VY Canis Majoris
VY Canis Majoris (abbreviated to VY CMa) is an extreme oxygen-rich (O-rich) red hypergiant (RHG) or red supergiant (RSG) and pulsating variable star located at 1.2 kiloparsecs (3,900 ly) away from Earth in the constellation of Canis Major. It is one of the largest known stars (sometimes considered as the largest known)[a], and is also one of the most luminous and massive red supergiants.
VY CMa is a single star with a large infrared (IR) excess, making it one of the brightest objects in the sky at wavelengths of between 5 and 20 microns (µm) and indicating a dust shell or disk heated by the star. It is about ±8 times the mass of the Sun ( 17M☉). It is also surrounded by a complex asymmetric circumstellar envelope (CSE) caused by mass loss from the star itself. It produces strong molecular maser emission and was one of the first radio masers discovered. VY CMa is embedded within the large molecular cloud Sharpless 310 (Sh2-310), one of largest star-forming H ii region with a diameter of 480 arcminutes (') or 681 ly (209 pc).
The diameter of VY CMa is around 1,400–2,000 times that of the Sun (R☉), which is close to the Hayashi limit and corresponds to a volume around 3 to 10 billion times bigger than the Sun. A hypothetical object travelling at the speed of light would take 6 to 8 hours to travel around the star's circumference, compared to 14.5 seconds for the Sun. If placed at the center of the Solar System, VY CMa's surface would extend beyond the orbit of Jupiter, although there is still considerable variation in estimates of the radius, with some making it larger than the orbit of Saturn.
The first known recorded observation of VY Canis Majoris is in the star catalogue of the French astronomer Jérôme Lalande, on 7 March 1801, which lists it as a 7th magnitude star. Further 19th- and 20th-century studies of its apparent magnitude suggested that the star had been fading since 1850.
Since 1847, VY Canis Majoris has been described as a crimson star. During the 19th century, observers measured at least six discrete components, suggesting that it might be a multiple star. These discrete components are now known to be bright areas in the surrounding nebula. Visual observations in 1957 and high-resolution imaging in 1998 showed that there are no companion stars. VY CMa was also discovered to be a strong source of OH (1612 MHz), H
2O (22235.08 MHz), and SiO (43122 MHz) masers emission, which is typical of an OH/IR star. Many molecules, such as HCN, NaCl, PN, CH, CO, CH
3OH, TiO, and TiO
2, have also been detected.
The variation in VY CMa's brightness was first described in 1931 when it was listed (in German) as a long period variable with a photographic magnitude range of 9.5 to 11.5. It was given the variable star designation VY Canis Majoris in 1939, the 43th variable star of the constellation Canis Major.
VY Canis Majoris is surrounded by an extensive and dense asymmetric red reflection nebula with a total ejected mass of 0.2-0.4 M☉ and a temperature of 800 K based on a DUSTY model atmosphere that has been formed by material expelled from its central star. The diameter of the inner shell is found to be 0".12, corresponding to 140 AU (0.0022 ly) at a distance of 1.2 kpc, whereas that of the outer one is 10", corresponding to 12,000 AU (0.19 ly). This nebula is so bright that it was discovered in 1917 with an 18 cm telescope, and also contains condensations that were once regarded as companion stars. It has been extensively studied with the aid of the Hubble Space Telescope (HST), showing that the nebula has a complex structure that includes filaments and arcs, which were caused by past eruptions; this structure is similar to that of the nebula surrounding the post-red supergiant (Post-RSG) or yellow hypergiant (YHG) IRC +10420. The similarity has led astronomers to propose that VY CMa will evolve blueward on the Hertzsprung–Russell diagram (HR diagram) to become a yellow hypergiant, then a Luminous blue variable (LBV), and finally a Wolf–Rayet star (WR star).
Observations combining Hubble Space Telescope data with that obtained from the Keck Telescope, located in Hawaii, it was possible to make a three-dimensional reconstruction of the material surrounding VY CMa. This reconstruction showed that VY CMa's mass loss is much more complex than expected for any red supergiant or hypergiant. It became clear that the bows and nodules appeared at different times; the jets are randomly oriented, which leads us to believe that they derive from explosions occurred in active regions of the stellar photosphere. The spectroscopic data showed that the jets move away from the star at different speeds, indicating that they occurred at different times and originate from different areas of the surface of VY CMa. Multiple asymmetric mass loss events and also the ejection of the outermost material are deduced to have occurred within the last 500–1,000 years, while that of a knot near the star would be less than 100 years. The mass loss is due to strong convection in the tenuous outer layers of the star, associated with magnetic fields. This is similar to the sunspots and coronal ejections of the Sun but on a much larger scale.
