The Milky Way at its best; the Perseid meteor shower; three bright morning planets, with two of them forming a close pair for several days around mid-month; the first appearance of the brightest star, Sirius; and a “blue moon.” These are some of August’s celestial highlights!
On Aug. 5 at dusk, from a place with an unobstructed view of the horizon between west and west-northwest, look for a young, 3% crescent moon paired with Venus, just 1-2° to its lower right. When the southernmost classical zodiac constellations of Scorpius and Sagittarius are in the south at dusk, conditions are far short of ideal for viewing Mercury and Venus as evening planets: The ecliptic, or plane of Earth’s orbit and centerline of the lunar and planetary highway, then makes a low angle with the horizon. On Aug. 6, the 6% moon is 12° to the upper left of Venus, but is still quite low. Note the crescent looks like a bowl tipped almost on its side, pouring out its contents.
The best Milky Way viewing during convenient early evening hours this summer—after twilight ends and within two hours after sunset—occurs from dark locations in the absence of moonlight through Aug. 7, and Aug. 24 through Sept. 6. The brightest patches of the Milky Way are the Cygnus Star Cloud, along the axis of the Northern Cross within the summer triangle; and the Great Sagittarius Star Cloud, looking like a puff of steam rising out of the spout of the Teapot.
Watch the waxing moon skip past Spica over two evenings: See the moon 4° to the star’s lower right on Aug. 9, and 8° to its upper left on the next evening. The moon appears very close to Antares during evening hours on Aug. 13. From Palm Springs, the upper edge of the moon passes one moon’s width below the star at 11:26 p.m.
The moon reaches its southernmost excursion this month on Aug. 15, appearing in gibbous phase, 84 percent illuminated, within the Teapot of Sagittarius. From Palm Springs, the moon is only 27° up when it passes its highest point directly south at 9:32 p.m. That’s 6° lower than the midday Winter Solstice sun of Dec. 21. In 2024 and 2025, the moon’s monthly north and south excursions are at their most extreme of their 18-to-19-year cycle.
The full moon at dawn and dusk on Aug. 19 is a “blue moon.” But didn’t we have one just last year, on Aug. 30, because it was the second full moon of that month? This time, using a different definition, we can again celebrate a blue moon, because summer 2024 has four full moons, and the third one within an astronomical season is designated as “blue.” This summer’s first full moon occurred on June 21, just 29 hours after the solstice, and this season’s fourth one fits in on Sept. 17, more than 100 hours before the autumnal equinox deadline. For a discussion of the multiple definitions of blue moon, visit en.wikipedia.org/wiki/Blue_moon.
At nightfall on Aug. 20, the moon, just past full, appears low in the east to east-southeast, with Saturn about one degree to its upper right. At dawn’s first light the next morning, Aug. 21, the waning gibbous moon is well up in the southwest, with Saturn5° to its lower right. Continue following the moon each morning through Sept. 1, and watch it pass three additional bright planets and three bright stars. On Aug. 26, the last quarter moon, half full and 90° west of the sun, appears a wide 10-11° north of Aldebaran, eye of Taurus, the Bull. On Aug. 27, the 38-percent crescent moon passes north of Jupiter and Mars, forming an eye-catching triangle. On Aug. 28, this month’s northernmost moon reaches its highest point just 5° south of overhead in Palm Springs 2 1/4 hours after sunrise. On Aug. 29 and 30, the thinning moon skips past Pollux and Castor, the “Twin” stars of Gemini. Shift your viewing time to one hour before sunrise, and look very low in the east-northeast, 12° below the 6 percent crescent moon on Aug. 31, and 4° to the right of the last, old 2 percent crescent moon on Sept. 1, for newly emergent Mercury.
The morning sky of August 2024 is nothing short of spectacular! Starting this month, 6.5° apart and moving half a degree closer each day, bright Jupiter and red Mars adorn the already beautiful constellation Taurus, with reddish Aldebaran and two standout star clusters, the Hyades and Pleiades. On Aug. 4, Mars passes 4.9° north of Aldebaran. On Aug. 14, Mars passes 0.3° north of Jupiter. The pair will be well worth getting out early to view for several mornings before and after this date of closest approach! On Aug. 24, Mars passes 5.6° south of Elnath, or Beta Tauri, tip of the Bull’s northern horn. Three days later, Mars passes 2° north of Eta, the tip of the southern horn. On what date(s) will Mars lie closest to a line joining them? By Aug. 31, the Mars-Jupiter gap widens to 8.4°. Jupiter and Saturn are well worth telescopic views. Saturn’s rings appear 3° from edgewise on Aug. 18, just as the planet passes 1.1° south of the 4.2-magnitude star Phi Aquarii.
Annually, after viewing the peak of the Perseid meteors (on Aug. 12 this year), it has been my custom to look for the rising of Sirius in the east-southeast morning twilight glow, below Orion. After Sirius has risen and before Altair (southernmost star of the Summer Triangle) sets, there are 11 stars of first magnitude or brighter visible simultaneously. Add the three bright outer planets to the total, and you have a treasure chest of jewels! You can enjoy the same starry scene four minutes earlier daily, or two hours earlier per month, until mid-January, when Altair disappears into the western evening twilight glow. The same three planets will still be around, with Venus added.
For charts following planets and bright stars in morning and evening twilight in coming months, as well as tips for locating the faint, distant two outer planets Uranus and Neptune, visit the Sky Calendar Extra Content Page at abramsplanetarium.org/msta.
The Astronomical Society of the Desert will host a star party on Saturday, Aug. 3, at Sawmill Trailhead, a site in the Santa Rosa Mountains at elevation 4,000 feet. For dates and times of other star parties, and maps and directions, visit astrorx.org.
The Abrams Planetarium Sky Calendar is available by subscription from www.abramsplanetarium.org/skycalendar. For $12 per year, subscribers receive quarterly mailings, each containing three monthly issues.
Robert Victor originated the Abrams Planetarium monthly Sky Calendar in October 1968 and still helps produce an occasional issue. He enjoys being outdoors sharing the beauty of the night sky and other wonders of nature. Robert Miller, who provided the evening and morning twilight charts, did graduate work in planetarium science, and later astronomy and computer science at Michigan State University, and remains active in research and public outreach in astronomy.
