Aquila
Aquila, glowing with Altair the Cowherd star. Here are a star flattened by dizzying rotation and the Cowherd of the Qixi legend.
Science
The scienceThe chief star Altair (the Cowherd Star) lies just 16.7 light-years from Earth, one of the nearest of all first-magnitude stars. Its most astonishing feature is its dizzying rotation: its equator spins at about 900,000 km per hour (100 times the Sun's rate). The centrifugal force leaves the star not round but squashed flat like a pumpkin, so that its equatorial diameter is a full 20% greater than its polar diameter. It was among the first stars to have its shape imaged directly. Intriguingly, the three stars that appear in a straight line are not truly close in space at all — Tarazed is a giant red star about 20 times farther away than Altair (some 380 light-years), merely lying in the same direction as seen from Earth, an "apparent alignment."
Mythology
How it became a constellationIn East Asia, Altair is the well-known Cowherd Star. Having fallen in love with the Weaver Maid (Vega) across the Milky Way and neglected his work, he was cast to the far bank of the river by the Jade Emperor, and the two may meet only one day a year — the seventh night of the seventh lunar month — upon a bridge of magpies who join heads to span the river. Tarazed and Alshain, on either side of Altair, are said to be the two children the Cowherd carries with him, which is why the three stars always travel together in a line. In the West, it is the sacred eagle that bore Zeus's thunderbolts, carrying the beautiful youth Ganymede up to the heavens.
Observing Guide
how to observe🔭 How to find it
On a summer evening, along the southern edge of the Milky Way, look for a bright star flanked in a straight line by a fainter star on each side — the bright one in the middle is Altair, Aquila's lead star. Altair forms the southern vertex of the "Summer Triangle" with Deneb in Cygnus and Vega in Lyra, so the triangle makes it easy to find. It faces Vega across the Milky Way.
✨ What to look for
Although Aquila lies over the Milky Way, it holds few conspicuous bright nebulae or clusters. Instead, in the southern part of the constellation is "Eta Aquilae," a textbook Cepheid variable that visibly changes brightness over a period of about seven days, a cycle you can follow with the naked eye. Sweep the Milky Way here with binoculars and dense star clouds and small clusters fill the background.
📍 Where to see it (US · Canada · UK · Australia)
Aquila sits close to the celestial equator, so all four countries see it well. From the US, Canada and UK it reaches a comfortable height in the southern sky on summer evenings (July–September), Altair climbing to around 50–60°. From Australia it rides fairly high in the northern sky on winter evenings, appearing upside down relative to the northern view, with the Milky Way running through it.