List of most massive stars

This is a list of the most massive stars that have been discovered, in solar mass units (M).

Uncertainties and caveats

Most of the masses listed below are contested and, being the subject of current research, remain under review and subject to constant revision of their masses and other characteristics. Indeed, many of the masses listed in the table below are inferred from theory, using difficult measurements of the stars' temperatures, composition, and absolute brightnesses. All the masses listed below are uncertain: Both the theory and the measurements are pushing the limits of current knowledge and technology. Both theories and measurements could be incorrect.

Complications with distance and obscuring clouds

Since massive stars are rare, astronomers must look very far from Earth to find them. All the listed stars are many thousands of light years away making their light especially faint, which makes measurements difficult. In addition to being far away, many stars of such extreme mass are surrounded by clouds of outflowing gas created by extremely powerful stellar winds. This outflow obscures the stars, making it difficult to determine the physical properties of the star needed to calculate its mass: The surrounding gas interferes with the already difficult-to-obtain measurements of stellar temperatures and brightnesses, which greatly complicates the issue of estimating internal chemical compositions and structures.

Both the obscuring clouds and the great distances also 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 be two or more companions orbiting too closely for our telescopes to distinguish, each star possibly being massive in itself but not necessarily "supermassive" to either be on this list, or near the top of it. And certainly other combinations are possible – for example a supermassive star with one or more smaller companions or more than one giant star – but without being able to clearly see inside the surrounding cloud, it is difficult to know what kind of object is actually generating the bright point of light seen from the Earth.

More globally, statistics on stellar populations seem to indicate that the upper mass limit is in the 120-solar-mass range, so any mass estimate above this range is suspect.

Rare reliable estimates

Eclipsing binary stars are the only stars whose masses are estimated with some confidence. However, note that almost all of the masses listed in the table below were inferred by indirect methods; only a few of the masses in the table were determined using eclipsing systems.

Amongst the most reliable listed masses are those for the eclipsing binaries NGC 3603-A1, WR 21a, and WR 20a. Masses for all three were obtained from orbital measurements. 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.

Relevance of stellar evolution

Some stars may once have been more massive than they are today. Many large stars have likely suffered significant mass loss – perhaps as much as several tens of solar masses. The lost mass is expected to have been expelled by superwinds: high velocity winds that are driven by the hot photosphere into interstellar space. The process forms an enlarged extended envelope around the star that interacts with the nearby interstellar medium and infuses the adjacent volume of space 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 their debris. The masses of the precursor stars that fueled these destructive events can be estimated from the type of explosion and the energy released, but those masses are not listed here.

This list only concerns "living" stars – those which are still seen by Earth-based observers existing as active stars: Still engaged in interior nuclear fusion that generates heat and light. That is, the light now arriving at the Earth as images of the stars listed still shows them to internally generate new energy as of the time (in the distant past) that light now being received was emitted. The list specifically excludes both white dwarfs – former stars that are now seen to be "dead" but radiating residual heat – and black holes – fragmentary remains of exploded stars which have gravitationally collapsed, even though accretion disks surrounding those black holes might generate heat or light exterior to the star's remains (now inside the black hole), radiated by infalling matter (see § Black holes below).

Mass limits

There are two related theoretical limits on how massive a star can possibly be: The accretion mass limit and the Eddington mass limit.

  • The accretion limit is related to star formation: After about 120 M have accreted in a protostar, the combined mass should have become hot enough for its heat to drive away any further incoming matter. In effect, the protostar reaches a temperature where it evaporates away material already collected as fast as it collects new material.
  • The Eddington limit is based on light pressure from the core of an already-formed star: As mass increases past ~150 M, the intensity of light radiated from a Population I star's core will become sufficient for the light-pressure pushing outward to exceed the gravitational force pulling inward, and the surface material of the star will be free to float away into space. Since their different compositions make them more transparent, Population II and Population III stars have higher and much higher mass limits, respectively.

