In this thesis, I present a detailed high-resolution spectroscopic study of post main sequence stars in the Globular Cluster M68. My sample, which covers a range of 4000 K in Teff, and 3.5 dex in log(g), is comprised of members from the red giant, red horizontal, and blue horizontal branch, making this the first high-resolution globular cluster study covering such a large evolutionary and parameter space. Initially, atmospheric parameters were determined using photometric as well as spectroscopic methods, both of which resulted in unphysical and unexpected Teff, log(g), vt, and [Fe/H] combinations. I therefore developed a hybrid approach that addresses most of these problems, and yields atmospheric parameters that agree well with other measurements in the literature. Furthermore, my derived stellar metallicities are consistent across all evolutionary stages, with [Fe/H] = 2.42 ( sigma = 0.14) from 25 stars. Chemical abundances obtained using my methodology also agree with previous studies and bear all the hallmarks of globular clusters, such as a Na-O anti-correlation, constant Ca abundances, and mild r-process enrichment.

The bright galaxies, star clusters, and nebulae catalogued in the late 1700s by the famous comet hunter Charles Messier are still the most widely observed celestial wonders in the sky. The second edition of Stephen James O'Meara's acclaimed observing guide to the Messier Objects features improved star charts for helping you find the objects, a much more robust telling of the history behind their discovery - including a glimpse into Messier's fascinating life - and updated astrophysical facts to put it all into context. These additions, along with new photos taken with the most advanced amateur telescopes, bring O'Meara's first edition more than a decade into the twenty-first century. Expand your universe and test your viewing skills with this truly modern Messier guide. It is a must for all budding night watchers.

Perhaps the most common question that a child asks when he or she sees the night sky from a dark site for the first time is: 'How many stars are there?' This happens to be a question which has exercised the intellectual skills of many astronomers over the course of most of the last century, including, for the last two decades, one of the authors of this text. Until recently, the most accurate answer was 'We are not certain, but there is a good chance that almost all of them are M dwarfs. ' Within the last three years, results from new sky-surveys - particularly the first deep surveys at near infrared wavelengths - have provided a breakthrough in this subject, solidifying our census of the lowest-mass stars and identifying large numbers of the hitherto almost mythical substellar-mass brown dwarfs. These extremely low-luminosity objects are the central subjects of this book, and the subtitle should be interpreted accordingly. The expression 'low-mass stars' carries a wide range of meanings in the astronomical literature, but is most frequently taken to refer to objects with masses comparable with that of the Sun - F and G dwarfs, and their red giant descendants. While this definition is eminently reasonable for the average extragalactic astronomer, our discussion centres on M dwarfs, with masses of no more than 60% that of the Sun, and extends to 'failed stars' - objects with insufficient mass to ignite central hydrogen fusion.

An exciting introduction to astronomy, using recent discoveries and stunning photography to inspire non-science majors about the Universe and science.

From the reviews: "Astronomy and Astrophysics Abstracts has appeared in semi-annual volumes since 1969 and it has already become one of the fundamental publications in the fields of astronomy, astrophysics and neighbouring sciences. It is the most important English-language abstracting journal in the mentioned branches. ...The abstracts are classified under more than a hundred subject categories, thus permitting a quick survey of the whole extended material. The AAA is a valuable and important publication for all students and scientists working in the fields of astronomy and related sciences. As such it represents a necessary ingredient of any astronomical library all over the world." Space Science Reviews#1 "Dividing the whole field plus related subjects into 108 categories, each work is numbered and most are accompanied by brief abstracts. Fairly comprehensive cross-referencing links relevant papers to more than one category, and exhaustive author and subject indices are to be found at the back, making the catalogues easy to use. The series appears to be so complete in its coverage and always less than a year out of date that I shall certainly have to make a little more space on those shelves for future volumes." The Observatory Magazine#2