List of most massive stars

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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 created by powerful stellar winds; 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.[citation needed]

Amongst the most reliable listed masses are those for the eclipsing binaries NGC 3603-A1, WR21a, and WR20a. Masses for all three were obtained from orbital measurements – 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 light curves of eclipsing binaries provide the missing information: inclination of the orbit to our line of sight. Therefore, eclipsing binaries are the only stars whose masses are derived with some confidence.

However note that almost all of the masses listed in the table below were inferred by indirect methods; only a few masses were determined using eclipsing systems.

Relevance of stellar evolution[edit]

Some stars may once have been heavier than they are today. It is likely that many have suffered significant mass loss, perhaps as much as several tens of solar masses, expelled by the process of superwind, where high velocity winds are expelled from the hot photosphere into interstellar space. This process is similar to superwinds generated by Asymptotic Giant Branch (AGB) stars in form red giants or planetary nebulae. The process forms an enlarged extended envelope around the star that interacts with the nearby interstellar medium and infusing the region with elements heavier than Hydrogen or Helium.

There are also – or rather were – stars that might have appeared on the list but no longer exist as stars or are supernova impostors. 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]

The following is a list of a few stars with an estimated mass of 25 M or greater, including the stars of Arches cluster, Cygnus OB2 cluster, Pismis 24 cluster, and R136 cluster. Note that all O-type stars have masses greater than 15 M and catalogs of such stars (GOSS, Reed) list hundreds of cases.

The majority of stars thought to be more than 100 M are shown, but this list is far from complete – especially below 80 M. The method used to determine the mass is included in the list to give an idea of uncertainty: direct methods (binary stars) being more secure than indirect ones (conversion from luminosity, extrapolation from stellar atmosphere models, ...).

The masses listed below are the stars’ current (evolved) mass, not their initial (formation) mass.

Wolf–Rayet star
Luminous blue variable star
O-class star
B-class star
The R136 cluster
Star name Mass
(M, Sun = 1)
Distance from earth (ly) Method used to estimate mass Refs.
R136a1  315 163,000 Evolutionary model [1]
R136c  230 163,000 Evolutionary model [1]
BAT99-98 226 165,000 Luminosity/Atmosphere model [2]
R136a2  195 163,000 Evolutionary model [1]
Melnick 42 189 163,000 Luminosity/Atmosphere model [3]
R136a3  180 163,000 Evolutionary model [1]
Melnick 34 179 163,000 Luminosity/Atmosphere model [4]
HD 15558 >152 ± 51 24,400 Binary [5][6]
VFTS 682  150 164,000 Luminosity/Atmosphere model [7]
R136a6  150 157,000 Evolutionary model [1]
LH 10-3209 A 140 ? [8]
NGC 3603-B  132 ± 13 24,700 Luminosity/Atmosphere model [9]
HD 269810   130 Luminosity/Atmosphere model [10]
P871 130 ? [8]
WR 42e 125–135 25,000 Ejection in triple system [11][a]
R136a4  124 157,000 Evolutionary model [1]
Arches-F9  111–131 25,000 Luminosity/Atmosphere model [12]
NGC 3603-A1a  120 24,700 Eclipsing binary [9]
LSS 4067 120 Evolutionary model [13]
NGC 3603-C 113 ± 10 22,500 Luminosity/Atmosphere model [9]
Cygnus OB2-12  110 5,220 Luminosity/Atmosphere model [14]
WR 25 110 10,500 Binary?
HD 93129 A  110 7,500 Luminosity/Atmosphere model
Arches-F1  101–119 25,000 Luminosity/Atmosphere model [12]
Arches-F6  101–119 25,000 Luminosity/Atmosphere model [12]
WR21a A 103.6 26,100 Binary [15]
BAT99-33 (R99) 103 16,400 Luminosity/Atmosphere model [2]
R136a5  101 157,000 Evolutionary model [1]
η Carinae A 100 - 200 7,500 Luminosity/Binary [16][17]
Peony Star (WR 102ka) 100 26,000 Luminosity/Atmosphere model? [18]
Cygnus OB2 #516 100 4,700 Luminosity?
Sk -68°137 99 ? [8]
R136a8  96 157,000 Evolutionary model [1]
HST-42 95 ? [8]
P1311 94 ? [8]
Sk -66°172 94 ? [8]
Arches-F7  86–102 25,000 Luminosity/Atmosphere model [12]
R136b  93 163,000 Evolutionary model [1]
NGC 3603-A1b  92 24,800 Eclipsing binary [9]
HST-A3 91 ? [8]
HD 38282 B >90 Luminosity [19]
Cygnus OB2 #771 90 Luminosity/Atmosphere model?
Arches-F15  80–97 Luminosity/Atmosphere model [12]
HSH95 31 87 Evolutionary model[1]
HD 93250  86.83 Luminosity/Atmosphere model [20]
LH 10-3061 85 ? [8]
BI 253 84
WR20a A 82.7 ± 5.5 Eclipsing binary [21]
MACHO 05:34-69:31 82 ? [8]
WR20a B  81.9 ± 5.5 Eclipsing binary [21]
NGC 346-3 81 ? [8]
HD 38282 A >80 Luminosity [19]
Sk -71 51 80 Luminosity [22]
Cygnus OB2-8B 80 Luminosity?
WR 148 80 ? [23]
HD 97950 80 ?

