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This is the Griffith Observatory Sky Report for the week ending Wednesday, September 24, 2014. Here is what’s happening in the skies of southern California:
Autumn begins in the earth’s northern hemisphere at 7:29 p.m., P.D.T. on the 22nd – the autumnal equinox. Spring begins in the southern hemisphere at the same time. The autumnal equinox is the moment when the sun crosses the celestial equator (the projection of the earth’s equator into space) moving south. For the next six months the sun is south of the equator, shining mostly on the earth’s southern hemisphere. The equinoxes are also the days when the sunrise is due east and sunset is due west, and the day is as long as the night, 12 hours. Autumn ends with the winter solstice on December 21.
A string of three planets and two bright stars can be seen in the southwest after sunset. The lowermost part of the string, the planet Mercury, is best found with binoculars starting at 7:26 p.m., when it is about 5 degrees above the west-southwest horizon. For reference, remember that the span of the knuckles of your clenched fist, when viewed from arm’s length, is about 10 degrees. The bright star Spica, of Virgo the maiden, appears a few degrees to the upper left on Mercury until the 20, when Mercury passes less than ½ degree south of Spica. On following days, Spica sinks toward the horizon, to the lower right of Mercury.
The bright golden object, 25 degrees to the upper left of Spica, is the planet Saturn, in Libra the Sales. Fifteen degrees to the upper left of Saturn is the orange planet Mars. Six degrees to the left of Mars is the orange star, Antares, of Scorpius the Scorpion. Compare the color of Mars and Antares. Antares means “rival of Ares” in Greek. Ares was the Greek equivalent of the Roman god of war, Mars. Mercury sets at 7:50 p.m., Saturn at 9:23 p.m., and Mars at 10:01 p.m.
The brilliant yellow planet Jupiter, in Gemini the Twins, is well placed for telescopic viewing when dawn starts at 5:15 a.m. Jupiter can’t be missed, gleaming 25 degrees high in the east at that time.
The brightest planet, Venus, is 5 degrees high in the east at 6:23 a.m., only 16 minutes before sunrise.
The waning crescent moon, visible in the early morning until the 22nd, passes close to Jupiter on the 20th and to Venus on the 22nd. The moon is new on the night of the 23rd.
NASA’s Maven Mars orbiter arrives at Mars on Sunday, September 21st. Live coverage of the critical engine firing, needed to put Maven in orbit around Mars, will start at 6:30 p.m., PDT on NASA TV. The engine firing is scheduled to take place at 6:37 p.m.
Free views of the sun during the day and of the moon, planets, and 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 our schedule. The next 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, October 4.
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From Griffith Observatory, I’m Anthony Cook and I can be reached at griffithobserver@gmail.com.