Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Cygnus |
Right ascension | 20h 25m 58.04s [1] |
Declination | +38° 21′ 07.7″ [1] |
Apparent magnitude (V) | 11.14 [2] (10.60 - 11.74 [3] ) |
Characteristics | |
Spectral type | M3 Ia [4] (M3.5 Ia [5] ) |
U−B color index | +2.91 [2] |
B−V color index | +3.39 [2] |
Variable type | Lc [5] |
Astrometry | |
Proper motion (μ) | RA: –3.556 [1] mas/yr Dec.: –6.061 [1] mas/yr |
Parallax (π) | 0.6687 ± 0.0517 mas [1] |
Distance | 4,900 ± 400 ly (1,500 ± 100 pc) |
Absolute magnitude (MV) | –8.18 [6] |
Details | |
Radius | 1,033 [7] –1,420 [6] R☉ |
Luminosity | 138,000 [2] – 270,000 [6] [8] L☉ |
Surface gravity (log g) | −0.5 (−0.9?) [6] cgs |
Temperature | 3,550 [9] K |
Other designations | |
Database references | |
SIMBAD | data |
KY Cygni is a red supergiant of spectral class M3.5Ia located in the constellation Cygnus. It is approximately 5,000 light-years away.
KY Cyg lies near the bright open cluster NGC 6913, but is not thought to be a member. The location is close to the bright star γ Cygni. [10] It was identified as a variable star in 1930, [11] and later named as KY Cygni. [12] The spectrum was given the MK classification of M3 Ia, with only minor adjustments since. [4]
KY Cygni is heavily reddened due to interstellar extinction, losing an estimated 7.75 magnitudes at visual wavelengths. It would be a naked eye star if no light was lost. [6]
KY Cygni is classified as a luminous red supergiant with a strong stellar wind. It is losing mass at around 4.9×10−6 M☉ and has been described as a cool hypergiant. [2] [13]
Its properties are uncertain, but the temperature is around 3,500 K. A model fit based on K-band infrared brightness gives a luminosity of 273,000 L☉, corresponding to a radius of 1,420 R☉. Another model based on visual brightness gives an unexpectedly large luminosity of 1,107,000 L☉, with the difference due mainly to the assumptions about the level of extinction. The radius corresponding to the higher luminosity would be 2,850 R☉. These parameters are larger and more luminous than expected for any red supergiant, making them doubtful. [6] More recently, integration of the spectral energy distributions across a full range of wavelengths from U band to the 60 micron microwave flux gives an even lower luminosity of 138,000 L☉, [2] and calculation of the bolometric luminosity based on its Gaia Data Release 2 parallax gives a luminosity below 70,000 L☉ with a corresponding radius of 672 R☉. [9]
KY Cygni is a variable star with a large amplitude but no clear periodicity. At times, it varies rapidly, at others it is fairly constant for long periods. [10] The photographic magnitude range is given as 13.5 - 15.5, [5] while a visual range is 10.60 - 11.74. [3]
Red supergiants (RSGs) are stars with a supergiant luminosity class of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Antares A are the brightest and best known red supergiants (RSGs), indeed the only first magnitude red supergiant stars.
Phi Cassiopeiae is a star in the constellation Cassiopeia. φ Cassiopeiae is a multiple star with a combined apparent magnitude of +4.95. The two brightest components are A and C, sometimes called φ1 and φ2 Cas. φ Cas A is an F0 bright supergiant of magnitude 4.95 and φ Cas C is a 7.08 magnitude B6 supergiant at 134".
A yellow hypergiant (YHG) is a massive star with an extended atmosphere, a spectral class from A to K, and, starting with an initial mass of about 20–60 solar masses, has lost as much as half that mass. They are amongst the most visually luminous stars, with absolute magnitude (MV) around −9, but also one of the rarest, with just 20 known in the Milky Way and six of those in just a single cluster. They are sometimes referred to as cool hypergiants in comparison with O- and B-type stars, and sometimes as warm hypergiants in comparison with red supergiants.
KW Sagittarii is a red supergiant, located approximately 1,900 parsecs away from the Sun in the direction of the constellation Sagittarius. It is one of the largest-known stars. If placed at the center of the Solar System, the star's surface would engulf Mars.
