In October 2022, all of the other planets of our solar system, except for Venus, appear to move retrograde, or backward/westward, against the starry background, for at least part of the month: Mercury, only until Oct. 2—much to the relief of friends who are devotees of astrology—and Saturn, in Capricornus until Oct. 22.
Mars begins retrograde in Taurus on Oct. 30; retrograding all month are Jupiter in Pisces; Uranus in Aries; and Neptune in Aquarius.
A planet appears to move retrograde when Earth overtakes it, or it overtakes Earth, always surrounding the dates when Earth and the other planet are on the same side of the sun and closest to each other. For the outer planets—Mars, Jupiter, Saturn, Uranus and Neptune—retrograde motion is centered on the date of opposition, when the planet appears 180° from the sun and is visible all night. For inner planets Mercury and Venus, retrograde occurs surrounding inferior conjunction, when the planet passes between Earth and the sun.
During October, Venus passes superior conjunction, on the far side of the sun, so it’s not moving retrograde.
Evening attractions: Brilliant Jupiter, magnitude -2.9 to -2.8, and Saturn, magnitude +0.5 to +0.6, adorn the southeast quarter of the sky at dusk. Saturn is 44° to the upper right of Jupiter on Oct. 1, decreasing to 41° by the 31st. Most of the change occurs because Jupiter retrogrades 3.3° against the faint background of Pisces, the Fishes, this month. The waxing gibbous moon appears near Saturn on Oct. 4 and 5, and near Jupiter on Oct. 7 and 8.
On Oct. 1, Saturn is within 1° east-northeast of the 4.3-magnitude star Iota in Capricornus. Saturn ends retrograde on Oct. 22, 0.6° east-northeast of 4.3-magnitude Iota Cap, and begins a slow return toward 2.9-magnitude Delta Cap, marking the end of the tail of the Sea-goat, 5.4° to Saturn’s east.
Ranking in brightness next after Jupiter in the early evening sky are golden Arcturus, sinking in the west to west-northwest, and blue-white Vega, overhead to very high in the west-northwest. Marsoutshines these stars, but it rises, far north of east, not until nearly four hours after sunset on Oct. 1, and nearly three hours after on Oct. 31.
Using binoculars, look for Neptune’s Dipper, six stars of magnitude 4.4 to 5.9, less than 5.3° in extent. This compact asterism consists of these stars: 20, 24, 27, 29, 33, 30 in Pisces, midway between Iota Ceti and the Circlet of Pisces. (The star field appears on Chart 4 of Sky and Telescope’s Pocket Sky Atlas. )
Useful for locating Neptune from 2022 to 2025, this asterism is now southwest to south (to the right) of Jupiter at nightfall, by 3.7° to 6.6° on Oct. 1, closing to 1.4° to 4.4° on Oct. 31. In October, Neptune is 2.8° to 3.5° west-southwest of 5.5-magnitude 20 Psc, northernmost star of the asterism, at the end of the handle of the “Dipper.” On Oct. 22, 7.8-magnitude Neptune passes 8-9 arcminutes south-southeast of a 7.2-magnitude star, HIP116402, so don’t be fooled! On Oct. 28, a line from Jupiter, west to 20 Psc, 3.5° long, extended its own length, locates 7.8-magnitude Neptune. Binoculars of at least 50-millimeter aperture and a clear dark sky are required to detect Neptune, the eighth and outermost planet known in our solar system.
Predawn attractions: Having our clocks remain on daylight saving time makes predawn sky-watching very attractive in October!
Starting very low in the east in morning twilight, Mercury emerges quickly, brightening a full magnitude, from +1.2 to +0.2, from Oct. 1-4. Mercury climbs higher until October 8-9, when it reaches greatest elongation, 18° from the sun, its best predawn showing this year, while brightening even further, to magnitude -0.5. Jupiter can be spotted low in the west in morning twilight early in month, but it sets 4 to 5 minutes earlier each day, from one hour before sunup on Oct. 8, to three hours before on the 31st. Mars gleams at magnitude -0.6 to -1.2 high in the southwest quadrant of the sky all month, against the beautiful backdrop of Taurus, the Bull.
