If the weather is clear on Friday evening, check out the west-southwest sky around mid-twilight — about an hour after sunset — to see the moon and Jupiter in an eye-catching tableau.
About one-quarter of the way up from the horizon to the overhead point, you'll spot a lovely crescent moon with what looks like a brilliant silvery-white "star" about 4 degrees to its upper left. This isn't a star, however, but rather the planet identified with the supreme sky god: Jupiter. To judge how far apart they will appear in the sky, recall that your clenched fist, correctly held, will measure 10 degrees. So you can use your fist to make a reasonable estimate of degrees either horizontally or vertically.
Even though they won't appear particularly close together, the moon and Jupiter will likely attract the attention of even nonstargazers. The duo will appear to descend in the western sky, finally disappearing beyond the western horizon — first the moon, at about 11:15 p.m. local daylight time, followed by Jupiter about 15 minutes later. [Find Jupiter and Other Skywatching Objects in July 2016 (Video)]
Jupiter is currently the brightest star-like object in the evening sky and the first to come out each night at dusk, outshining the brightest true stars. Just over a month ago, yellow-orange Mars nearly equaled it in brightness, but since Memorial Day, Mars, which can be found glowing in the south-southeast at dusk, has been rapidly receding from Earth and now shines with only about half of Jupiter's radiance.
During July, Jupiter will slip farther down into the glow of evening twilight in the western sky, and by the end of February, it will be setting right around the time evening twilight ends. This month, Jupiter is falling far behind Earth in the never-ending planetary race around the sun, and it continues to move slowly eastward among the stars. Because Jupiter takes nearly 12 years to circle the sun and there are 12 zodiacal constellations, Jupiter spends roughly one year in each of the 12 zodiacal signs.
Currently, Jupiter is in the constellation Leo, the lion. It officially moved into Leo's boundaries on June 10, 2015, and it will depart Leo and move into Virgo on Aug. 9.
If you have binoculars, take note of the much dimmer (magnitude 4.1) star Sigma Leonis shining to the upper left of Jupiter. They will be closest together, with the star appearing one-half of a degree above Jupiter, on July 13.
Jupiter still reigns supreme as the brightest evening planet, but in a few weeks, it will face competition from the dazzling queen of the night, Venus. Venus will appear much lower in the sky during sunset than Jupiter through most of August. However, Venus will be nearly eight times brighter, and it will gain prominence as it works its way slowly upward toward Jupiter as the weeks go by. They finally will meet in a very close conjunction on Aug. 27, when they'll be less than 0.1 degrees apart as seen from the eastern half of North America. This event will be worth a special trip with binoculars to someplace commanding a scenic view of the western horizon.
In the interim, enjoy Jupiter's visit with the moon on Friday evening.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmer's Almanac and other publications, and he is also an on-camera meteorologist for News 12 in Westchester, New York. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.