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This is the Griffith Observatory Sky Report through December 13, 2017. Here’s what’s happening in the skies of southern California.
By 9:00 p.m., the brightest nighttime star, Sirius–in the constellation Canis Major the Big Dog–sparkles just above the east-southeast horizon. During the night, the Earth’s rotation will make Sirius slowly arc up and to the right until about 1:15 a.m. It then reaches its highest point and crosses the meridian, 39 degrees above the southern horizon. During the remainder of the night, Sirius arcs down and to the right until it sinks beneath the west-southwest horizon at dawn. At a distance of 8.7 light years, Sirius is the nearest star to the sun that is visible from Los Angeles.
The waning moon makes its appearance nearly an hour later from one night to the next through the 13th. Its phase changes from gibbous to last quarter on the night of the 9th, and then it is crescent on the following nights. It rises at 8:26 p.m. on the 6th and at 2:34 a.m. on the 13th.
The moon will be largely out of the way in time for the maximum of the annual Geminid meteor shower, on Wednesday night, December 13th. The shower can be seen from 7:00 p.m. until dawn, but is at its very best between about midnight and 3 a.m. when up to 120 meteors per hour may be seen from dark, wilderness conditions far from urban light pollution. Fewer numbers can be seen in urban and suburban surroundings. Griffith Observatory and Griffith Park are not open during the hours at which the meteors can best be seen.
The bright planets Mercury, Venus, and Saturn are all lost in the glare of the sun and cannot be easily observed now. The faint outer planets, Uranus and Neptune, can be observed in the early evening through telescopes with the aid of finder charts, such as those found on the Sky and Telescope Magazine website. Mars and Jupiter are currently the only planets visible to the unaided eye that can be observed, and they are best placed for observing at dawn.
The morning planets are best seen starting at about 5:15 a.m. Brilliant Jupiter, in the constellation Virgo the Maiden, is then the brightest object above the east-southeastern horizon. The bright white star Spica, in the constellation Virgo the Maiden, shines to the upper right of Jupiter. Orange planet Mars, also in Virgo, appears roughly between Jupiter and Spica. The crescent moon will join this attractive grouping of objects, appearing just above Mars on the 13th.
Free views of the Sun during the day and of other celestial objects at night are available to the public in clear weather through Griffith Observatory’s telescopes from Tuesday through Sunday, before 9:30 p.m. 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, December 16th.
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From Griffith Observatory, I’m Anthony Cook, and I can be reached at griffithobserver@gmail.com.