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What’s In December’s Night Skies

Planets

Mercury will be visible very low in the Eastern sky just before sun rise for the first three week of the month, but it’ll then enter the Sun’s glare and move below the horizon. Mars can also be found in the low in the Eastern sky in the Constellation of Libra (The Scales) before sunrise. In the early morning of the 13th of December, Mars can be seen within a Moon’s width of the star Zubenelgenubi. Zubenelgenubi is actually a double star, but you’ll need at least a set of binoculars to see the faint companion star.

Venus, the closest thing in our Solar System to hell and also Earth’s twisted sister continues to be easily viewable in the west at sunset. The planet will move from the Constellation of Sagittarius (The Centaur Chiron) to the Constellation of Capricornus (The Sea Goat) in the second half the December. Jupiter can be found below Venus in December, but it’ll enter the Sun’s glare and below the horizon in the second week of the month. Saturn can be found near Venus in December, with Saturn passing Venus on the 10th and 11th of December with a separation of two degrees.

Uranus will be viewable in the early evening in between the Constellations of Pisces (The Fish), Cetus (The Sea Dragon) and Aries (The Ram). At the start of December, the planet will set at 3:14 am and by the end of the month it’ll set at 01:15 am (AWST). The last planet in the Solar System, Neptune will be viewable in the early evening in the Aquarius (The Water Bearer) Constellation. At the start of December, the planet will set at 1:04 am and by the end of the month it’ll set at 11:10 pm (AWST).

Mars on the 15/11/19 at 03:30 am. Image Credit: Stellarium Venus and Saturn on the 15/12/19 at 08:30 pm. Image Credit: Stellarium
Uranus on the 15/12/19 at 09:00 pm. Image Credit: Stellarium Neptune on the 15/12/19 at 09:00 pm. Image Credit: Stellarium

Conjunctions and Occultation

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.

Astronomical Events This Month:

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 a two-week period from the 4th of December to the 17th of December and unfortunately for this year, there is a Full Moon close to the radiant point for the shower so you’ll get to see anywhere from 10 to 30 meteors per hour in dark locations around Perth. If you’re travelling, in locations around the equator where the Gemini constellation is high in the sky you’ll see 40 to 70 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 which were first discovered in 1862 and 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 tail or surface jets. The Gemini Constellation after which the meteor shower is named after appears in our sky around 22:00 pm so it’s best to go out and watch for them after midnight when Gemini is a higher in the sky as the shower gets better throughout the night.

Geminids Meteor Shower on the 15/12/19 at 02:00 am. Image Credit: Stellarium 2012 Geminids taken from Perth Observatory. Image Credit: Perth Observatory volunteer Roger Groom 3200 Phaethon's orbit. Image Credit: vox.com
The December Solstice

The December Solstice occurs on Sunday the 22nd of December at 12:19 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 fall on the 21st and the 22nd of December until 2043 and will start occasionally falling 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).

The Earth's position around the Sun at Solstices and Equinoxes. Image credit: Almanac.com

Boxing Day Annular Solar Eclipse:

On Thursday the 26th of December, the Moon passes between the Earth and Sun and will almost completely eclipse the Sun for a small region on the Earth between 10:29 am (AWST) and 04:05 pm (AWST). This is called an Annular Solar Eclipse and what happens is the Moon covers the Sun’s center, leaving the Sun’s visible outer edges to form a “ring of fire” or annulus around the Moon. Unfortunately, Perth we’ll miss out on this Annular Solar Eclipse as the path will start in Saudi Arabia and moves through India, Singapore and parts of Indonesia and Malaysia. It won’t be all bad for us in Australia, as if you’re any where north of Gingin here in Western Australia or north of Mackay in Queenland you’ll be able to see some form of Partial Solar Eclipse. The best place in Australia to be for this Eclipse will be Darwin in the North Territory where the Moon will cover 43% of the Sun at 04:03 pm (ACST)

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

An Annular Solar Eclipse. Image Credit: Universetoday.com Annular Solar Eclipse viewing map. Image Credit: timeanddate.com Types of Solar Eclipses. Image Credit: timeanddate.com

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 15/12/19 at 09:00pm. 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 15/12/19 at 09:00pm. Image Credit: Stellarium The Orion Nebula - Image credit: wallpaperswide.com
Winter Albireo:

Winter Albireo (H3945 and SAO173349) is a visual double star in the constellation Canis Major and is named by Sir John Herschel (son of Sir William) and sometimes referred to as “Herschel’s Lovely Double” or the “Southern Albireo”.

This is not a binary system, but two stars on the same line of sight. The primary star HIP35210 is a Supergiant, ‘citrus orange’ in colour and magnitude at +4.8 is much further away at ~6523 light years away compared to its companion star HIP35213 which is a ‘royal blue’ coloured star which at a distance of ~258 light-years away and magnitude +6.0. Both stars are actually close double stars themselves with narrow separation, not visible in our modest telescopes.

The orange star is a Supergiant over twice the diameter of Betelgeuse with a diameter of 2.6 billion km. It would encompass the orbit of Jupiter if in place of our Sun. It is also ~365,000 times brighter than the sun because of its size, however, it has a much cooler surface temperature of ~3 300 K.

The secondary star is a much smaller main sequence star at ~2.9 times the diameter of the sun and ~22 times the brightness with a much higher surface temperature of ~7 300K.

Winter Albireo on the 15/12/19 at 09:00pm. Image Credit: Stellarium Winter Albireo - Image credi: cs.astronomy.com
Tarantula Nebula:

The Tarantula Nebula is an Emission Nebula which 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 15/12/19 at 09:00pm. Image Credit: Stellarium Tarantula Nebula - Image copyright: Roger Goom - astrophotography.com.au
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 Constellation Tucana (Named after the Tucan bird) and it’s a naked eye ‘star’ and clearly 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 at the centre are 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 15/12/19 at 09:00pm. Image Credit: Stellarium 47 Tucanae. Image Credit & Copyright: Mike O'Day

Phases of The Moon:

December 2019 Moon phases

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