List of most massive stars known

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This is a list of the most-massive stars so far discovered, in solar masses (M).

Uncertainties and caveats[edit]

Most of the masses listed below are contested and, being the subject of current research, remain under review and subject to revision. Indeed, many of the masses listed in the table below are inferred from theory, using difficult measurements of the stars’ temperatures and absolute brightnesses. All the listed masses are uncertain: both the theory and the measurements are pushing the limits of current knowledge and technology. Either measurement or theory, or both, could be incorrect. For example, VV Cephei could be between 25–40 M, or 100 M, depending on which property of the star is examined.

Artist's impression of disc of obscuring material around a massive star.

Massive stars are rare; astronomers must look very far from the Earth to find one. All the listed stars are many thousands of light years away and that alone makes measurements difficult. In addition to being far away, many stars of such extreme mass are surrounded by clouds of outflowing gas; the surrounding gas interferes with the already difficult-to-obtain measurements of stellar temperatures and brightnesses and greatly complicates the issue of estimating internal chemical compositions. For some methods, different determinations of chemical composition lead to different estimates of mass. In addition, the clouds of gas make it difficult to judge whether the star is just a single supermassive object or, instead, a multiple star system. A number of the "stars" listed below may actually consist of two or more companions in close orbit, each star being massive in itself but not necessarily supermassive. Other combinations are possible – for example a supermassive star with one or more smaller companions or more than one giant star. Without being able to see inside the surrounding cloud, it is difficult to know the truth of the matter. More globally, statistics on stellar populations seem to indicate that the upper mass limit is in the 100-200 solar mass range.

Amongst the most reliable listed masses are those for the eclipsing binaries NGC 3603-A1, WR21a and WR20a, which were obtained from orbital measurements. Indeed, for a binary star, it is possible to measure the individual masses of the two stars by studying their orbital motions, using Kepler's laws of planetary motion. This involves measuring their radial velocities and also their light curves. The radial velocities only yield minimum values for the masses, depending on inclination, but lightcurves of eclipsing binaries provide the missing information, inclination. Therefore, the masses of eclipsing binaries are the sole ones to be derived with some accuracy. The list below lists however also masses derived by indirect methods, not only those derived for eclipsing systems.

Relevance of stellar evolution[edit]

Some stars may once have been heavier than they are today. It is likely that many have lost tens of solar masses of material in the process of degassing, or in sub-supernova and supernova impostor explosion events.

There are also – or rather were – stars that might have appeared on the list but no longer exist as stars. Today we see only the debris (see for example hypernovae and supernova remnant). The masses of the precursor stars that fueled these cataclysms can be estimated from the type of explosion and the energy released, but those masses are not listed here.

List of the most massive stars[edit]

A few known stars with an estimated mass of 25 or greater M, including the stars of Arches cluster, Cygnus OB2 cluster, Pismis 24 cluster and R136 cluster. Note that all O-stars have masses > 15 M and catalogs of such stars (GOSS, Reed) contain hundreds of cases. Masses quoted below are their current (evolutionary) mass, not their initial (formation) mass. The list is very far from complete, especially below 80 M - although the majority of stars thought to be more than 100 M are shown. Method is provided to get an idea of uncertainty - direct methods (binarity) being more secure than indirect ones (conversion form luminosity, extrapolation from atmosphere models,...).

The R136 cluster
Star name Mass
(M, Sun = 1)
Method Refs.
R136a1  265 Luminosity/Atmosphere model [1]
BAT99-98 226 Luminosity/Atmosphere model [1]
R136a2  179 Luminosity/Atmosphere model [1]
HD 15558 >152 ± 51 Binary [2][3]
VFTS 682  150 Luminosity/Atmosphere model [4]
NGC 3603-B  132 ± 13 Luminosity/Atmosphere model [5]
R136a3  130 Luminosity/Atmosphere model [1]
HD 269810   130 Luminosity/Atmosphere model [6]
R136c  130 Luminosity/Atmosphere model [1]
WR 42e 125–135 Ejection in triple system [7][a]
Arches-F9  111–131 Luminosity/Atmosphere model [8]
η Carinae A 120  ?
R136b  118 Luminosity/Atmosphere model [1]
R145 >116 ± 33 Binary [9][b]
NGC 3603-A1a  116 ± 31 Eclipsing binary [10]
Cygnus OB2-7  114 revised to 69 ± 10 Luminosity/Atmosphere model [11]
NGC 3603-C 113 ± 10 Luminosity/Atmosphere model [5]
Melnick 42 113 Luminosity/Atmosphere model [1]
Cygnus OB2-12  110 Luminosity/Atmosphere model [12]
WR 25 110 Binary?
Arches-F1  101–119 Luminosity/Atmosphere model [8]
Arches-F6  101–119 Luminosity/Atmosphere model [8]
BAT99-33 (R99) 103 Luminosity/Atmosphere model [1]
Peony Star 100 Luminosity/Atmosphere model? [13]
516 Cygnus 100 Luminosity ?
R136a in LMC About 10 other stars between 80 and 200.   Luminosity/Atmosphere model [1]
HD 93129 A  95 Luminosity/Atmosphere model [14]
Arches-F7  86–102 Luminosity/Atmosphere model [8]
HD 38282 B >90 Luminosity [15]
771 Cygnus 90 Luminosity/Atmosphere model?
NGC 3603-A1b  89 ± 16 Eclipsing binary [10]
The Pistol Star 86–92 Luminosity?
Arches-F15  80–97 Luminosity/Atmosphere model [8]
WR21a A >87 ± 6 Binary [16]
HD 93250  86.83 Luminosity/Atmosphere model [14]
WR20a A 82.7 ± 5.5 Eclipsing binary [17]
WR20a B  81.9 ± 5.5 Eclipsing binary [17]
HD 38282 A >80 Luminosity [15]
Sk -71 51 80 Luminosity [18]
Cygnus OB2-8B 80 Luminosity?

