Pismis 18 photometry and radial velocities

Pismis 18 is a moderately populated, intermediate-age open cluster located within the solar circle at a Galactocentric distance of about seven kpc. Few open clusters have been...皮斯米斯18（Pismis 18）是一个恒星密度适中、年龄处于中等阶段的疏散星团（open cluster），其银心距（Galactocentric distance）约为7千秒差距，坐落于太阳圆周范围之内。目前已被研究的疏散星团为数不多……