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 occuring on the 20th of December in 2080.

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).

Things to Look at This Month:

The Pleiades:

The Pleiades star cluster, also known as Messier 45, the Seven Sisters and in Japan as Subaru, is a very young Open Star Cluster. The cluster contains hundreds of stars, of which only a handful are commonly visible to the unaided eye. The stars in the Pleiades formed together in a nebula around 100 million years ago and are 425 light-years away from our Solar System. In our skies, the Pleiades appear to the left of the Taurus Constellation and they are best viewed through binoculars or a wide-field Telescope.

The Pleiades on the 15/12/21 at 09:00 pm. Image Credit: Stellarium
The Pleiades - Image credit: Wiki Commons
The Orion Nebula:

The Orion Nebula is a diffuse nebula situated north of Orion’s Belt (In the southern hemisphere) in the constellation of Orion. It is one of the brightest nebulae in our skies and is visible to the naked eye. Messier 42 as it’s also called, is located at a distance of 1,344 light-years away from our Solar System and is estimated to be 24 light-years across. The nebula has revealed much about the process of how stars and planetary systems are formed from collapsing clouds of gas and dust.

Orion Nebula on the 15/12/21 at 09:00 pm. Image Credit: Stellarium
The Orion Nebula - Image credit: wallpaperswide.com
Tarantula Nebula:

The Tarantula Nebula is an Emission Nebula that isn’t even located in our galaxy, but in one of our galaxies satellite galaxies, the Large Magellanic Cloud. The Nebula is some 160,000 light-years away from our Solar System and is 300 light-years across. This Nebula is an extremely luminous object, its luminosity is so great that if it were as close to Earth as the Orion Nebula, the Tarantula Nebula would cast shadows and take up 60% of the horizon. It’s is the most active starburst region known in the Local Group of galaxies, this is because the nebula resides on the leading edge of the Large Magellanic Cloud where ram pressure is stripping, and the compression of the interstellar medium likely resulting from this, is at a maximum.

Tarantula Nebula on the 15/12/21 at 09:00 pm. Image Credit: Stellarium
Tarantula Nebula. Image Credit: Peter Ward (Barden Ridge Observatory)
47 Tucanae:

47 Tucanae or NGC 104 is the second-largest and second brightest globular cluster in Milky Way. The Globular cluster is 16,000 light-years away from us and is located in the constellation Tucana (Named after the Tucan bird) and it’s a naked eye ‘star’ and visible in binoculars as a ‘fuzzy blob’. Omega Centauri contains at least 1 – 2 million stars and the cluster has a diameter of roughly 120 light-years and the stars are roughly 10 billion years old. The average distance between the stars in the centre of the cluster is around 10% of a light-year or more than 100 times the diameter of our solar system. In February 2017, indirect evidence for a likely intermediate-mass black hole in 47 Tucanae was announced.

47 Tucanae on the 15/12/21 at 09:00 pm. Image Credit: Stellarium
47 Tucanae. Image Credit & Copyright: Mike O'Day

Phases Of The Moon:

December 2021 Moon phases