Venus, ending its reign as morning “star,” rises in the east just 27 minutes before sunup on Oct. 1. Sinking into even brighter twilight, Venus passes superior conjunction, on far side of the sun, on Oct. 22. In December, Venus will emerge into the southwestern evening sky, joining all the other planets. The departure of Venus and Jupiter from the morning sky in October leaves the twinkling blue-white Dog Star, Sirius, in the southern sky at magnitude -1.4, as the brightest morning star until red Mars exceeds it in November.
The waning moon passes through Taurus Oct. 13-15: Look about an hour before sunrise, before twilight brightens much, to catch the moon 4° from the Pleiades cluster on Oct. 13; and 10° from Aldebaran, eye of the Bull, on Oct. 13 and 14; and 5° to 6° from Mars on Oct. 15. Continuing eastward through the zodiac, the last quarter moon, half full, passes only 2° south of Pollux in Gemini on Oct. 17. The other twin, Castor, is 4.5° from Pollux. On Oct. 13-16, Spaceship Earth is headed approximately in the direction of these two stars: 10° south of Castor on Oct. 13, and 7° south of Pollux on Oct. 16.
On Oct. 20, the moon appears in Leo, within 5° of Regulus, the Lion’s heart. Use a telescope to watch one of Leo’s stars get occulted. From Reno, the lower, leading sunlit edge of the crescent moon covers the 3.5-mag star Eta in Leo at 3:48 a.m., and the upper, trailing dimly earthlit edge of the moon uncovers the star at 4:56 a.m.
Just four days later, on Oct. 24, the moon occults Mercury. At morning mid-twilight, from Reno, 43 minutes before sunrise, or at 6:35 a.m., the very thin 1 percent crescent moon is less than 2 degrees above the horizon, with Mercury, shining at magnitude -1.1, hovering very closely below it. Mercury disappears behind the sunlit lower right edge of the moon shortly before 6:44 a.m., 35 minutes before sunrise. The event will be visible through binoculars or a telescope for those who keep track of the moon and Mercury until then.
Mars goes east 5.4° against the stars Oct. 1-30. On the latter date, the red planet commences 74 days of retrograde (westward) motion, ending Jan. 12, 2023. A chart depicting nearly all of Mars’ 7.5-month visit to Taurus, from early August 2022 to late March 2023, including its retrograde motion, appeared with last month’s column at RenoNR.com.
In October, watch Mars drift between Bull’s horns. The tips of the horns, nearly 8° apart, are marked by 1.7-magnitude Beta Tauri and 3.0-magnitude Zeta. On Oct. 14, Mars passes 5.7° south of Beta; on Oct 18, 2.2° north of Zeta (least separations). On the morning of Oct. 17, in the first of three passes between tips of the horns, Mars is 5.7° from Beta and 2.2° from Zeta. On the morning of Oct. 30, Mars begins retrograde 2.7° north-northeast of Zeta. Mars will peak at magnitude -1.9 between its closest approach to Earth on Nov. 30 and its opposition and all-night visibility on Dec 7.
Through the telescope: In the evenings, Jupiter’s cloud belts and changing positions of the four bright satellites are fascinating to watch. Saturn’s rings in are tipped 15° from edgewise, our best view until Spring 2028. Late in the evening on Oct. 11, the narrow dark edge of the moon, just past full, uncovers Uranus just after 10:50 p.m. for Reno-area skywatchers. The planet will be very difficult to observe because of the moon’s brightness. Mornings, Syrtis Major, the most prominent dark marking on Mars, appears near the center of the Martian disk on Oct. 27 at 12:24 a.m., and 37-38 minutes later each day, until Nov. 7 at 6:12 a.m.
Sky Calendar includes illustrations of many of the events described in this article. To subscribe or to view a 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 the October and December 2022 editions. He enjoys being outdoors sharing the wonders of the night sky. 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.