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 spend the month of August in the western post-sunset sky, swinging to its widest elongation from the Sun of 27 degrees on August 27, and then rewinding sunward again at month’s end. The severely inclined evening ecliptic will prevent Mercury from ever climbing very high over the horizon for Northern Hemisphere observers, especially after it dips south of the ecliptic around mid-month, making this a poor appearance for northerners. Conversely, August’s apparition will be the best of the year for Southern Hemisphere viewers. Mercury will fade in brightness, from magnitude -0.54 to +0.29, over the month. At the same time, telescope views will reveal the planet’s apparent disk size growing from 5.35 to 7.79 arcseconds and its illuminated phase waning from 85 per cent to 46 per cent. Mercury will pass 0.7 degrees north of Leo’s brightest star Regulus on August 3-4. The young crescent Moon will shine 9 degrees to the right, and then 6 degrees above Mercury, on August 28 and 29, respectively.
Venus will continue to gleam in the east-northeastern pre-dawn sky during August, but its angle from the Sun will steadily decrease from 22 to 14 degrees, keeping it rather low in the sky and reducing viewing time before sunrise. Venus’ easterly motion will carry it out of Gemini on August 10, across the middle of Cancer from August 11 to 26, and then into Leo for the rest of August and most of September. Venus will shine at a very bright magnitude -3.9 all month long. In a telescope, it will display a disk size that shrinks slightly from 10.7 to 10.1 arcseconds and an illuminated phase that increases from 92.6 per cent to 97 per cent. On August 18, Venus will travel through the southern outskirts of the Beehive Cluster (Messier 44) in Cancer, but only observers at tropical latitudes will have skies dark enough to see the “bees.” On August 25 the slender crescent of the old Moon will shine 6.5 degrees to the northwest of Venus, with the magnitude 8.7 speck of the dwarf planet Ceres nearby.
Mars will begin the month shining among the stars of southeastern Aries, and only 1.3 degrees south of 170 times fainter Uranus. Their conjunction will best seen before dawn, when the two planets will be highest. As the days pass, Mars will slide eastward, departing Aries for Taurus on August 9, passing less than 5.5 degrees south of the Pleiades from August 17 to 22, and then ending the month a few degrees north of the bright, reddish star Aldebaran and the rest of the bull’s triangular face. For mid-northern latitude observers, the red planet will rise about two minutes earlier each night – ahead of midnight local time starting around mid-month. Due to the reduction in the Earth-Mars distance Mars will brighten from magnitude +0.20 to -0.12 during August. Telescope views of the planet will show an 85-per-cent-illuminated, rusty disk with hints of the dark markings that will be obvious come December. The planet’s apparent disk size will grow from 8.3 to 9.7 arcseconds. On August 18 the waning, third quarter Moon will shine two degrees to the west of Mars.
Bright, white Jupiter will be well-placed for observing after late evening during August. The magnitude -2.7 planet will be creeping slowly westward across the stars in the northwestern corner of Cetus – about midway between reddish Mars, shining well off to its lower left (or celestial northeast), and yellowish Saturn, to its right (or southwest). Unfortunately, the low summertime ecliptic will prevent the planets from climbing very high in the southern sky. On August 1, Jupiter will rise over the eastern horizon at around 10:40 p.m. local time and reach halfway up the southern sky before the sunrise hides it. At month’s end, the by-then slightly brighter planet will then rise around 8:30 p.m. local time. Jupiter will be an excellent telescope target during August. With Jupiter approaching perihelion in January, 2023, the planet’s disk will grow from 45 arcseconds to a generous 49 arcseconds. Views of Jupiter in amateur telescopes will show its equatorial bands, the Great Red Spot appearing every 2nd or 3rd night, and Jupiter’s four large Galilean satellites frequently eclipsing and occulting one another. They’ll cast their round, black shadows on the planet individually on August 19 and 23, and in pairs on August 8 and 15-16. On August 14 the waning gibbous Moon will shine just below (or celestial southwest of) Jupiter.
Yellowish Saturn will be available for viewing all night long during August because it will be rising shortly after dusk. The ringed planet will be travelling retrograde westward above the two bright tail stars of eastern Capricornus – with much brighter Jupiter positioned 45 degrees to its left (east). Unfortunately, the low summertime ecliptic will prevent the planet from climbing very high in in the southern sky. On August 14, Saturn will reach opposition. At that time, the ringed planet will be at a distance of 823.3 million miles, 1.325 billion km, or 73.7 light-minutes from Earth. While planets at opposition always look their brightest, Saturn’s peak magnitude 0.28 will be enhanced by the Seeliger effect, backscattered sunlight from its rings. In a telescope at opposition Saturn will show an apparent disk diameter of 18.8 arcseconds, and its rings will subtend 43.7 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 well beyond them. Opposition is also the best time to view Saturn’s moons with a backyard telescope in a dark sky. The recently full Moon will sit several finger widths below Saturn on August 11.
Blue-green Uranus will begin August in a close conjunction with Mars, positioned only 1.3 degrees north of the 170 times brighter red planet. As Mars flees east, the two planets will remain binoculars-close until about August 11. Although it will begin to rise before midnight local time around August 4, magnitude 5.7 Uranus will be most visible in binoculars and backyard telescopes during the second half of the night – rising at 12:20 a.m. local time on August 1, and then around 10:20 p.m. local time at month’s end. The planet will look best in a telescope before dawn, when it will sit more than halfway up the southern sky. Uranus will be the lower right (southernmost) corner of a diamond formed with the 4th and 5th magnitude stars Botein or Delta Arietis, Epsilon Arietis, and Pi Arietis – creating a distinctive asterism for anyone searching in binoculars. On August 24, Uranus will cease its easterly motion across the stars of southeastern Aries and commence a westward retrograde loop that will last until January, 2023. On August 17 in the Americas, the waning gibbous Moon will shine several degrees to Uranus’ upper right. Observers from Micronesia to most of Hawaii and the Bering Sea can see the Moon occult Uranus at around 16:00 UTC on August 18 — the eighth in a series of consecutive lunar occultations of that planet.
During August the distant planet Neptune will be observable during most of the night while it travels slowly retrograde westward – crossing from Pisces into Aquarius on August 18. There will be no nearby bright stars to guide us to it, but you can find blue, magnitude 7.8 Neptune positioned a few degrees to the right (or celestial west) of the midpoint between the magnitude 4.4 stars 30 Piscium and Lambda Piscium. Or, hop 1.5 binoculars fields to the left of the 4th-magnitude stars Psi, Xi, and Phi Aquarii, a triple star. The best times for viewing Neptune through good binoculars and backyard telescopes will be during the wee hours, when it will be highest. In a telescope Neptune will show a 2.3 arcseconds wide-disk. Watch for its large Moon Triton tucked close-in to the planet. Jupiter’s faster retrograde motion will carry it to within 13 degrees east of Neptune at month’s end. On July 13, the bright, waning gibbous Moon will shine 5 degrees to the lower right (or celestial southwest of) Neptune.
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.