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Cygnus is a northern constellation on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan. Cygnus is one of the most recognizable constellations of the northern summer and autumn, and it features a prominent asterism known as the Northern Cross. Cygnus was among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.
Cygnus X-1 (abbreviated Cyg X-1) is a galactic X-ray source in the constellation Cygnus and was the first such source widely accepted to be a black hole. It was discovered in 1971 during a rocket flight and is one of the strongest X-ray sources detectable from Earth, producing a peak X-ray flux density of 2.3×10−23 W/(m2⋅Hz) (2.3×103 jansky). It remains among the most studied astronomical objects in its class. The compact object is now estimated to have a mass about 21.2 times the mass of the Sun and has been shown to be too small to be any known kind of normal star or other likely object besides a black hole. If so, the radius of its event horizon has 300 km "as upper bound to the linear dimension of the source region" of occasional X-ray bursts lasting only for about 1 ms.
A proplyd, short for ionized protoplanetary disk, is an externally illuminated photoevaporating protoplanetary disk around a young star. Nearly 180 proplyds have been discovered in the Orion Nebula. Images of proplyds in other star-forming regions are rare, while Orion is the only region with a large known sample due to its relative proximity to Earth.
Cygnus X-3 is a high-mass X-ray binary (HMXB), one of the stronger binary X-ray sources in the sky. It is often considered to be a microquasar, and it is believed to be a compact object in a binary system which is pulling in a stream of gas from an ordinary star companion. It is one of only two known HMXBs containing a Wolf-Rayet star. It is invisible visually, but can be observed at radio, infrared, X-ray, and gamma-ray wavelengths.
Cygnus OB2 #12 is an extremely luminous blue hypergiant with an absolute bolometric magnitude of −10.9, among the most luminous stars known in the galaxy. This makes the star nearly two million times more luminous than the Sun, although estimates were even higher when the star was first discovered. It is now known to be a binary, with the companion approximately a tenth as bright. A very approximate initial estimate of the orbit gives the total system mass as 120 M☉ and the period as 30 years.
Cygnus OB2 #8A is a double-lined spectroscopic binary located near the centre of the Cygnus OB2 association located 5,500 light years away.
Cygnus OB2 is an OB association that is home to some of the most massive and most luminous stars known, including suspected Luminous blue variable Cyg OB2 #12. It also includes one of the largest known stars, NML Cygni. The region is embedded within a wider one of star formation known as Cygnus X, which is one of the most luminous objects in the sky at radio wavelengths. The region is approximately 1,570 parsecs from Earth in the constellation of Cygnus.
NGC 6604 is a young open cluster of stars in the equatorial constellation of Serpens, positioned about 1.5° north of the Eagle Nebula. The cluster was discovered by William Herschel on July 15, 1784. It is located at a distance of 4,580 light years from the Sun, about 210 ly (65 pc) above the galactic plane. NGC 6604 forms the densest part of the Ser OB2 association of co-moving stars.
NML Cygni or V1489 Cygni is a red hypergiant or red supergiant (RSG) in the constellation Cygnus. It is one of the largest stars currently known by radius, and is also one of the most luminous and massive cool hypergiants, as well as one of the most luminous stars in the Milky Way.
Sigma Cygni, Latinised from σ Cygni, is a blue supergiant star in the constellation Cygnus. Its apparent magnitude is 4.2. It belongs to the Cygnus OB4 stellar association and is located approximately 3,300 light years away from Earth.
55 Cygni is a blue supergiant star in the constellation Cygnus. It is thought to be a member of the Cygnus OB7 stellar association at about 2,700 light years.
Cygnus-X is a massive star formation region located in the constellation of Cygnus at a distance from the Sun of 1.4 kiloparsecs.
BD+40°4210 is a hot luminous giant star located in the constellation Cygnus. It is a member of the Cygnus OB2 association and a candidate luminous blue variable.
BD+43 3654 is a massive luminous blue supergiant runaway star in the constellation Cygnus.
Carina OB1 is a giant OB association in the Carina Nebula, which is home to some of the most massive and luminous stars in the Milky Way Galaxy. It includes the young star clusters Collinder 228, NGC 3293, NGC 3324, IC 2581, Trumpler 14, Trumpler 15 and Trumpler 16, the last being the home of Eta Carinae. It also includes another massive and luminous star, HD 93129A. It is approximately 2,680 parsecs (8,700 ly) from Earth.
Cygnus OB7 is an OB association in the giant Cygnus molecular cloud complex, which also contains the star-forming regions Cygnus X, the North America Nebula and the Pelican Nebula. The Northern Coalsack Nebula of the Cygnus Rift lies in the foreground of this region. The molecular cloud has a large angular size of ~4° × 7°.
BC Cygni is a red supergiant and pulsating variable star of spectral type M3.5Ia in the constellation Cygnus.
RW Cygni is a semiregular variable star in the constellation Cygnus, about a degree east of 2nd magnitude γ Cygni. Its apparent magnitude varies between 8.05 and 9.70 and its spectral type between M3 and M4.
HM 1, also known as Havlen-Moffat 1, is an open cluster located in the constellation of Scorpius, close to the galactic plane. It was first observed by R. J. Havlen and A. F. J. Moffat in 1976. HM 1 is thought to be 9,500 to 12,700 light-years away from the Earth, beyond the Carina–Sagittarius Arm. It is heavily reddened by interstellar extinction, so although it comprises mostly blue-colored stars, it appears brighter for longer-wavelength passbands. It is projected against the H II region known as RCW 121, and appears to be the source of ionization for the nearby regions RCW 122 and RCW 123.
Berkeley 86 is a young open cluster in Cygnus. It is located inside the OB Stellar association Cyg OB 1, and obscured by a foreground dust cloud.
References
- ↑ "Ass Cyg OB 9". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2021-01-02.
- ↑ Pickett, Daniel Edward (1993). "Photoelectric UBV photometry of Cygnus OB3 and Cygnus OB9". ProQuest Dissertations and Theses; Thesis (M.S.)--University of Montana. 52–03: 39. Bibcode:1993PhDT.......160P.
- ↑ Zakirov, M. M.; Eshankulova, M. U. (2008). "Close binary systems in regions of OB associations. VI. V498 Cyg in Cyg OB9". Kinematics and Physics of Celestial Bodies. 24 (2): 77–88. Bibcode:2008KPCB...24...77Z. doi:10.3103/S0884591308020037. S2CID 121799853.
- ↑ Comerón, F.; Pasquali, A. (2012). "New members of the massive stellar population in Cygnus". Astronomy & Astrophysics. 110: 2715. Bibcode:2012A&A...543A.101C. doi: 10.1051/0004-6361/201219022 .
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