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 masses listed below 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.
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.[a]
Both the obscuring clouds and the great distances 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 to distinguish, 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 – but 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.
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.[b] 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.
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 driven by 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.[c] 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 (see § Black holes below).
There are two related theoretical limits on how massive a star can possibly be: the accretion 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 point where it evaporates away material 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.
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.
Rare ultramassive stars that exceed this limit – for example in the R136 star cluster – might be explained by the following proposal: Some of the pairs of massive stars in close orbit in young, unstable multiple-star systems must occasionally collide and merge where certain unusual circumstances hold that make a collision possible.
A 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. This effect is called 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, maintainable 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, with the hypothetical metal-free Population III stars having 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.
The first list gives stars that are estimated to be 80 M☉ or larger. The majority of stars thought to be more than 100 M☉ are shown, but the list is incomplete.
The second list gives examples of stars 25–79 M☉, but is far from a complete list. Note that all O-type stars have masses greater than 15 M☉ and catalogs of such stars (GOSS, Reed) list hundreds of cases.
In each list, the method used to determine the mass is included to give an idea of uncertainty: Binary stars being more securely determined than indirect methods such as conversion from luminosity, extrapolation from stellar atmosphere models, ... . The masses listed below are the stars’ current (evolved) mass, not their initial (formation) mass.
|Luminous blue variable star|
(M☉, Sun = 1)
|Distance from earth (ly)||Method used to estimate mass||Refs.|
|Melnick 42||189||163,000||Luminosity/Atmosphere model|||
|Melnick 34||179||163,000||Luminosity/Atmosphere model|||
|HD 15558 A||>152 ± 51||24,400||Binary|||
|VFTS 682||150||164,000||Luminosity/Atmosphere model|||
|LH 10-3209 A||140||?|||
|NGC 3603-B||132 ± 13||24,700||Luminosity/Atmosphere model|||
|HD 269810||130||Luminosity/Atmosphere model|||
|WR 42e||125–135||25,000||Ejection in triple system||[d]|
|NGC 3603-A1a||120||24,700||Eclipsing binary|||
|LSS 4067||120||Evolutionary model|||
|NGC 3603-C||113 ± 10||22,500||Luminosity/Atmosphere model|||
|Cygnus OB2-12||110||5,220||Luminosity/Atmosphere model|||
|HD 93129 A||110||7,500||Luminosity/Atmosphere model|
|BAT99-33 (R99)||103||16,400||Luminosity/Atmosphere model|||
|η Carinae A||100–200||7,500||Luminosity/Binary|| The most massive star that has a Bayer designation|
|Peony Star (WR 102ka)||100||26,000||Luminosity/Atmosphere model?|||
|Cygnus OB2 #516||100||4,700||Luminosity?|
|NGC 3603-A1b||92||24,800||Eclipsing binary|||
|HD 38282 B||>90||Luminosity|||
|Cygnus OB2 #771||90||Luminosity/Atmosphere model?|
|HSH95 31||87||Evolutionary model|
|HD 93250||86.83||Luminosity/Atmosphere model|||
|WR20a A||82.7 ± 5.5||Eclipsing binary|||
|WR20a B||81.9 ± 5.5||Eclipsing binary|||
|HD 38282 A||>80||Luminosity|||
|Sk -71 51||80||Luminosity|||
A few additional examples with masses lower than 80 M☉.
