Andromeda Nebula[‚an′dräm·ə·də ′ne·byə·lə]
the brightest galaxy in the northern sky and one of the closest to our galaxy. It is visible to the naked eye as a weakly shining misty “patch” in the line of the constellation Andromeda. The angular dimensions, measured on photographs, are approximately 200’ x 90’, which correspond to the linear dimensions of approximately 40 x 18 kiloparsecs (130,000 x 60,000 light-years) measured from a distance of approximately 700 kiloparsecs (2.3 million light-years). Its size as determined by radar is greater than that determined from its optical image. The nebula’s real dimensions exceed those of our galaxy. Both these stellar systems are included among the giants; they have spiral structures and are approximately of the same age. The stellar nature of the Andromeda nebula was established in 1925, when stars were first observed in it with the aid of a 2.5-m telescope. The Andromeda nebula is seen almost from on edge, which gives it an elliptical form. Dark patches of dust clouds are observed in the region of the spiral arms. The nebula’s mass is (3–5) x 1011times the mass of the sun. The Andromeda nebula is surrounded by four elliptical galaxies of much smaller mass, which are considered to be its satellites.
E. K. KHARADZE