A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They are usually considered to be those with luminosity class I and spectral class B9 or earlier, although sometimes A-class supergiants are also deemed blue supergiants.
P Cygni is a variable star in the constellation Cygnus. The designation "P" was originally assigned by Johann Bayer in Uranometria as a nova. Located about 5,300 light-years from Earth, it is a hypergiant luminous blue variable (LBV) star of spectral type B1-2 Ia-0ep that is one of the most luminous stars in the Milky Way.
Alpha Cygni variables are variable stars which exhibit non-radial pulsations, meaning that some portions of the stellar surface are contracting at the same time other parts expand. They are supergiant stars of spectral types B or A. Variations in brightness on the order of 0.1 magnitudes are associated with the pulsations, which often seem irregular, due to beating of multiple pulsation periods. The pulsations typically have periods of several days to several weeks.
AG Carinae is a star in the constellation Carina. It is classified as a luminous blue variable (LBV) and is one of the most luminous stars in the Milky Way. The great distance and intervening dust mean that the star is not usually visible to the naked eye; its apparent brightness varies erratically between magnitude 5.7 and 9.0.
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.
HD 97950, is the central core of a super star cluster within the NGC 3603 H II region. It was catalogued as a single star, but has now been resolved into one of the densest clusterings of stars in the galaxy.
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.
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. Notable examples of hypergiants include the Pistol Star, a blue hypergiant located close to the Galactic Center and one of the most luminous stars known; Rho Cassiopeiae, a yellow hypergiant that is one of the brightest to the naked eye; and Mu Cephei (Herschel's "Garnet Star"), one of the largest and brightest stars known.
Wray 17-96 is a very luminous star in the Scorpius constellation, about 20,000 light-years (7 kpc) away. It is a suspected luminous blue variable (LBV), although it has not shown the characteristic spectral variations.
IRAS 17163−3907, also known as Hen 3-1379, is a yellow hypergiant star located 13,000 light years from Earth in the constellation of Scorpius. The star is embedded in thick shells of expelled gases and dust, and owing to its appearance has been nicknamed by astronomers the "Fried Egg Nebula". Yellow hypergiants are in an extremely active phase of their evolution.
IRC +10420, also known as V1302 Aquilae, is a yellow hypergiant star located in the constellation of Aquila at a distance of 4-6 kiloparsecs of the Sun.
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, 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.
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.
Westerlund 1 W26 or Westerlund 1 BKS AS is a red supergiant located at the outskirts of the Westerlund 1 super star cluster. It is one of the largest known stars and the most luminous supergiant stars discovered so far with radius calculated to be in excess of a thousand times the solar radius, and a luminosity of over 200,000 times the solar luminosity. If placed at the center of the Solar System, its photosphere would engulf the orbit of Jupiter.
HR 5171, also known as V766 Centauri, is a yellow hypergiant in the constellation Centaurus. It is said to be either an extreme red supergiant (RSG) or recent post-red supergiant (Post-RSG) yellow hypergiant (YHG), both of which suggest it is one of the largest known stars. The star's diameter is uncertain but likely to be between 1,100 and 1,600 times that of the Sun. It is 3.6 kpc from Earth.
HDE 316285 is a blue supergiant star in the constellation Sagittarius. It is a candidate luminous blue variable and lies about 6,000 light years away in the direction of the Galactic Center.
HD 87643 is a B[e] class binary star embedded in a reflection nebula.
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.
