A Spiral Galaxy Gallery

A progression of beautiful spiral galaxies is illustrated above with
three photographs from NASA's Ultraviolet Imaging Telescope (UIT). Flying
above the Earth's obscuring layer of atmosphere on the Space Shuttle Columbia
during the Astro-1 mission in 1990, UIT's cameras were able to image these
distant spirals in the ultraviolet light produced by hot, young stars. These bright
stars, newly condensed from gas and dust clouds, give away the location of the
spiral arms they are born in. Because they are massive (many times the mass of
the Sun), they are shortlived. Dying and fading before they move too far from
their birth place they make excellent tracers of spiral structure. From left to right
the galaxies are known as M33, M74, and M81 and have progressively more
tightly wound spiral arms. Astronomers would classify these as Scd, Sc, and Sb
type spirals using a galaxy classification scheme first worked out by Edwin Hubble.