Stargazing in the December Skies

by Cam Wipper, CFHT remote observer

What You Need: Just your eyes! Everything in this guide can be seen with nothing more than your very own eyes. No special equipment required.

Where To Go: We here on the Big Island are blessed with some of the greatest night skies on Earth. You can find many of the targets listed here from your own backyard. Of course, if you live in Waimea, Hilo or Kailua, the lights of your town can make fainter objects more difficult to see. The best locations are those far from light sources. Some of my favourite locations are Pu’u Huluhulu off of Saddle Road (across from the Maunakea Access Road), along Chain of Craters Road in Hawai’i Volcanoes National Park (remember: there is no entrance fee after 8pm— perfect for stargazers) and along Mana Road on the slopes of Maunakea.

Surprisingly, the summit of Maunakea, though unbeatable for telescopes, is not the best site for human observers. Due to the thinness of the air, and resultant dearth of oxygen, at the altitude of the summit, human night vision becomes far less efficient than at altitudes closer to sea level. For this reason, it is best to stargaze no higher than 10,000 feet (3000 m). The Maunakea Visitor Information Station is an example of a site located near this elevation.

December sunrise and sunset times for Waimea
December sunrise and sunset times for Waimea

What To Look For: December is an excellent month for stargazing for a couple of reasons. The first is fairly obvious: long nights. Here in Hawai’i, the relatively long nights of December—with 12 hours of dark time and 13 hours between sunset and sunrise—mean that stargazing is possible in the early evening. The second reason is that the winter sky is, in my opinion, the best sky to stargaze under. The myriad of bright stars and easy-to-spot constellations make it enjoyable for even beginner stargazers.

As we’ve discussed over the past couple months: we have a Supermoon. December’s Supermoon, is the third and final Supermoon of this sequence and it will be roughly on par with the Supermoon in October. Last month’s Supermoon will remain unmatched until 2034!

December Moon phases for Waimea
December Moon phases for Waimea

As mentioned last month, visible in the winter sky is one of the most famous of constellations, the hunter Orion. Early in the month Orion will rise in the east around 7:30pm. By the end of the month, he will be visible as soon as the sun sets. Look for the famous Belt of Orion, a line of three fairly bright stars, rising near vertically. To the north of the belt, in Orion’s shoulder, is the bright red star Betelgeuse. This star is a red supergiant; a star near the end of its life. In fact, it is possible that Betelgeuse’s life has already ended in a colossal supernova explosion—but, due to the finite speed of light and the incredible vastness of the universe, it still appears whole in the skies of Earth.

Preceding Orion in the sky is the beautiful star cluster of the Pleiades. This open star cluster can be found by lining up Betelgeuse with the star Aldebaran, the glowing red eye of Taurus the Bull. If you continue this line past Aldebaran, it will lead you to the Pleiades. This star cluster is well known around the world. In Hawai’i it is called Makali’i, a name which has been variously interpreted as “Little Eyes”, “Little Stars”, “High-Born Stars” and “Eyes of the Chief”. The Makali’i are mentioned several times in the Kumulipo, the Hawaiian Creation Chant, including on the fifth line of very first verse. This cluster is also well known in Japan where it is called Subaru. You may be familiar with this word for there is a successful automobile manufacturer with

Pleiades rising caught by the CFHT cloud cam
Pleiades rising caught by the CFHT cloud cam

this name. This is why the logo of the company is a cluster of stars.

High overhead in the early evening are a pair of constellations that are more tricky to find than most: Perseus and Andromeda. These two figures are central characters in Greek mythology. It is said that Perseus saved Andromeda from the horrible sea-beast Cetus. This monster was sent by Poseidon to destroy the kingdom of Andromeda’s father King Cepheus as punishment for his wife Queen Cassiopeia’s vanity and boastfulness. Perseus defeated Cetus atop the winged horse Pegasus by using the head of the conquered witch Medusa, whose gaze, even after death, turned all who looked upon her to stone. Most of this tale is told in the stars as one can find Pegasus, Cepheus, Cassiopeia and Cetus in the sky next to Perseus and Andromeda. Because some of these figures are quite dim, if looking for them, wait for a dark night with little or no moon to brighten the sky.

This month also hosts what is roundly described as the best meteor shower of the year: the Geminids. Reaching rates near 120 meteors per hour at its peak on the nights of December 13th and 14th, the Geminids will wow…or at least they would if not for the Moon. Our bright Supermoon peaks on the night of the 14th, so many of the dimmer Geminids will be lost to the glare. This unfortunate timing will mean that this shower won’t be quite as good as years past. Still, the sheer quantity of meteors will mean that some will be able to outshine the Moon and light up the sky.

A second smaller shower is also visible this month. This shower, called the Ursids, produces only 5-10 meteors per hour and peaks on the nights of December 21st and 22nd. The meteors will appear from Ursa Minor, also known as the Little Dipper.

Finally, we have some planets visible this month. The rarest of these is Mercury. On December 11th, Mercury reaches a point known as ‘Greatest Eastern Elongation’. At this point, Mercury is as far from the Sun as it can be, and as a result, is at it’s best to locate. To find it, look low in the west just after sunset. In addition to Mercury, we also have Venus and Mars in the western sky. Venus is rather low, with Mars much higher at the start of the month. As the month goes on they will get closer and closer together. Finally, we have Jupiter. It is visible in the east, starting around 4:00am, at the beginning of the month. By the end of the month, it will appear as early as 1:30am. On December 22nd, the Moon and Jupiter come together for a beautiful pre- Christmas pairing of celestial mistletoe.

With that, I wish you clear skies and happy stargazing!

If you have any questions, comments or are new to stargazing and would like some tips on getting started, email me at wipper@cfht.hawaii.edu . Aloha!

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