In 1976, Charles J. Lada and Mark J. Reid published observations of the bright-rimmed molecular cloud Sh2-310, which is 15' east of VY Canis Majoris. At the edge of the cloud bordered by the bright rim, an abrupt decrease in the CO emission and an increase in brightness of the 12
CO emission were observed, indicating possible destruction of molecular material and enhanced heating at the cloud-rim interface, respectively. Lada and Reid assumed the distance of Sh2-310 is approximately equal to that of the stars, which are members of the open cluster NGC 2362, that ionize the rim. NGC 2362 has a distance of ±0.5 kiloparsecs (kpc) or roughly 1.5±1,630 light-years (ly) as determined from its 4,890color-magnitude diagram. VY CMa is projected onto the tip of the cloud rim, suggesting its association with Sh2-310. In addition to that, the velocity of Sh2-310 is very close to the velocity of the star. This further indicates the association of the star with Sh2-310, and consequently with NGC 2362, which means VY Canis Majoris is at the same distance. A more recent measurement of the distance to NGC 2362 gives 1.2 kpc or about 3,910 ly.
Stellar distances can be calculated by measuring parallaxes as Earth orbits around the Sun. However, VY Canis Majoris has a small parallax due to its great distance, and standard visual observations have a margin of error too large for a hypergiant star with an extended CSE to be useful, for example, the Hipparcos Catalogue (1997) gives a parallax of ±3.54 milliarcseconds (mas), yelding a distance of 1.78pc or about 561.8 . 1,832.34 ly The parallax of VY CMa can be precisely measured with high accuracy from the observation of masers using a long baseline interferometry. In 2008, observations of H
2O masers using VERA interferometry from the National Astronomical Observatory of Japan give a parallax of ±0.08 mas, corresponding to a distance of 0.88+0.11
−0.09 kpc or about 1.14+360
−300 ly. 3,720 In 2012, observations of SiO masers using Very-long-baseline interferometry (VLBI) from Very Long Baseline Array (VLBA) independently derived a parallax of ±0.08 mas, corresponding to a distance of 0.83+0.13
−0.10 kpc or about 1.20+423
−326 ly. 3,910 These new distance estimates imply that either Sh2-310 is less remote than usually estimated or that VY CMa is a foreground object.
VY Canis Majoris is a variable star that varies in brightness from apparent magnitude of +6.5 to +9.6. in the General Catalogue of Variable Stars (GCVS) it is classed a semiregular variable of sub-type SRc, indicating a cool supergiant, with an estimated pulsational period of 956 days, although it is classed as a type LC slow irregular variable star in the American Association of Variable Star Observers (AAVSO) Variable Star Index. Other periods of 1,600 and 2,200 days have been derived.
The spectrum of VY Canis Majoris is that of a high luminosity M class star. The hydrogen lines, however, have P Cygni profiles fit for Luminous Blue Variables. The spectrum is dominated by TiO bands whose strengths suggest a classification of M5. The H-alpha (Hα) line is not visible yet and there are unusual emission lines of neutral elements such as sodium and calcium. The luminosity class as determined from different spectral features varies from bright giant (II) to bright supergiant (Ia), with a compromise being given as M5eIbp. Early attempts at classification were confused by the interpretation of surrounding nebulosity as companion stars.
The derived spectral class varies depending on the features examined. The spectral features also vary noticeably over time. It is considered to be unambiguously cooler, and thus redder, than M2, and is usually classified between M3 and M5. Classes as extreme as M2.5 and M5 have been given. The luminosity class is likewise confused and often given only as I, partly because luminosity classes are poorly defined in the red and infrared portions of the spectrum. One study though, gives a luminosity class of Ia+ which means a hypergiant or extremely luminous supergiant.
A very large and luminous star, VY CMa is among the most extreme stars in the Milky Way and has an effective temperature below 4,000 K (3,730 °C; 6,740 °F). It occupies the upper-right hand corner of the HR diagram although its exact luminosity and temperature are uncertain. Most of the properties of the star depend directly on its distance.
