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Dec
12
Sat
Venus 0.8°S of Moon (13:40 MST).
Dec 12 all-day
Dec
13
Sun
Geminid Meteor Shower.
Dec 13 all-day

Geminid Meteor Shower

Next period of activity: December 4th, 2020 to December 17th, 2020

Peak: Dec 13-14, 2020 – the Moon will be 0.2% illuminated.

The Geminids are usually the strongest meteor shower of the year and meteor enthusiasts are certain to circle December 13 and 14 on their calendars. This is the one major shower that provides good activity prior to midnight as the constellation of Gemini is well placed from 22:00 onward. The Geminids are often bright and intensely colored. Due to their medium-slow velocity, persistent trains are not usually seen. These meteors are also seen in the southern hemisphere, but only during the middle of the night and at a reduced rate.

Shower details – Radiant: 07:28 +32.2° – ZHR: 150 – Velocity: 22 miles/sec (medium – 35km/sec) – Parent Object: 3200 Phaethon (asteroid)

Data from the American Meteor Society.

Interactive animation from MeteorShowers.org.

Dec
14
Mon
New Moon (09:17 MST).
Dec 14 all-day

New Moon

By the modern definition, New Moon occurs when the Moon and Sun are at the same geocentric ecliptic longitude. The part of the Moon facing us is completely in shadow then. Pictured here is the traditional New Moon, the earliest visible waxing crescent, which signals the start of a new month in many lunar and lunisolar calendars.

Moon overview on solarsystem.nasa.gov

Total Solar Eclipse, Southern Chile and Argentina.
Dec 14 all-day
Dec
19
Sat
Mercury at Superior Conjunction.
Dec 19 all-day
Dec
21
Mon
Jupiter 6′ of Saturn (11:20 MST)
Dec 21 all-day

At 11:20 MST Jupiter and Saturn will be in an extremely close conjunction, separated only by 6 minutes of arc, i.e., 1/5 moon’s diameter. It will be quite a treat because it will be possible to observe both planets at the same time, and not just with binoculars but also with most professional telescopes!

Do not miss this spectacle because it will not repeat until March 15, 2080. The moment of the closest approach is during the daytime in the USA but the conjunction will be impressive the nights before and after December 21.

Johannes Kepler observed a similar conjunction on July 16, 1623, when the separation of the two great gas giants was 5 arcmins.

Winter Solstice (03:03 MST).
Dec 21 all-day
Dec
22
Tue
Ursids Meteor Shower.
Dec 22 all-day

Ursids Meteor Shower

Next period of activity: December 17th, 2020 to December 26th, 2020

Peak: Dec 21-22, 2020 – the moon will be 52% illuminated.

The Ursids are often neglected due to the fact it peaks just before Christmas and the rates are much less than the Geminds, which peaks just a week before the Ursids. Observers will normally see 5-10 Ursids per hour during the late morning hours on the date of maximum activity. There have been occasional outbursts when rates have exceeded 25 per hour. These outbursts appear unrelated to the perihelion dates of comet 8P/Tuttle. This shower is strictly a northern hemisphere event as the radiant fails to clear the horizon or does so simultaneously with the start of morning twilight as seen from the southern tropics.

Shower details – Radiant: 14:28 +74.8° – ZHR: 10 – Velocity: 20 miles/sec (medium – 32km/sec) – Parent Object: 8P/Tuttle

Data from the American Meteor Society.

Interactive animation from MeteorShowers.org.

Dec
24
Thu
Moon at Apogee (09:32 MST).
Dec 24 all-day
Dec
29
Tue
Full Moon (20:28 MST).
Dec 29 all-day

Full Moon. Rises at sunset, high in the sky around midnight. Visible all night.

Moon overview on solarsystem.nasa.gov