A few additional examples with masses lower than 80 M.

Star name Mass
(M, Sun = 1)
Method Refs.
R139 A 78 [24]
V429 Carinae A 78
WR 22 78
Pismis 24-17 78 [25]
Cygnus OB2-11 73+32
Arches-F12 70–82
Arches-F18 67–82
Var 83 in M33 60–85
Arches-F4 66–76
Arches-F28 66–76
R126 70
Companion to M33 X-7 70 [27]
BD+43° 3654 70
HD 93205 69 [8]
R136a7  69 Evolutionary model[1]
HD 93403 A 68.5
HD 5980 B 66
HD 5980 A 61
BAT99-119 (R145) 53+20
+ 54+20
Binary [28][b]
Arches-F21 56–70
Arches-F10 55–69
AG Carinae 55
Arches-F14 54–65
S Monocerotis 59
WR21a B 58.3 [15]
WR 102ea 58 [29]
Arches-F3 52–63
CD Crucis A 57 [30]
Arches-B1 50–60
HD 16691 56.6
ζ Puppis (Naos) 56.1
Plaskett's star B 56
9 Sagittarii A 55
η Carinae B 30-80 Luminosity/Binary [17]
BD+40° 4210 54
Plaskett's star A 54
HD 93129 B 52 [31]
Cygnus OB2-4 52
Arches-F20 47–57
LH54-425 A=47 ± 2, B=28 ± 1 Binary[32] [32]
Arches-F16 46–56
WR 102c 45–55 [18]
CD Crucis B 48 [30]
Arches-F8 43–51
Sher 25 in NGC 3603 40–52
Arches-F2 42–49
HD 15558 45 ± 11 [5][6]
S Doradus 45
HD 50064 45
WR 141 45 [23]
IRS-8* 44.5 [33]
Cygnus OB2-8A A 44.1
Cygnus OB2-1 44
Cygnus OB2-10 43.1±14 [26]
α Camelopardalis 43
Pismis 24-2 43
χ2 Orionis 42.3
Cygnus OB2-8C 42.2±14 [26]
Cygnus OB2-6 42
ε Orionis (Alnilam) 30-64.5[34]
θ1 Orionis C 40
μ Nor 40
Cygnus OB2-7  39.7+17
Companion to NGC 300 X-1 38 [35]
Pismis 24-16 38
Pismis 24-25 38
Cygnus OB2-8A B 37.4
HD 93403 B 37.3
ζ1 Scorpii 36
Pismis 24-13 35
Companion to IC 10 X-1[36] 35
Cygnus OB2-9 A >34
Arches-F5 31–36
Cygnus OB2-18 33
ζ Orionis (Alnitak) 33
19 Cephei 30–35
ξ Persei 26–36
Cygnus OB2-5 A 31
Cygnus OB2-9 B >30
γ Velorum A (Regor A) 30
P Cygni 30
VFTS 352 A=28.63 ± 0.3, B=28.85 ± 0.3 [37]
The Pistol Star (V4647 Sgr) 27.5
10 Lacertae 26.9
6 Cassiopeiae 25 [38]
Pismis 24-3 25
NGC 7538 S 25 [39]
VFTS 102 25
ρ Cassiopeiae 14–30
  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. ^ The masses were revised with better data, but refinements are still needed.

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]

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.[40]

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 although 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 currently the densest 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.[41]

See also[edit]


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