Michael A. Stecker


Cygnus X-1 and Sharpless-101
The red emission nebula Sh2-101 (RA 19 hrs 59.9 min and Dec. +35 degrees 17.5 min) is found within the borders of  Barnard 144 in the rich
Cygnus Star Cloud.  Southeast of this nebula is a strong x-ray source called Cygnus X-1.  This source is a binary system (distant of 2.5 kpc)
consisting of the O9.7 Iab type supergiant HDE 226868 (star arrowed in the photo above).  Orbiting this star is a compact optically invisible
object with a period of 5.6 days. The mass of the unseen companion, significantly larger then 5 solar masses, suggests that it may be a
black hole.  An excellent source of information about Cygnus X-1 can be found at:
Photographic Data
Telescope: Astro-Physics 155 mm f/7 EDF refractor
Camera: Nikon F2 camera
Film: unhypersensitized Kodak Pro 400 PPF (35 mm format)
Exposures: Two 50-minutes, stacked
Photographed from: Mt. Pinos, California at 8300 feet