Red supergiants (RSGs) are stars with a supergiant luminosity class and a stellar classification 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.
Zeta Puppis, formally named Naos, is the brightest star in the constellation of Puppis.
HD 84810, also known as l Carinae, is a star in the southern constellation of Carina. Its apparent magnitude varies from about 3.4 to 4.1, making it readily visible to the naked eye and one of the brightest members of Carina. Based upon parallax measurements, it is approximately 1,600 light-years from Earth.
Phi Cassiopeiae is a multiple star in the constellation Cassiopeia 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.
RS Puppis is a Cepheid variable star around 6,000 ly away in the constellation of Puppis. It is one of the biggest and brightest known Cepheids in the Milky Way galaxy and has one of the longest periods for this class of star at 41.5 days.
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.
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.
VY Canis Majoris is an extreme oxygen-rich red hypergiant or red supergiant and pulsating variable star 1.2 kiloparsecs from the Solar System in the slightly southern constellation of Canis Major. It is one of the largest known stars, one of the most luminous and massive red supergiants, and one of the most luminous stars in the Milky Way.
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.
VX Sagittarii is an asymptotic giant branch star located more than 1.5 kiloparsec away from the Sun in the constellation of Sagittarius. It is a pulsating variable star with an unusually large magnitude range. It is one of the largest stars discovered, with a radius varying between 1,350 and 1,940 solar radii (940,000,000 and 1.35×109 km; 6.3 and 9.0 au). It is the most luminous known AGB star, at bolometric magnitude –8.6, which is brighter than the theoretical limit at –8.0.
CPD−57°2874 is a B[e] supergiant in the constellation Carina. It is a rare star as it is hot but has dust which shows forbidden lines and IR emissions. In 2007 the high spatial and spectral resolution of the star's circumstellar envelope was studied. This was the first time such a study was carried out on a class B[e] supergiant.
V602 Carinae is a red supergiant and variable star of spectral type M3 in the constellation Carina. It is considered to be one of largest known stars, being around 1,000 times larger than the Sun.
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.
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.
V1429 Aquilae is a candidate luminous blue variable multiple star system located in the constellation of Aquila. It is often referred to by its Mount Wilson Observatory catalog number as MWC 314. It is a hot luminous star with strong emission lines in its spectrum.
HD 179821 or V1427 Aquilae is either a post-red supergiant yellow hypergiant or a post-AGB yellow supergiant star in the constellation of Aquila, surrounded by a detached dust shell. It is a semi-regular variable nearing the end of its life.
AS 314, also known as V452 Scuti, is a protoplanetary nebula once believed to be a white hypergiant star or luminous blue variable located in the constellation of Scutum. It has an apparent magnitude of 9.85 and can be seen with small telescopes.
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.
HD 271182, occasionally referred to as G266 and R92, is a rare yellow hypergiant (YHG) and an Alpha Cygni variable. It is one of the brightest stars in the Large Magellanic Cloud (LMC), positioned in the deep southern constellation of Dorado. Gaia DR2 parallax measurements indicate that it is located around 200,000 light-years away, though this value is extremely uncertain. Despite this vast distance from Earth, the star is observable through a small telescope due to its immense luminosity, at an apparent magnitude of 9.6. It is receding away from the Sun at a heliocentric radial velocity of +311.9185 km/s, confirming its membership in the LMC.
