In May, find an asterism spans all of the seasons.
We’re used to thinking of star patterns as seasonal. In the Northern Hemisphere, we spend the cooler months watching Orion and the bright lights of the Winter Hexagon cross the sky, while summer just wouldn’t be the same without Scorpius, Sagittarius, and the Summer Triangle.
But there’s one spring asterism that lets us span the whole year at once.
Three of the night’s brightest stars, Arcturus, Vega, and Capella seem to hand the sky off to each other as the sky turns throughout the year, as at least one is easy to find every night of the year. And in May, it’s almost like we can hop from season to season just by letting our eyes hop from one star to the next. When all three of these bright stars are in the night sky at the same time, they form what I like to call the All-season Triangle.
From Season to Season
Arcturus, an orange-giant star about 37 light-years away in Boötes, the Herdsman, is the fourth brightest in the night sky. We can usually start to spot it in the east in mid-February, when it lags a bit behind Regulus, one of the other corners of the Spring Triangle. That bright, red-orange color is gorgeous and striking against the still bare late-winter branches. Arcturus culminates, reaching its highest point for the night, at 9:00 p.m. local time in mid-June, not long before the summer solstice. It disappears from nights in October.
But before Arcturus disappears from autumn nights, Capella, the brightest star in Auriga, the Charioteer, joins the night to carry us through wintertime. Capella is the first of the bright winter stars to come to autumn skies, a stunning sight when it pops into view above the neighbors’ chimneys as the leaves fall at our feet. Although it appears as one star, the system is actually four stars in two pairs — two bright yellow giants and two dim, red dwarfs — orbiting around each other like a teacups ride at an amusement park.
Capella culminates at 9:00 p.m. toward the end of January and we can still see it in May, just above the horizon as its story comes to an end.
Then there’s luminous Vega, about 25 light-years away in Lyra, the Harp. Rising into the night toward the northeast in late spring, it will form the Summer Triangle together with Deneb in Cygnus, the Swan and Altair in Aquila, the Eagle. In just a few weeks, this trio will be an amazing sight, soaring across sweltering summer nights. Vega culminates in late-August; then it and its Summer Triangle start their slow dive toward the horizon before Vega disappears in December.
Spot May’s All-Season Triangle
When we head out tonight, in mid-May, let’s look high in the east to spot Arcturus in mid-evening. Turn to find Capella setting in the northwest, its orange-yellow color almost melting into the springtime dusk. Meanwhile, Vega is just rising in the northeast. If we widen our gaze, we’ll see these three bright stars as the All-season Triangle, covering most of the northern half of the sky.
With just that one turn from west to east, we can watch our lives rewind, sending us back through chilly walks outside, thawing with a mug of hot chocolate, festive lights, sticky summer nights, and fireflies. As we do, it’s hard not to feel like there are more good days to come, too, and with these stars we can always find a familiar face lighting the way.