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This is the Griffith Observatory Sky Report through September 12th, 2018. Here’s what’s happening in the skies of southern California.
Shortly after sunset, the bright planets Venus, Jupiter, Saturn, and Mars are the most obvious objects. They are draped in a huge bow across the southern sky that spans from the west-southwest to the southeast.
Venus appears noticeably lower in the west-southwest sky night by night. As a result, the amount of time during which it may be seen is shortening. At the end of civil twilight, or roughly 30 minutes after sunset, the elevation of Venus drops from 14 degrees to 12 degrees between the 5th and 12th, and over the same period its setting time changes from 8:53 to 8:35 p.m. Use a telescope to see the phase of Venus, which is currently crescent.
Jupiter, currently located in the southwest and to the upper left of Venus in the early evening, will be hidden behind the sun in November. As a result, it also appears closer to the horizon at the same time every evening. Its elevation at the end of civil twilight decreases from 26 to 24 degrees through the 12th, while its setting time changes from 10:12 to 9:50 p.m. At 8:30 p.m., the planet is still high enough to see Jupiter’s Great Red Spot through telescopes when it is on the side of the planet facing the west coast on the 7th, 9th, and 11th.
Saturn appears similar to a bright star in the south-southwest sky, far to the left of Jupiter, and against the starry background of the constellation Sagittarius the Archer. The incomparable ring system of Saturn is a stunning sight through nearly any telescope. Saturn sets in the west-southwest by about 12:30 a.m.
The planet Mars gleams brightly with an orange hue against the dim constellation Capricornus the Sea Goat. It moves from the south-southeast to the south-southwest sky between 8:30 and 10:30 p.m., the period through which it is best positioned for observing with a telescope. As the effects of the global dust storm that masked the planet’s features from June through early August subside, Mars remains a worthy telescopic target in spite of its increasing distance from us. Mars sets by 2:30 a.m.
The moon is visible only briefly through the 12th. Its waning crescent disappears from the early morning sky on the 8th. After new moon, on the 9th, it will be back in the evening sky on the 10th as a waxing crescent. It appears near Venus on the 11th and 12th.
The absence of bright moonlight is fortunately timed for seeing the periodic comet Giacobini-Zinner at its brightest. The comet orbits the sun every 6.6 years, and its closest approach to the sun–its perihelion–on September 10th is also when it is closest to the Earth. It will then be 36 million miles away, about the same distance from us that Mars was at the end of July. While the comet will probably not be bright enough to see with the unaided eye, Giacobini-Zinner is visible as a hazy glowing cloud through binoculars when viewed from a dark wilderness site. It may be found within the constellation Auriga the Charioteer, below the bright star Capella, where it can be spotted high in the northeast sky before dawn. This comet is proving to be a beautiful sight through telescopes, which can reveal this comet’s characteristically slender tail. See sky observer Bob King’s detailed guide to observing the comet on the Sky and Telescope website.
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 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, September 22nd.
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From Griffith Observatory, I’m Anthony Cook, and I can be reached at griffithobserver@gmail.com.