Star profile

Sigma Aquilae

Variable star

3D likeness based on its real data · class B · ~15,000 K

What is Sigma Aquilae

Sigma Aquilae is an eclipsing binary some 780 light-years away, made of two near-twin blue B3 V stars that eclipse each other every 1.95 days with clockwork precision. The primary burns at 18,493 K, radiates 1,862 times the Sun's light and carries 5.8 solar masses. Each eclipse dims the pair by two-tenths of a magnitude: a regular pulse at the heart of the Eagle, discovered in the early twentieth century and refined ever since.

Where it is and when to see it

Sigma Aquilae lies in the northern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is July, when it culminates around midnight.

From London it culminates about 44° above the horizon.
From New York it culminates about 55° above the horizon.
From Sydney it culminates about 51° above the horizon.

It can be seen from anywhere north of 85° S.

It ranks no. 29 in brightness among the 72 stars of Aquila in our catalogue. To find it, start from Altair, the brightest: it lies about 5° away (a fist at arm's length covers about 10°).

The light you see today left it about 780 years ago.

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Astronomical data for Sigma Aquilae

Constellation: Aquila
Apparent magnitude: 5.18
Distance: 780.4 light years
Coordinates (J2000): RA 294.799° · Dec 5.398°
Catalogue: HIP 96665 · HD 185507

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Other stars in Aquila

Aquila has 72 stars in Stelvia's catalogue. Here are a few of them.

See all 72 stars in Aquila