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.
For observers along mid-northern latitudes, Mercury will only be observable during the first week of September, when it might be glimpsed shining a short distance above the western horizon immediately after sunset. Skywatchers located farther south can more easily see the speedy planet sitting higher and in a darker sky until about mid-month. During those two weeks, Mercury will markedly decrease in brightness from magnitude 0.32 to 2.25. Viewed in a telescope (only after the Sun has completely set), Mercury will exhibit a waning crescent phase and an apparent disk size that swells from 7.9 to 10 arcseconds. Mercury will pass the Sun at inferior conjunction on September 23 and then join much brighter Venus in the eastern sky before sunrise during the final mornings of September. Mercury, by then at magnitude 3.4, will pass 3.3 degrees to the southwest of Venus on September 27.
Venus will continue to shine brightly in the east-northeastern sky before sunrise during September, but its angular separation from the Sun will steadily diminish from 13 to 6 degrees, keeping Venus rather low in the sky and reducing viewing time before sunrise. Venus’ easterly motion will carry it out of Leo and into Virgo on September 24. Venus will shine at a very bright magnitude -3.9 all month long. In a telescope, the planet will display a disk size that shrinks slightly from 10.0 to 9.8 arcseconds and a waxing, nearly fully-illuminated phase. On September 25, the slender crescent of the old Moon will shine three degrees to the lower left (east) of Venus. On the mornings surrounding September 27, much fainter Mercury will pass several degrees to the southwest.
Mars will be well positioned for viewing between late evening and dawn during September. On September 1, it will rise just after 11 p.m. local time and approach 60 degrees elevation by sunrise. By month’s end, Mars’ rising time will advance by an hour. The red planet will spend September travelling prograde eastward through central Taurus, passing between the bright star Aldebaran and the Pleiades cluster (M45) on September 1, two degrees north of the open cluster NGC 1647 on September 1, and 1.8 degrees south of the open cluster NGC 1746 on September 24. Due to the ongoing reduction in the Earth-Mars distance, Mars will brighten from magnitude 0.14 to -0.59 during September. Telescope views of the planet will show an 87-per-cent-illuminated, ruddy disk with hints of the dark markings that will be clearer come December. The planet’s apparent disk size will grow from 9.8 to 12 arcseconds. On September 16, the waning, third quarter Moon will shine about four degrees to the left (or celestial north) of Mars.
Bright, white Jupiter will be well-placed for observing from mid-evening to dawn during September. The planet will be advancing westward across the stars of western Pisces — and towards Neptune. Its separation from Neptune will decrease from 12 to 9 degrees over the month. Jupiter will also be bracketed by the bright planets Saturn to the southwest and Mars well to the northeast. On September 26, Jupiter will reach opposition for 2022. Since Earth will be positioned between the Sun and the gas giant on that date, Jupiter will rise at sunset, remain visible all night long, and set at sunrise. At opposition, Jupiter will be 591.3 million kilometres, 367.4 million miles or 32.9 light-minutes from Earth, and it will shine at its maximum brightness for 2022 of magnitude -2.94. Because Jupiter is approaching perihelion in January, 2023, the planet will sport a generous, 49.9 arcseconds-wide disk at this year’s opposition. Views of Jupiter in amateur telescopes will show its equatorial bands, and the Great Red Spot every second or third night. Around opposition, Jupiter and its four large Galilean satellites frequently eclipse and occult one another, and cast their round, black shadows on the planet — singly and in pairs. From September 10 to 11 the full Moon will hop past Jupiter.
The yellowish dot of Saturn will appear in the lower part of the southeastern sky as the sky darkens after dusk during September. Much brighter Jupiter will be positioned 45 degrees to its left (or celestial east). Saturn will be travelling retrograde westward toward the magnitude 4.2 star Iota Capricorni in central Capricornus — although its pace will be slowing toward month’s end as it prepares to complete a retrograde loop. The ringed planet will look best in a telescope when it culminates, a third of the way up the southern sky, in late evening. In a telescope, Saturn will show an apparent disk diameter of 18.4 arcseconds, and its rings will subtend 43 arcseconds. Saturn’s rings will be tilting more edge-on to us every year until the spring of 2025. This year they are already closed enough for Saturn’s southern polar region to extend beyond them. The nearly full Moon will hop past Saturn on September 7 and 8.
Blue-green Uranus will be observable overnight during September, rising shortly after 10 p.m. local time on the September 1 and then climbing highest in the southern sky before dawn. Toward month’s-end, Uranus will rise before 8:30 p.m. local time and then culminate during the wee hours. Over the month, the planet will be accelerating its westward motion through the stars of southeastern Aries. Look for magnitude 5.7 Uranus positioned just south and between the stars Botein or Delta Arietis and Pi Arietis — creating a triangular asterism for anyone searching in binoculars. On September 14, the bright, waning gibbous Moon will shine 3.5 degrees to the lower left (or celestial east) of Uranus. Hours earlier, observers in much of Northern Africa, Europe, parts of the Middle East, and western Russia can see the Moon occult Uranus around 21:30 UTC — the ninth in a series of consecutive lunar occultations of that planet.
During September, the distant, blue planet Neptune will be an all-night target that will already be climbing the southeastern sky after dusk. It will be traveling retrograde westward among the stars of northeastern Aquarius, about seven degrees to the northeast of the medium-bright stars Phi, Chi, and Psi Aquarii. When Neptune reaches opposition on September 16, it will be closest to Earth for this year — a distance of 4.32 billion kilometres, 2.68 billion miles, 4 light-hours or 28.9 Astronomical Units. The blue planet will then shine at a slightly brighter magnitude of 7.8, and Neptune’s apparent disk size will peak at 2.4 arcseconds. Since it’s directly opposite the Sun in the sky, Neptune will be visible from about 10 p.m. local time, when the blue planet has climbed higher, until dawn. Use good binoculars if your sky is very dark, and a backyard telescopes from almost any site. Neptune’s large Moon Triton can be seen more easily around opposition, too. The very bright, nearly full Moon will shine 4.5 degrees southeast of Neptune on September 10.
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.