Aquila the Eagle: Altair and the Summer Sky

Aquila is a constellation that soars along the celestial equator, carrying one of the sky's most famous stars on its wings. Altair, the brightest star in Aquila and the 12th-brightest in the entire sky, forms one vertex of the Summer Triangle, one of the most prominent asterisms visible during warm-weather months. Whether you observe from the Northern or Southern Hemisphere, Aquila is accessible to nearly everyone on the planet. Point your phone at the sky with StarGlobe to find Altair instantly.

Finding Aquila in the Night Sky

The simplest way to locate Aquila is through the Summer Triangle. Find brilliant Vega in Lyra high overhead on summer evenings, then look for Deneb in Cygnus to the northeast. The third bright star, sitting lower and to the south, is Altair. Once you have Altair, the rest of Aquila takes shape as a broad diamond or cross pattern stretching along the Milky Way.

Altair is flanked by two companion stars that make it particularly easy to identify. Tarazed (Gamma Aquilae) sits just above Altair, and Alshain (Beta Aquilae) sits just below. This trio of stars forms a compact line that acts as the eagle's head and body. The wings extend to either side, and a short chain of stars trails southward as the tail.

Altair: A Rapid Spinner

Altair shines at magnitude 0.76 and lies only 16.7 light-years from Earth, making it one of our nearest bright stellar neighbors. It is an A-type main-sequence star roughly 1.8 times the mass of the Sun and about 11 times more luminous. What sets Altair apart from many other bright stars is its extraordinary rotation speed. It completes a full rotation in just about 8.9 hours, compared to the Sun's leisurely 25-day rotation period.

This rapid spin has a dramatic physical consequence. Altair is not spherical. Its equatorial diameter is about 22 percent larger than its polar diameter, giving it a noticeably oblate shape. Interferometric observations have actually resolved this flattening directly, making Altair one of only a handful of stars whose surface shape has been measured. The equatorial bulge also means the star's equator is cooler and dimmer than its poles, a phenomenon called gravity darkening.

Other Notable Stars

Tarazed (Gamma Aquilae) is a bright orange giant at magnitude 2.7, sitting about 460 light-years away. Its deep orange hue contrasts beautifully with Altair's white light. The name Tarazed comes from a Persian phrase meaning "the beam of the scale." Alshain (Beta Aquilae) is a fainter yellow star at magnitude 3.7, located about 45 light-years from Earth.

Eta Aquilae is one of the most prominent Cepheid variable stars visible to the naked eye. It varies between magnitudes 3.5 and 4.4 over a period of about 7.2 days. Watching its brightness change over the course of a week is an accessible project for beginners and a good introduction to variable star observing.

Deep Sky Objects

Because Aquila lies along the Milky Way, it contains a wealth of deep sky objects. NGC 6709 is an open cluster visible in binoculars as a faint misty patch about 3,000 light-years away. NGC 6755 is another open cluster worth seeking out with a small telescope.

The most dramatic deep sky feature near Aquila is the Great Rift, a band of dark interstellar dust clouds that splits the Milky Way into two parallel streams. This dark lane runs right through the constellation and is best seen under truly dark skies. The planetary nebula NGC 6781 and the dark nebula B143 are challenging but rewarding targets for experienced observers with larger telescopes.

Mythology and Cultural Significance

In Greek mythology, Aquila represented the eagle that served Zeus. One prominent story tells how Zeus sent the eagle to carry the young shepherd Ganymede up to Mount Olympus to serve as cupbearer to the gods. Ganymede is commemorated in the neighboring constellation Aquarius. Another myth describes the eagle as the bird that carried Zeus's thunderbolts into battle during the war against the Titans.

Aquila features prominently in East Asian astronomy as well. In the Chinese and Japanese tradition of the Qixi and Tanabata festivals, Altair represents the cowherd Niulang, separated from his beloved weaver girl Zhinyu (represented by Vega) by the river of the Milky Way. Once a year, magpies form a bridge across the celestial river so the lovers can reunite. This beautiful story has been told for over two thousand years and remains one of the most celebrated star legends in East Asia. For more constellation stories from around the world, read our constellation mythology guide.

The Summer Triangle Connection

Altair's role in the Summer Triangle makes it a cornerstone of summer sky navigation. The triangle, formed by Altair, Vega, and Deneb, is visible from June through November for Northern Hemisphere observers and serves as a launchpad for exploring dozens of constellations and deep sky objects along the Milky Way. The triangle is not a constellation itself but rather an asterism spanning three separate constellations.

From the Summer Triangle, you can navigate to Hercules and its great globular cluster, follow the Milky Way down through Sagittarius, or trace the path to the constellation Delphinus, a charming little dolphin that sits just east of Aquila.

Observing Tips

Aquila is best viewed from July through September, when it rides high across the southern sky for Northern Hemisphere observers. From the Southern Hemisphere, the constellation appears in the northern sky during the same months. Altair's position on the celestial equator at a declination of about +9 degrees means it is well placed for observers worldwide.

Binoculars are excellent tools for sweeping through Aquila's section of the Milky Way, revealing numerous star fields and clusters. For variable star enthusiasts, monitoring Eta Aquilae requires nothing more than the naked eye and a comparison chart. Use StarGlobe to identify Altair and its flanking stars, then explore the eagle's territory along the summer Milky Way.