Astronomically speaking, 2021 was a great year so far. We had four supermoons, the century’s longest partial lunar eclipse, planet parade in August, and the triple conjunction of Mercury, Jupiter, and Saturn in January. But the year is all set to end on a great note as December has some exciting events in store for us. Here are all the astronomical events that you should not miss this month.
Having one of these space apps will help you quickly locate celestial objects such as comets and planets.
December 3: Conjunction of Moon and Mars
The Moon will pass just 0°41′ to the North of Mars in the constellation of Libra. Look for them above the south-eastern horizon about an hour before sunrise.
December 4: Total Solar Eclipse
The total solar eclipse of December 4 will be the last eclipse of the year, following the partial lunar eclipse of November 18. It will last for about four hours and will be mainly seen over Antarctica. People located at the southernmost tips of South America, Africa, and Oceania will experience the partial phases. Here’s the complete map of the eclipse.
December 6: Comet Leonard
On January 3 this year, Senior research specialist Greg Leonard at Mt. Lemmon Observatory discovered a faint speck. The 19th magnitude speck was an incoming comet, now called A1 Leonard (or simply comet Leonard). This comet will pass the closest to the Sun, its perihelion, on January 3, 2022, exactly a year after its discovery. But before that, comet Leonard is all set to decorate the skies of the Northern Hemisphere and will be visible with naked eyes.
Comet Leonard’s apparent magnitude will fall below +6 in the first week of December. It is currently predicted to peak at +4. December 6 is one of the best days to see the comet because of its proximity to the fourth brightest star in the night sky, Arcturus.
All you have to do is wake up early in the morning — about 90 minutes before the sunrise — and look east. First, try to locate Arcturus in the Bootes constellation. An easy way is to look for Ursa Major and extend its arc of stars, as shown above. The first bright star you spot along the extended arc is Arcturus (Remember the ‘arc to Arcturus’). Look to the left of this star, and you will have an excellent chance to see comet Leonard.
The reason why December 6 is a perfect date is because of its vicinity to Arcturus. Even those who don’t know much about the night sky can have a ‘reference point’ to locate the comet. If you have any difficulty in locating Arcturus, you can try one of these space apps.
December 7: Venus at its greatest brightness
Venus will reach its greatest brightness in its 2021 evening apparition. At an apparent magnitude of -4.7, Venus is the brightest speck of light at dusk in the southwest.
December 8-9: Moon, Jupiter, and Saturn
The waning Moon will pass close to Jupiter and Saturn on December 8 and 9.
December 12: Comet Leonard at perigee
The comet is moving at an impressive speed of ~254,000 km/hr. It’s so fast that it will change its position every day with respect to the background stars. As the month progresses, comet Leonard will travel closer to the horizon, and each day, it will become trickier to spot it. Finally, on December 12, A1 Leonard will pass the celestial equator Southward and pass 0.233 AU from the Earth — its closest approach to our planet. By now, the comet will be close to the Sun, as seen from the Earth, and won’t be easily visible.
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December 13: Comet Leonard becomes an evening object
December 12 will be the last day when comet Leonard can be seen in the morning sky. After that, it will switch to an evening object, lying at the western horizon at dusk. Around this time, the comet will top out at a magnitude of +4. Observers in the Southern Hemisphere now have a chance to spot the fading comet in the coming days.
December 14: Geminid meteor shower
The best meteor shower of the year will be active between Dec. 6 and 19, reaching its peak on December 13-14. The radiant of the Geminids lies in the constellation of Gemini. Annual meteor showers occur when the Earth passes through the stream of debris left in the wake of a comet or an asteroid. The parent body associated with the Geminid meteor shower is Asteroid Phaethon. You can expect up to 120 bright meteors per hour flying at a speed of 34 km/s.
The Geminids are particularly noted for their colors compared to the other meteor showers. 65% white, 26% yellow, and the remaining 9% are blue, red, and green. The Geminid meteor shower is one of the three major meteor showers of a year, the others being the Quadrantids and the Perseids.
Residents of the Northern Hemisphere can watch the shower soon after dusk. They remain active till dawn. However, the best displays of the shower are produced a couple of hours after midnight. In the Southern Hemisphere (Sydney), the Geminids don’t appear until about 11 p.m. and then on the horizon.
December 17: Comet Leonard and Venus
On December 17, about 30 minutes after sunset, A1 Leonard will be located below planet Venus. You will need access to very clear horizons to see comet Leonard near Venus. The following day, the comet will pass just 0.028 AU (4.2 million km) from Venus, probably creating a Venusian meteor shower.
December 19: Full Moon
On December 19, the Moon will reach its full phase for the last time in 2021. The Full Moon of December is also called the Cold Moon or the Long Nights Moon.
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December 19: December Leonis Minorid Meteor Shower
The December Leonis Minoris takes place within the boundaries of the constellation of Leo Minor between Dec. 5 and Feb. 4. It peaks on Dec. 20 every year. You may see up to 5 meteors per hour flying at a speed of 64 km/s.
December 21: The Winter Solstice
The Sun will shine directly over the Tropic of Capricorn for the first time this year. The December Solstice marks the first day of winters in the North and the first day of summers in the South. December 21 is the shortest day (longest day) in the north (south). From here on, days will start getting longer in the northern hemisphere, equaling the duration of nights on the Spring Equinox day.
December 22: Ursid Meteor Shower
The last meteor shower of 2020 will peak on December 22. The Ursids take place within the boundaries of the constellation of Ursa Minor between Dec. 17 and Dec. 25 and peak on Dec. 22 every year. The source of the meteor shower is believed to be Comet 8P/Tuttle. You can see up to 10 bright meteors per hour at a speed of 33 km/s.
December 2021 Planet Round-Up
Mercury recently passed behind the Sun and will remain hidden in its glare this month. It might become visible by the end of the month but will remain close to the horizon.
Venus rules the evening sky in the southwest. Its magnitude of -4.7 makes it the second brightest object in the sky at dusk. Don’t miss the conjunction of Venus with comet Leonard on December 17 and its alignment with Jupiter and Saturn throughout the month.
Mars recently passed behind the Sun and is tricky to observe in the southeast at dawn.
Jupiter was at opposition in August and hence it becomes visible as the dusk sky fades to darkness. Look for it in the south/southwest after sunset.
Saturn shines along with Jupiter in the southwest. The ringed planet is the fainter of the two.
Uranus was at opposition on November 5 as is now well up in the sky in Aries at dusk. You’ll need a telescope to see the planet.
Neptune passed its opposition in September and can be seen through a telescope throughout the night in Aquarius.
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Admin and Founder of ‘The Secrets Of The Universe’ and former intern at Indian Institute of Astrophysics, Bangalore, I am a science student pursuing a Master’s in Physics from India. I love to study and write about Stellar Astrophysics, Relativity & Quantum Mechanics.