APOD: April 9, 1996 - A Spiral Galaxy Gallery (original) (raw)

Astronomy Picture of the Day

Discover the cosmos!Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

April 9, 1996

A Spiral Galaxy Gallery
Credit: NASA,UIT

Explanation: A progression of beautiful spiral galaxies is illustrated above with threephotographs from NASA's Ultraviolet Imaging Telescope (UIT). Flying above the Earth's obscuring layer of atmosphere on theSpace Shuttle Columbia duringthe 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 wouldclassify these as Scd, Sc, and Sb type spirals using agalaxy classification scheme first worked out byEdwin Hubble.

Information: The Scale of the Universe Debate in April 1996
Tomorrow's picture: Comet Hyakutake and a Tree

Authors & editors: Robert Nemiroff(GMU) &Jerry Bonnell (USRA).
NASA Technical Rep.: Sherri Calvo. Specific rights apply.
A service of: LHEAatNASA/GSFC