--- title: Supergiant canonical_url: https://paxabyssi.com/wiki/Supergiant markdown_url: https://paxabyssi.com/wiki/Supergiant.md type: wiki-page revision_id: 482 revision_view: stable last_updated: 2026-09-27 license: CC BY-SA 4.0 license_url: https://creativecommons.org/licenses/by-sa/4.0/ science_status: - observed - model - sim summary: A massive star in a late stage of life, tens of thousands to hundreds of thousands of times as luminous as the Sun, of luminosity class I. Red supergiants such as Betelgeuse are among the largest stars known; blue ones such as Rigel are among the brightest. Most end as supernovae within a few million years of forming. categories: - Stars - Supergiant stars - Stellar evolution - Massive stars aliases: - Supergiants - Supergiant star - Red supergiant - Red supergiants - Blue supergiant - Blue supergiants - Yellow supergiant - Hypergiant - Hypergiants - Luminosity class I - Ia supergiant - RSP - BSP - Humphreys-Davidson limit - Red supergiant problem - Siwarha - Betelgeuse B infobox: type: star_class code: BSP, BWP, WSP, YWP, YSP, OGP, RSP (blue to red supergiants); hypergiant classes defined but unused mass: unit: M_Sun value: about 8 to several tens (initial) source: model name: Supergiant image: File:Betelgeuse_Great_Dimming_ESO_eso2109a.jpg radius: unit: R_Sun value: tens (blue) to about 1,500 (red) source: observed caption: "Observation: Betelgeuse before and during its Great Dimming of 2019 to 2020, imaged with ESO's Very Large Telescope. Credit: ESO/M. Montargès et al." activity: Strong winds and mass loss; pulsations; giant convection cells; episodic mass ejections subtypes: Blue, blue-white, white, yellow-white, yellow, orange and red supergiants (sim classes by spectral letter) luminosity: unit: L_Sun value: about 10,000 to about 500,000 source: observed science_doc: The sim's supergiant science references last_verified: 2026-09-27, writer B real_examples: Betelgeuse (M1-M2Ia-Iab), Antares (M1.5Iab), Rigel (B8Ia), Deneb (A2Ia), Polaris (F8Ib), VY Canis Majoris, WOH G64 physics_engine: Supergiant physics engines and subtype classifiers; measured overrides for named stars share_of_stars: "Tiny: none within 10 pc; about 5,000 of the 119,626 stars in the game's catalogue, because they are visible from far away" luminosity_class: Ia, Iab, Ib (supergiants); 0 or Ia+ (hypergiants) perceived_colour: From blue-white (Rigel, Deneb) to deep orange (Betelgeuse, Antares) planet_occurrence: No confirmed planets around supergiants stellar_class_key: blue_supergiant to red_supergiant (seven colours) effective_temperature: unit: K value: about 3,400 (red) to above 20,000 (blue) source: observed main_sequence_lifetime: unit: yr value: a few million to a few tens of millions of years in all; the supergiant phase is the last tenth or so source: model spectral_types_covered: O to M related: - https://paxabyssi.com/wiki/Red_giant.md - https://paxabyssi.com/wiki/Stellar_classification.md - https://paxabyssi.com/wiki/Brown_dwarf.md - https://paxabyssi.com/wiki/G-type_main-sequence_star.md - https://paxabyssi.com/wiki/K-type_main-sequence_star.md - https://paxabyssi.com/wiki/Red_dwarf.md --- # Supergiant > Source: https://paxabyssi.com/wiki/Supergiant > > Licence: [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/). Text by Pax Abyssi Wiki contributors; history at https://paxabyssi.com/wiki/Supergiant/history > > Revision 482, 27 September 2026 A **supergiant** is a massive star in a late stage of its life, so luminous that it is given its own luminosity class, I, in the MK system of stellar classification. Supergiants are born with at least about eight times the Sun's mass and shine with tens of thousands to hundreds of thousands of times its light. They span every spectral type: blue supergiants such