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The Summer Constellations

On summer nights, the three bright stars Deneb (α Cygni), Vega (α Lyrae) and Altair (α Aquilae) form the striking ‘Summer Triangle’. The constellations of Cygnus (the Swan) and Aquila (the Eagle) represent birds ‘flying’ down the length of the Milky Way. This part of the Milky Way contains the Great Rift, an elongated dark region, where the light from distant stars is obscured by intervening dust. The dark Rift is clearly visible even to the naked eye.

The most prominent stars of Cygnus are sometimes known as the ‘Northern Cross’ (as a counterpart to the ‘Southern Cross’ – the constellation of Crux – in the southern hemisphere). The central line of Cygnus through Albireo (β Cygni), extended well to the southwest, points to Sabik (η Ophiuchi) in the large, sprawling constellation of Ophiuchus (the Serpent Bearer) and beyond to Antares (α Scorpii) in the constellation of Scorpius. Like Cepheus, the shape of Ophiuchus somewhat resembles the gable-end of a house, and the brightest star Rasalhague (α Ophiuchi) is at the ‘apex’ of the ‘gable’.

A line from the central star of Cygnus, Sadr (γ Cygni) through δ Cygni, in the northwestern ‘wing’ points towards the Head of Draco, and is another way of locating that part of the constellation. Another line from Sadr to Vega indicates the central portion, ‘The Keystone’, of the constellation of Hercules. An arc through the same stars, in the opposite direction, points towards the constellation of Pegasus, and more specifically to the ‘Great Square of Pegasus’.

Aquila is less conspicuous than Cygnus and consists of a diamond shape of stars, representing the body and wings of the eagle, together with a rather faint star, λ Aquilae, marking the ‘head’. Lyra (the Lyre) mainly consists of Vega (α Lyrae) and a small quadrilateral of stars to its southeast. Continuation of a line from Vega through Altair indicates the zodiacal constellation of Capricornus.