Accretion limits

Astronomers have long hypothesized 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 known cluster of stars in our galaxy, astronomers have confirmed that no stars in that cluster exceed about 150 M.

Rare ultramassive stars that exceed this limit – for example in the R136 star cluster – might be explained by an exceptional event hypothesized to have occurred: some of the pairs of massive stars in close orbit in young, unstable multiple-star systems must, on rare occasions, collide and merge when certain unusual circumstances hold that make a collision possible.

Eddington mass limit

Eddington's limit on stellar mass arises because of light-pressure: 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. The lowest mass for which this effect is active is the Eddington limit.

Stars of greater mass have a higher rate of core energy generation, and heavier stars' luminosities increase far out of proportion to the increase in their masses. The Eddington limit is the point beyond which a star ought to push itself apart, or at least shed enough mass to reduce its internal energy generation to a lower, sustainable rate. The actual limit-point mass depends on how opaque the gas in the star is, and metal-rich Population I stars have lower mass limits than metal-poor Population II stars. Before their demise, the hypothetical metal-free Population III stars would have had the highest allowed mass, somewhere around 300 M.

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 used instead.

List of the most massive known stars

Legend
Wolf–Rayet star
Slash star
O-type star
B-type star or LBV

The following two lists show a few of the known stars, including the stars in open clusters, OB associations, and H II regions. Despite their high luminosity, many of them are nevertheless too distant to be observed with the naked eye. Stars that are at least sometimes visible to the unaided eye have their apparent magnitude (6.5 or brighter) highlighted with a sky blue background.

The first list gives stars that are estimated to be 60 M or larger; the majority of which are shown. The second list includes some notable stars which are below 60 M for the purpose of comparison. The method used to determine each star's mass is included to give an idea of the data's uncertainty; note that the mass of binary stars can be determined far more accurately. The masses listed below are the stars' current (evolved) mass, not their initial (formation) mass.

A few notable large stars with masses less than 60 M are shown in the table below for the purpose of comparison, ending with the Sun, which is very close, but would otherwise be too small to be included in the list. At present, all the listed stars are naked-eye visible and relatively nearby.

