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This is the Griffith Observatory Sky Report through June 22nd, 2016. Here’s what’s happening in the skies of southern California.
Summer begins in the northern hemisphere at 3:34 p.m., PDT on Monday, June 20. In Los Angeles, the day is 14 hours and 26 minutes long, and is the longest day of the year. Although Griffith Observatory is not open on Mondays, the public is invited to observe the local noon at the Gottleib Transit Corridor Meridian Arc at 12:55 p.m., and at the Summer Solstice Radial Sunset Line on the west side of the Observatory’s exterior at 8:00 p.m. Observatory Curator Dr. Laura Danly and Observatory Astronomical Lecturer Dr. David Reitzel will explain the workings of the seasons and of the Observatory’s equipment for observing these events in free presentations given at 12:45 p.m. and at 7:45 p.m.
The moon changes phase from waxing to waning gibbous and it lights most of the nighttime hours through the 22nd. Even with ordinary binoculars, shadow filled craters are usually visible along the moon’s terminator, the region on the moon dividing the moon’s day and night sides. These shadows emphasize the moon’s rugged relief.
Full moon is on Monday morning, the 20th. When the moon is full, it is nearly opposite to the sun in the sky, so the lunar features do not cast noticeable shadows and the face of the moon appears dazzlingly bright. While the relief of the full moon is not obvious, the range of reflectivity of its different features is dramatic.
Especially noticeable are the bright streaks, called rays, which surround several craters. The rays are made of the material ejected from the crater when it was formed in a collision with an asteroid or comet. Because exposure to the sun fades the rays over millions of years, we know that the craters with the brightest rays are also the most recently formed. The most obvious rays are from the crater Tycho, on the lower part of the moon. At about 100 million years old, Tycho is the youngest large crater, and is dozens of times younger than the rayless craters that surround it.
The planet Jupiter, in the constellation Leo the Lion, starts the evening as the brightest object that is high in the western sky. It gradually nears the western horizon and sets at about 12:30 a.m. Look through a telescope at 9:00 p.m., PDT to see Jupiter’s Great Red Spot on June 16th, 18th, and 20th. Jupiter’s four largest moons can be seen through binoculars.
As darkness falls, the orange planet Mars, in the constellation Libra the Scales, and the golden-hued planet Saturn, in the constellation Ophiuchus the Serpent Bearer, are obvious above the southeast horizon. Saturn is the bright object to the left of even brighter Mars. The sparkling orange star below the planets is Antares, the brightest star of the constellation Scorpius the Scorpion. The moon will appear near Mars on Friday the 17th and next to Saturn on Saturday the 18th. The dusky markings of Mars and the spectacular rings of Saturn, together with the features of Jupiter and the Moon, are all currently featured through Griffith Observatory’s public telescopes.
The International Space Station should easily outshine Jupiter as it passes directly over Los Angeles on the evening of Thursday the 16th. The ISS will cross the sky from the northwest to the southeast between 8:53 and 8:59 p.m., and will be at its highest, nearly overhead, at 8:56 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 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, July 9th.
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From Griffith Observatory, I’m Anthony Cook and I can be reached at griffithobserver@gmail.com