Averaging 15 hours of daylight, July is a sunny month. At the beginning of the month, the sun sets at 8:42 p.m., but true darkness, defined as the end of astronomical twilight, when the sun is far enough below the horizon that the faintest stars can be seen, doesn’t begin until 11 p.m. True night only lasts until 3:04 a.m., when astronomical twilight again begins as dawn approaches at 5:22 a.m. By July 31, these times have shifted a bit, with sunset at 8:21 p.m. and the true darkness of night from 10:20 p.m. to 3:48 a.m., and sunrise at 5:48 a.m.
Look west-northwest after sunset to spot brilliant Venus and a fainter Mars. Our two neighboring planets slide close together early in the month. On July 11, the pair are less than a degree apart with a crescent moon off to the right. Venus moves a little above Mars as they get even closer on July 12, but now the moon has jumped above the pair and is in Leo, not too far from the star Regulus.
On July 13, Venus is stacked right above Mars, and from then on the pair separate further as Mars gets closer to the horizon and Venus moves on toward Regulus. Venus passes Regulus on July 21, but the planets get lower in the sky and become more difficult to see as they stay near sunset. Mars gets even closer to Regulus than Venus did, with the Red Planet and the brightest star in Leo pairing up on July 29.
Early risers can spot the closest planet to the sun, Mercury, on July mornings. July 7, finds the old crescent moon near Mercury.
Jupiter and Saturn rise in the east-southeast on July evenings and spend most of the night as great observing targets. Check out Jupiter’s moons through binoculars and Saturn’s rings through a telescope. As the moon hopscotches one-step across the sky each night, the moon will appear near Saturn on July 23, reach full stage between the two giant planets on July 24, and start to wane a bit below Jupiter on July 25.
Prime Milky Way season
Don’t miss the majestic Milky Way, passing overhead every summer evening. July allows you a peek at the galactic center. Thick clouds of gas and dust obscure the heart of the Milky Way and, of course, the black hole at its center, but this region is an excellent area for spotting clusters and nebulae.
Look toward the southern horizon to spot Sagittarius and Scorpius, the constellations that lie in the direction of the center of the galaxy. To find the precise center, look for the teapot shape, known as an asterism, in Sagittarius. Imagine you see steam roiling out of the teapot’s spout, and you’re looking toward the galactic center. With a telescope, you can scan this region and stumble across many deep-sky delights.
Kelly Kizer Whitt fell in love with astronomy while a student at Sauk Prairie High School, earned her degree at UW-Madison and shares her love with this column.