A few additional examples with masses lower than 80 M.

Star name Mass
(M, Sun = 1)
Refs.
R139 A 78 [19]
V429 Carinae A 78
WR 22 78
Pismis 24-17 78 [20]
Arches-F12 70–82
Cygnus OB2-10 75
Arches-F18 67–82
Var 83 in M33 60–85
Cygnus OB2-8C 71
Arches-F4 66–76
R126 70
Companion to M33 X-7 70 [21]
AG Carinae 70
BD+43° 3654 70
HD 5980 A 58-79
Pismis 24-1 SW 66
LBV 1806-20 A + B A=65, B=65
Arches-F28 66–76
LH54-425 A 62
Arches-F21 56–70
Arches-F10 55–69
HD 148937 60 [22]
Arches-F14 54–65
HD 5980 B 51-67
WR 102ea 58 [23]
Cygnus OB2-11 58
Arches-F3 52–63
CD Crucis A 57 [24]
Arches-B1 50–60
Plaskett's star B 56
BD+40° 4210 54
Plaskett's star A 54
WR21a B 53 [16]
HD 93129A B 52 [25]
Cygnus OB2-4 52
Arches-F20 47–57
Arches-F16 46–56
WR102c 45–55 [13]
CD Crucis B 48 [24]
Arches-F8 43–51
Sher 25 in NGC 3603 40–52
HD 15558 45 ± 11 [2][26]
Arches-F2 42–49
S Doradus 45
IRS-8* 44.5 [27]
Cygnus OB2-8A A 44.1
Cygnus OB2-1 44
α Camelopardalis 43
Pismis 24-2 43
χ2 Orionis 42.3
Cygnus OB2-6 42
ε Orionis 40[citation needed]
RW Cephei 40
θ1 Orionis C 40
ζ Puppis 22.5–56.6
Companion to NGC 300 X-1 38 [28]
Pismis 24-16 38
Pismis 24-25 38
Cygnus OB2-8A B 37.4
LH54-425 B 37
ζ1 Scorpii 36
Pismis 24-13 35
Companion to IC 10 X-1[29] 35
Cygnus OB2-9 A >34
Arches-F5 31–36
Cygnus OB2-18 33
ζ Orionis 33
19 Cephei 30–35
ξ Persei 26–36
Cygnus OB2-5 A 31
Cygnus OB2-9 B >30
γ Velorum A 30
P Cygni 30
IRS 15[30] 26
6 Cassiopeiae 25 [31]
Pismis 24-3 25
KY Cygni 25[citation needed]
NGC 7538 S 25 [32]
VFTS 102 25
ρ Cassiopeiae 14-30
Legend
Wolf-Rayet star
O-class star
B-class star
Luminous blue variable star
Hypergiant
  1. ^ This unusual measurement was made by assuming the star was ejected from a three-body encounter in NGC 3603. This assumption also means that the current star is the result of a merger between two original close binary components. The mass is consistent with evolutionary mass for a star with the observed parameters.
  2. ^ These are minimum values with the orbital solution still uncertain.

Black holes[edit]

Black holes are the end point evolution of massive stars. Technically they are not stars, as they no longer generate heat and light via nuclear fusion in their cores.

Eddington's size limit[edit]

Main article: Eddington luminosity

The limit on mass arises because stars of greater mass have a higher rate of core energy generation, their luminosity increasing far out of proportion to their mass. For a sufficiently massive star the outward pressure of radiant energy generated by nuclear fusion in the star’s core exceeds the inward pull of its own gravity. This is called the Eddington limit. Beyond this limit, a star ought to push itself apart, or at least shed enough mass to reduce its internal energy generation to a lower, maintainable rate. In theory, a more massive star could not hold itself together, because of the mass loss resulting from the outflow of stellar material. In practice the theoretical Eddington Limit must be modified for high luminosity stars and the empirical Humphreys Davidson Limit is derived.[33]

Astronomers have long theorized that as a protostar grows to a size beyond 120 M, something drastic must happen. Although the limit can be stretched for very early Population III stars, and the exact value is uncertain, if any stars still exist above 150-200 M, they would challenge current theories of stellar evolution. Studying the Arches cluster, which is the densest known cluster of stars in our galaxy, astronomers have confirmed that stars in that cluster do not occur any larger than about 150 M. One theory to explain rare ultramassive stars that exceed this limit, for example in the R136 star cluster, is the collision and merger of two massive stars in a close binary system.[34]

See also[edit]

References[edit]

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External links[edit]