Related Research Articles
Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars spans from about 3,400 K to over 20,000 K.
The Triangulum Galaxy is a spiral galaxy 2.73 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC (New General Catalogue) 598. With the D25 isophotal diameter of 18.74 kiloparsecs (61,100 light-years), the Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Andromeda Galaxy and the Milky Way.
The Pistol Star is an extremely luminous blue hypergiant star, one of the most luminous and massive known in the Milky Way. It is one of many massive young stars in the Quintuplet cluster in the Galactic Center region. The star owes its name to the shape of the Pistol Nebula, which it illuminates. It is located approximately 25,000 light-years from Earth in the direction of Sagittarius. The star has a large mass comparable to V4998 Sagittarii and a luminosity 3.3 million times that of the Sun (L☉). It would be visible to the naked eye as a 4th-magnitude star if it were not for the interstellar dust near the Center of the Milky Way that absorbs almost all of its visible light.
S Doradus is one of the brightest stars in the Large Magellanic Cloud (LMC), a satellite galaxy of the Milky Way, located roughly 160,000 light-years away. The star is a luminous blue variable, and one of the most luminous stars known, having a luminosity varying widely above and below 1,000,000 times the luminosity of the Sun, although it is too far away to be seen with the naked eye.
Andromeda I is a dwarf spheroidal galaxy (dSph) about 2.40 million light-years away in the constellation Andromeda. Andromeda I is part of the local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It is roughly 3.5 degrees south and slightly east of M31. As of 2005, it is the closest known dSph companion to M31 at an estimated projected distance of ~40 kpc or ~150,000 light-years.
Luminous blue variables (LBVs) are massive evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of the Large Magellanic Cloud. They are considered to be rare.
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.
NGC 4559 is an intermediate spiral galaxy with a weak inner ring structure in the constellation Coma Berenices. Distance estimates for NGC 4559 range from about 28 million light-years to 31 million light-years, averaging about 29 million light-years.
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.
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.
NGC 2363-V1 is a luminous blue variable star in the star-forming region NGC 2363, at the far southwestern part of the irregular galaxy NGC 2366 in the constellation Camelopardalis, near the north celestial pole nearly 11 million light years away from our galaxy. It was discovered in 1996 by Laurent Drissen, Jean-René Roy, and Carmelle Robert while examining images taken by the Hubble Space Telescope Wide Field Planetary Camera 2.
AFGL 2298, also known as IRAS 18576+0341, is a luminous blue variable star (LBV) located in the constellation Aquila, very close to the galactic plane. Its distance is not well known; it may be anywhere between 23,000 and 42,000 light years away from the Earth. Despite being extremely luminous, it is extremely reddened by interstellar extinction, so its apparent magnitude is brighter for longer-wavelength passbands; in fact, in visual wavelengths it is completely undetectable.
AE Andromedae is a luminous blue variable (LBV), a type of variable star. The star is one of the most luminous variables in M31, the Andromeda Galaxy.
V4998 Sagittarii is a luminous blue variable star (LBV) in the constellation of Sagittarius. Located some 25,000 light-years away, the star is positioned about 7 pc away from a starburst cluster known as the Quintuplet cluster. It has an ejection nebula measuring over 0.8 pc in diameter, formed 5000-10,000 years ago through large eruptions. The star has a large mass comparable to the Pistol Star and a luminosity of around 4 million times the Sun (L☉). This places the star as one of the most massive and luminous stars known.
V4650 Sagittarii (qF362) is a luminous blue variable star (LBV) in the constellation of Sagittarius. Located some 25,000 light years away, the star is positioned on the edge of a starburst cluster known as the Quintuplet cluster.
Romano's Star is a luminous blue variable star located in the Messier 33 galaxy in the constellation of Triangulum.
M33-013406.63, also known as B416 or UIT301, is a O-type blue evolved supergiant star in the constellation of Triangulum. It is located within the Triangulum Galaxy, which is approximately 2,380,000–3,070,000 light years away from Earth.
AF Andromedae is a luminous blue variable (LBV), a type of variable star. The star is one of the most luminous variables in M31, the Andromeda Galaxy.
B324 is a yellow hypergiant in the Triangulum Galaxy, located near the giant H II region IC 142 around 2.7 million light years away. It is the brightest star in the Triangulum Galaxy in terms of apparent magnitude.
References
- 1 2 Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
- 1 2 3 4 5 6 Humphreys, R. M.; Blaha, C.; d'Odorico, S.; Gull, T. R.; Benvenuti, P. (1984). "IUE and ground-based observations of the Hubble-Sandage variables in M31 and M33". The Astrophysical Journal. 278: 124. Bibcode:1984ApJ...278..124H. doi: 10.1086/161774 .
- 1 2 Khrutskaya, E. V.; Khovritchev, M. Yu.; Bronnikova, N. M. (2004). "The Pul-3 catalogue of 58483 stars in the Tycho-2 system". Astronomy and Astrophysics. 418: 357–362. Bibcode:2004A&A...418..357K. doi: 10.1051/0004-6361:20034232 .
- ↑ Burggraf, B.; Weis, K.; Bomans, D. J. (2006). "LBVs in M33: Their Environments and Ages". Stellar Evolution at Low Metallicity: Mass Loss. 353: 245. Bibcode:2006ASPC..353..245B.
- 1 2 3 4 Valeev, A. F.; Sholukhova, O.; Fabrika, S. (2009). "A new luminous variable in M33". Monthly Notices of the Royal Astronomical Society: Letters. 396 (1): L21. arXiv: 0903.5222 . Bibcode:2009MNRAS.396L..21V. doi: 10.1111/j.1745-3933.2009.00654.x . S2CID 14666975.
- 1 2 Van Den Bergh, S.; Herbst, E.; Kowal, C. T. (1975). "A survey of bright variable stars in M33". The Astrophysical Journal Supplement Series. 29: 303. Bibcode:1975ApJS...29..303V. doi:10.1086/190344.
- ↑ Humphreys, R. M. (1978). "Luminous variable stars in M31 and M33". The Astrophysical Journal. 219: 445. Bibcode:1978ApJ...219..445H. doi: 10.1086/155797 .
