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This is the Griffith Observatory Sky Report through December 27, 2017. Here’s what’s happening in the skies of southern California.
The Winter Solstice, marking the start of winter season in the northern hemisphere, occurs on Thursday the 21st at 8:21 a.m., PST. Because of the tilt of Earth’s axis, on this date the sun makes its most southerly and shortest track across the sky, at Los Angeles appearing only 32½ degrees above the southern horizon at noon. It rises at 6:55 a.m. and sets at 4:48 p.m. With sunshine lasting only 9 hours and 53 minutes, this is the shortest day of the year.
The moon gains prominence in the evening sky, waxing from crescent to first quarter on the night of the 25th, and then gibbous before it becomes full on New Year’s Day. It is visible for a longer time each successive night; it sets at 7:09 p.m. on the 20th and at 12:48 a.m. on the 27th. Binoculars or a telescope will show different craters come into view each night along the moon’s rugged terminator, the harshly lit dividing line of day and night on the airless moon.
The dim outer planets, Uranus and Neptune, can only be seen with the aid of a telescope, and they are best observed as soon as the sky is dark. Advice on how to find and observe them is given on the Sky and Telescope Magazine website.
Before dawn is far advanced, the bright planets Jupiter, in the constellation Libra the Scales, and Mars, that moves from Virgo the Maiden into Libra on the 21st, are visible above the southeastern horizon. Jupiter is the lowest and brightest of three bright objects appearing in a line in the southeast after 3:00 a.m. To Jupiter’s upper right is orange Mars, and beyond Mars is the brightest star of Virgo, Spica. On the 20th, Mars appears nearly between Spica and Jupiter, but morning-by-morning it will draw closer to Jupiter.
The launch of a SpaceX Falcon 9 rocket on Friday evening, the 22nd, should be a spectacular sight from southern California. The rocket, carrying ten Iridium communication satellites, is scheduled to launch at 5:23 p.m. from Vandenberg Air Force Base California, located 180 miles to the west-northwest of Los Angeles. If the air is clear, the rocket should be visible low in the western sky as it arcs to the south and ascends above Earth’s shadow into the sunlight. Binoculars will help to see what happens. There will be no attempt to recover the previously used first stage this time. Follow the live streaming coverage of the launch (on spacex.com) to monitor the progress of the launch, and then look at the sky when the rocket is on its way. SpaceX will also provide information in case the launch has to be re-scheduled.
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 5:30 p.m. on Sunday, December 24th. 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 27th.
Follow the Sky Report on Twitter for updates of astronomy and space-related events.
From Griffith Observatory, I’m Anthony Cook, and I can be reached at griffithobserver@gmail.com.