Skywatch December 2016

Skywatch December 2016

Planets in December 2016

Venus: queen of the sunset sky

Venus maintains the role it has had all fall as a blazing beacon in the west sky at dusk. In early December Venus shines at minus 4.2 magnitude, and is about 1/3 of the way up in the western sky as it gets dark; in early December it sets around 8:45 p.m. By the end of December, Venus is nearly halfway up in the west at dusk, shines at minus 4.2, and sets quite late, about 9:20 p.m.

Mercury hangs out below Venus

For the first two weeks of December, Mercury behaves remarkably consistently for such a fast-moving planet. Look for Mercury at dusk about six degrees (the width of three fingers) above the western horizon; the elusive planet emerges around 6:15 p.m. and sets by 6:50 p.m. Spotting the planet will be easier in the first week of the month, since Mercury is a brilliant minus 0.4 magnitude for the first week of December. The planet remains brighter than 0 magnitude through the 14th; after that, it will be harder to see it Mercury, as the planet fades quickly mid-month. By the 21st, Mercury will have faded to 1.2 magnitude, and barely emerges from twilight before it sets.

Mars consistent but fading

Like Venus this month, Mars holds steady in December; Mars emerges halfway up in the southwest at dusk and sets just after 10 p.m. That said, Mars seems infinitely fainter than Venus. The red planet continues its slow fade from its springtime glory, dropping from 0.6 magnitude in early December to 0.9 at the end of the month.

Lineup of the three rocky worlds and one crescent moon

Mercury, Venus and Mars can all be seen in the west at dusk in the early part of December; the tricky part is catching the lowest planet, Mercury, before it sets at 6:45 p.m. Venus can be your guide to the others, since it’s so bright. In early December, find Venus first; then look about 20 degrees above Venus for the pale amber spark of Mars, and 20 degrees below Venus for the bright dot of Mercury. By mid-month Venus appears closer to Mars than Mercury, but is still a great guide for locating the other two planets.

Look for the crescent moon to the lower right of Venus, and just above Mercury, around 6:30 p.m. on December 1. On the following night, the moon will be beside Venus; and on the 4th, the moon stands to the lower right of Mars.

Jupiter in the morning

Jupiter, sole dawn planet this December, comes up at 3 a.m. early in the month and is halfway up in the east at daybreak.  By end of month, the king of the planets rises at 1:20 a.m. at is 2/3rds of the way up in the east at dawn. The planet shines at minus 1.8 magnitude: brighter than any star, but heading for much brighter times in the late winter, when it will shine at minus 2.4.

Saturn returns, barely

Saturn left our evening skies in mid-November and pops into the morning sky at the very end of December. The Ringed Planet rises in the east at 5:45 a.m. on December 31, about 45 minutes before dawn washes it away.

Other sky events in December

The Southern Cross returns

The Southern Cross, or Crux, missing as always from our skies from July through November, returns to our skies in early December. This compact Roman Cross of a constellation rises in the south southwest right at daybreak on December 1; by mid-month you’ll have an hour to find it from the time the cross rises at 5 a.m. to daybreak at 6:15 a.m. Prospects are much better by the last days of December; Crux rises in the south southeast at 4 a.m. and is due south as day breaks at 6 a.m.

The third supermoon of 2016 is an ‘un-supermoon’

The ‘super’ full moon of November 13-14 was in fact the closest full moon since 1948. On the night of November 13 we had about 300 people attending planetarium shows at Bishop Museum and trying to catch views of the bright moon; though from our Kalihi campus, the moon took its own sweet time clearing a pile of clouds in our eastern sky.

While the full moon of December 13 is still being referred to as a supermoon, it’s barely in the club! The term ‘supermoon’ is a recently-coined term that refers to a full moon that occurs within 24 hours of perigee, which is that moment when the moon is closest to earth in its monthly orbit. A moon is officially ‘full’ when the sun, earth and moon are in a straight line, with the earth in between the two other celestial bodies. This December, the moon will be full at 2:06 p.m. on December 13, Hawai‘i Standard Time. However, perigee occurs some 25 hours earlier than the moment of the full moon, at 1 p.m. on December 12 HST. So actually by the technical definition (coined by astrologer Richard Nolle in the 1970s), this December 13 full moon is outside of the club by one hour, since it occurs 25 hours after perigee. That said, the moon will be a little brighter than a normal full moon.

Geminids meteor shower

That full moon does, unfortunately, occur right at the time of the Geminid meteor shower. The peak nights of this famous shower are the nights of December 12-13 and 13-14, from 12:01 a.m. to dawn each night.

For all meteor showers, the viewing will be better after midnight. These repeating annual events are caused as the earth enters into debris left over from a specific comet (or, in the case of the Geminids, debris from an asteroid, 3200 Phaeton). As the earth goes around the sun, our planet runs into the same debris at the same time each year. This is why these showers occur at the same time each year. After midnight, the part of the earth that you are on is facing toward the debris that causes the meteor shower. This is why all meteor showers are better after midnight.

Meteor star showers are named for the constellation where the meteors appear to come from. By midnight in mid-December, the constellation of the Gemini is high in the east. That said, don’t just look east – scan the entire sky for shooting stars. To view shooting star showers, just find a dark location (as little city light as possible) and get comfortable (a lawn chair is a good idea). It’s still worth the effort this year, even if a semi-supermoon will make it challenging to see all but the brightest streaks of light.

December 21

Winter starts at 12:45 a.m. Hawai‘i Standard Time on December 21 (10:45 Universal Time on December 21). This is the shortest day of the year in the northern hemisphere; though in our tropical location, we still get nearly 11 hours of daylight on this day.

December Sky Map

Like all of our monthly maps, this one is good for 10 p.m. on the first day of the month, 9 p.m. for the middle of the month, and for 8 p.m. at the end.

Moon phases (Hawaiian Time zone):

New: November 29, December 28
First Quarter: December 6
Full: December 13
Third Quarter: December 20

At the Bishop Museum dome:

  • We debuted our Christmas laser light show Laser Holidays on Friday November 25. Laser Holidays was our post popular laser show when we rented a system last year, and has returned at 11:30 a.m. and 2:30 p.m. daily (except Christmas Day) through the end of December.
  • Stars and Guitars continues on the first and third Saturdays at 8 p.m. (December 3 and 17) with live classical guitar music interspersed into the show. This December we’ll also be adding some laser effects to the Stars and Guitars experience!

Reservations and more information:

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2017-06-05T12:04:37+00:00Monthly Astronomy Article|