One month before summer solstice, which occurs on June 20, we find two of summer’s brightest stars rising above the east-northeast skyline as twilight deepens. Foretelling the summer season, Vega, third brightest star in northern skies at 0.00 magnitude, rises in the northeast while less bright Deneb, 1.25 m, appears to the lower left of the blue-white beacon. (The brighter the star, the smaller the number.) Deneb is the furthest star from Earth visible with the unaided eye.* About two and a half hours after sunset, Altair, 0.75 m, rises in the east, joining Vega and Deneb to complete the Summer Triangle, one of the most prominent star patterns in northern skies.
Today, May 18, sunset is at 8:10. The sun sets about a minute later every evening for the rest of the month. Civil twilight begins about half an hour after sundown; nightfall, or astronomical twilight, two hours after sunset.
As the Summer Triangle rises in the east-northeast, the last of the great stars of the Winter Circle set in the west-northwest. Most prominent among them, Procyon, 0.37 m, sets before midnight and Capella 0.06 m, after midnight this week. The Gemini Twins, Castor, 1.56 m, and brighter Pollux 1.15 m, are poised above and between Procyon and Capella.
