Jupiter is now the most prominent “star” in the evening sky, and Venus, even brighter and near peak brilliance, rules predawn. By May’s end, Saturn rises at a convenient evening hour, allowing both giant planets to be viewed well in the early evening. The moon always appears as a crescent in its monthly encounters with Venus, but is full whenever it appears near Jupiter or Saturn in the eastern evening sky opposite the sun.
The young crescent moon at dusk on May 26 marks the beginning of Ramadan, and appears to the lower left of faint, departing Mars.
May evenings: A huge conclave of seven stars of first magnitude or brighter in the western sky begins its annual departure in early May. The collection consists of the six stars of the Winter Hexagon, with Betelgeuse inside. The entire Hex is still visible at the start of May, but sky watchers must look sharply for Rigel, about to set in bright twilight a little south of due west. On each successive evening, the stars’ setting times occur nearly 4 minutes earlier, ever closer to the time of sunset. During May, in order of disappearance, Rigel, Aldebaran, Sirius and Betelgeuse sink into the bright western twilight glow, as shown on our evening twilight chart for May. By Memorial Day, all that remains of the Hexagon is its upper edge, forming aMemorial Arch: Procyon low in the west, Pollux (and slightly fainter Castor, not plotted, 4.5 degrees to its right) atop the arch, and Capella, low in the northwest.
Venus left our evening sky in late March, leaving Jupiter to reign as the brightest “star” in the evening sky. Our evening twilight chart shows Jupiter ascending from the southeast toward the south during May. Last month, our planet Earth passed between the sun and Jupiter, and that planet appeared 180 degrees away from the sun in our sky on April 7, at opposition and visible all night, from dusk until dawn. Go outside on the evening of May 20, and visualize Earth’s motion of 18.6 miles per second around the sun and directly away from the star Regulus, while the Pleiades star cluster is hidden beyond the sun. Ten days later, in a grand annual syzygy on May 30, three stars and our planet lie in a nearly straight line in space, in the order of Aldebaran-sun-Earth-Antares. Aldebaran, eye of Taurus, is then invisible on the far side of the sun, while Antares, heart of the Scorpion, is at opposition to the sun and visible nearly all night. On our twilight chart, Antares is shown rising into view in the southeast late in May.
Other prominent stars on May evenings include bright golden Arcturus, high in the east to south; Spica, near Jupiter; Regulus, just south of a line connecting Jupiter to Pollux; and bright blue-white Vega, rising in the northeast, with Deneb following to its lower left.
The Abrams Planetarium Sky Calendar is available at www.abramsplanetarium.org/skycalendar. The May issue may be reprinted and distributed at no charge. The calendar includes illustrations of the moon passing by planets and bright stars, and the sky map depicts more stars and constellations than our twilight charts show.
In May’s morning twilight, we find brilliant Venus low in the east. Telescopes reveal Venus still in crescent phase in May, filling out to being half-lit by early June, but shrinking in size as the planet speeds away from Earth. Use binoculars to spot Mercury to the lower left of Venus starting in the second week. Follow Arcturus, sinking in the west to west-northwest; the Summer Triangle, passing overhead; and Saturn, with twinkling Antares to its lower right, sinking in the southwest. Fomalhaut is rising in the southeast.
The moon near planets and stars in May: Check illustrations on the May Sky Calendar to remind yourself to catch the moon near Jupiter and Spica on the evening of May 7. After the moon passes full on May 10, switch your viewing time to before dawn to see the moon pass widely north of Antares on May 12, and skip from west of Saturn to east of it on the next two mornings. The moon is near last-quarter phase (half full) on the mornings of May 18 and 19. Glance up to see the moon in the daytime before the morning start of your workday, and note how the side toward the sun is illuminated. If you hold a ball up at arm’s length to appear near the moon, you’ll notice the ball is illuminated in the same way.
In a spectacular conjunction before dawn on Monday, May 22, the waning crescent moon passes closely south of Venus. Seize the occasion to spot Venus in the daytime. Before dawn on May 23, the moon is to the lower left of Venus and to the upper right of Mercury. On May 24, use binoculars about 30 minutes before sunrise to try to see the rising of the old moon, just 3 percent full, some 8 degrees to the lower left of Mercury, and within 32 hours before new. It’ll be very low in bright twilight; you’ll need perfect skies and a low horizon to see it.
New moon occurs on May 25 at 12:44 p.m., only five hours after perigee, when the moon is closest to Earth. As a result, the moon ascends quickly from one evening to the next at the same stage of twilight. On May 26, 30 minutes after sunset, the first crescent moon, marking the start of the fasting month of Ramadan, should be easily seen if skies are clear. It will appear 3 percent full and about 7 degrees up in the west-northwest for sky watchers in the Coachella Valley. (You’ll need to go to a place where our high mountains won’t block the view.) As twilight deepens, binoculars may show faint Mars about 6 degrees to the moon’s upper right. In the rest of May, watch the waxing moon pass widely south of the Gemini twins Pollux and Castor on May 28, and leapfrog past Regulus on May 30 to 31. On the latter night, the moon is approaching first-quarter phase and is nearly half full.
The Astronomical Society of the Desert will host the last of the season’s monthly public star parties at the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument, on Saturday, May 20, from 8 to 10 p.m. The Visitor Center is on Highway 74, within four miles south of Highway 111 in Palm Desert. After May 20, the next star party at the same location will be on Oct. 28. Check www.astrorx.org for listings. Star parties at the Sawmill Trailhead, our high-altitude site (4,000 feet—wear warm clothes), start at dusk on Saturday. June 24, July 22, Aug. 19, Sept. 23, and Oct. 14. Follow links to maps and directions.
Also, check the link to our “Impromptu Star Parties,” which could be announced on short notice at any time. Sessions might be scheduled at dusk or dawn to view planets—Jupiter with its moons, or Saturn with its rings—or a young or old crescent moon. In May 2017, special sessions will be held in daytime and at dawn to observe Venus at its brightest, in crescent phase. A session might include a bright flyover of the International Space Station.
It’s not too early to make plans for a very special event on Monday, Aug. 21, if you want to travel to see the event at its best: It’s a solar eclipse, visible throughout North America, and visible as a total solar eclipse within a narrow track across the U.S., tracking coast to coast from Oregon to South Carolina. Get to the path of totality if you can! Whether you do so, or you stay here at home to see the partial eclipse, the following web resources should help you prepare yourself and your family and friends for the event, and observe it safely.
Robert C. Victor, formerly a staff astronomer at Abrams Planetarium at Michigan State University, is now retired and enjoys providing sky watching opportunities for school children in and around Palm Springs. Robert D. Miller 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.