Gaze into the night sky this spring and you’ll see one of the oldest known constellations, Boötes (Latin for “herdsman”). The ancient Greeks saw Boötes as a man herding seven oxen represented by the stars in Ursa Major. The herdsman is assisted by a pair of dogs in the constellation Canes Venatici (Latin for “hunting dogs”) lying alongside Boötes in the sky.
Boötes is shaped much like a slightly skewed kite. To spot the constellation, first look for the seven bright stars in Ursa Major making up the famous Big Dipper. Follow the curve of the dipper’s handle (in fact, the Great Bear’s tail) toward the horizon till you come across the brilliant star found at the bottom of the kite. This star is Arcturus, the fourth brightest star in the night sky and the brightest in the northern celestial hemisphere.
Arcturus is a giant star 25 times larger and 110 times brighter than the Sun. It’s “only” 37 light-years from our solar system, so on a cosmic scale, it’s in our neighbourhood of stars. To the naked eye, Arcturus looks golden-yellow thanks to its surface temperature slightly cooler than the Sun’s.
In early March, Boötes emerges around 8 p.m. above the east-northeast horizon and then earlier and earlier as the days go by. By month’s end, the constellation rises just before sunset and remains visible all night long.
Evenings with Venus and Mercury
Early in the month, two planets are visible at twilight. Vivid Venus is the first to rear its head as it shines above the west horizon a half hour after sunset but soon dips below the horizon. Observation conditions improve later in the month as the Evening Star moves away from the Sun and appears higher in the twilight sky.
The first half of March provides a good opportunity to spot Mercury. The planet nearest the Sun is usually difficult to observe because it stays fairly close to our star from our perspective on Earth. But early in the month, Mercury is quite bright and passes just to the right of the dazzling, hard-to-miss Venus. From March 2 to 4, the two planets are only about one degree apart, so you have a great chance to glimpse Mercury in the twilight glow. The two remain neighbours for several days, but Mercury dims gradually from night to night and even faster after March 20 and eventually gets lost in the glare of sunset. On March 18 at twilight, the thin crescent Moon drifts to the left of the pair of planets.
Mornings with the planets
Brilliant Jupiter, which rises toward the east-southeast just before midnight, is clearly visible in the second half of the night. On the night between March 6 and 7, the waning gibbous Moon lies about 3 degrees to the upper right of the gas giant.
Mars and Saturn are also visible above the southeast horizon during the final hours of the night. Saturn shines this year in the constellation Sagittarius, whose brightest stars form a teapot. In the early dawn, the teapot is clearly visible above the southeast horizon in a sky without too much light pollution. The ringed planet is found to the upper left of the teapot’s lid. To the right of the teapot and a bit higher, you can also see a reddish celestial body, Mars. Remember that planets, unlike stars, don’t twinkle in the sky.
From March 9 to 11, the Moon can help you pick out the two planets. On the morning of the 9th, the last quarter Moon is to the right of Mars. The next day, the lunar crescent drifts between the two planets, and together the trio creates a large flat triangle. Finally, on the 11th, the crescent appears to the left of Saturn.
Daylight saving time and the equinox
Don’t forget that daylight saving time begins in the early morning on Sunday, March 11, so be sure to set your watches and clocks forward. As for astronomical spring, it stars with the equinox on March 20 at 12:15 p.m. EDT.