Minnesota Starwatch
MARCH 2023
March always brings passages—winter to spring, ice to slush, sun to the Northern Hemisphere. This year, the month begins with an uncommon passage as the two brightest planets sweep by each other above the southwest horizon.
On Wednesday, the 1st, Jupiter passes within a moon width of brilliant Venus. The gap between them quickly widens as Jupiter falls into the sun’s afterglow. On Wednesday, the 22nd, a thin crescent moon appears above Jupiter about 40 minutes after sunset. The next night, the moon hangs below Venus.
East of the planetary pair, Mars rides high at nightfall as the bright winter stars stream past it. In mid-month Mars glides between Betelgeuse, the giant red star at Orion’s right shoulder, and brilliant Capella, in Auriga, the charioteer. At month’s end the red planet will be heading into Gemini. Enjoy this feast of stars and Mars now, before the winter constellations also slip into the sunset.
March’s full moon arrives at 6:40 a.m. on Tuesday, the 7th, after crossing the night sky below the spring constellation Leo, the lion. The moon sets in the west shortly after reaching fullness, so plan accordingly.
Spring begins with the vernal equinox at 4:24 p.m. Monday, the 20th. At that moment the sun crosses the equator heading north, and Earth will be lighted from pole to pole. From then until the September equinox, the day length increases as we travel north. Also, the day length increases most rapidly near the spring equinox because the sun is then moving most rapidly northward.
If you’re out at the end of evening twilight between the 10th and the 22nd, look for a faint, broad cone of light extending up from the western horizon along the sun’s path. This is the elusive zodiacal light, the result of sunlight reflecting off dust in the plane of the solar system. Recent evidence has suggested a Martian origin for the dust.
FEBRUARY 2023
In February Venus climbs above the sunset horizon and settles into its latest reign as an “evening star.” But the sun is also climbing, so we have to go out later each night to see our sister planet against a dark sky.
As Venus surges, Jupiter drops toward it, thanks to Earth leaving the giant planet behind in the orbital race. Look for Jupiter in the southwest and watch the two brightest planets draw closer each night. The pair ends the month poised to pass each other on March 1.
While Earth regularly leaves Jupiter in the dust, it can’t do that to Venus because it’s closer to the sun and speedier than Earth. Thus, Venus climbs and falls due to its own movement. When it’s an evening star it’s chasing us, but when it appears in the morning sky we’re “eating its dust.”
Mars is now high in the south at nightfall. The red planet is fading but still easy to find; look east of the Pleiades star cluster and above Aldebaran, the eye of Taurus, the bull. Also, take this chance to compare Venus, the brightest planet, to Sirius, the brightest star in the night sky. Sirius is the lowest of the bright winter stars now assembled in the southeast and shines to the lower left of Orion’s hourglass figure. Try in mid-month, when Venus will be higher at nightfall and no moon will interfere.
February’s full moon arrives on the 5th. During the moon’s next cycle it visits Jupiter and Venus on the 21st and 22nd and Mars on the 27th.
On Groundhog Day we celebrate an ancient astronomically based Celtic holiday called Imbolc, or lamb’s milk. It marked the start of the lambing season and was one of four cross-quarter days falling midway between a solstice and an equinox. How the groundhog became linked to this day isn’t clear. As for why seeing its shadow, or not, was important, one theory suggests that if the day was cloudy and shadowless, it portended rain and softening farm fields. But a clear and cold day signaled a more stubborn winter.
JANUARY 2023
The new year opens with Venus climbing out of the sun’s afterglow. On Sunday, January 22, Saturn drops past Venus as Earth’s orbital motion sends the ringed planet tumbling into the sunset. Look for the pair of planets very low in the southwest just as the sky darkens.
If you catch Venus and Saturn, also turn your eyes to Jupiter, the beacon high in the southwest, and high-flying, reddish Mars, the second-brightest object in the knot of winter constellations in the east. With the right timing, you can simultaneously view Venus—the brightest planet—and Sirius, the brightest star (after the sun) and the last of the iconic winter stars to clear the eastern horizon.
January’s full moon arrives on Friday, the 6th. It rises before sunset and becomes full at 5:08 p.m. After nightfall it shines to the right of the Gemini twins Pollux (the brighter) and Castor. Between about 9 p.m. and midnight on Friday the 30th, you’ll have plenty of time to watch a waxing moon of the next cycle glide close below Mars.
In the predawn sky, the Northern Cross lies on its side below brilliant Vega, the jewel of Lyra, the lyre. On the 18th, a thin waning moon rises close to Antares, the heart of Scorpius.
Earth reaches perihelion, the closest point to the sun in its orbit, at 10:17 a.m. on the 4th, when our planet reaches its top speed. Changes in Earth’s speed go largely unnoticed, but they show up in the length of the seasons. Because Earth goes so fast in the middle of its journey from the September to the March equinox, the combined fall-winter season is about seven days shorter for us than for our friends in the Southern Hemisphere.