The bolometric luminosity (Lbol) of VY CMa can be calculated from Spectral energy distribution (SED) or bolometric flux, which can be determined from photometry in several visible and infrared bands. Earlier calculations of the luminosity using an assumed distance of 1.5 kpc gave luminosities between 200,000 and 500,000 solar luminosities (L☉), very close to the empirical upper limit of luminosity for the cool hypergiants (e.g. Humphreys-Davidson limit). One study gave nearly one million L☉ at a distance of 2.1 kpc (6,800 ly). In 2006 a luminosity of 430,000 L☉ was calculated by integrating the total fluxes over the entire nebula, since most of the radiation coming from the star is reprocessed by the dust in the surrounding cloud. More recent estimates of the luminosity derive values below 350,000 L☉ based on distances below 1.2 kpc. Most of the output of VY CMa is emitted as infrared radiation, with a maximum emission at 5–10 μm, which is in part caused by reprocessing of the radiation by the circumstellar nebula. Many older luminosity estimates are consistent with current ones if they are re-scaled to the distance of 1.2 kpc. Despite being one of the most luminous stars in the Milky Way, much of the visible light of VY CMa is absorbed by the circumstellar envelope, so it cannot be seen with the naked eye and needs a telescope to be observed. It would be a naked eye star if no light was absorbed.
Since VY CMa has no companion star, its mass cannot be measured directly through gravitational interactions. Comparison of the effective temperature and bolometric luminosity of VY CMa compared to evolutionary tracks for massive stars suggest an initial mass of ±10 M☉ for a rotating star with a current mass of 15 M☉, or 32 M☉ for a non-rotating star with a current mass of 19 M☉ 25, and an age of 8.2 million years (MYr). Older studies have found much higher initial masses (thus also higher current masses) or a progenitor mass of 40 to 60 M☉ based on old luminosity estimates.
VY CMa has a strong stellar wind and is losing a lot of material due to its high luminosity and relatively low surface gravity. It has an average mass loss rate of ×10−4 M☉ per year, among the highest known and unusually high even for a red supergiant, as evidenced by the extensive circumstellar envelope. 6 It is consequently one of most important stars for understanding the high-mass loss episodes near the end of massive star evolution. The mass loss rate probably exceeded /yr during the most violent mass loss events. 10−3 M☉
The effective temperature of VY CMa is uncertain but as the spectrum of VY CMa varies, then also the temperature may vary. Early estimates of the temperature of VY CMa assumed values below 3,000 K based on a spectral class of M5. In 2006, Dr. Philip Massey used a MARCS model atmosphere to directly determine the temperature of VY CMa and calculated that the effective temperature of VY CMa is as high as ±25 K, corresponding to a spectral class of M2.5, 3,650 although VY CMa is usually considered as an M4-M5 star. Adopting the spectral class of M4-M5 with the temperature scale proposed by Emily Levesque gives a range of between 3,450 and 3,535 K.
The calculation of the radius of VY CMa is complicated by the extensive circumstellar envelope of the star and also VY CMa is a pulsating star, so its size changes with time. Earlier direct measurements of the radius at infrared (K-band = 2.2 µm) wavelength gave an angular diameter of ±0.5 mas, corresponding to radii above 3,000 R☉ at an assumed distance of 1.5 kpc, considerably larger than expected for any red supergiant or hypergiant. 18.7 However, this is probably larger than the actual size of the underlying star and the angular diameter estimate appears exceedingly large due to interference by the circumstellar envelope. In 2006–2007 radii of 1,800 and 2,100 R☉ (1.3×109 and 1.5×109 km; 8.4 and 9.8 au; 780,000,000 and 910,000,000 mi) have been dervied by Humphreys from the estimated luminosity of 430,000 L☉ and temperatures of 3,200–3,535 K.
On 6 and 7 March 2011, VY CMa was observed by Wittkowski et al. using VLTI/AMBER interferometry with the Very Large Telescope (VLT) in a range of 2.20–2.25 μm. The size of VY CMa was calculated using the Rosseland Radius, the location at which the optical depth is 2⁄3, with two modern distances of +0.11
−0.09 and 1.14+0.13
−0.10 kpc. 1.20 The angular diameter of VY CMa was directly and precisely measured at ±0.3 mas based on a PHOENIX atmosphere model, which corresponds to a radius of 11.3±120 R☉ at a distance of 1,420+0.08
−0.07 kpc. The high spectral resolution of these observations allowed to minimize the effect of contamination by the circumstellar layers. An effective temperature of 1.17±90 K was then derived from the radius and a luminosity of 3,490±40,000 L☉ which is based on distance and measured flux of 270,000±0.3)×10−13 W/cm2, resulting to a spectral class of M4. (6.3 In 2013, Alcolea et al. referred to VY Canis Majoris as the largest star discovered so far, referring to the Wittkowski radius, which is considered the highest radius among well-characterised stars. Several other red supergiants or hypergiants are possibly larger, but they have less accurate radius estimates.[a]
Most radius estimates of the VY CMa are considered as the size for the optical photosphere while the size of the star for the radio photosphere is calculated to be twice that of the size of the star for the optical photosphere.
