May’s evening twilight scene is dominated by two brilliant planets: Venus, of magnitude -4, low in the west-northwest; and Jupiter, of magnitude -2, in the west, to Venus’ upper left.
At dusk mid-twilight on May 1, Jupiter is halfway from horizon to overhead and nearly 40° from Venus. The gap between them closes to 30° on May 10; to 20° on May 20; and to within 9° on May 31, all building up to their spectacular conjunction on June 9. Both planets are moving east against the starry background, while the zodiacal backdrop itself is sinking lower in the west as weeks pass, a consequence of Earth’s revolution around the sun. Jupiter this month shifts daily by 0.14° to 0.19°, while fast-moving Venus goes 1.2° daily, bringing it closer to Jupiter.
Many of the sky events described below are illustrated on the Abrams Planetarium Sky Calendar. For $12 per year, subscribers receive quarterly mailings, each containing three months of calendars and evening star maps. Subscription info and a free printable sample of the May 2026 calendar and sky map are available at abramsplanetarium.natsci.msu.edu.
Watch the changing configurations of Venus and Jupiter with the stars of Taurus and Gemini—with plenty of photo-ops! On May 1, watch Venus pass just more than 6° north (to the upper right) of Aldebaran, eye of Taurus. Farther left, in the west-southwest, look for Orion, with his three-star belt pointing left to Sirius, the brightest star, twinkling in the southwest. Follow these stars and others until their annual exits from the western sky.
Watch these evening events: On May 12, Venus is 4° south of Beta Tauri, tip of the Bull’s northern horn, and between the horns the next evening. On May 17, the young crescent moon, just 3% full with earthshine, is low in the west-northwest at dusk, 14° to the lower right of Venus. Look nightly for rest of May and watch the moon pass two brilliant planets and four first-magnitude zodiacal stars.
On May 18, spot Venus in the daytime! Look near the 8% crescent moon in the west shortly before sunset, with Venus 2°-3° to its lower left. As the sky darkens after sunset, a spectacular conjunction awaits!
On the next evening, May 19, the 16% crescent moon climbs to 14° to the upper left of Venus and 7° to the lower right of Jupiter. Note the “Twin” stars Pollux and Castor, 4.5° apart, within 9° above the moon, and 6°-10° to the upper right of Jupiter.
On May 20, Mercury, at magnitude -1.6, sets 40 minutes after sunset, so look for it earlier, with optical aid, within 25° to the lower right of Venus. By an hour after sunset on May 20, Mercury has set, but the 25% moon appears 8° to the upper left of Jupiter and left of the Twins. (See more about Mercury below.)
On May 20 and 21, Venus sets farthest north along the horizon—farther north than even the setting sun on the first day of summer, June 21. For the rest of Venus’ evening apparition, ending in early October, watch Venus’ setting point shift progressively farther south along the western horizon.
On May 25, Venus forms an isosceles triangle with Jupiter and Castor, nearly 15° from each. Mercury is at magnitude -1.1, now easy for the unaided eye, 20° to the lower right of Venus. From May 26-31, Jupiter is within 6.3° to the south of Pollux. On May 30, Jupiter forms an isosceles triangle with Pollux and Castor, 10.3° from each.
Watch for a special event the night of May 30-31: There are two full moons this month, one on May 1 at 10:23 a.m., and the second one on May 31 at 1:45 a.m. Since the red supergiant star Antares, heart of Scorpius, is at opposition to the sun on the night of May 30-31, the full moon will appear close to that star all night. The closest approach, with Antares within 1° above the moon’s northern edge, occurs on the morning of May 31, shortly after 2:40 a.m. in Reno. Since this is the most distant full moon of the year, and it is a “Blue Moon,” then we have a Blue Micromoon in conjunction with a red supergiant star! After the “Blue Moon” overnight on May 30-31, the next one—if defined as the second full moon in a calendar month—will take place on Dec. 31, 2028. But if a Blue Moon is defined as the third full moon of a season with four, then tonight’s was not a Blue Moon, and the next will occur on May 20, 2027. Learn more at skyandtelescope.org/stargazing-and-observing/what-is-a-blue-moon.
In morning twilight: Use binoculars to spot 0.9-magnitude Saturn, very low in the east; and 1.2-magnitude Mars, within 8° to Saturn’s lower left, on May 1. Even though they’re 32° and 24° from the sun, the viewing conditions are poor (and get worse further north), with the zodiacal belt inclined so low. Use the waning crescent moon May 13-15 to help find them. By month’s end, these planets are a bit higher and 27° apart. Further enrich your May mornings by utilizing your binoculars and your ears to experience sights and sounds of birds in springtime!
Now, here’s a bit more about Mercury’s sudden, unusually bright appearance into May’s evening sky: During the hours surrounding its superior conjunction on May 14, Mercury, shining brilliantly at magnitude -2.4, will appear on LASCO coronagraph videos of NASA’s Space Weather Prediction Center. Solar conjunction occurs at 7 a.m. Pacific, and Mercury’s disappearance behind the sun lasts from about 4 1/2 hours before until 4 1/2 hours after that time. To view Mercury on NASA’s videos just before and after its 8 1/2-hour occultation by the sun, visit www.swpc.noaa.gov/products/lasco-coronagraph.
The near-coincidence of three events—Mercury passing the ascending node of its orbit and crossing north of the plane of Earth’s orbit on May 13; superior conjunction behind the sun on May 14; and Mercury’s perihelion, closest to the sun on May 18—makes the innermost planet ascend rapidly and brightly into the post-sunset sky in following days.
How soon after May 14 can you spot Mercury just above the west-northwest horizon shortly after sunset, with optical aid? With the unaided eye? (For optically aided sightings: Be sure to look after sunset, when the sun’s disk is safely hidden below the horizon; this will be possible by May 20, less than a week after its passage behind the sun, with Mercury 8° from the sun, and still at shining at magnitude -1.6.)
From Reno on May 20, Mercury is 8° to the upper left of the setting sun and sets 41 minutes after sunset, 24.5° to the lower right of Venus. On May 21, Mercury is 9.2° to the upper left of the setting sun, and sets 48 minutes after sunset, 23.6° to the lower right of Venus. Remaining above the horizon nearly seven minutes longer after sunset is a marked improvement after 24 hours, and it accumulates: By May 24, Mercury is 12.5° from the sun; sets 65 minutes after sundown; and will be easy for unaided eye. By May 31, Mercury, still prominent at magnitude -0.6, widens its elongation to nearly 19° from the sun, and follows the sun over the horizon by more than 1 1/2 hours. Mercury will climb highest in evening twilight in the second week of June, a few days before reaching greatest elongation on June 15, while 24.5° from the sun, and still visible with unaided eye at magnitude +0.4. Later that month, it will drop low in bright twilight and fade from view.
Robert Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys promoting sky watching to folks of all ages. 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.
