What planetary events are coming up in the night sky? Read about Venus, Mercury, Mars, Jupiter, Saturn, Uranus and Neptune and what’s going on in our Solar System in Planets at a Glance.
Mercury will open May shining at magnitude 0.59 in the northwestern sky after sunset, completing its best evening appearance of the year for mid-northern latitude observers. On May 1, the planet will be positioned only one degree to the upper left (or celestial southeast) of the Pleiades Cluster. The following evening, the young crescent Moon will join them, shining several degrees to their upper left. The optimal observing time then will be 8:30 to 9 p.m. local time. Telescope views of Mercury will display a waning crescent phase and an apparent disk diameter greater than 8.5 arcseconds. Mercury will fade in brightness and sink deeper into the evening twilight every night, rendering it unobservable from mid-month onward. The planet will pass the Sun at inferior conjunction on May 21.
Venus will continue to dominate the eastern pre-dawn sky during May. On May 1, the extremely bright, magnitude -4.1 planet will be passing one-sixth as bright Jupiter in a very close conjunction best seen before 5:30 a.m. local time. Earlier risers can see the string of fainter planets Mars and Saturn extending 33 degrees to their west. On each subsequent morning Venus’ rapid eastward motion through Pisces will increase its distance from Jupiter. That sunward swing will also drop the planet closer to the horizon. By month’s end, Venus will have diminished slightly in brightness to magnitude -3.95. Viewed in a telescope during early May, Venus will exhibit a 67%-illuminated gibbous phase and a disk 16.7 arcseconds across. At month’s end, the planet will show a 13.7 arcsecond-wide, 78-per-cent illuminated disk. On May 27, the old crescent Moon will shine several degrees to Venus’ lower left (or celestial east). Hours earlier, observers in southern Madagascar, most of southeast Asia, southeastern China and most of Micronesia can see the Moon occult Venus in daytime around 04:00 UTC.
Red-tinted Mars will continue to increase its angle from the Sun in the eastern sky during May, rising around 3:40 a.m. local time on May 1 and an hour earlier at month’s end. The ruddy planet will begin the month in Aquarius, with yellowish Saturn 18 degrees to its west and the close-together pair of much brighter Jupiter and Venus shining 15 degrees to its east. Mars’ faster orbital motion will carry it steadily away from Saturn and towards Jupiter. After passing half a degree south of magnitude 7.9 Neptune on May 18, Mars will cross into Pisces for a close conjunction 0.6 degrees south of 15 times brighter Jupiter on May 29. Over the month, Mars will brighten from magnitude 0.87 to 0.67. Its apparent disk size will grow from 5.8 to 6.4 arcseconds. The waning crescent Moon will hop past Mars and Jupiter on May 24 and 25, offering two nice photo opportunities.
Jupiter will begin May in a picturesque close conjunction with six times brighter Venus. The duo will be best seen, shining very low in the eastern sky, before 5:30 a.m. local time. Earlier risers can look for the line of fainter planets Mars and Saturn extending 33 degrees to their west. Jupiter will spend the entire month in western Pisces, but it won’t stretch far enough west of the Sun to see those stars until after mid-month. The faster motions of Venus and Mars will cause the former to leave Jupiter behind and the latter to overtake Jupiter in another close conjunction on May 29. Jupiter will remain rather low in the sky for clear telescopic views at mid-northern latitudes during May. Jupiter’s four Galilean moons will dance to the east and west of its 34.8 arcsecond-wide, banded disk. The Great Red Spot will appear every second or third morning. Occasionally, the small, round, black shadows of its four Galilean moons will transit. The waning crescent Moon will hop past Jupiter and Mars on May 24 and 25, making a pair of nice photo opportunities.
During May, Saturn will rise in the wee hours of the night, shining at magnitude 0.8 as it moves slowly prograde eastward among the stars of eastern Capricornus. It will remain visible in the southeastern sky until dawn. The planets Mars, Neptune, Jupiter, and Venus will be strung along the ecliptic to its lower left (or celestial east). Viewed in a telescope during May, Saturn’s 17-arcsecond wide globe, adorned with its 40-arcsecond wide ring system, will be surrounded by a number of its brightest moons. With the planet’s tilt diminishing until 2025, a good deal of Saturn’s southern hemisphere will extend below its ring plane this year. On May 22, the waning crescent Moon will pass five degrees below (or celestial south) of Saturn.
Uranus will pass solar conjunction on May 5, but it will be the end of May before the magnitude 5.9 planet returns to visibility from mid-northern latitudes, where it will sit very low in the eastern pre-dawn twilight among the stars of southern Aries. On May 28, the waning crescent Moon will shine a short distance to Uranus’ left (or celestial northeast). The same day, the Moon will occult Uranus around 14:00 UTC for Easter Island, most of South America, the Cape Verde Islands and most of west Africa — the fourth of 15 consecutive monthly lunar occultations of the seventh planet.
Throughout May, the magnitude 7.9 planet Neptune will be parked near the border between Aquarius and Pisces. It will be observable in the dark southeastern sky for an hour or so after it rises, during the wee hours. On May 1, the planet will be positioned just 3.5 degrees west of Jupiter’s close conjunction with Venus. While Venus races east on the following mornings, Jupiter will pull away from Neptune at a slower rate. At the same time, Mars will approach Neptune rapidly from the west. At their closest approach on May 17-18, Neptune will be 0.5 degrees above (or celestial north) of Mars, allowing them to share the view in a backyard telescope over several mornings. Mars’ reddish disk will appear several times larger than blue Neptune’s 2.25 arcsecond-wide disk.
Chris Vaughan is a science writer, geophysicist, astronomer, planetary scientist and an “outreach RASCal.” He writes Astronomy Skylights, and you can follow him on Twitter at @astrogeoguy. He can also bring his Digital Starlab portable inflatable planetarium to your school or other daytime or evening event. Contact him through AstroGeo.ca to tour the Universe together.