Despite the mass and very large size, VY CMa has an average density of 5.33 to 8.38 mg/m3 (0.00000533 to 0.00000838 kg/m3), it is over 100,000 times less dense than Earth's atmosphere at sea level (1.2 kg/m3).
In 2006, Massey, Levesque and Plez's study, based on the effective temperature of 3,650 K, derived an assumed luminosity of 60,000 L☉ (which is also based on a distance of 1.5 kpc), a radius of 600 R☉, and an initial mass of 15 M☉, considering VY CMa and also another notable extreme cool hypergiant star, NML Cygni, as normal early-type red supergiants rather than extremely large, luminous, and massive late-type red hypergiants. They assert that very high luminosities of ×105 L☉ and very large radii of 2,800 to 3,230 R☉ 5 (up to 4,000 R☉) were based on effective temperatures below 3,000 K that was too low, far cooler than work of Emily Levesque has shown cool supergiants to be, and they noted that these parameters violate the bounds of current stellar evolutionary theory, larger than the 1,500 R☉ value, more luminous than the ~300,000 L☉ (Mbol = −9), and cooler than the 3,450–3,715 K measured for the largest, most luminous, and coolest red supergiants (i.e. µ Cep, KY Cyg, KW Sgr, and V354 Cep) in a sample of 74 analyzed galactic red supergiants. And thus, the location of VY CMa in the HR diagram would be in the Hayashi forbidden zone, where the stars cannot be in hydrostatic equilibrium. However, these parameters derived by this study do not agree with most of observed properties of VY CMa, such as the high mass loss rate and the methodology of this study has been challenged as it ignored the effects of the circumstellar enveloppe in the observed flux of the star, and thus the luminosity and radius of VY CMa according to this study are too low and somewhere inaccurate.
Humphreys has well-determined the luminosity VY CMa, being close to the Humphreys-Davidson limit, and concluded that VY CMa is a true hypergiant. VY CMa was found to be not alone (before being revised to be 1,420 R☉, 270,000 L☉ and 3,490 K) and there are other galactic red supergiants that are larger than 1,500 R☉, more luminous than 300,000 L☉ and cooler than 3,450 K but most are known OH/IR stars (although some could have less accurrate parameters). She therefore calculated that the largest and coolest possible cool supergiants (thus the theoretical maximum size limit for a cool supergiant) are more likely to be around 2,600 R☉ and around 3,000 K based on the Humphreys-Davidson limit.
VY Canis Majoris is a highly evolved star with an age less than 10 MYr although some older authors argued that it would rather either be a very young protostar or a massive pre-main sequence star with an age of only 1 MYr and also a circumstellar disk around the star. It has probably evolved from an O9 main sequence star with a radius of 5 to 20 R☉. The star has evolved rapidly because of its high mass. The time spent to the red hypergiant phase is estimated to be between 100,000 and 500,000 years, and thus VY CMa had left its main sequence more than a million years ago.
The future evolution of VY CMa is uncertain, but like the most cool supergiants, the star will certainly explode as a supernova. It has begun to fuse helium into carbon, whereas a main sequence star fuses hydrogen into helium. In 2009, Nathan Smith of the University of California, Ken Hinkle and Nils Ride of the Lund Observatory have used the PHOENIX near-infrared spectrograph on Gemini South to study the geometry and kinematics of the active circumstellar envelopes of two large supergiant stars: Betelgeuse and VY Canis Majoris. These two stars are losing huge amounts of mass in their "last gasps" and could explode as a supernova at any time now although the stars like VY CMa (>15 M☉) are too massive to produce type II-P supernovae at red supergiant stage and will probably evolve to higher temperature, likely producing a different type of supernova explosion. It is also expected that VY CMa will explode in the next 100,000 years. VY CMa has been discovered to be very unstable, having a prodigious mass loss rate. In this case, the CO emission is coincident with the bright KI shell in its asymmetric nebula. VY CMa will produce a moderately luminous and long-lasting type IIn supernova (SN IIn), or even a hypernova or superluminous supernova (SLSN) comparable to SN 1988Z (or possibly a type Ib supernova), but it is unlikely that the supernova would be extremely luminous like SN 2006tf or SN 2006gy. The explosion can be associated with gamma-ray bursts (GRB) and it will also produce a shock wave of a speed of a few thousand kilometers-per-second that could slam into the surrounding envelope of material and detectable interaction with the surrounding envelope for about a decade after the explosion. This demonstrates that LBVs, such as Eta Carinae, are not the only progenitors of SNe IIn or HN, but it stressed the requirement that these types of supernovae increased episodic mass loss just prior to the explosion. For a star as massive as VY CMa, the remnant would be likely a black hole rather than a neutron star.
