On these March mornings before sunup, look for the Summer Triangle. It’s not summer for our northern temperate latitudes, but the three brilliant stars of the Summer Triangle – Vega, Deneb and Altair – are visible now in this part of the sky. These three stars are bright, although not as bright as Venus, which is also in the east before dawn now. The chart above shows the Summer Triangle’s relationship to Venus on or near March 7.
For much of Earth, the Summer Triangle stars are up for at least part of the night every night of the year. Are you in the Southern Hemisphere? You won’t see the entire Summer Triangle yet before sunup, but you can see that the stars Vega and Altair point to Venus, as shown on our chart above. For you, these stars will lie more nearly parallel to your eastern horizon.
The Summer Triangle isn’t one of the officially recognized 88 constellations. Like the Big Dipper, it’s what’s called an asterism, a pattern of stars that’s easy to pick out.
To gauge the size of this signpost star formation, hold a one-foot ruler an arm’s length from your eye. The ruler (about 1/3 of a meter) pretty much fills the gap between Vega and Altair, the Summer Triangle’s first and second brightest stars, respectively.
Like all the stars, the stars of the Summer Triangle rise four minutes earlier every day, or two hours earlier every month. Why is this happening? It’s happening because Earth is orbiting the sun, and our night sky is pointing out on an ever-changing panorama of stars.
Around May Day – May 1 – the Summer Triangle will climb over the eastern horizon around local midnight (1 a.m. daylight time). When middle to late June comes rolling along, you’ll see the Summer Triangle sparkling in the east at evening dusk – a sure sign of summer’s return to the Northern Hemisphere.
Bottom line: The Summer Triangle’s three brilliant stars – Vega, Deneb and Altair – are up before dawn in March, before midnight in May and at dusk on the summer solstice. Right now, they’re in the east before sunup, near Venus!