Transient Events That Can Give Us a Good Enough Reason to Get Outside and Do a Little Observing
All month: the morning people begin to release their hold on the planets, as Venus now joins Mercury as an evening star, beginning a sunset apparition that will extend into 2025 – but neither of the inner planets ever wanders very far from the Sun, and they’ll be challenging targets for much of this month. Venus will be a startlingly bright beacon at mag -3.8 or brighter all month, with a nearly-full disk 10 arcseconds across, while Mercury will begin July as a gibbous 6” disk at mag -0.6 and end it as a thick crescent, mag +0.9 and 10” wide. Meanwhile, Saturn begins to slowly slip into the late-night slot on its way back to evening splendor, cresting the horizon shortly before midnight as July opens and before 10 pm as it ends, its 18” disk glowing right around mag +1.0 as its 41” rings now appear nearly edge-on, tilted only 2° to our line of sight. Neptune continues to tag along behind Saturn, following it by about 20 minutes all month, its 2¼” disk reflecting 7.9 magnitudes of pretty blue light in our direction. Mars rises next, shortly after 2 am on July 1 and an hour earlier on July 31, its ruddy red face lit to mag +1.0 and its disk a tiny 5½ arcseconds. The soft blue 3½” disk of Uranus pops up a half hour after Mars as the month opens but a half hour before it as July ends, teasing naked-eye visibility at mag 5.8. Last of the bunch is majestic Jupiter, its big 35” disk blazing at mag -2; it rises around 3:15 am (two hours before the Sun) in early July, and shortly after 1:30 am at its end. Among the asteroids, 1 Ceres continues its trek across the handle and into the teapot of Sagittarius as it reaches opposition on July 5 at mag 7.3. It should be a good binocular target all month long. This month’s charts will show you where to find it.
July 1-3: the month opens with a series of pretty tableaux spread across the predawn sky, as the crescent Moon, Mars, Jupiter, Aldebaran, the Pleiades (M45), and even Uranus participate in an ever-changing celestial dance. This month’s charts will show you what’s what. Notice especially how Mars and Aldebaran are nearly identical in color and brightness this month.
July 1: see if you can spot Mercury around 9:00 pm CDT tonight (a half hour after sunset). The innermost planet will be glowing at mag -0.6, 7° above the horizon and 9° left of the spot where the Sun went down. Pollux and Castor (Beta [] and Alpha [] Geminorum) are 7° and 12° to its right.
July 5: Earth is now at aphelion, its farthest point from the Sun, although you might not guess that from the temperature – proof that the seasons are caused by how the Earth tilts, not by how far from the Sun it is.
July 6: new Moon came yesterday at 5:57 pm CDT, so at 8:59 pm CDT tonight (a half hour after sunset), it will be a real challenge to spot: 27 hours old, just 1.4% illuminated, 5° above the horizon, and 3° left of the spot where the Sun went down. Once you find it, look 9° farther left and 3° higher to spot mag -0.2 Mercury trailing it towards the horizon. If your binoculars or telescope shows any stars near Mercury tonight, it’s because it sits directly in front of the Beehive Cluster (M44).
July 7: around 9 pm CDT (a half hour after sunset), get out your binoculars and find the slender crescent Moon, just 2 days old and 5% illuminated, 11° above the horizon and 13° to the left of the spot where the Sun went down. Then drop your gaze 3° directly below the Moon and find tiny Mercury, glowing at mag -0.2. Later tonight, look for 1 Ceres just ½° north of mag 3.3 star Zeta () Sagitarii, marking the spot where the bottom of the teapot’s handle joins the bowl. At mag 7.3, Ceres should be an easy catch in almost any binoculars. Then stay up late to see Saturn occult its moon Titan at 1:40 am CDT. It will take several minutes for the moon to slowly slip behind the planet’s disk, so start watching by 1:30 am to be sure you don’t miss it, and make sure you bring plenty of aperture so you can see the show.
July 12: Mercury reaches its greatest elevation of this apparition, 8° above the horizon at 8:57 pm CDT (a half hour after sunset). Look for it 16° left of the spot where the Sun went down.
July 13: it’s an impressive view tonight when the first quarter Moon seems to step backwards in front of mag +1.0 Spica (Alpha [] Virginis) at 10:10 pm CDT. It will take several minutes for the dark edge of the Moon to cover the star, so start watching no later than 10:00 pm (and preferably earlier) if you want to see it all. Stick around later to watch the star reemerge from behind the bright side of the Moon at 11:22 pm.
July 14: it’s another lunar occultation tonight, as mag 4.9 star ET Virginis slips behind the Moon’s dark limb at 10:40 pm CDT. Again, be sure to start watching several minutes ahead of time so you don’t miss the show.
July 15 (night of July 14): it’s a pretty view for night owls and early risers as Mars breaches the horizon in tandem with Uranus just after 1:30 am CDT and the pair cross the sky together, powder blue and ruddy red, with just 0.6° separating them until morning twilight erases the colorful scene. Because Mars is over 80 times as bright as Uranus, though, you might have to look carefully to make out the contrast.
July 16: stay up past midnight tonight for one more occultation, as the Moon covers up mag 4.5 star 2 Scorpii at 12:22 am CDT. 2 Sco forms one of the “tail feathers” of a mini-Sagitta asterism, a narrow arrow composed of four stars pointing north, just west of The Scorpion’s head.
July 22: Mercury reaches greatest eastern elongation for this apparition, at 27° from the Sun, but due to the flat evening ecliptic at this time of year, it’s only 6° above the horizon at 8:50 pm CDT (a half hour after sunset).
July 23: Saturn’s occultation of Titan is replayed tonight: start watching shortly after midnight and expect the planet to completely cover the moon by 12:30 am CDT. Pluto also reaches opposition tonight, but at mag 14.4 you’ll need at least a 10” scope to see it, and a good, detailed chart to pick it out from the dozens of similarly-dim targets in the field – then come back in a week or so to make sure it’s the one that moved!
July 29-31: the Moon, Mars, Jupiter, Aldebaran, the Pleiades (M45), and Uranus reprise their month-opening predawn show, with new variations; see this month’s charts for details.
July 30: the South Delta Aquarids meteor shower peaks tonight, with a crescent Moon rising at 1:30 am CDT. Expect to see around 10 meteors per hour from a dark site until moonrise, a few fewer from then until sunrise, and fewer still from the suburbs – along with some early Perseids to augment the count.
July 31: at 8:41 pm CDT (a half hour after sunset), look for mag -3.9 Venus just 3° above the horizon and 7° left of the spot where the Sun went down. Then look for mag +1.3 Regulus (Alpha [] Leonis) 5° farther left and 1° higher up, and mag +0.9 crescent Mercury 4° still farther left and even with Venus in elevation.
Rick Gering / July 2024
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