as Rigel are hot and compact for their class, while red supergiants such as Betelgeuse and Antares are cool, swollen to hundreds or more than a thousand times the Sun's radius, and among the largest stars known. Their lives are short, a few million to a few tens of millions of years, and most end in core-collapse supernovae. ## Characteristics ### Classes and colours Supergiants are graded Ia (luminous), Iab and Ib (less luminous); the most extreme, with luminosity class 0 or Ia+, are **hypergiants**, such as the yellow hypergiants that lie near the upper edge of stellar brightness [1]. By temperature they run from blue (O and B types, above about 10,000 K) through white and yellow (A, F and G) to red (K and M, down to about 3,400 K). The spread is mostly one of size: a massive star keeps roughly the same luminosity as it moves across the Hertzsprung-Russell diagram after leaving the main sequence, so as its surface cools from blue to red its radius must grow by tens of times to radiate the same energy. ### How bright a star can be There is an upper boundary to the luminosity of cool supergiants. Humphreys and Davidson found in 1979 that stars cooler than about 15,000 K do not exceed a bolometric absolute magnitude of about -9.5 to -10, about 500,000 to 800,000 times the Sun's luminosity, and attributed the limit to mass loss that strips the most massive stars before they can become red supergiants [2]. A modern census of the Magellanic Clouds places the limit for cool supergiants lower, at about 320,000 solar luminosities [3]. ### Winds, cells and pulsations Red supergiants lose mass rapidly in slow, dusty winds, and their surfaces are dominated by a few enormous convection cells. Interferometric maps of Antares show turbulent gas rising and falling at up to 20 km/s in an atmosphere extending to about 1.7 times the star's radius [4]. Betelgeuse pulsates with a period of about 400 days [5]. Blue supergiants drive fast winds with the pressure of their own light. ## Betelgeuse Betelgeuse, the red supergiant at the shoulder of Orion, is the best-studied example. Combining its evolution, pulsations and hydrodynamics, Joyce et al. (2020) estimated a present mass of 16.5 to 19 solar masses, a radius of 764 solar radii and a distance of 168 parsecs (548 light years) [5]; other methods give distances up to about 220 parsecs [6], so its true size and luminosity remain uncertain by tens of per cent. It is burning helium in its core and is expected to explode as a supernova, probably not for about a hundred thousand years [5]. Between late 2019 and early 2020 Betelgeuse faded by more than a magnitude, its **Great Dimming**. Images from the Very Large Telescope showed the southern half of the star darkened about tenfold, explained by a cloud of dust that formed over a cooler patch of the surface [6]; the star's temperature fell too little to explain the fading on its own [7]. Ultraviolet and optical spectra point to a large surface mass ejection as the cause, after which the star's 400-day pulsation disappeared for more than two years [8]. ![Four images of Betelgeuse's disc from 2019 and 2020, the lower half growing darker in the later frames](https://media.paxabyssi.com/public/8e662b03de58bd93536c9297ac4e8e55042adc709b00a81923f08d1134ac4d6f/1866.webp "Observation: Betelgeuse's surface in January 2019 and during the Great Dimming of December 2019 to March 2020, imaged with the VLT's SPHERE instrument. Credit: ESO/M. Montargès et al.") *Figure 1.