August ’24 – Rick’s Picks

Transient Events That Can Give Us a Good Enough Reason to Get Outside and Do a Little Observing

All month: the planets continue their slow and hesitant return to the evening sky this month. As August opens, Mercury is a mag +0.9 waning crescent 9 arcseconds from tip to tip, setting a half hour or more after sunset until August 5, when it’s a thin mag +1.5 crescent 10 arcseconds across. It then scoots into the solar glare and reaches inferior conjunction on the 18th before returning to the morning sky for the final week of the month. Venus is visible after sunset all month, setting 46 minutes after the Sun as August begins and 56 minutes after sunset as it ends, its disk blazing at mag -3.8 as it grows slightly from 10 to 11 arcseconds. Due to the flat evening ecliptic, Venus remains close to the horizon even as it continues to increase its distance from the Sun: at month’s end , it reaches 24° of elongation, but only 5° of elevation a half hour after sunset. Saturn takes a big step into the evening sky, rising just before 10 pm as August opens and before 8 pm as it ends, its 29 arcsecond disk brightening from +0.8 to +0.6 as it nears opposition on Sept 8. The rings remain nearly flat (2.5° to 3.5° tilt) as the planet comes ever closer to ring plane crossing next March. Neptune follows Saturn by less than a half hour throughout the month, its 2¼ arcsecond disk dim at mag 7.8 as it approaches its own opposition on Sept 21. Uranus now precedes both Mars and Jupiter, its 3½ arcsecond disk glowing at mag 5.7. It rises just after 12:30 am on August 1 and two hours earlier on Aug 31, remaining within 6° of The Pleiades (M45) all month. Mars follows Uranus into the late night sky, rising shortly after 1 am as the month begins and before 12:30 am as it ends, growing ever so slightly from 6 to 6½ arcseconds and brightening from mag +0.9 to +0.7 along the way. That leaves mighty Jupiter, which rises just after 1:30 am on August 1 and just before midnight on the 31st, brightening from mag -2.1 to -2.3 as its disk swells from 35 to 38 arcseconds during the month. Among the asteroids, 1 Ceres ranges from mag 7.8 to 8.4 as it crosses the Teapot of Sagittarius, while 7 Iris reaches opposition on August 6 at mag 8.3 in Aquarius. This month’s charts will show you where to find them both.

Aug 1 (night of July 31): begin the month with a challenge as Titan transits Saturn’s south polar region from 12:15 to 2:45 am CDT tonight. You’ll need plenty of aperture to spot the tiny (0.8 arcsecond) mag 8.4 moon against the shadowy Saturnian cloudtops. The fact that the scene will play out barely 20° above the horizon will make it that much more dicey – but that also makes it that much more satisfying when you pull it off!

Aug 1 (dusk): aim your binoculars or a wide-field eyepiece west at 8:40 pm CDT (a half hour after sunset) to catch Venus, Regulus (Alpha [a] Leonis), and Mercury as they form a ragged line from right to left in the evening gloaming. Start with brilliant mag -3.8 Venus, 3° above the horizon and 8° left of the spot where the Sun went down, then pan left 9° for mag +0.9 Mercury, 1° lower than Venus. Once you have those two, look roughly midway between them and 1° higher than Venus to tease out the mag +1.4 star.

Aug 5: new Moon arrived yesterday at 6:13 am CDT, so at 8:35 pm tonight (a half hour after sunset) it will be 38 hours old, 2.4% illuminated, 4° above the horizon, and 10° to the left of the spot where the Sun went down. More importantly, it’s just 40 arcminutes above mag -3.8 Venus, which will make the paper-thin crescent a little easier to find – but you’ll still need quick eyes, and probably a pair of binoculars, to admire the pair before Venus sets at 8:53 pm. If you spot a tiny glimmer of light just over 1° below Venus, it’s Regulus (Alpha [a] Leonis) reprising its role from earlier this week.

Aug 7 (night of Aug 6): if you’re up very late or very early, check out the double shadow transit from 1:54 to 3:57 am, as Io’s shadow crosses Jove’s disk from 1:47 to 3:57 am followed by Europa’s shadow from 1:54 to 4:22 am. There’s also a double transit of the moons themselves, with Io making the trek from 2:56 to 5:06 am and Europa doing it from 4:17 am until after sunrise (double transit from 4:17 to 5:06 am).

Aug 8: Saturn and Titan stage another of their dances tonight, as the ringed planet’s equator continues to line up within a few degrees of our own. In tonight’s show, mag 8.4 Titan s-l-o-w-l-y slips behind its parent planet’s disk, taking around 50 minutes beginning at 10:44 pm CDT to fully disappear, then taking just as long beginning at 12:40 am to pop back out. The moon disappears behind Saturn’s NE limb and reappears from behind its NW one.

Aug 11: the venerable Perseids meteor shower peaks after midnight tonight, and the first-quarter Moon cooperates by setting at 11 pm CDT, leaving a dark late night sky that will allow the streakers to shine after midnight when Earth turns directly into the stream. Expect 50 meteors/hour at a dark site, but only 10 or fewer under light-polluted urban skies. The Perseids are active from July 17 to August 24, and are made of debris from comet 109P/Swift-Tuttle, which passes through our neighborhood every 133 years or so. They’re fast-movers, entering our atmosphere at 59 km/s (132,000 mph) and leaving more than their share of persistent trains.

Aug 13: see if you can detect the color contrast between tonight’s 9-day-old Moon and ruddy Antares (Alpha [a] Scorpii) just 1½° to its upper left.

Aug 14 (night of Aug 13): it’s a good show for night owls and early risers as mag +0.8 Mars crests the eastern horizon at 12:48 am CDT, followed just three minutes later by mag -2.2 Jupiter. The pair rise together into the predawn sky with less than a half-degree separating them until the approach of sunrise erases the scene around 5:30 am. Along the way, don’t miss the double shadow transit beginning at 4:30 am (with Io’s shadow marching across the disk from 3:41 to 5:50 and Europa’s shadow doing so from 4:30 until after sunrise); Io itself begins a transit at 4:54 am. In case you miss the close pairing of Mars and Jupiter tonight, they’ll be less than 2° apart each morning from now through Aug 18. Any of those mornings, look about 10° west of the pair to find Aldebaran (Alpha [a] Tauri) mimicking Mars in both color and brightness.

Aug 20: at 8:34 pm CDT (50 minutes after sunset), the almost-full Moon rises less than a half degree behind mag +0.7 Saturn. The pair are closest at 9:07 pm CDT with just 15 arcminutes’ separation, and remain within 2° of each other until midnight, but the gap widens to a ho-hum 4° before sunrise. Aug 25: the third-quarter Moon rises between 10 and 11 pm CDT practically touching the stars of The Pleiades (M45). Although the two of them move slightly away from each other as the night progresses, they’re still less than 5° apart when morning twilight rolls around.

Aug 27 (night of Aug 26): the fat crescent Moon rises at 11:26 pm CDT, followed by Jupiter at 12:07 am and Mars at 12:29, climbing into the overnight sky in an inverted-T formation with the Moon at its base and mag -2.3 Jupiter to the Moon’s lower right, while mag +0.8 Mars to Jupiter’s lower left and mag +0.9 Aldebaran (Alpha [a] Tauri) to its upper right sit like reflections of each other at the tips of the T.

Rick Gering / August 2024