- Alcolea et al 2013 refer to VY CMa as having the highest radius "among well-characterised stars in our galaxy", referring to the Wittkowski et al. 2012 value of 1,420 R☉ which is based on the distances from Choi et al. 2008 and Zhang et al. 2012 plus an angular diameter, or even as the largest known star by radius. Several red supergiants (or hypergiants) are possibly larger, although they could have less accurate radius estimates.
- Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv: . Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
- "GCVS Query=VY CMa". General Catalogue of Variable Stars @ Sternberg Astronomical Institute, Moscow, Russia. Retrieved 2010-11-24.
- Wittkowski, M.; Hauschildt, P.H.; Arroyo-Torres, B.; Marcaide, J.M. (5 April 2012). "Fundamental properties and atmospheric structure of the red supergiant VY CMa based on VLTI/AMBER spectro-interferometry". Astronomy & Astrophysics. 540: L12. arXiv: . Bibcode:2012A&A...540L..12W. doi:10.1051/0004-6361/201219126.
- Massey, Philip; Levesque, Emily M.; Plez, Bertrand (1 August 2006). "Bringing VY Canis Majoris down to size: an improved determination of its effective temperature". The Astrophysical Journal. 646 (2): 1203–1208. arXiv: . Bibcode:2006ApJ...646.1203M. doi:10.1086/505025.
- Lipscy, S. J.; Jura, M.; Reid, M. J. (10 June 2005). "Radio photosphere and mass-loss envelope of VY Canis Majoris". The Astrophysical Journal. 626 (1): 439–445. arXiv: . Bibcode:2005ApJ...626..439L. doi:10.1086/429900.
- Ducati, J. R (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". Vizier Online Data Catalog. Bibcode:2002yCat.2237....0D.
- De Beck, E.; Decin, L.; De Koter, A.; Justtanont, K.; Verhoelst, T.; Kemper, F.; Menten, K. M. (2010). "Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles. II. CO line survey of evolved stars: Derivation of mass-loss rate formulae". Astronomy and Astrophysics. 523: A18. arXiv: . Bibcode:2010A&A...523A..18D. doi:10.1051/0004-6361/200913771.
- Serkowski, K (1969). "Large Optical Polarization of the OH Emission Source VY Canis Majoris". The Astrophysical Journal. 156: L139. Bibcode:1969ApJ...156L.139S. doi:10.1086/180366.
- "VSX: Detail for VY CMa". American Association of Variable Star Observers. Retrieved 2018-07-20.
- Humphreys, Roberta M.; Helton, L. Andrew; Jones, Terry J. (2007). "The Three-Dimensional Morphology of VY Canis Majoris. I. The Kinematics of the Ejecta". The Astronomical Journal. 133 (6): 2716–2729. arXiv: . Bibcode:2007AJ....133.2716H. doi:10.1086/517609.
- Zhang, B.; Reid, M. J.; Menten, K. M.; Zheng, X. W. (January 2012) [14 Sep 2011 (v1)]. "Distance and Kinematics of the Red Hypergiant VY CMa: VLBA and VLA Astrometry". The Astrophysical Journal. 744 (1): 23. arXiv: . Bibcode:2012ApJ...744...23Z. doi:10.1088/0004-637X/744/1/23.
- David Darling. "VY Canis Majoris". Retrieved 9 July 2018.
- Matsuura, Mikako; Sargent, B; Swinyard, Bruce; Yates, Jeremy; Royer, P; Barlow, M. J; Boyer, Martha; Decin, L; Khouri, Theo; Meixner, Margaret; van Loon, Jacco Th; Woods, Paul M (2016). "The mass-loss rates of red supergiants at low metallicity: Detection of rotational CO emission from two red supergiants in the Large Magellanic Cloud". Monthly Notices of the Royal Astronomical Society. 462 (3): 2995–3005. arXiv: . Bibcode:2016MNRAS.462.2995M. doi:10.1093/mnras/stw1853.
- Alcolea, J; Bujarrabal, V; Planesas, P; Teyssier, D; Cernicharo, J; De Beck, E; Decin, L; Dominik, C; Justtanont, K; De Koter, A; Marston, A. P; Melnick, G; Menten, K. M; Neufeld, D. A; Olofsson, H; Schmidt, M; Schöier, F. L; Szczerba, R; Waters, L. B. F. M (2013). "HIFISTARSHerschel/HIFI observations of VY Canis Majoris. Molecular-line inventory of the envelope around the largest known star". Astronomy & Astrophysics. 559: A93. arXiv: . Bibcode:2013A&A...559A..93A. doi:10.1051/0004-6361/201321683.