(M☉, Sun = 1)
|V429 Carinae A||78|
|Companion to M33 X-7||70|||
|HD 93403 A||68.5|
|HD 5980 B||66|
|HD 5980 A||61|
|Var 83 in M33||60–85|
|WR 21a B||58.3|||
|CD Crucis A||57|||
|ζ Puppis (Naos)||56.1|||
|Plaskett's Star B||56|
|9 Sagittarii A||55|
−40 + 54+20
|Plaskett's Star A||54|
|HD 93129 B||52|||
|CD Crucis B||48|||
|LH54-425||A=47 ± 2, B=28 ± 1||Binary|||
|HD 15558 B||45 ± 11|||
|Cygnus OB2-8A A||44.1|
|Sher 25 in NGC 3603||40–52|
|θ1 Orionis C||40|
|Companion to NGC 300 X-1||38|||
|Cygnus OB2-8A B||37.4|
|HD 93403 B||37.3|
|Companion to IC 10 X-1||35|
|Cygnus OB2-9 A||>34|
|ζ Orionis (Alnitak)||33|
|Cygnus OB2-5 A||31|
|Cygnus OB2-9 B||>30|
|η Carinae B||30–80||Luminosity/Binary |
|ε Orionis (Alnilam)||30–64.5|
|γ Velorum A (Regor A)||30|
|VY Canis Majoris||30 (17–40)|||
|VFTS 352||A=28.63 ± 0.3, B=28.85 ± 0.3|||
|The Pistol Star (V4647 Sgr)||27.5|
|ξ Persei (Menkib)||26–36|
|NGC 7538 S||25|||
BAT99-98 is a star in the Large Magellanic Cloud. It is located near the R136 cluster in the 30 Doradus nebula. At 226 M☉ and 5,000,000 L☉ it is the third most massive and the fifth most luminous star known.Eddington luminosity
The Eddington luminosity, also referred to as the Eddington limit, is the maximum luminosity a body (such as a star) can achieve when there is balance between the force of radiation acting outward and the gravitational force acting inward. The state of balance is called hydrostatic equilibrium. When a star exceeds the Eddington luminosity, it will initiate a very intense radiation-driven stellar wind from its outer layers. Since most massive stars have luminosities far below the Eddington luminosity, their winds are mostly driven by the less intense line absorption. The Eddington limit is invoked to explain the observed luminosity of accreting black holes such as quasars.
Originally, Sir Arthur Eddington took only the electron scattering into account when calculating this limit, something that now is called the classical Eddington limit. Nowadays, the modified Eddington limit also counts on other radiation processes such as bound-free and free-free radiation (see Bremsstrahlung) interaction.HD 15558
HD 15558 (HIP 11832) is a massive O-type multiple star system in the constellation of Cassiopeia. It is located in the Heart Nebula in open cluster IC 1805. The primary is a very massive star with 152 M☉ and 660,000 L☉.Hypergiant
A hypergiant (luminosity class 0 or Ia+) is among the very rare kinds of stars that typically show tremendous luminosities and very high rates of mass loss by stellar winds. The term hypergiant is defined as luminosity class 0 (zero) in the MKK system. However, this is rarely seen in the literature or in published spectral classifications, except for specific well-defined groups such as the yellow hypergiants, RSG (red supergiants), or blue B(e) supergiants with emission spectra. More commonly, hypergiants are classed as Ia-0 or Ia+, but red supergiants are rarely assigned these spectral classifications. Astronomers are interested in these stars because they relate to understanding stellar evolution, especially with star formation, stability, and their expected demise as supernovae.List of coolest stars
This is a list of coolest stars discovered, arranged by decreasing temperature. The stars with temperatures lower than 3,000 K are included.List of hottest stars
This is a list of hottest stars so far discovered (excluding degenerate stars), arranged by decreasing temperature. The stars with temperatures higher than 60,000 K are included.List of largest stars
Below is an ordered list of the largest stars currently known by radius. The unit of measurement used is the radius of the Sun (approximately 695,700 km; 432,288 mi).
The exact order of this list is very incomplete, as great uncertainties currently remain, especially when deriving various important parameters used in calculations, such as stellar luminosity and effective temperature. Often stellar radii can only be expressed as an average or within a large range of values. Values for stellar radii vary significantly in sources and throughout the literature, mostly as the boundary of the very tenuous atmosphere (opacity) greatly differs depending on the wavelength of light in which the star is observed.
