ISO's first light image: Unprocessed 7 micron ISOCAM image of M51, as seen on November 28, 1995.
The Whirlpool Galaxy, catalogd as M51 or NGC 5194, is a relatively near neighbour of our own Galaxy, the Milky Way Galaxy. Historically, it was the first "spiral nebula" identified by astronomers. In the infrared image the galaxy broadly resembles the whirlpool-like object seen by visible light.
Bright spots in the spiral arms correspond with warm dust clouds where star formation is proceeding on a large scale. These are linked by regions of cooler dust along the spiral arms and in the spaces between the arms, where previous generations of stars have left their debris. In the infrared image the spiral arms can be traced right into the heart of the galaxy, where there are hotspots of star formation on either side of a bright central nucleus.
A companion galaxy (M51B (NGC 5195)) at the top of the image looks much smaller than it does by visible light. This is because starmaking is concentrated near its nucleus.
Star formation in the Milky Way and other galaxies is a major thread for ISO's observing program.
Read the original ESA press release on the ISO observations of M51
Last Modification: July 6, 1999