V354 Cephei is a red supergiant star located within the Milky Way. It is an irregular variable located over 8,900 light-years away from the Sun. It has an estimated radius of 685 solar radii. If it were placed in the center of the Solar System, it would extend to between the orbits of Mars and Jupiter.
MY Cephei is a red supergiant located in open cluster NGC 7419 in the constellation of Cepheus. It is a semiregular variable star with a maximum brightness of magnitude 14.4 and a minimum of magnitude 15.5.
HR Carinae is a luminous blue variable star located in the constellation Carina. It is surrounded by a vast nebula of ejected nuclear-processed material because this star has a multiple shell expanding atmosphere. This star is among the most luminous stars in the Milky Way. It has very broad emission wings on the Balmer lines, reminiscent from the broad lines observed in the spectra of O and Wolf–Rayet stars. A distance of 5 kpc and a bolometric magnitude of -9.4 put HR Car among the most luminous stars of the galaxy.
S Persei is a red supergiant or hypergiant located near the Double Cluster in Perseus, north of the cluster NGC 869. It is a member of the Perseus OB1 association and one of the largest known stars. If placed in the Solar System, its photosphere would engulf the orbit of Jupiter. It is also a semiregular variable, a star whose variations are less regular than those of Mira variables.
NO Aurigae is a pulsating variable star in the constellation Auriga. It is an unusually-luminous asymptotic giant branch star about 3,500 light years away.
A hypergiant (luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term hypergiant is defined as luminosity class 0 (zero) in the MKK system. However, this is rarely seen in literature or in published spectral classifications, except for specific well-defined groups such as the yellow hypergiants, RSG (red supergiants), or blue B(e) supergiants with emission spectra. More commonly, hypergiants are classed as Ia-0 or Ia+, but red supergiants are rarely assigned these spectral classifications. Astronomers are interested in these stars because they relate to understanding stellar evolution, especially star formation, stability, and their expected demise as supernovae.
HD 168607 is a blue hypergiant and luminous blue variable (LBV) star located in the constellation of Sagittarius, easy to see with amateur telescopes. It forms a pair with HD 168625, also a blue hypergiant and possible luminous blue variable, that can be seen at the south-east of M17, the Omega Nebula.
NML Cygni or V1489 Cygni is a red hypergiant or red supergiant (RSG) in the constellation Cygnus. It is possibly one of the largest known stars currently known by radius, and is also possibly one of the most luminous and massive cool hypergiants, as well as one of the most luminous stars in the Milky Way.
PZ Cassiopeiae is a red supergiant star located in the Cassiopeia constellation, and a semi-regular variable star.
AH Scorpii is a red supergiant variable star located in the constellation Scorpius. It is one of the largest stars known by radius and is also one of the most luminous red supergiant stars in the Milky Way.
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.
BI Cygni(BI Cyg, IRC +40408, BD+36 4025) is a red supergiant in the constellation Cygnus. It is an irregular variable star with a maximum brightness of magnitude 8.4 and a minimum of magnitude 9.9. It is considered a member of the stellar Cygnus OB1 association, its distance is around 2,600 parsecs (8,500 ly) of the Solar System. It is less than a degree south of another variable red supergiant, BC Cygni.
HD 143183 is a red supergiant variable star of spectral type M3Ia in constellation Norma. It is a member of the Norma OB1 association, at a distance of about 2 kiloparsecs. It is one of the most luminous red supergiants with a luminosity over 100,000 times greater than the Sun (L☉), and is as well one of the largest stars with a radius more than a thousand times that of the Sun (R☉). Older studies frequently calculated higher luminosities and radii. It has an estimated mass loss rate of 5×10−5 M☉ per year and has been once described as a cool hypergiant. It is surrounded by a dozen early-type stars and a circumstellar nebula which extends 0.12 parsecs (0.39 ly).
V1936 Aquilae is a blue supergiant and candidate Luminous blue variable located in the nebula Westerhout 51, in the constellation Aquila, about 20,000 light years away. The star was originally identified as a massive star in 2000, and was thought to be an O-type supergiant. However, subsequent analyses have shown it to be not O but B-type, as well as being possibly an LBV.
V1027 Cygni is a luminous yellow supergiant star located in the constellation of Cygnus, about 14,000 light years away. For a time, it was thought that it could be a low-mass post-AGB star, however recent parallax measurements published in Gaia DR3 have shown this to likely not be the case, and instead it is likely a massive yellow supergiant star.