The Summer Triangle is one of the easiest landmarks to recognize in the summer night sky. Formed by the bright stars Vega, Deneb and Altair, it spans the constellations Lyra, Cygnus and Aquila and provides a useful starting point for finding several smaller constellations nearby. Under dark skies, the Milky Way can also be seen running through this part of the sky.
How to Find the Summer Triangle
Vega is usually the easiest place to start, as it is the brightest of the three Summer Triangle stars. From Vega, look for Deneb, the brightest star in Cygnus, and then Altair, the brightest star in Aquila. Together, the three stars form a large, obvious triangle that dominates the summer sky from mid-northern latitudes. It is especially prominent on summer evenings, but remains visible well into fall.
Lyra
Vega, the brightest star in Lyra and the fifth-brightest star in the night sky, appears blue-white and makes an obvious marker for this small constellation. Lyra represents a lyre, or harp, with most of its much fainter stars lying close to Vega. Four of these form a small parallelogram that helps reveal the constellation’s compact shape once you know where to look.
Cygnus
Deneb, the brightest star in Cygnus, marks the tail of the Swan and appears blue-white in the night sky. From Deneb, the Swan’s stars can be traced along its body toward Albireo at the head, while a second line of stars forms its outstretched wings, creating the distinctive Northern Cross. Cygnus lies along the Milky Way, so under dark skies the Swan appears to be flying through the hazy band of our galaxy.
Aquila
Altair, the brightest star in Aquila, marks the heart of the Eagle and is easy to recognize because it sits between two noticeably fainter stars, Tarazed and Alshain. These three stars form a short, almost straight line, with Altair shining white in the middle. From there, the rest of Aquila stretches away on either side to form the wings of the Eagle, although its overall shape is less distinctive than the Northern Cross.
The three brilliant stars of the Summer Triangle also provide useful markers for finding several much fainter constellations nearby. Delphinus, Sagitta and Vulpecula are far less conspicuous than the Triangle itself, but knowing where to look makes them much easier to pick out.
Delphinus
From Altair, look roughly a fist-width away for Delphinus, the Dolphin, just outside the imaginary line running from Altair toward Deneb. It has no particularly bright stars, but four of them form a compact diamond traditionally known as Job’s Coffin, with another star extending away to form the Dolphin’s tail. Despite its faintness, Delphinus is one of those rare constellations whose stars really can suggest the figure it represents — a small dolphin leaping through the sky.
Sagitta
Look about 10° from Altair, inside the Summer Triangle, for Sagitta, the Arrow. It is one of the smallest constellations in the sky and contains no bright stars, but its main stars form a surprisingly convincing arrow shape, complete with a pointed tip. Despite its small size and faint stars, Sagitta’s distinctive arrow shape makes it easier to recognize once you know where to look.
Vulpecula
Near Albireo and just inside the Summer Triangle lies Vulpecula, the Little Fox. Unlike Sagitta, it has no obvious naked-eye shape, and its brightest star is only around fourth magnitude, making it one of the more challenging constellations in the area to identify. In this case, knowing where Vulpecula should be is often easier than trying to recognize a fox among its faint stars.
The Milky Way Through the Summer Triangle
Under dark skies, the Milky Way can be seen as a broad, faint band of light stretching across the Summer Triangle. This hazy glow comes from the combined light of countless distant stars in our galaxy and passes through both Cygnus and Aquila. It is especially noticeable around Cygnus, where the Swan appears to fly along the Milky Way.