Star name Location Mass
(M, Sun = 1)
Eff. temp.
(K)
Approx. dist.
(ly)
Appt. vis. mag. Mass est. method Link Ref.
λ Cephei Runaway star from Cepheus OB3 51.4 36,000 3,100 5.05 spectroscopy SIMBAD
τ Canis Majoris Aa NGC 2362 50 32,000 5,120 4.89 evolution SIMBAD
θ Muscae Ab Centaurus OB1 44 33,000 7,400 5.53
combined
evolution SIMBAD
θ2 Orionis A Orion OB1 of Orion complex 39 34,900 1,500 5.02 evolution SIMBAD
α Camelopardalis Runaway star from NGC 1502 37.6 29,000 6,000 4.29 evolution SIMBAD
P Cygni IC 4996 of Cygnus OB1 37 18,700 5,100 4.82 spectroscopy SIMBAD
ζ1 Scorpii NGC 6231 of Scorpius OB1 36 - 53 17,200 8,210 4.705 spectroscopy SIMBAD
ζ Orionis Aa Alnitak in Orion OB1 of Orion complex 33 29,500 1,260 2.08 evolution SIMBAD
θ1 Orionis C1 Trapezium Cluster of Orion complex 33 39,000 1,340 5.13
combined
evolution SIMBAD
κ Cassiopeiae Cassiopeia OB14 33 23,500 4,000 4.16 evolution SIMBAD
μ Normae NGC 6169 33 28,000 3,260 4.91 spectroscopy SIMBAD
η Carinae B Trumpler 16 of Carina Nebula 30 37,200 7,500 4.3
combined
binary SIMBAD
γ2 Velorum B Vela OB2 28.5 35,000 1,230 1.83
combined
evolution SIMBAD
Alnilam ε Orionis in Orion OB1 of Orion complex 28.4±2.0 25,000 1,250 1.69 spectroscopy + interferometry SIMBAD
Meissa A In Collinder 69 of Orion complex 27.9 37,700 1,300 3.54 spectroscopy SIMBAD
ξ Persei Menkib in California Nebula of Perseus OB2 26.1 35,000 1,200 4.04 evolution SIMBAD
ζ Puppis Naos in Vela R2 of Vela Molecular Ridge 25.3±5.3 40,000 1,080 2.25 empirical SIMBAD
WR 79a NGC 6231 of Scorpius OB1 24.4 35,000 5,600 5.77 spectroscopy SIMBAD
Mintaka Aa1 In Orion OB1 of Orion complex 24 29,500 1,200 2.5
combined
evolution SIMBAD
ι Orionis Aa1 Hatysa in NGC 1980 of Orion complex 23.1 32,500 1,340 2.77
combined
evolution SIMBAD
κ Crucis Jewel Box Cluster of Centaurus OB1 23 16,300 7,500 5.98 evolution SIMBAD
WR 78 NGC 6231 of Scorpius OB1 22 50,100 4,100 6.48 spectroscopy SIMBAD
ο2 Canis Majoris Field star 21.4 15,500 2,800 3.043 evolution SIMBAD
Rigel A In Orion OB1 of Orion complex 21 12,100 860 0.13 evolution SIMBAD
ζ Ophiuchi Upper Scorpius subgroup of Scorpius OB2 20.2 34,000 370 2.569 evolution SIMBAD
υ Orionis Orion OB1 of Orion complex 20 33,400 2,900 4.618 evolution SIMBAD
σ Orionis Aa Orion OB1 of Orion complex 18 35,000 1,260 4.07
combined
spectroscopy SIMBAD
μ Columbae Runaway star from Trapezium Cluster 16 33,000 1,300 5.18 spectroscopy SIMBAD
Saiph In Orion OB1 of Orion complex 15.5 26,500 650 2.09 evolution SIMBAD
σ Cygni Cygnus OB4 15 10,800 3,260 4.233 evolution SIMBAD
θ Carinae A IC 2602 of Scorpius OB2 14.9 31,000 460 2.76
combined
evolution SIMBAD
θ2 Orionis B Orion OB1 of Orion complex 14.8 29,300 1,500 6.38 spectroscopy SIMBAD
ζ Persei Perseus OB2 14.5 20,800 750 2.86 evolution SIMBAD
σ Orionis B Orion OB1 of Orion complex 14 31,000 1,260 4.07
combined
spectroscopy SIMBAD
β Canis Majoris Mirzam in Local Bubble of Scorpius OB2 13.5 23,200 490 1.985 evolution SIMBAD
ε Persei A α Persei Cluster 13.5 26,500 640 2.88
combined
evolution SIMBAD
ι Orionis Aa2 NGC 1980 of Orion complex 13.1 27,000 1,340 2.77
combined
evolution SIMBAD
δ Scorpii A Dschubba in Upper Scorpius subgroup of Scorpius OB2 13 27,400 440 2.307
combined
evolution SIMBAD
σ Orionis Ab Orion OB1 of Orion complex 13 29,000 1,260 4.07
combined
spectroscopy SIMBAD
θ Muscae Aa WR 48 in Centaurus OB1 11.5 83,000 7,400 5.53
combined
spectroscopy SIMBAD
γ2 Velorum A WR 11 in Vela OB2 9 57,000 1,230 1.83
combined
spectroscopy SIMBAD
ρ Ophiuchi A ρ Ophiuchi cloud complex of Scorpius OB2 8.7 22,000 360 4.63
combined
evolution SIMBAD
Bellatrix In Bellatrix Cluster of Orion complex 7.7 21,800 250 1.64 evolution SIMBAD
Antares B Loop I Bubble of Scorpius OB2 7.2 18,500 550 5.5 evolution SIMBAD
