منابع مشابه
The Ages of Stars: The Horizontal Branch
Horizontal branch (HB) stars have long played a central role in the age debate. These low-mass stars, which burn helium in the core and hydrogen in a shell, are the immediate progeny of the luminous, vigorously mass-losing red giant branch (RGB) stars. Most importantly in the present context, their temperatures depend strongly on their total masses. More specifically, the lower the mass of an H...
متن کاملThe Ages of Pre-main-sequence Stars
The position of pre-main-sequence or protostars in the Hertzsprung–Russell diagram is often used to determine their mass and age by comparison with pre-main-sequence evolution tracks. On the assumption that the stellar models are accurate, we demonstrate that, if the metallicity is known, the mass obtained is a good estimate. However, the age determination can be very misleading because it is s...
متن کاملNew Methods for Determining the Ages of PMS Stars
We present three new methods for determining the age of groups of pre-mainsequence stars. The first, creating empirical isochrones allows us to create a robust age ordering, but not to derive actual ages. The second, using the width of the gap in colour-magnitude space between the pre-main-sequence and main-sequence (the radiative convective gap) has promise as a distance and extinction indepen...
متن کاملRevised ages for stars in the solar neighbourhood ?
New ages are computed for the stars from the Edvardsson et al. (1993) data set. The revised values are systematically larger toward older ages (t > 4 Gyr), while they are slightly lower for t<4 Gyr. A similar, but considerably smaller trend is present when the ages are computed with the distances based on Hipparcos parallaxes. The resulting age-metallicity relation has a small, but distinct slo...
متن کاملMassive Stars as Cosmic Engines through the Ages
Some useful developments in the model physics are briefly presented, followed by model results on chemical enrichments and WR stars. We discuss the expected rotation velocities of WR stars. We emphasize that the (C+O)/He ratio is a better chemical indicator of evolution for WC stars than the C/He ratios. With or without rotation, at a given luminosity the (C+O)/He ratios should be higher in reg...
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ژورنال
عنوان ژورنال: Annual Review of Astronomy and Astrophysics
سال: 2010
ISSN: 0066-4146,1545-4282
DOI: 10.1146/annurev-astro-081309-130806