Evenings in January 2023 feature a spectacular array of four bright planets in a long line across the sky at dusk, shrinking from 130° on Jan. 1 to 104° on Jan. 22.
In the first three weeks, in order from very low in the west-southwest to well up in the east, they are Venus, Saturn, Jupiter and Mars. In a pretty conjunction of planets on Jan. 22—from sites with no mountains nearby blocking the view toward the west-southwest—Venus passes within 0.4° to the south (left) of Saturn. It will be fun to keep an eye on the pairing for several evenings before and after, to watch for daily changes. Nine days before and after the pairing, on Jan. 13 and 31, Venus-Saturn are 10° apart! After Jan. 22, the changed order of planets will be Saturn-Venus-Jupiter-Mars. Saturn will drop from view, sinking into bright twilight by early in February.
January’s evening twilights also feature an unusually large number of bright stars—11 of the 15 stars of first magnitude or brighter ever visible from our home latitude. The 11 stars are all shown on our evening twilight map for January. Castor, of magnitude +1.6, should not be counted in the total, but it’s plotted anyway, to help identify its brighter “twin,” Pollux, 4.5° away. In mid-January at dusk, we see the Summer Triangle of Vega, Deneb and Altair in the northwest to west; Fomalhaut, mouth of the Southern Fish, low in the southwest, to the left of Saturn and below Jupiter; Aldebaran, eye of Taurus, near Mars in the east; and Orion’s red Betelgeuse, with blue-white Rigel below (with his three-star belt between them). Capella, the “mother goat” star, is in the northeast to east-northwest, to the upper left of Orion; and the “Twin” stars of Gemini, Castor and Pollux, are below Capella and to the left of Orion. Finally, watch for the rising of Procyon, just north of due east, and the brightest star Sirius, in the east-southeast, in line with Orion’s belt extended downward. Sirius and Procyon are the “dog stars” of Canis Major and Canis Minor. These dog stars complete the nearly equilateral Winter Triangle with Orion’s shoulder, Betelgeuse, and they chase Orion across the sky. If mountains don’t block your view, you can catch Sirius rising before Altair sets just north of west, and you’ve got your 11 bright stars—six of them in the Summer and Winter Triangles, simultaneously.
The waxing moon adds its beauty and presence to the planetary lineup at dusk through Jan. 6, and again Jan. 22-Feb. 5. Catch the moon near Mars and Aldebaran, eye of Taurus, on Jan. 2 and 3; and the full moon near Pollux and Castor, the “Twin” stars of Gemini, on Jan. 6.
Starting another two-week journey through the sky at dusk on Jan. 22, the very thin young crescent moon appears 7° below the Venus-Saturn pairing; on the next evening, Jan. 23, the moon is 9° to the upper left of Venus. For the next week, until dusk on Jan. 30, the moon and four bright planets span 104° as our satellite shifts more than 13° daily against the background stars of the zodiac. On Jan. 25, the moon is 2-3° to the lower left of Jupiter.
On Jan. 30 at dusk, the moon will dance with Mars. Observers in Reno will see the moon’s northern edge pass narrowly south of Mars. The least separation of Mars from the moon’s northern limb will be 2.7 arcminutes, or less than one-tenth of the moon’s half-degree diameter, at 9:01 p.m.
At dusk on Jan. 31, the moon will have moved 11° east of Mars.
Telescopic views: Only three months out from its passage on the far side of the sun, Venus still appears small and full. Its best display at dusk will be in June and July, when it transforms into a thin crescent, growing five times as large in apparent size as it is now. In January, Saturn is best seen early in the month, before it sinks low. On Jan. 22, Venus and the ringed planet will appear within 0.4°, easily fitting into the same low- or medium-power telescopic field. End-to-end, the rings, tipped less than 13° from edge-on, appear nearly as wide as Jupiter, currently the most impressive planet for viewing. Jupiter displays cloud belts parallel to its equator and a system of four bright satellites discovered by Galileo in 1610. Mars is currently the closest planet to Earth, but because of its small actual size, its disk appears only about one-third of the size as Jupiter’s. It is now early spring in Mars’ northern hemisphere, and a 6-inch telescope at 150-power reveals a bright polar cap of frozen carbon dioxide. Syrtis Major, a dark triangular surface feature on Mars first recorded in 1659 and now known to consist of volcanic rock, can be spotted near the center of the Martian disk on Jan. 6 near 6 p.m., and 37-38 minutes later each evening, until Jan. 14 at 11 p.m.
In the morning sky in mid-January, find the “twin stars” Pollux and Castor sinking in the west-northwest; Regulus in the west, to upper left of the twins; golden Arcturus and blue-white Spica well up in the southern sky; Antares, heart of the Scorpion, in the southeast; and the Summer Triangle of Vega, Deneb and Altair in the northeast to east. Notice that in mid-January, you can observe the Summer Triangle both at dawn, in the eastern sky, and at dusk, in the western sky. Its stars are far north of the Earth’s orbit plane. Its stars are above the horizon all day and for longer than the sun, making their appearance possible at both times. In mid-January, the Summer Triangle, visible at dusk, sets early, and rises in time to bring up the rear of the overnight parade of stars. Of all the other bright stars, only Capella in early June, and Arcturus in late October, are far enough north of the Earth’s orbit plane to have two separate appearances on the same night.
After passing inferior conjunction on Jan. 7, Mercury is faint for several mornings and overwhelmed by the dawn glow, but it flares up to magnitude +1.1 by Jan. 15, to 0.0 by Jan. 22, and brightens slowly thereafter. Mercury is highest in the east-southeast to southeast morning twilight on Jan. 24 and 25, and reaches greatest elongation, 25° from sun, on Jan. 30.
Follow the waning moon mornings from Jan. 7 to Jan. 19 or 20. Catch the full moon near Pollux on Jan. 7; a gibbous moon near Regulus on Jan. 10; close to last quarter phase (half-full) near Spica on Jan. 14 and 15; as a crescent near Antares on Jan. 18; 13° to the right of Mercury on Jan. 19; and, very thin and challenging in bright twilight, 9° below Mercury, on Jan. 20.
Binoculars provide good views of the moon; conjunctions of planets; and star clusters such as the Pleiades and Hyades in Taurus, the Great Nebula in Orion’s Sword, Andromeda Galaxy, and even an occasional comet.
Comet ZTF (C/2022 E3)—Zwicky Transient Facility—is predicted to reach magnitude 5.5 near the end of January. It will pass closest to Earth, within 26 million miles, on Feb. 2. It passes within 10° of Polaris on Jan. 29 (on a line from the North Star toward the Pointer Stars of the Big Dipper), and on Jan. 30 (on a line from the North Star toward Omicron in Ursa Major, marking the nose of the Great Bear). For a few days, the comet moves 6° daily, on a line toward Capella, which it passes on Feb. 5. On the night of Feb. 10-11, the fading comet passes about 1° east of Mars.
Robert Victor originated the Abrams Planetarium monthly Sky Calendar in October 1968, and still produces issues occasionally. He enjoys being outdoors sharing the wonders of the night sky.
