PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
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PHOTO CAPTION                           P-49186
                                        September 18, 1997
                                        2MASS/Whirlpool Galaxy

This image shows the spiral galaxy Messier 51 (the 
"Whirlpool Galaxy"), and its companion, NGC 5195. These two 
galaxies are nearly 28 million light years from the Milky Way.  
The image was acquired by the Northern Two Micron All-Sky Survey 
(2MASS) telescope on Mount Hopkins, AZ, running in normal survey 
scanning mode on April 17 Mountain Standard Time, its first night 
of operation.  The telescope was constructed by M3 Engineering, 
Tucson, AZ under the direction of 2MASS Project Manager Rae 
Stiening of the University of Massachussetts, Amherst, MA. The 
classical cassegrain design has a 1.3 meter (51 inch) primary 
mirror that was figured by Rayleigh Optical, Tucson, AZ.

This 2MASS telescope, along with an identical telescope that 
will operate at a National Optical Astronomy Observatories site 
in Cerro Tololo, Chile, is most sensitive to light that 
originates from the smoothly distributed, relatively old stars in 
galaxies like M51. However, sites of active formation of massive 
stars can also be seen as the knots in the spiral arms and around 
the nucleus of the galaxy. Note that the companion galaxy does 
not have star forming regions in its disk.

The pair of 2MASS telescopes will conduct an ambitious near-
infrared survey of the entire celestial sky, with a mission to 
catalogue 300 million stars and one million galaxies in our local 
Universe, as well as quasars, brown dwarfs and galaxies with 
black holes.

The Jet Propulsion Laboratory, Pasadena, CA, manages the 
2MASS program for NASA's Office of Space Science, Washington, DC.  
2MASS is funded by NASA, the National Science Foundation, the 
U.S. Naval Observatory, and the University of Massachusetts.  The 
observatories are operated by the University of Massachusetts and 
data is being processed at JPL's Infrared Processing and Analysis 
Center (IPAC) at California Institute of Technology, Pasadena, 
CA. 

Additional 2MASS information and images are available at the 
2MASS website at   http://www.ipac.caltech.edu/2mass/ or 
http://pegasus.phast.umass.edu/2mass/

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