* Observation: Betelgeuse's surface in January 2019 and during the Great Dimming of December 2019 to March 2020, imaged with the VLT's SPHERE instrument. Credit: ESO/M. Montargès et al. Licence: CC BY 4.0. ### A companion Betelgeuse also brightens and fades on a long secondary period of about 2,100 days. In 2024 and 2025 two teams argued that this is caused by a companion star orbiting just outside the supergiant, of about one solar mass or less [9] [10]. A speckle-imaging search with the Gemini North telescope then reported a probable detection, 52 milliarcseconds from Betelgeuse and about six magnitudes fainter in blue light [11], and the companion has been given the name Siwarha by the International Astronomical Union [12]. The Hubble Space Telescope saw no ultraviolet light from it, which rules out certain kinds of companion [13]. On 28 July 2026 ESO announced the strongest evidence yet: images from the VLT's SPHERE instrument taken on 6 December 2024 show a source at a separation of 52.3 milliarcseconds, detected at more than six standard deviations [14] [15]. If it is a young star of the same age as Betelgeuse, its brightness implies 2.6 to 3.1 solar masses, above the dynamical estimates, and the authors describe it as a candidate whose confirmation awaits a second epoch of observation [15]. ![Betelgeuse's bright disc with a faint point of light beside it](https://media.paxabyssi.com/public/1abafae02c63750f95e69efd7c24b010d3201995f5da9f71bf6eee8006e58e92/2560.webp "Observation: VLT/SPHERE images of Betelgeuse and its candidate companion, released in July 2026. Credit: ESO/M. Montargès et al. Background: N. Rissinger (skysurvey.org).") *Figure 2.* Observation: VLT/SPHERE images of Betelgeuse and its candidate companion, released in July 2026. Credit: ESO/M. Montargès et al. Background: N. Rissinger (skysurvey.org). Licence: CC BY 4.0. ## Other notable supergiants | Star | Type | Distance | Notes | | ---------------- | -------------------- | ------------- | ----------------------------------------------------------------------------------- | | Betelgeuse | M1-M2Ia-Iab | 168 to 220 pc | 764 solar radii, 16.5 to 19 solar masses; candidate companion [5] [15] | | Antares | M1.5Iab | about 170 pc | 680 solar radii (3.2 AU), 3,660 K [16] | | Rigel | B8Ia | about 260 pc | About 120,000 solar luminosities; a nearby future supernova [17] [18] | | Deneb | A2Ia | uncertain | 8,525 K; about 200,000 solar luminosities if at the larger distance estimates [19] | | Polaris | F8Ib | | Pole Star; a pulsating Cepheid of 5.1 solar masses in a 30-year binary orbit [20] | | VY Canis Majoris | M5Iae | 1.2 kpc | About 1,420 solar radii, among the largest stars known [21] [22] | | WOH G64 | red supergiant (LMC) | 50 kpc | First close-up image of a star in another galaxy [23] | WOH G64, in the Large Magellanic Cloud, shows how fast a supergiant can change. After the VLT Interferometer produced the first close-up image of a star outside the Milky Way in 2024 [23], one team reported that its spectrum had changed between 2013 and 2014 from a red supergiant's to that of a hotter yellow hypergiant [24], while another found titanium oxide bands, the signature of a red supergiant, at every epoch from late 2024 to 2025 and argued that it may never have stopped being one [25]. The question is open. ## The end of a supergiant Stars above about eight solar masses end with a collapsing iron core. Red supergiants are the progenitors of the commonest core-collapse supernovae, Type II-P; blue and yellow supergiants and stripped stars make other kinds; and the most massive may collapse to black holes, with or without an explosion [26]. Archival images of exploded stars show that the progenitors of Type II-P supernovae range from about 8.5 to 16.5 solar masses, while red supergiants exist up to about 25: the **red supergiant problem** [27]. One explanation is that the heaviest red supergiants collapse to black holes without a visible supernova [28]. Others argue that the gap is not statistically significant once the uncertainties in progenitor brightness are included [29] [30]. The first supernova progenitor found with JWST, the star that became SN 2025pht in the galaxy NGC 1637, was a red supergiant of about 100,000 solar luminosities wrapped in carbon-rich dust [31]. ![A reconstructed image of the red supergiant Antares showing a mottled disc](https://media.paxabyssi.com/public/2e70891a6b63d48f0c5851b5540fde577fe64ae0787758a3c93dcc52838a6c81/600.webp "Observation: the surface of Antares reconstructed from VLTI measurements, the first map of gas motions on another star. Credit: ESO/K. Ohnaka.") *Figure 3.