ﻻ يوجد ملخص باللغة العربية
The existence of life based on carbon chemistry and water oceans relies upon planetary properties, chiefly climate stability, and stellar properties, such as mass, age, metallicity and Galactic orbits. The latter can be well constrained with present knowledge. We present a detailed, up-to-date compilation of the atmospheric parameters, chemical composition, multiplicity and degree of chromospheric activity for the astrobiologically interesting solar-type stars within 10 parsecs of the Sun. We determine their state of evolution, masses, ages and space velocities, and produce an optimized list of candidates that merit serious scientific consideration by the future space-based interferometry probes aimed at directly detecting Earth-sized extrasolar planets and seeking spectroscopic infrared biomarkers as evidence of photosynthetic life. The initially selected stars number 33 solar-type within the population of 182 stars (excluding late M-dwarfs) closer than 10 pc. A comprehensive and detailed data compilation for these objects is still essentially lacking: a considerable amount of recent data has so far gone unexplored in this context. We present 13 objects as the nearest biostars, after eliminating multiple stars, young, chromospherically active, hard X-ray emitting stars, and low metallicity objects. Three of these biostars, HD 1581, 109358 and 115617, closely reproduce most of the solar properties and are considered as premier targets. We show that approximately 7% of the nearby stars are optimally interesting targets for exobiology.
We describe the 44 systems discovered to be within 10 parsecs of the Sun by the RECONS team, primarily via the long-term astrometry program at CTIO that began in 1999. The systems --- including 41 with red dwarf primaries, 2 white dwarfs, and 1 brown
Solar twins and analogs are fundamental in the characterization of the Suns place in the context of stellar measurements, as they are in understanding how typical the solar properties are in its neighborhood. They are also important for representing
Direct imaging is a powerful exoplanet discovery technique that is complementary to other techniques and offers great promise in the era of 30 meter class telescopes. Space-based transit surveys have revolutionized our understanding of the frequency
Context. Monitoring of the photometric and chromospheric HK emission data series of stars similar to the Sun in age and average activity level showed that there is an empirical correlation between the average stellar chromospheric activity level and
We present radio and infrared observations indicating on-going star formation activity inside the $sim2-5$ pc circumnuclear ring at the Galactic center. Collectively these measurements suggest a continued disk-based mode of on-going star formation ha