Radii of several stars can be directly obtained by stellar interferometry. Other methods can use lunar occultations or from eclipsing binaries, which can be used to test other indirect methods of finding true stellar size. Only a few useful supergiant stars can be occulted by the Moon, including Antares and Aldebaran. Examples of eclipsing binaries include Epsilon Aurigae, VV Cephei, and HR 5171.List of most luminous stars
Below is a list of stars arranged in order of decreasing luminosity (increasing bolometric magnitude). Accurate measurement of stellar luminosities is quite difficult in practice, even when the apparent magnitude is measured accurately, for four reasons:
The distance d to the star must be known, to convert apparent to absolute magnitude. Absolute magnitude is the apparent magnitude a star would have if it were 10 parsecs away from the viewer. Since apparent brightness decreases as the square of the distance (i.e. as 1/d2), a small error (e.g. 10%) in determining d implies an error ~2× as large (thus 20%) in luminosity. Stellar distances are only directly measured accurately out to d ~1000 lt-yrs.
The observed magnitudes must be corrected for the absorb/o cygtion or extinction of intervening interstellar or circumstellar dust and gas. This correction can be enormous and difficult to determine precisely. For example, until accurate infrared observations became possible ~50 years ago, the Galactic Center of the Milky Way was totally obscured to visual observations.
The magnitudes at the wavelengths measured must be corrected for those not observed. "Absolute bolometric magnitude" (which term is redundant, practically speaking, since bolometric magnitudes are nearly always "absolute", i.e. corrected for distance) is a measure of the star's luminosity, summing over its emission at all wavelengths, and thus the total amount of energy radiated by a star every second. Bolometric magnitudes can only be estimated by correcting for unobserved portions of the spectrum that have to be modelled, which is always an issue, and often a large correction. The list is dominated by hot blue stars which produce the majority of their energy output in the ultraviolet, but these may not necessarily be the brightest stars at visual wavelengths.
A large proportion of stellar systems discovered with very high luminosity have later been found to be binary. Usually, this results in the total system luminosity being reduced and spread among several components. These binaries are common both because the conditions that produce high mass high luminosity stars also favour multiple star systems, but also because searches for highly luminous stars are inevitably biased towards detecting systems with multiple more normal stars combining to appear luminous.Because of all these problems, other references may give very different lists of the most luminous stars (different ordering or different stars altogether). Data on different stars can be of somewhat different reliability, depending on the attention one particular star has received as well as largely differing physical difficulties in analysis (see the Pistol Star for an example). The last stars in the list are familiar nearby stars put there for comparison, and not among the most luminous known. It may also interest the reader to know that the Sun is more luminous than approximately 95% of all known stars in the local neighbourhood (out to, say, a few hundred light years), due to enormous numbers of somewhat less massive stars that are cooler and often much less luminous. For perspective, the overall range of stellar luminosities runs from dwarfs less than 1/10,000th as luminous as the Sun to supergiants over 1,000,000 times more luminous.List of most massive black holes
This is an ordered list of the most massive black holes so far discovered (and probable candidates), measured in units of solar masses (M☉), or the mass of the Sun (approx. 2×1030 kilograms).List of star extremes
A star is a sphere that is mainly composed of hydrogen and plasma, held together by gravity and is able to produce light through nuclear fusion. Stars exhibit many diverse properties, resulting from different masses, volumes, velocities, stage in stellar evolution and even proximity to earth. Some of these properties are considered extreme and sometimes disproportionate by astronomers.Lists of extreme points
This is a list of lists of the points that are the farthest, highest, lowest, greatest or least.Lists of stars
The following are lists of stars. These are astronomical objects that spend some portion of their existence generating energy through thermonuclear fusion.Outline of astronomy
The following outline is provided as an overview of and topical guide to astronomy:
Astronomy – studies the universe beyond Earth, including its formation and development, and the evolution, physics, chemistry, meteorology, and motion of celestial objects (such as galaxies, planets, etc.) and phenomena that originate outside the atmosphere of Earth (such as the cosmic background radiation).WR 102ka
WR 102ka, also known as the Peony star, is a Wolf–Rayet star that is one of several candidates for the most luminous-known star in the Milky Way.
Category:Stars · Stars portal