List of most massive stars

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

Uncertainties and caveats

Most of the masses listed below are contested and, being the subject of current research, are constantly being revised.

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 obscures the already difficult-to-obtain measurements of the stars’ temperatures and brightnesses, and greatly complicates the issue of measuring their internal chemical compositions. For some methods, different chemical composition leads to different mass estimates. In addition, the clouds of gas obscure observations of whether the star is just one supermassive star, or instead a multiple star system. A number of the stars below may actually consist of two or more companions in close orbit, each star being massive in itself, but not necessarily supermassive. Alternatively, it is possible for a multiple-star system to still have one (or more) supermassive star, with one (or more) much smaller companion(s). Without being able to see inside of the surrounding cloud, it is difficult to know which scenario might be the case.

Amongst the most reliable listed masses are NGC 3603-A1, WR21a and WR20a, which were obtained from orbital measurements. They are members of (different) binary star systems, and it is possible to measure in both cases the individual masses of the two stars by studying their orbital motion, via Kepler's laws of planetary motion. This involves measuring their radial velocities and also their light curves, as they are eclipsing binaries. The derivation of binary masses requires relatively limited information about the orbital parameters, but one key value that isn't always accurately known is the inclination. Without this only a minimum value for the masses can be derived, so several binaries are shown with masses as greater than a particular value. For eclipsing binaries, the inclination can be derived with better accuracy.

Stellar evolution

The list only gives the inferred current masses of stars, not previous masses. A number of these and other stars may have started out with even greater masses than the listed current estimates, but have probably lost many tens of solar masses of material due to the huge amount of gas they outflow, and sub-supernova and supernova impostor explosion events.

Also there are a number of supernovae and hypernovae remnants whose precursor stars' masses can be estimated based on pre-super/hypernova observations and the energy and type of explosion. These stars would have easily appeared in this list, had they survived.

List of the most massive stars

Known stars with an estimated mass of 25 or greater M_☉. Masses are their current (evolutionary) mass, not their initial (formation) mass. The list is far from complete, although the majority of stars thought to be more than 100 M_☉ are shown.

Eta Carinae

VY Canis Majoris

Star name	Mass (M☉, Sun = 1)
R136a1	265
R136a2	195
R136c	175
HD 269810	150
VFTS 682	150
Peony Star	>150
R136a3	135
NGC 3603-B	132
WR42e	125-135
Arches-F9	111–131
η Carinae A	120
NGC 3603-A1	116 + 89
Arches-F1	101–119
Arches-F6	111–131
R144 A + B	>118 + >48
HD 93250	118
NGC 3603-C	113
Cygnus OB2-12	110
Arches-F7	86–102
Cluster R136a	About 20 more stars around 100
HD 93129 A	95
WR21a	A=87, B=53
WR20a	A=83, B=82
The Pistol Star	80–150
Melnick 42	80–100
Arches-F15	80–97
Sk-71 51	80
R139	A=78, B=66
V429 Carinae A + B	A=78, B=21
Pismis 24-17	78
R126	70
Companion to M33 X-7	70
Pismis 24-1SW	66
LBV 1806-20 A + B	A=65, B=65
LY Aurigae	64
LH54-425 A + B	A=62, B=37
Var 83 in M33	60–85
CD Crucis A + B	A=57, B=48
Plaskett's star	A=54, B=56
HD 93129B	52
AG Carinae	50
WR102c	45–55
S Doradus	45
IRS-8*	44.5
HD 5980 A + B	A=40–62, B=30
Sher 25 in NGC 3603	40–52
DL Crucis	40–50
α Camelopardalis	43
χ2 Orionis	42.3
ε Orionis	40
HD 148937	40
IRAS 05423-7120	40
ρ Cassiopeiae	40
RW Cephei	40
θ1 Orionis C	40
V382 Carinae	39
Companion to NGC 300 X-1	38
ζ1 Scorpii	36
Companion to IC 10 X-1	35
ν Aquilae	30–45
19 Cephei	30–35
γ Velorum A	30
P Cygni	30
R 66	30
η Canis Majoris	30
ζ Orionis	28
IRS 15	26
VV Cephei	25–40
ξ Persei	26–36
6 Cassiopeiae	25
EZ Canis Majoris	25
KY Cygni	25
μ Cephei	25
V509 Cassiopeiae	25
NGC 7538 S	20–40
S Monocerotis A	18–30
ζ Puppis	22.5
VY Canis Majoris	9–25

Black holes

Main articles: Black hole and List of black holes

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.

• Stellar black holes are objects with approx. 4-15 M_☉.
• Intermediate-mass black holes range from 100-10000 M_☉.
• Supermassive black holes are in the range of millions or billions M_☉.

Eddington's size limit

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.

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.

See also

• Luminous blue variable
• Wolf–Rayet star
• Hypergiant
• List of least massive stars
• List of largest known stars
• List of most luminous stars
• List of brightest stars
• Lists of stars
• Supergiant

External links

• Most Massive Star Discovered
• Arches cluster
• How Heavy Can a Star Get?
• LBV 1806-20