* Observation: the surface of Antares reconstructed from VLTI measurements, the first map of gas motions on another star. Credit: ESO/K. Ohnaka. Licence: CC BY 4.0. > **In Pax Abyssi** > > The sim assigns a star to a supergiant class whenever its catalogue spectral type carries luminosity class I, and names the class by the colour of its spectral letter, from blue (O) through blue-white, white, yellow-white, yellow and orange to red (M) supergiants. Hypergiant classes exist in the taxonomy but no catalogue star is assigned one yet. The game's catalogue holds about 5,000 real supergiants of every spectral type, K supergiants the largest group. Well-studied supergiants carry measured values in place of estimates from their colours: Betelgeuse is drawn at 764 solar radii, 3,600 K and 168 parsecs after Joyce et al. (2020), and Antares at 680 solar radii after Ohnaka et al. (2013). At the end of their lives the sim turns stars of 8 to 25 solar masses into neutron stars and heavier ones into black holes. ## See also - [Stellar classification](https://paxabyssi.com/wiki/Stellar_classification.md) - [Red giant](https://paxabyssi.com/wiki/Red_giant.md) - [Neutron star](https://paxabyssi.com/wiki/Neutron_star.md) - [Black hole](https://paxabyssi.com/wiki/Black_hole.md) - [Wolf-Rayet star](https://paxabyssi.com/wiki/Wolf-Rayet_star.md) - [Milky Way](https://paxabyssi.com/wiki/Milky_Way.md) ## References 1. de Jager, C. (1998). The yellow hypergiants. Astronomy and Astrophysics Review 8, 145-180. 2. Humphreys, R. M. and Davidson, K. (1979). Studies of luminous stars in nearby galaxies. III. Comments on the evolution of the most massive stars in the Milky Way and the Large Magellanic Cloud. The Astrophysical Journal 232, 409. 3. Davies, B., Crowther, P. A. and Beasor, E. R. (2018). The luminosities of cool supergiants in the Magellanic Clouds, and the Humphreys-Davidson limit revisited. Monthly Notices of the Royal Astronomical Society 478, 3138-3148. 4. Ohnaka, K., Weigelt, G. and Hofmann, K. H. (2017). Vigorous atmospheric motion in the red supergiant star Antares. Nature 548, 310-312. 5. Joyce, M. et al. (2020). Standing on the Shoulders of Giants: New Mass and Distance Estimates for Betelgeuse through Combined Evolutionary, Asteroseismic, and Hydrodynamic Simulations with MESA. The Astrophysical Journal 902, 63. 6. Montargès, M. et al. (2021). A dusty veil shading Betelgeuse during its Great Dimming. Nature 594, 365-368. 7. Levesque, E. M. and Massey, P. (2020). Betelgeuse Just Is Not That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse. The Astrophysical Journal Letters 891, L37. 8. Dupree, A. K. et al. (2022). The Great Dimming of Betelgeuse: A Surface Mass Ejection and Its Consequences. The Astrophysical Journal 936, 18. 9. Goldberg, J. A., Joyce, M. and Molnár, L. (2024). A Buddy for Betelgeuse: Binarity as the Origin of the Long Secondary Period in alpha Orionis. The Astrophysical Journal 977, 35. 10. MacLeod, M. et al. (2025). Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse. The Astrophysical Journal 978, 50. 11. Howell, S. B. et al. (2025). The Probable Direct-imaging Detection of the Stellar Companion to Betelgeuse. The Astrophysical Journal Letters 988, L47. 