λ Tauri A Pisces-Eridanus stellar stream 7.18 18,700 480 3.47
combined
evolution SIMBAD
δ Persei α Persei Cluster 7 14,900 520 3.01 evolution SIMBAD
ψ Persei α Persei Cluster 6.2 16,000 580 4.31 evolution SIMBAD
α Pavonis Aa Peacock in Tucana-Horologium association 5.91 17,700 180 1.94 evolution SIMBAD
Alcyone In Pleiades 5.9 12,300 440 2.87
combined
evolution SIMBAD
γ Canis Majoris Muliphein in Collinder 121 5.6 13,600 440 4.1 evolution SIMBAD
η Canis Majoris Aludra in Collinder 121 5.5 or 9.5 15,000 2,000 2.45 SED modelling / spectroscopy SIMBAD
ο Velorum IC 2391 of Scorpius OB2 5.5 16,200 490 3.6 evolution SIMBAD
ο Aquarii Pisces-Eridanus stellar stream 4.2 13,500 440 4.71 evolution SIMBAD
ν Fornacis Pisces-Eridanus stellar stream 3.65 13,400 370 4.69 evolution SIMBAD
φ Eridani Tucana-Horologium association 3.55 13,700 150 3.55 evolution SIMBAD
η Chamaeleontis η Chamaeleontis moving group of Scorpius OB2 3.2 12,500 310 5.453 evolution SIMBAD
ε Chamaeleontis ε Chamaeleontis moving group of Scorpius OB2 2.87 10,900 360 4.91 evolution SIMBAD
τ1 Aquarii Pisces-Eridanus stellar stream 2.68 10,600 320 5.66 evolution SIMBAD
ε Hydri Tucana-Horologium association 2.64 11,000 150 4.12 evolution SIMBAD
β1 Tucanae Tucana-Horologium association 2.5 10,600 140 4.37 evolution SIMBAD
Sirius A ~11 th nearest star 2.06 9,850 8.6 −1.46 evolution SIMBAD
Sun Solar System 1 5,772 0.0000158 −26.744 standard IAU
  1. For methods that involve modelling the a star's internal dynamics, different chemical composition indicates a different estimate for stellar mass for any one measured temperature and / or brightness.
  2. 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.
  3. The superwinds from massive stars are similar to the superwinds generated by asymptotic giant branch (AGB) stars – red giants – that form planetary nebulae. These stars' later remnants become the (technically non-stellar) white dwarf cores of planetary nebulae.
  4. For examples of stellar debris see hypernovae and supernova remnant.
  5. This is a binary system but the secondary is much less massive than the primary.
  6. Mercer 30 is an open cluster in Dragonfish Nebula.
  7. BSDL 1830 is a star cluster in Large Magellanic Cloud.
  8. BSDL 2527 is a star cluster in Large Magellanic Cloud.
  9. DEM S10 is a H II region in Small Magellanic Cloud.
  10. DEM S80 is a H II region in Small Magellanic Cloud.
  11. IC 4996 is an open cluster in Cygnus OB1.
  12. Vela R2 is a OB association in Vela Molecular Ridge.

Black holes

Black holes are the end point of the evolution of massive stars. Technically they are not stars, as they no longer generate heat and light via nuclear fusion in their cores. Some black holes may have cosmological origins, and would then never have been stars. This is thought to be especially likely in the cases of the most massive black holes.

  • Stellar black holes are objects with approximately 4–15 M .
  • Intermediate-mass black holes range from 100 to 10000 M .
  • Supermassive black holes are in the range of millions or billions M.

See also

Footnotes

  1. A very few low / no metallicity stars (populations II and III) between 140–250 M end their lives by a type II-P supernova explosion, which is powerful enough to blow (almost) all matter away from the vicinity of the star, so that not enough material remains to create either a black hole, or a neutron star, or a white dwarf: There is no central remnant; all that remains is an expanding shell of shocked gas from the SN explosion colliding with previously quiescent material ejected before the core collapse explosion.

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