  During the course of a search for compact, isolated gas clouds moving with
anomalous velocities in or near our own Galaxy (Braun and Burton 1998 A&A, in
press), we have discovered, in the data of the Leiden/Dwingeloo survey
(Hartmann and Burton 1997, Atlas of Galactic Neutral Hydrogen, CUP) of Galactic
hydrogen, the HI signature of a large galaxy, moving at a recession velocity of
282 km/s, with respect to our Galaxy. Deep multicolor and spectroscopic optical
observations show the presence of star formation in scattered HII regions;
radio HI synthesis interferometry confirms that the galaxy is rich in HI and
has the rotation signature of a spiral galaxy; a submillimeter observation
failed to detect the CO molecule. The radio and optical evidence combined
suggest its classification as a low-surface-brightness spiral galaxy. It is
located in close spatial and kinematic proximity to the galaxy NGC 6946. The
newly-discovered galaxy, which we call Cepheus 1, is at a distance of about 6
Mpc. It is probably to be numbered amongst the nearest few LSB spirals.

Astrophysics