- Smith, Nathan; Humphreys, Roberta M.; Davidson, Kriz; Gehrz, Robert D.; Schuster, M. T.; Krautter, Joachim (February 2001). "The Asymmetric Nebula Surrounding the Extreme Red Supergiant Vy Canis Majoris". The Astronomical Journal. 121 (2): 1111–1125. Bibcode:2001AJ....121.1111S. doi:10.1086/318748.
- Herbig, G. H (1970). "VY Canis Majoris. II. Interpretation of the Energy Distribution". The Astrophysical Journal. 162: 557. Bibcode:1970ApJ...162..557H.
- "Result for Sh-2 310". Galaxy Map. Retrieved 20 August 2018.
- Sharpless, Stewart (1959). "A Catalogue of H II Regions". The Astrophysical Journal Supplement Series. 4: 257. doi:10.1086/190049.
- "Solar System Exploration: Planets: Sun: Facts & Figures". NASA. Archived from the original on January 2, 2008. Retrieved 15 January 2016.
- Robinson, L. J. (1971). "Three Somewhat Overlooked Facets of VY Canis Majoris". Information Bulletin on Variable Stars. 599: 1. Bibcode:1971IBVS..599....1R.
- Wittkowski, M.; Langer, N.; Weigelt, G. (1998). "Diffraction-limited speckle-masking interferometry of the red supergiant VY CMa". Astronomy and Astrophysics. 340 (2004): 77–87. arXiv: . Bibcode:1998A&A...340L..39W.
- Wilson, William J; Barrett, Alan H (1968). "Discovery of Hydroxyl Radio Emission from Infrared Stars". Science. 161 (3843): 778–9. Bibcode:1968Sci...161..778W. doi:10.1126/science.161.3843.778. PMID 17802620.
- Eliasson, B; Bartlett, J. F (1969). "Discovery of an Intense OH Emission Source". The Astrophysical Journal. 155: L79. Bibcode:1969ApJ...155L..79E. doi:10.1086/180306.
- Snyder, L. E; Buhl, D (1975). "Detection of new stellar sources of vibrationally excited silicon monoxide maser emission at 6.95 millimeters". The Astrophysical Journal. 197: 329. Bibcode:1975ApJ...197..329S. doi:10.1086/153517.
- "VY Canis Majoris". American Association of Variable Star Observers. 13 April 2010.
- De Beck, E; Vlemmings, W; Muller, S; Black, J. H; O'Gorman, E; Richards, A. M. S; Baudry, A; Maercker, M; Decin, L; Humphreys, E. M (2015). "ALMA observations of TiO2 around VY Canis Majoris". Astronomy and Astrophysics. 580: A36. Bibcode:2015A&A...580A..36D. doi:10.1051/0004-6361/201525990.
- Kamiński, T; Gottlieb, C. A; Menten, K. M; Patel, N. A; Young, K. H; Brünken, S; Müller, H. S. P; McCarthy, M. C; Winters, J. M; Decin, L (2013). "Pure rotational spectra of TiO and TiO2 in VY Canis Majoris". Astronomy and Astrophysics. 551 (2013): A113. arXiv: [astro-ph.SR]. Bibcode:2013A&A...551A.113K. doi:10.1051/0004-6361/201220290.
- Hoffmeister, Cuno (1931). "316 neue Veränderlilche". Astronomische Nachrichten. 242 (7): 129–142. Bibcode:1931AN....242..129H. doi:10.1002/asna.19312420702.
- Guthnick, P.; Schneller, H. (1939). "Benennung von veränderlichen Sternen". Astronomische Nachrichten. 268 (11–12): 165. Bibcode:1939AN....268..165G. doi:10.1002/asna.19392681102.
- Shenoy, Dinesh; Humphreys, Roberta M; Terry Jay Jones; Marengo, Massimo; Gehrz, Robert D; Andrew Helton, L; Hoffmann, William F; Skemer, Andrew J; Hinz, Philip M (2015). "Searching for Cool Dust in the Mid-to-Far Infrared: The Mass Loss Histories of the Hypergiants μ Cep, VY CMa, IRC+10420, and ρ Cas". The Astronomical Journal. 151 (3): 51. arXiv: . Bibcode:2016AJ....151...51S. doi:10.3847/0004-6256/151/3/51.
- "Astronomers Map a Hypergiant Star's Massive Outbursts". HubbleSite. 8 January 2007. Retrieved 9 July 2018.
- Humphreys, Roberta M. (2006). "VY Canis Majoris: The Astrophysical Basis of Its Luminosity": astro–ph/0610433. arXiv: . Bibcode:2006astro.ph.10433H.