12. IAU Working Group on Star Names. IAU Catalog of Star Names (Siwarha, alpha Orionis B, approved 2025-09-22). 13. Goldberg, J. A. et al. (2025). Betelgeuse, Betelgeuse, Betelgeuse, Betel-buddy? Constraints on the Dynamical Companion to alpha Orionis from HST. The Astrophysical Journal 994, 101. 14. ESO (2026). Astronomers find strongest evidence yet that Betelgeuse has a companion (press release eso2611). 15. Montargès, M. et al. (2026). VLT/SPHERE images of the candidate companion of Betelgeuse. Astronomy & Astrophysics 711, L12. 16. Ohnaka, K. et al. (2013). High spectral resolution imaging of the dynamical atmosphere of the red supergiant Antares in the CO first overtone lines with VLTI/AMBER. Astronomy & Astrophysics 555, A24. 17. de Almeida, E. S. G. et al. (2022). Combined spectroscopy and intensity interferometry to determine the distances of the blue supergiants P Cygni and Rigel. Monthly Notices of the Royal Astronomical Society 515, 1-12. 18. Moravveji, E. et al. (2012). Asteroseismology of the Nearby SN-II Progenitor: Rigel. I. The MOST High-precision Photometry and Radial Velocity Monitoring. The Astrophysical Journal 747, 108. 19. Schiller, F. and Przybilla, N. (2008). Quantitative spectroscopy of Deneb. Astronomy & Astrophysics 479, 849-858. 20. Evans, N. R. et al. (2024). The Orbit and Dynamical Mass of Polaris: Observations with the CHARA Array. The Astrophysical Journal 971, 190. 21. Wittkowski, M. et al. (2012). Fundamental properties and atmospheric structure of the red supergiant VY Canis Majoris based on VLTI/AMBER spectro-interferometry. Astronomy & Astrophysics 540, L12. 22. Zhang, B. et al. (2012). Distance and Kinematics of the Red Hypergiant VY CMa: Very Long Baseline Array and Very Large Array Astrometry. The Astrophysical Journal 744, 23. 23. Ohnaka, K. et al. (2024). Imaging the innermost circumstellar environment of the red supergiant WOH G64 in the Large Magellanic Cloud. Astronomy & Astrophysics 691, L15. 24. Muñoz-Sanchez, G. et al. (2026). The dramatic transition of the extreme red supergiant WOH G64 to a yellow hypergiant. Nature Astronomy 10, 702-713. 25. van Loon, J. T. and Ohnaka, K. (2026). A phoenix rises from the ashes: WOH G64 is still a red supergiant, for now. Monthly Notices of the Royal Astronomical Society 546, stag012. 26. Heger, A. et al. (2003). How Massive Single Stars End Their Life. The Astrophysical Journal 591, 288-300. 27. Smartt, S. J. et al. (2009). The death of massive stars. I. Observational constraints on the progenitors of Type II-P supernovae. Monthly Notices of the Royal Astronomical Society 395, 1409-1437. 28. Smartt, S. J. (2015). Observational Constraints on the Progenitors of Core-Collapse Supernovae: The Case for Missing High-Mass Stars. Publications of the Astronomical Society of Australia 32, e016. 29. Davies, B. and Beasor, E. R. (2020). The 'red supergiant problem': the upper luminosity boundary of Type II supernova progenitors. Monthly Notices of the Royal Astronomical Society 493, 468-476. 30. Beasor, E. R., Smith, N. and Jencson, J. E. (2025). The Red Supergiant Progenitor Luminosity Problem. The Astrophysical Journal 979, 117. 31. Kilpatrick, C. D. et al. (2025). The Type II SN 2025pht in NGC 1637: A Red Supergiant with Carbon-rich Circumstellar Dust as the First JWST Detection of a Supernova Progenitor Star. The Astrophysical Journal Letters 992, L10. ## Infobox (star class) | Field | Value | | --- | --- | | Code | BSP, BWP, WSP, YWP, YSP, OGP, RSP (blue to red supergiants); hypergiant classes defined but unused | | Mass | about 8 to several tens (initial) M_Sun | | Name | Supergiant | | Image | File:Betelgeuse_Great_Dimming_ESO_eso2109a.jpg | | Radius | tens (blue) to about 1,500 (red) R_Sun | | Caption | Observation: Betelgeuse before and during