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This is the Griffith Observatory Sky Report through May 23, 2018. Here’s what’s happening in the skies of southern California.
The moon joins the two brightest planets after sunset. Venus, the brightest planet, blazes in the west-northwest at sunset. On Wednesday the 16th, the crescent moon makes its first appearance in the evening following the new moon, and it then appears between Venus and the horizon at about 30 minutes after sunset.
By that time, Jupiter, the second brightest planet, is radiant in the east-southeast sky, directly opposite from Venus, and it is then seen just as easily as Venus because of the darker backdrop of sky in that direction, away from the lingering glow of the sun.
The moon, which orbits around the earth in less than a month, changes its position swiftly from night to night, as compared to the more stately motions of the planets. On the 17th, the moon appears to the upper right of Venus, and it appears higher and farther from Venus on following nights. Its phase waxes, changing from crescent to first quarter on the 21st, and it is gibbous after that. The moon is visible for a longer period each night; it sets at 9:22 p.m. on the 16th and at 2:31 a.m. on the 23rd.
Venus sets before 10:30 p.m., while Jupiter, in the constellation Libra the Scales, moves higher and into the southern sky at about midnight. It gradually sets in the west-southwest at dawn.
By 1:00 a.m., two other bright planets are visible in the southeast sky. Saturn, in Sagittarius the Archer is then to the upper right of orange planet Mars. Saturn is in the constellation adjacent to Sagittarius, Capricornus the Sea Goat. These planets are highest in the south before sunrise.
Of all the solar system objects that are visible this week, the moon and Jupiter are the most rewarding through binoculars. Night by night, the craggy shadows of craters and mountains cast by the lunar sunrise at the terminator–the dividing line between day and night on the moon–highlights different lunar features that come into view. In addition to the bright light of the planet Jupiter, the four largest moons of Jupiter, first reported by Galileo in 1609, are visible through binoculars. They appear small and tightly clustered around the planet in patterns that change from night to night as they orbit their world.
Through a telescope, Jupiter is a very rewarding sight. Tan stripes, called belts, lie parallel to Jupiter’s equator, and alternate with bright regions, called zones. Careful examination will reveal small irregularities in brightness and in the form of these swirling clouds. The most unusual feature is Jupiter’s giant oval storm, called the Great Red Spot. Currently this spot has a deep pumpkin-orange hue, and it will be on the side of Jupiter facing observers in Los Angeles at 10:00 p.m. on the 17th, 19th, and 21st.
A telescope currently shows that Venus and Mars appear the same size, although in reality, Venus is nearly twice the diameter of Mars, but it is also now more than twice as far away. Venus, however, is blanketed by nearly blank white clouds, and almost never reveals features that are visible through telescopes. Mars, on the other hand, has a thin atmosphere and occasional clouds. Its predominant feature is its dusty, butterscotch-colored desert, broken by irregular dark grey markings, made where dusky rocks are scoured clean of brighter dust by Martian winds. Frozen carbon dioxide polar caps and misty clouds add patches of white to the disk and, sometimes, yellow patches appear where dust storms rage. Mars will appear to nearly double in size by late July, when the distance between it and the Earth will be at their minimum.
Golden Saturn, however, is the most memorable object through a telescope. Its system of magnificent rings surround the planet marked with its own belts and zones, although with much more subtle contrast than displayed by Jupiter’s clouds.
A SpaceX Falcon 9 rocket is scheduled to launch from Vandenberg Air Force Base on Monday, May 21 at 12:53 p.m., PDT, on a mission to place five Iridium communication satellites and two small NASA satellites to study Earth’s gravitational field, into orbit. Because the launch occurs during bright daylight, the conditions will probably make it difficult to see the rocket from southern California as it arcs upwards from the west to the southwest, although binoculars should help.
There won’t be any problem seeing the International Space Station when it passes directly over Los Angeles, later on the evening of the 21st. The space station should gleam as brilliantly as Venus while it crosses the sky from the southwest to the northeast between 8:55 and 9:02 p.m. It will pass directly overhead, 253 miles above Los Angeles, a few seconds before 8:59 p.m.
Free views of the Sun during the day and of the moon and other interesting 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, May 19th.
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From Griffith Observatory, I’m Anthony Cook, and I can be reached at griffithobserver@gmail.com.