An Etymological Dictionary of Astronomy and Astrophysics
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The Swan. A prominent northern → constellation that lies in the glowing band of the Milky way, east of Lyra and north of Vulpecula, and represents a swan. The brightest stars of Cygnus form a cross, so it is also known as the Northern Cross. Abbreviation: Cyg, genitive: Cygni.

From L. cygnus "swan," from Gk. kuknos.

Mâkiyân "a hen, fowl."

The strongest extragalactic radio source in the sky approximately 10⁹ light-years away in the → constellation  → Cygnus. Also called 3C 405.

→ Cygnus.

A large supernova remnant in the → constellation  → Cygnus, some 80 light-years across, lying about 2,500 light-years away. The loop is expanding at over 100 km/s and is thought to be about 30 000 years old.

→ Cygnus, → loop.

One of nine → OB associations located in the Cygnus → constellation. The central association, → Cygnus OB2, is the most famous and the youngest of the Cygnus region. (L. Mahy et al. 2013, astro-ph/1301.0500 and references therein).

→ Cygnus; → OB star; → association.

The nearest example of a → massive star region of → star formation, containing 65 known → O-type stars and hundreds of → B-type stars. Cygnus OB2 lies at a distance of 1.45 → kpc. It is the central association, the most famous, and one of the youngest of the Cygnus region. Cyg OB2 possibly has two → populations with ages of 3.5-5 Myr, while the → O stars seem to belong to a younger population, aged about 2 Myr.

→ Cygnus; → OB association; 2 because there are several OB associations in Cygnus; → Cygnus OB association.

A → binary system containing one of the best candidates for a → black hole. Cygnus X-1 was discovered as an → X-ray source in 1965. It is one of the brightest X-ray sources on the sky, so that it was detected by the earliest → X-ray observation attempts. This binary system, distant of 2.5 kpc, consists of the O9.7 Iab type → supergiant HDE 226868 and a → compact object orbiting around with a period of 5.6 days. The mass of the unseen companion, significantly larger than 5 → solar masses, suggests that it is a black hole. Focused → wind accretion from a → primary star being extremely close to filling the → Roche lobe drives the powerful source of the X-ray radiation.

→ Cygnus.

Same as → Orion Arm.

→ Orion; → Cygnus; → arm.