- Lada, Charles J.; Reid, Mark J. (1 January 1978). "CO observations of a molecular cloud complex associated with the bright rim near VY Canis Majoris". The Astrophysical Journal. 219: 95–104. Bibcode:1978ApJ...219...95L. doi:10.1086/155758.
- Lada, C. J.; Reid, M. (1976). "The Discovery of a Molecular Cloud Associated with VY CMa". Bulletin of the American Astronomical Society. 8: 322. Bibcode:1976BAAS....8R.322L.
- Mel'nik, A.M.; Dambis, A.K. (2009). "Kinematics of OB-associations and the new reduction of the Hipparcos data". Monthly Notices of the Royal Astronomical Society. 400 (1): 518–523. arXiv: . Bibcode:2009MNRAS.400..518M. doi:10.1111/j.1365-2966.2009.15484.x.
- . Bibcode:1997HIP...C......0E. Missing or empty
- Choi, Y. K.; Hirota, Tomoya; Honma, Mareki; Kobayashi, Hideyuki; Bushimata, Takeshi; Imai, Hiroshi; Iwadate, Kenzaburo; Jike, Takaaki; Kameno, Seiji; Kameya, O.; Kamohara, R.; Kan-Ya, Y.; Kawaguchi, N.; Kijima, M.; Kim, M. K.; Kuji, S.; Kurayama, T.; Manabe, S.; Maruyama, K.; Matsui, M.; Matsumoto, N.; Miyaji, T.; Nagayama, T.; Nakagawa, A.; Nakamura, K.; Oh, C. S.; Omodaka, T.; Oyama, T.; Sakai, S.; et al. (2008). "Distance to VY Canis Majoris with VERA". Publications of the Astronomical Society of Japan. 60 (5): 1007. arXiv: . Bibcode:2008PASJ...60.1007C. doi:10.1093/pasj/60.5.1007.
- Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv: . Bibcode: . doi: . Gaia DR2 record for this source at VizieR.
- Humphreys, E. M. L; Immer, K; Gray, M. D; De Beck, E; Vlemmings, W. H. T; Baudry, A; Richards, A. M. S; Wittkowski, M; Torstensson, K; De Breuck, C; Moller, P; Etoka, S; Olberg, M (2017). "Simultaneous 183 GHz H2O Maser and SiO Observations Towards Evolved Stars Using APEX SEPIA Band 5". Astronomy & Astrophysics. 603: A77. arXiv: . Bibcode:2017A&A...603A..77H. doi:10.1051/0004-6361/201730718.
- Kastner, Joel (1996). "FOC Imaging of the Dusty Envelopes of Mass-Losing Supergiants". Hst Proposal: 6416. Bibcode:1996hst..prop.6416K.
- Wallerstein, George (1958). "The Spectrum of the Irregular Variable VY Canis Majoris". Publications of the Astronomical Society of the Pacific. 70 (416): 479. Bibcode:1958PASP...70..479W. doi:10.1086/127278.
- Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009-2016)". VizieR On-line Data Catalog: B/mk. Originally Published In: Lowell Observatory (October 2014). 1: B/mk. Bibcode:2014yCat....1.2023S.
- Monnier, J. D; Millan-Gabet, R; Tuthill, P. G; Traub, W. A; Carleton, N. P; Coudé Du Foresto, V; Danchi, W. C; Lacasse, M. G; Morel, S; Perrin, G; Porro, I. L; Schloerb, F. P; Townes, C. H (2004). "High-Resolution Imaging of Dust Shells by Using Keck Aperture Masking and the IOTA Interferometer". The Astrophysical Journal. 605 (1): 436–461. arXiv: . Bibcode:2004ApJ...605..436M. doi:10.1086/382218.
- Le Sidaner, P; Le Bertre, T (1996). "Optical and infrared observations of 27 oxygen-rich stars. Modelling of the circumstellar dust shells". Astronomy and Astrophysics. 314: 896. Bibcode:1996A&A...314..896L.
- Mauron, N.; Josselin, E. (2011). "The mass-loss rates of red supergiants and the de Jager prescription". Astronomy and Astrophysics. 526: A156. arXiv: . Bibcode:2011A&A...526A.156M. doi:10.1051/0004-6361/201013993.
- Knapp, G. R; Sandell, G; Robson, E. I (1993). "The Dust Content of Evolved Circumstellar Envelopes and the Optical Properties of Dust at Submillimeter to Radio Wavelengths". The Astrophysical Journal Supplement Series. 88: 173. Bibcode:1993ApJS...88..173K. doi:10.1086/191820.
