| An upper limit to the masses of stars (2005) | |||||||||||||||
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| upper limit the masses stars Donald Figer STScI San Martin Drive Baltimore There accepted upper mass limit for stars Such basic quantity escapes both theory because incomplete understanding star formation and observation because incompleteness surveying the Galaxy The Arches cluster ideal for such test being massive enough expect stars least massive solar masses and young enough for its most massive members still visible old enough free its natal molecular cloud and close enough and well established distance for discern its individual stars Here report absence stars with initial masses greater than the Arches cluster where the typical mass function predicts conclude that this indicates firm limit for stars the probability that the observations are consistent with limit Theory provides little guide determining the most massive star that can form Pulsational instabilities were once thought destroy stars more massive than however these pulsations may damped Radiation pressure and ionizing flux inhibit accretion for stellar masses greater than but direct collisions protostellar clumps may overcome these effects While stellar evolution models have been computed for massive stars covering large range mass M such stars have ever been observed Indeed some the most massive candidates have proven systems multiple stars Stars generally form with frequency that decreases with increasing mass for masses greater than i log log where observed For stellar clusters young enough not have lost . There is no accepted upper mass limit for stars. Such a basic quantity escapes both theory, because of incomplete understanding of star formation, and observation, because of incompleteness in surveying the Galaxy. The Arches cluster is ideal for such a test, being massive enough to expect stars at least as massive as 400 solar masses, and young enough for its most massive members to still be visible. It is old enough to be free of its natal molecular cloud, and close enough, and at a well-established distance, for us to discern its individual stars. Here I report an absence of stars with initial masses greater than 130 M_Sun in the Arches cluster, where the typical mass function predicts 18. I conclude that this indicates a firm limit of 150 M_Sun for stars as the probability that the observations are consistent with no limit is 10^-8. (Refer to PDF file for exact formulas). | |||||||||||||||
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