Patience will be a virtue in the month of July since our night skies will likely be storm-laden much of the time.
Cloud-to-cloud lightning. Photo taken June 19, 2021.
This month, the summer Milky Way moves into prime time – easily viewed deep sky objects abound within it.
The Milky Way is visible all night in July. By the time dawn tinges the sky in the ENE, the Milky Way appears to dive into the WSW horizon. Photo taken July 1, 2020.
Mercury reaches its farthest apparent distance west of the Sun on July 4th. On that date, the solar system’s innermost planet rises in the ENE, near Taurus the Bull’s easternmost (lower) horn, about 4:35am MDT.
Venus dominates the western sky after sunset. On the first of the month, Venus is located near the Beehive Cluster (M44) in Cancer. On July 13th, Venus and Mars will be in conjunction, a mere 0.5 degrees from one another. On the 21st, Venus will pass 1.0 degrees from Regulus, the brightest star in Leo. By month’s end, the brightest planet will have traveled halfway across the constellation Leo, setting in the WNW near the end of twilight (about 9:40pm MDT).
Mars is now a second magnitude object and is falling deeper into the glare of evening twilight. It’s in conjunction with Venus on the 13th, separated by 0.5 degrees. On the 29th, Mars is in conjunction with first magnitude star, Regulus, separated by 0.6 degrees. Optical aid will be needed to pick the Red Planet and star out of the glare.
Saturn is a first magnitude object, visible for most of the night in July. Please see ‘July Spotlight’ for more information regarding the ringed planet.
Jupiter chases Saturn into the evening sky, brightening as it gets closer to Earth. In a telescope, the flattened disk of the planet (caused by its rapid nine-hour rotation) grows in size during July. Look for the atmospheric belts and Great Red Spot as the planet rotates during the night. I like to watch the dance of the four Galilean moons as they orbit Jupiter, changing position from hour to hour and night to night.
Now a first-magnitude evening object, Saturn rises just after sunset. On the first of the month, the ringed planet rises at about 10:15pm MDT in the constellation Capricorn. By month’s end, it rises about 8:15pm MDT, just a quarter-hour after the Sun sets.
Saturn (right of center, 3:30 from Jupiter) precedes bright Jupiter into the sky. Photo taken June 21, 2021.
Since ancient times, Saturn was known as one of the five ‘planetes’ – Greek for ‘wanderer.’ Saturn was observed to be relatively slow-moving, yellowish in color, bright, but not terribly so. The Romans named the planet ‘Saturn,’ after their god of agriculture and prosperity.
Notions of Saturn changed in 1610 (the year Santa Fe was founded as the capital of Nuevo Mexico) when Galileo Galilei pointed a telescope at the sixth planet from the Sun. What Galileo saw (or thought he saw) through his crude new optical instrument was a large disk, with two smaller disks, one on either side of the main body – a three body planet. Other astronomers saw a single, oval body. Several years later, Galileo observed Saturn and found that the two attendant bodies to the larger, middle body had disappeared.
In 1616, the planet’s attendants were back. Galileo sketched the planet, this time showing a main body with a ‘handle’ on either side, a dark space between the main planet and each handle. Confusion about the shape and composition of Saturn continued until the second half of the 17th century when Christiaan Huygens, a Dutch astronomer, proposed that the ‘handles’ were really a single, flat, solid ring that encircled the planet.
Today, we know that Saturn is a large gaseous planet with a core likely composed of iron-nickel and rock. Saturn is orbited by 82 known moons. Most of Saturn’s retinue of moons are small, but one, Titan, is the second largest moon in the solar system — larger than the planet Mercury. Titan’s the only moon in the solar system with a dense atmosphere and, with the exception of Earth, the only object known to support a permanent body of surface liquid.
The planet’s surrounded by a series of rings, mostly composed of ice particles, ranging from dust-sized specks to 30-foot chunks. The rings are about 70,000 miles wide, from the inner to the outer edges. The inner edge of the ring system orbits the planet about 4,000 miles above the cloud tops.
Despite the enormous spread of the rings, the rings are incredibly thin – less than 70 feet thick. If Saturn’s rings could be reduced to the size of a sheet of paper, the rings would be 100 times thinner than a comparable sheet of paper! Presently, Saturn’s rings are inclined toward Earth by 17 degrees, making them easily visible telescopically.
Saturn’s so far from the Sun that it takes 29.4 Earth-years to complete one orbit, making Saturn the tortoise of the five visible planets. The planet’s so wide that about 19 Earths could be placed side-by-side across its equator. Saturn’s rapid rotation (a day and night on Saturn lasts about 10.4 hours) causes the equator to bulge, making its appearance slightly oval when viewed through a telescope. The visible ‘surface’ of Saturn that we see is the top of Saturn’s atmosphere, which is banded by parallel atmospheric belts shaped by the planet’s fast rotation and strong upper level winds. Saturn’s yellowish color comes from ammonia crystals in its upper atmosphere.
Saturn and its ring system. Courtesy of Hubble/NASA.
If this spotlight peaked your interest, I encourage you to learn more about this uniquely beautiful planet that will be opposite the Sun and closest to Earth on August 2nd.
July Night Sky Events:
July 1: The pre-dawn zodiacal light is visible in the east all month. You must be an early riser to see this phenomenon since dawn begins about 4am MDT this month.
Zodiacal light (sunlight reflecting off of interplanetary dust particles) glows over Galisteo, June 30, 2020. Since the photo was taken less than two weeks after summer solstice, the zodiacal light is ‘bent’ toward the right. By the autumnal equinox, it will be more vertical to the horizon. Venus is just rising beneath the Pleiades; Mars is at the upper right; the Milky Way stands straight up on the left.
July 4: Mercury is at its farthest apparent distance from the Sun, visible in the dawn sky.
July 9: New moon.
July 23: Full moon occurs at 8:37pm MDT in the constellation Capricorn. Often called the ‘Buck Moon’ because male deer begin to grow their antlers in early summer, it’s also referred to by some Algonquin tribes as the ‘Thunder Moon’ in recognition of the thunderstorms that occur in summer. The Hopi people gave the July moon a name that translates to, ‘Raptor Moon.’
July 28-29: The Delta Aquariid meteor shower peaks on the night of July 28th and morning of the 29th. Under ideal conditions, 10-20 meteors per hour can be seen during the shower’s peak. While most meteor showers have short-lived peaks, the Delta Aquariid shower can remain near peak for a day or two on either side of the 28th/29th. Unfortunately, the waning gibbous moon will hamper late night viewing.