- Humphreys, Roberta M; Davidson, Kris; Ruch, Gerald; Wallerstein, George (2005). "High-Resolution, Long-Slit Spectroscopy of VY Canis Majoris: The Evidence for Localized High Mass Loss Events". The Astronomical Journal. 129 (1): 492–510. Bibcode:2005AJ....129..492H. doi:10.1086/426565.
- Levesque, Emily M.; Massey, Philip; Olsen, K. A. G.; Plez, Bertrand; Josselin, Eric; Maeder, Andre; Meynet, Georges (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not as Cool as We Thought". The Astrophysical Journal. 628 (2): 973–985. arXiv: . Bibcode:2005ApJ...628..973L. doi:10.1086/430901.
- Wehrse, R.; Scholz, M.; Baschek, B. (June 1991). "The parameters R and Teff in stellar models and observations". Astronomy and Astrophysics. 246 (2): 374–382. Bibcode:1991A&A...246..374B.
- Massey, Philip; Levesque, Emily M; Plez, Bertrand; Olsen, Knut A. G; Bresolin, F; Crowther, P. A; Puls, J (2008). "The Physical Properties of Red Supergiants: Comparing Theory and Observations". Massive Stars as Cosmic Engines. 250: 97. arXiv: . Bibcode:2008IAUS..250...97M. doi:10.1017/S1743921308020383.
- Zubko, Viktor; Li, Di; Lim, Tanya; Feuchtgruber, Helmut; Harwit, Martin (2004). "Observations of Water Vapor Outflow from NML Cygnus". The Astrophysical Journal. 610 (1): 427–435. arXiv: . Bibcode:2004ApJ...610..427Z. doi:10.1086/421700.
- Wallerstein, G (1978). "An interpretation of the apparent orbit of VY CMa AB: The rotating holey dust cloud hypothesis". The Observatory. 98: 224. Bibcode:1978Obs....98..224W.
- Smith, Nathan; Hinkle, Kenneth H.; Ryde, Nils (March 2009). "Red Supergiants as Potential Type IIn Supernova Progenitors: Spatially Resolved 4.6 μm CO Emission Around VY CMa and Betelgeuse". The Astronomical Journal. 137 (3): 3558–3573. arXiv: . Bibcode:2009AJ....137.3558S. doi:10.1088/0004-6256/137/3/3558.
- Kastner, Joel H.; Weintraub, David A. (1998). "Hubble Space Telescope Imaging of the Mass-losing Supergiant VY Canis Majoris". Astronomical Journal. 115 (4): 1592–1598. Bibcode:1998AJ....115.1592K. doi:10.1086/300297.
- Meynet, G; Chomienne, V; Ekström, S; Georgy, C; Granada, A; Groh, J; Maeder, A; Eggenberger, P; Levesque, E; Massey, P (2015). "Impact of mass-loss on the evolution and pre-supernova properties of red supergiants". Astronomy & Astrophysics. 575 (60): A60. arXiv: [astro-ph.SR]. Bibcode:2015A&A...575A..60M. doi:10.1051/0004-6361/201424671.
- Scicluna, P; Siebenmorgen, R; Wesson, R; Blommaert, J. A. D. L; Kasper, M; Voshchinnikov, N. V; Wolf, S (2015). "Large dust grains in the wind of VY Canis Majoris". Astronomy and Astrophysics. 584: L10. Bibcode:2015A&A...584L..10S. doi:10.1051/0004-6361/201527563.
- Wittkowski, M; Arroyo-Torres, B; Marcaide, J. M; Abellan, F. J; Chiavassa, A; Freytag, B; Scholz, M; Wood, P. R; Hauschildt, P. H; Meynet, Georges; Georgy, Cyril; Groh, José; Stee, Philippe (2015). "On the atmospheric structure and fundamental parameters of red supergiants". New Windows on Massive Stars. 307: 280–285. Bibcode:2015IAUS..307..280W. doi:10.1017/S1743921314006930.
|Wikimedia Commons has media related to VY Canis Majoris.|
- VLT image of the surroundings of VY Canis Majoris seen with SPHERE www.eso.org
- Astronomers Map a Hypergiant Star's Massive Outbursts, HubbleSite NewsCenter, 2007-01-08
- "What is the Biggest Star in the Universe?", Fraser Cain, Universe Today, published 2008-04-06, updated 13 May 2013
- Amos, Jonathan (27 November 2009). "Herschel telescope 'fingerprints' colossal star". BBC News. Retrieved 30 November 2009.
The death throes of one of the biggest stars known to science have been spied by Europe's Herschel space telescope.
- Structure and Evolution of Stars. "Lecture 16: The IMF, Lithium Burning, P Cygni Profiles and Mass Loss" (PDF). Retrieved 2018-06-29.
- Remote Sensing Tutorial Page A-5 archive