April mornings feature a spread of four planets in the southeast to east all month, including a gathering of Venus, Mars and Saturn in the first week, and a brilliant, close pairing of Venus and Jupiter at month’s end.
A meteor shower peaks in predawn on April 22 and 23. The moon sweeps past four planets on four mornings, April 24-27, as Venus closes in on Jupiter, leading up to their spectacular conjunction of April 30 and May 1. Evenings feature the year’s best appearance of Mercury in latter half of month, along with the annual gathering of winter’s bright stars in the western sky before their impending departure.
In the southeastern sky, about an hour before sunrise, the predawn planet shuffle continues! Three planets fit within a 10-degree span through April 7. Mars passes within 0.5 degrees below Saturn on April 4 and 5, creating a Venus-Mars-Saturn order on April 5, with Venus 7 to 8 degrees to the lower left of the Mars-Saturn pair.
The three planets fit within 6.5 degrees on April 2, as Jupiter emerges 25 degrees to the lower left of Venus, bringing the morning planet total to four. Jupiter-Venus-Mars-Saturn reach a minimum span of 30 degrees on April 5. Watch the gap between the two brightest planets, Venus and Jupiter, shrink until their spectacular conjunction at month’s end.
The waning moon passes by two first-magnitude stars and four bright planets in morning twilight from April 16 to 27. Look about one hour before sunup on April 16 to see Spica 4 degrees to the lower left of the full moon. On April 19, Antares appears 5 degrees to the lower left of a gibbous moon, 90 percent full. The brightest stars as dawn brightens in April are golden Arcturus, well up in the west, 33 degrees to the upper right of Spica; and blue-white Vega, very high in east to overhead. (Venus and Jupiter appear much brighter than any stars.) Altair and Deneb complete the Summer Triangle with Vega.
Lyrid meteors in 2022 are best Thursday night, April 21-22 and Friday night, April 22-23. Meteors normally increase in number through the night as the radiant, to the upper right of Vega, ascends from near the northeast horizon at nightfall, to nearly overhead as dawn begins to brighten. Meteors can light up anywhere in the sky, streaking away from the radiant. But a waning gibbous moon on Friday morning, and the last quarter moon on Saturday morning, rises into view and reduces the count. Start watching by four hours before sunup on April 22, and three hours before sunup on April 23, for an hour or two of moonless skies.
The last week of April offers lunar and planetary events well worth getting up for—every morning! On April 24, about an hour before sunrise, Saturn appears 8 degrees to the upper left of a fat, 39 percent crescent moon. On April 25, Saturn appears 9 degrees to the upper right of a 28 percent crescent moon, with Mars 8 degrees to the moon’s upper left. On the same morning, Mars is midway between Saturn and Venus, 14 degrees from each, while Jupiter appears within 5 degrees to the lower left of Venus. On April 26, Mars appears within 8 degrees to the upper right of a 19 percent moon, with brilliant Venus 9 degrees to the moon’s upper left.
April 27 features a spectacular, bright gathering of the moon, Venus and Jupiter. Venus and Jupiter are just 3.1 degrees apart, with the 12 percent moon rising 4 to 6 degrees below them. The waning crescent moon is visible for one additional morning: On April 28, Venus and Jupiter are 2.2 degrees apart, with the 6 percent moon rising exactly in the east, in brighter twilight, 16 degrees to the lower left of Venus. That morning, the best viewing time to catch the old moon may be about 35-40 minutes before sunrise. You’ll need an unobstructed view to see it. There’s no chance to see the moon on April 29; Venus and Jupiter are 1.3 degrees apart that morning. April 30 and May 1 provide the closest pairings of these two brightest planets: 0.4 degrees and 0.6 degrees apart, respectively. The four planets, from the Venus-Jupiter pair through Mars to Saturn, span about 34 degrees both mornings.
Magnitudes of morning planets in April: Venus, the brightest, -4.4 to -4.1; Jupiter -2.0 to -2.1; Saturn +0.9 to +0.8; Mars +1.1 to +0.9. Telescopic views: Venus appears in gibbous phase, 56% to 67% illuminated, and 22 to 17 arcseconds in diameter. Compare it to Jupiter’s disk, 33 to 35 arcseconds wide, and to the extent of Saturn’s rings, 36 to 37 arcseconds across, tipped 13 degrees from edge-on. Don’t forget to include some closeup views of the moon!
While you’re up early enjoying the show, listen for the springtime chorus of birds! In spring of 1971, I had the pleasure of taking a class in field ornithology taught by Michigan State University Prof. George J. Wallace. We visited many natural areas and learned to identify birds by sight and song. I am grateful for another aspect of nature which enriches my life. I dedicate this month’s column to him.