its Great Dimming of 2019 to 2020, imaged with ESO's Very Large Telescope. Credit: ESO/M. Montargès et al. | | Activity | Strong winds and mass loss; pulsations; giant convection cells; episodic mass ejections | | Subtypes | Blue, blue-white, white, yellow-white, yellow, orange and red supergiants (sim classes by spectral letter) | | Luminosity | about 10,000 to about 500,000 L_Sun | | Science doc | The sim's supergiant science references | | Last verified | 2026-09-27, writer B | | Real examples | Betelgeuse (M1-M2Ia-Iab), Antares (M1.5Iab), Rigel (B8Ia), Deneb (A2Ia), Polaris (F8Ib), VY Canis Majoris, WOH G64 | | Physics engine | Supergiant physics engines and subtype classifiers; measured overrides for named stars | | Share of stars | Tiny: none within 10 pc; about 5,000 of the 119,626 stars in the game's catalogue, because they are visible from far away | | Luminosity class | Ia, Iab, Ib (supergiants); 0 or Ia+ (hypergiants) | | Perceived colour | From blue-white (Rigel, Deneb) to deep orange (Betelgeuse, Antares) | | Planet occurrence | No confirmed planets around supergiants | | Stellar class key | blue_supergiant to red_supergiant (seven colours) | | Effective temperature | about 3,400 (red) to above 20,000 (blue) K | | Main sequence lifetime | a few million to a few tens of millions of years in all; the supergiant phase is the last tenth or so yr | | Spectral types covered | O to M | ## Related pages - [Red giant](https://paxabyssi.com/wiki/Red_giant.md): A star in a late stage of life that has run out of hydrogen in its core and swollen to tens or hundreds of times the Sun's size, with a cool, orange-red surface. Stars from about 0.8 to 8 solar masses pass through this stage; the Sun will, in about seven and a half billion years. - [Stellar classification](https://paxabyssi.com/wiki/Stellar_classification.md): How astronomers sort stars by their spectra. A letter (O, B, A, F, G, K, M, and L, T, Y for the coolest objects) and a number give the surface temperature; a Roman numeral gives the size and brightness. The Sun is a G2V star. - [Brown dwarf](https://paxabyssi.com/wiki/Brown_dwarf.md): An object between a planet and a star, roughly 13 to 75 times Jupiter's mass, too light to sustain hydrogen fusion. Brown dwarfs glow with the heat of their formation and cool for ever, passing through the spectral classes L, T and Y; there is about one for every four stars. - [G-type main-sequence star](https://paxabyssi.com/wiki/G-type_main-sequence_star.md): A hydrogen-burning star of spectral class G, like the Sun, with a surface temperature of about 5,300 to 6,000 K and roughly 0.9 to 1.1 times the Sun's mass. Often called yellow dwarfs, they look white with a faint warm tint from space and shine steadily for about ten billion years. - [K-type main-sequence star](https://paxabyssi.com/wiki/K-type_main-sequence_star.md): A hydrogen-burning star of spectral class K, between about 0.6 and 0.9 times the Sun's mass, with a surface temperature of about 3,900 to 5,300 K. Often called orange dwarfs, they outnumber Sun-like stars two to one, live for tens of billions of years, and are among the best places to look for habitable planets. - [Red dwarf](https://paxabyssi.com/wiki/Red_dwarf.md): A small, cool, faint main-sequence star of spectral class M, between about 8% and 60% of the Sun's mass. Red dwarfs are about three quarters of all stars, live for trillions of years, flare violently when young, and host many of the nearest known rocky planets. Categories: [Stars](https://paxabyssi.com/wiki/Category:Stars.md), [Supergiant stars](https://paxabyssi.com/wiki/Category:Supergiant_stars.md), [Stellar evolution](https://paxabyssi.com/wiki/Category:Stellar_evolution.md), [Massive stars](https://paxabyssi.com/wiki/Category:Massive_stars.md)