Protostars And Planets

PSU QB806.P78
Ch1: Near-Infrared Extinction and Molecular Cloud Structure, Charles J. Lada
p3 10K does not excite H₂ lowest energy rotational transitions in mid-IR
p4 2448 dark clouds 6 and 18 arcminutes ref: 2005 Dobashi K., Uehara H. Publ. Astr. Soc. Japan, 57 1-368
p7 Fig 2 Barnard 68 cloud about 200 arcseconds across, maybe 20K as², 100 AU/as
- 2 solar masses, 0.15? pc across
- sky is (4/π)(360*3600)^{2& as}2^{, 2.138e12 as}2^
E. E. Barnard's Catalog of Dark Nebulae diameters in arcseconds, "UM2 Pg" is page number in Uranometria, early 1600s 418K am² -> 1.5e9 as² -> 700 ppm of sky, assume 2/3 are missing, 0.2%