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This is the Griffith Observatory Sky Report through the period ending June 18th, 2020. Here’s what’s happening in the skies of southern California.
The northern hemisphere’s most famous grouping of stars, known in the United States as the Big Dipper, is high up in the west-northwest sky as night falls. At that time the Dipper is oriented with its “bowl” open downward, to the north, and with its bent “handle” to the left.
The Big Dipper’s recognizable shape and its visibility during most nighttime hours in the northern hemisphere makes it ideal for pointing the way to a number of other stars that are key to identifying objects in the sky.
As you face the Big Dipper in the early evening, remember that the rightmost two stars of the Big Dipper’s bowl are called the pointers. If you use your imagination to connect them and then to extend that imaginary line downward by an amount five times the stars’ separation, you will come to another star of similar brightness. This is Polaris, the North Star. The rotational axis of Earth points very close to Polaris. As a result, all celestial objects appear to circle Polaris every day. Polaris marks true north, so it is valuable to travelers.
Use your imagination to extend the curve of the Big Dipper’s handle to the left and use the curve to identify two other bright and widely separated stars.
The curve first leads you to the brightest star visible at nightfall, fiery orange Arcturus, located nearly overhead in the early evenings of late spring. Along the same imaginary curve of the Big Dipper’s Handle, but low in the south below Arcturus, you should be led to a second star, glittering white Spica. The utility of the Big Dipper’s handle in finding these stars may be remembered by the phrase “Arc to Arcturus, spin off to Spica”, or other versions of it, such as “Arc to Arcturus, spike to Spica,” “Arc to Arcturus, spiral to Spica,” and “Arc to Arcturus, speed to Spica.”
These and other tricks for finding your way around the sky from the Big Dipper are contained in a handy guide on the Web Page of the Fort Worth, Texas Astronomical Society.
The bright planets Jupiter and Saturn are eye-catching when they appear together in the southeast sky around 11:30 p.m. Jupiter, on the right, is the brighter planet of the pair. By 3:30 a.m., Earth’s rotation moves Jupiter and Saturn to their highest point in the sky and located due south at the meridian. The pair continues to move, descending toward the west-southwest sky as dawn starts.
The moon rises at 1:02 a.m. on the 12th, and an additional half-hour later on each morning that follows. As a result, by the 18th, the moon won’t appear until 3:53 a.m. The moon reaches last quarter phase shortly before it rises on the 13th, and it is waning crescent on the following mornings.
Mars arcs through the sky far behind Jupiter and Saturn; it first appears low in the southeast by 2:30 a.m. Mars is higher and in the east-southeast sky when dawn starts. The moon is close to Mars on the 12th and 13th.
Because of measures in place that are intended to reduce the spread of the COVID-19 Corona virus, Griffith Observatory remains closed until further notice. Consequently, all public telescopes are closed, and all public events have been cancelled. Please check the Griffith Observatory homepage for current information and continued updates of the situation.
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From Griffith Observatory, I’m Anthony Cook, and I can be reached at Anthony.Cook@lacity.org.