May’s first morning features a last-quarter moon, half full, in the southeast as twilight begins to brighten. Since the lower left half of the moon is illuminated, you’ll know that the sun is in the northeast, below the direction of the brightest twilight glow.
To the moon’s lower left, between the moon and the sun’s known position, look for a string of first-magnitude planets, in order of increasing distance from the moon: Saturn, Mars and Mercury. You’ll likely need binoculars to see Mercury rising in bright twilight.
As the moon approaches the sun the next five mornings, it goes through waning crescent phases and slides down the lineup of planets. It is to upper right of Saturn on May 3; between Saturn and Mars on May 4; to the lower left of Mars and to the upper right of Mercury on May 5; and to left of Mercury on May 6.
The Abrams Planetarium Sky Calendar for May 2024 illustrates these events, as well as the evening gatherings of the moon and stars mentioned below. The May calendar and a detailed evening star map will be posted online at abramsplanetarium.org/skycalendar.
The brightest stars in May’s morning sky shine at zero magnitude: Golden Arcturus is in the west, and blue-white Vega is nearly overhead. Note the stars Altair and Deneb completing the summer triangle with Vega. Also noteworthy is the red supergiant star Antares, heart of the Scorpion, in the southwest. On May 30, as the Earth passes between Antares and the sun, the star stands at opposition, and is visible all night: low in the southeast at dusk, in the south in the middle of night, and low in the southwest at dawn.
Mercury is highest for several mornings around May 12, but only 3° to 4° up in mid-twilight from the Coachella Valley. During this worst apparition of the year, the planet’s brightening through magnitude zero to nearly -1 doesn’t help much.
For the best Milky Way viewing, get out to a dark place two hours before sunrise May 5-17. You’ll notice the Cygnus Star Cloud along the neck of the Swan inside the summer triangle nearly overhead, and the Greater Sagittarius Star Cloud looking like a puff of steam rising up from the spout of the Teapot in the south.
The moon returns to the morning sky after the full moon of May 23. Catch the moon near Antares on May 24, near Saturn on May 31, and near Mars on the morning of June 2.
At dusk at the start of May, since Jupiter is nearly on the horizon, the brightest object easily seen is the “Dog Star,” Sirius, in the southwest. Start there, and go clockwise around the huge oval of bright stars—Procyon, Pollux, Castor, Capella, Aldebaran, Rigel and back to Sirius. The red supergiant star Betelgeuse lies inside the oval. By the end of May, of all these stars, only the “spring arch” of Procyon, Pollux, Castor and Capella will remain. Look nightly, using the sky watcher’s log (click here to access) to keep track of your observations.
Pollux and Procyon are 23° apart. Trailing behind them as they slide down the western sky, look for a star at the apex of an isosceles triangle, 37° from each—Regulus, heart of Leo, the Lion.
Other bright stars at dusk in May are Arcturus, starting out in the east, and Spica, in the southeast, both moving higher toward the south as the month progresses. Later in the month (and/or later in the evening), keep an eye out for Antares rising in the southeast, and Deneb rising in the northeast, to the lower left of Vega.
Watch the moon nightly at dusk May 8-23, waxing from a thin crescent, very low in the west-northwest, to full on May 23, passing the five first-magnitude zodiacal stars Aldebaran, Pollux, Regulus, Spica and Antares as it goes east at an average rate of 13° per day. The conjunctions of the latter four stars on the evenings of May 12, 15, 19 and 23, respectively, are very close and noteworthy. Binoculars will help you enjoy the view.
The Astronomical Society of the Desert will host a star party on Saturday, May 4, at the Santa Rosa and San Jacinto Mountains National Monument Visitor Center; and on Saturday, May 11, 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 to the two sites, 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.
