stellar mass

stellar mass

The mass of a star is its most fundamental property, upon which its other properties depend strongly. It is usually given in terms of the Sun's mass, i.e. as some number of solar masses, MO; it ranges from about 0.08 to about 60 to 120 MO. Stars of higher mass are much less common than those of low mass. Low-mass stars have an initial mass smaller than about 2.2–2.5 MO, the exact value depending on chemical composition. Intermediate-mass stars have masses between about 2.2–8 MO; they evolve from the main sequence without developing a degenerate core, unlike low-mass stars (see stellar evolution). More massive stars evolve to a state where their core temperatures are high enough to burn carbon under nondegenerate conditions.

The symbol ψ(M) is given to the number of stars with a particular mass M in a unit volume of space, and Salpeter (1955) showed that it is related to the star mass by the formula

ψ(M) ∝ M –2.35

Because of mass loss and mass transfer, this Salpeter mass function holds strictly only for stars at the instant of birth, and it is therefore sometimes called the initial mass function (IMF). The IMF is determined by fragmentation and other little-understood processes during star formation.

The lower limit on a star's mass is the minimum amount of gas whose gravitational compression will raise the central temperature high enough for nuclear fusion to occur; less massive fragments from the initial cloud may contract directly to become a degenerate star known as a brown dwarf. It is still uncertain whether there is a theoretical upper limit to star masses, or whether the rarity of very massive stars means that a galaxy is unlikely to contain a star over about 120 MO. Indirect methods indicate that Eta Carinae and some other luminous blue variables may be as massive as 120 MO .

Most stars lie on the main sequence of the Hertzsprung–Russell diagram. Their position on the main sequence, i.e. their spectral type, depends on their mass, which varies from 0.1 MO (M stars) to over 20 MO (O stars). Supergiants are generally 10 to 20 MO but young O and B supergiants are much more massive.

The mass of a star can be determined directly if it has a significant gravitational effect on a neighboring star. Thus the combined mass and in some cases the individual masses of visual and spectroscopic binary stars have been found (see also dynamical parallax). Mass can be estimated using the mass-luminosity relation, or from a detailed study of the spectrum that indicates the star's surface gravity.

The evolutionary pattern and lifetime of a star depend on its mass. The least massive stars have the longest lifetimes of thousands of millions of years; the most massive exist only a few million years before exploding as supernovae. At the end of its life, following mass loss in a planetary nebula, etc., a star will become a white dwarf if its mass is less than about 1.4 MO; if the mass exceeds about 3 MO it is likely that the star will become a black hole; a star with intermediate mass will end up a neutron star.

stellar mass

[′stel·ər ′mas]
The mass of a star, usually expressed in terms of the sun's mass.
References in periodicals archive ?
The IMF predicts that most stellar mass is in low-mass stars and that less than 1% of all stars are born with masses in excess of ten times that of the Sun.
The two Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington, USA and the Virgo detector, located at the European Gravitational Observatory (EGO) in Cascina, near Pisa, Italy, detected a transient gravitational-wave signal produced by the coalescence of two stellar mass black holes.
And he gets the vote to beat The Grey Gatsby and Stellar Mass.
Stellar Mass, third in last year's Irish Derby, won this a year ago and the Jim Bolger-trained fouryear-old will be attempting to become the fourth dual winner of the contest, the most recent of the previous three having been Profound Beauty in 2009 and 2010.
Instead, a black hole's growth rate seems more strongly connected to a galaxy's total stellar mass than to the number of new stars forming in it.
Their topics include applying an electromagnetism-like algorithm to solve the problem of designing a manufacturing cell, stellar mass black holes for engineering optimization, collective-animal-behavior-based optimized null placement in time-modulated linear antenna arrays, particle swarm optimization for reducing the cost of managing mobile locations using the reporting cell planning approach, and an intelligent demand forecasting and replenishment system using nature-inspired computing.
The Galileo colt is ante-post jolly for the final Classic after being placed in both the Epsom and Irish Derbys and could face Jim Bolger's progressive Stellar Mass.
At the line he had half a length to spare, with Stellar Mass running a tremendous third just a week after landing the Ulster Derby.
Title: Assembly of stellar mass galaxy cluster cores since z=1
This limits the maximum mass that a stellar mass black hole could ever grow to.
The black hole candidates belong to the stellar mass category, meaning they formed in the death throes of very massive stars and typically have masses five to 10 times that of our sun.
It is also very important as dust affects star formation, stellar mass loss rates, the formation of molecular hydrogen and planets.