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This is the Griffith Observatory Sky Report through January 3rd, 2018. Here’s what’s happening in the skies of southern California.
The moon brightens most of the nighttime hours, changing from waxing gibbous to waning gibbous between December 27th and January 3rd. It is full at 6:24 p.m. on New Years Day. The moon’s elliptical orbit brings it to its closest point to the earth, called its perigee, a little less than five hours later. In recent years, it is common to call the full moon that coincides with perigee a “super moon,” but in fact, the moon appears only seven-percent larger than average, and as its distance only gradually changes from one full moon to the next, any difference from other full moons may not be obvious–but observe for yourself. The average distance to the moon is about 239,000 miles. At perigee it comes as close as about 221,000 miles of us, and at its farthest point, called apogee, it is about 252,000 miles away. The New Year full moon is the first of two full moons happening this month. The second full moon on the 31st is called a blue moon, and will also be the occasion of a total lunar eclipse.
Earth travels on an elliptical orbit around the sun, and as a result our planet will be at its closest point to the sun, called the perihelion, at 9:35 p.m. on January 2nd. 91,401,986 miles will then separate the centers of the Earth and the sun. This is 1,553,821 miles closer than its average distance, according to the computations of Jet Propulsion Laboratory’s Horizons on-line service.
The only planet well placed to see in the evening sky is Uranus, in the faint constellation Pisces the Fishes. It is bright enough to spot with ordinary binoculars, but a more powerful telescope is required to see its round disk. Information on how to hunt it down can be found on the Sky and Telescope magazine website. It is currently one of the interesting objects featured through the public telescopes at Griffith Observatory.
The planets Venus and Saturn are currently hidden in the glare of the sun, but other planets can be seen before sunrise. Brilliant Jupiter, in the constellation Libra the Scales, is eye catching above the east-southeastern horizon by 3:30 a.m. The orange planet Mars, also in Libra, is close enough to Jupiter in the sky that both planets will fit together in the same binocular field of view. Mars will then be four degrees to the upper right of Jupiter on December 27th; it closes to within less than 2˚ of Jupiter on January 3rd.
Look for the innermost planet Mercury at 6:30 a.m., about half an hour before sunrise. Mercury will then appear 13 degrees above the southeastern horizon and 10 degrees to the left of the slightly fainter orange star Antares, in Scorpius the Scorpion. For reference, your clenched fist spans an angle of 10 degrees when viewed at arm’s length.
Free views of the Sun during the day and of the moon, planets, and other celestial objects at night are usually available to the public in clear weather through Griffith Observatory’s telescopes from Tuesday through Sunday, before 9:30 p.m. Note, however, that Griffith Observatory will close at 5:00 p.m. on Sunday, December 31st. Check our website for the schedule. The next free public star party on the grounds of Griffith Observatory, hosted by the Los Angeles Astronomical Society, the Sidewalk Astronomers, and the Planetary Society, will take place on Saturday, January 17th.
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From Griffith Observatory, I’m Anthony Cook, and I can be reached at griffithobserver@gmail.com.