Evenings: The first sighting of the lunar crescent on April 1 or 2 marks start of the month of Ramadan, and fasting begins the next day. Near Reno and Palm Springs on April 1, the 1 percent crescent might be found with optical aid 20-25 minutes after sunset, less than 3 degrees above the horizon, 5 degrees north of west. On April 2, the 4 percent crescent moon, setting after twilight, will be widely seen.
Follow the moon in the early evening for two weeks as it moves eastward through the constellations of the zodiac and waxes toward full. On April 4, the 15 percent crescent moon will appear within 4 degrees south of the Pleiades star cluster. On April 5, the 22 percent moon will pass 7 degrees north of Aldebaran, eye of Taurus, the Bull. On April 8, the nearly first quarter moon, almost half full and 90 degrees from the sun, will appear within 7 degrees below Pollux and Castor, the bright stars marking the heads of the twins, Gemini. On the next evening, the 58 percent gibbous moon appears 6 to 7 degrees southeast of Pollux. On April 11, the 77 percent moon appears 7 degrees above Regulus, heart of Leo, the Lion, and on the next evening, the 85 percent moon will appear 8 to 9 degrees to the star’s lower left.
The star Spica in Virgo is at opposition on April 13. This event occurs annually as Earth passes between that star and the sun. Watch for Spica low in east-southeast at dusk, highest in south in middle of night (near 1 a.m. on April 14), and low in the west-southwest at dawn. As you look at Spica on this night, you are facing directly away from the sun. At dusk on April 15, Spica appears 7 degrees to the lower right of the nearly full moon. The moon creeps closer to star through the night, and an hour before sunup on April 16, Spica appears 4 degrees to the moon’s lower left. At dusk mid-twilight on April 16, the moon appears about 5 degrees up in the east-southeast (with Spica 9 degrees to its upper right), while Mercury appears at the same 5 degrees elevation, but in the opposite direction, west-northwest.
Mercury, after passing superior conjunction on far side of the sun on April 2, proceeds to its finest apparition of the year—while it quickly and brightly emerges at dusk. By April 11, Mercury shines at magnitude -1.4 and sets just after mid-twilight, when the sun is 9 degrees below the horizon. Fading slowly, Mercury still shines at magnitude -1.0 on April 17, while 6 degrees up at mid-twilight, and 3 degrees up at end of nautical twilight, when the sun is 12 degrees down, about one hour after sunset. Still fading slowly, through magnitude -0.5 on April 23 and 0.0 on April 27, Mercury continues to climb higher until April 28, when it reaches greatest elongation, 21 degrees from the sun, and sits nearly 7 to 8 degrees up in the west-northwest at the end of nautical twilight. Evenings around that date, binoculars show the Pleiades cluster in the same field, while Mercury sets in the dark sky, after twilight’s end. Becoming more backlit as it approaches inferior conjunction on near side of the sun on May 21, Mercury fades to magnitude +1 by May 3, and +2 by May 8, sinking into bright twilight.
April is the final month to catch all of winter’s bright stars and its two prominent star clusters together in the western evening sky. At month’s end, the star Rigel, marking Orion’s foot, and the Pleiades, or Seven Sisters star cluster, are almost gone. It’s fun to watch the sky each clear night within an hour after sunset, recording the presence or absence of each of these stars. After Rigel and the Pleiades, watch for these departures, in order: Aldebaran and the Hyades cluster, forming the head of Taurus, the Bull; Sirius, the Dog Star; and Betelgeuse, Orion’s shoulder. Binoculars may delay the date of your last sightings, but by late in May, all the aforementioned stars are gone. Procyon, the Little Dog Star, departs by mid-June, and then only Capella, the “Mother Goat Star”, and the “Twin” stars, Pollux and Castor, remain.
Face the eastern sky at dusk in April for spring’s recent arrivals. Use the curved handle of the Big Dipper to locate two bright stars: “Follow the arc to Arcturus and drive a spike to Spica.” By late in April, Vega, the brightest and leading star of the Summer Triangle, is rising at dusk, far to the northeast, 59 degrees to the lower left of Arcturus.
Illustrations of events in this article appear in the Abrams Planetarium April Sky Calendar included with this article. To subscribe for $12 per year or to view another sample issue, visit www.abramsplanetarium.org/skycalendar.
Robert Victor originated the Abrams Planetarium monthly Sky Calendar in October 1968, and still produces issues occasionally, including April 2022. He enjoys being outdoors sharing the wonders of the night sky, and is hoping for the pandemic to end! Robert Miller, who provided the 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.