Tonight – July 1, 2017 – as the setting sun closes the curtains on the day, and the darkening skies bring out a myriad of far-off suns, let the moon introduce you to a very special star. The nearby bright star to tonight’s moon and the planet Jupiter is none other than Spica, the sole 1st-magnitude star in the constellation Virgo the Maiden.
The much brighter object in the vicinity of tonight’s moon and Spica is the giant planet Jupiter. Jupiter, the fifth planet outward from the sun, will remain in front of the constellation Virgo until mid-November 2017.
Did you see the moon yesterday, on the evening of June 30? Note the moon’s change of position relative to Spica and Jupiter as darkness falls tonight, on July 1. The moon continually moves eastward in front of the backdrop stars of the zodiac at the rate of about one-half degree per hour or about 13o per day.
For a convenient measuring stick, the moon’s diameter approximates one-half degree of sky, and your fist at an arm’s length spans about 10o on the sky’s dome. Also, for reference, Jupiter shines to the west of Spica – or conversely, Spica resides to the east of Jupiter.
In a few to several more days, in fact, the moon will be farther east of Spica on the sky’s dome, and closer to the star Antares and the planet Saturn. When that happens, use the dazzling planet Jupiter as your guide “star” to Spica. Or next year, in 2018, when Jupiter is no longer close to Spica, you might find it helpful to “star-hop” to Spica instead, as shown on the sky chart below.
If you live in the Northern Hemisphere, and you’re familiar with the Big Dipper, you can count on this famous pattern of stars to guide you to Spica. Simply extend the Big Dipper handle to arc to the brilliant yellow-orange star Arcturus and then to spike Spica, a blue-white gem of a star. (If you have difficulty discerning stellar color with the eye alone, try your luck with binoculars.)
Bottom line: Let the moon guide you to Spica on July 1, 2017, and then use the Big Dipper to locate Virgo’s brightest star, after the moon’s flirtation with Spica ends.