Barnard 68とは 意味・読み方・使い方

Barnard 68 is a molecular cloud, dark absorption nebula or Bok globule, towards the southern constellation Ophiuchus and well within our own galaxy at a distance of about 500 light-years, so close that not a single star can be seen between it and the Sun. American astronomer Edward Emerson Barnard added this nebula to his catalogue of dark nebulae in 1919. He published his catalogue in 1927, at which stage it included some 350 objects. Because of its opacity, its interior is extremely cold, its temperature being about 16 K (−257 °C). Its mass is about twice that of the Sun and it measures about half a light-year across.