The Whirlpool Galaxy is a classic spiral galaxy. At only 30 million light years [ http://www.pa.msu.edu/~sciencet/ask_st/012292.html ] distant and fully 60 thousand light years across, M51 [ http://www.seds.org/messier/m/m051.html ], also known as NGC [ http://www.seds.org/billa/ngc.html ] 5194, is one of the brightest and most picturesque galaxies [ http://www.seds.org/messier/more/m051_m2.html ] on the sky. The above image [ http://heritage.stsci.edu/public/2001apr/display.html ] is a digital combination of a ground-based image from the 0.9-meter telescope [ http://www.noao.edu/0.9m/manual.html ] at Kitt Peak National Observatory [ http://www.noao.edu/kpno/ ] and a space-based image from the Hubble Space Telescope [ http://www.stsci.edu/hst/ ] highlighting sharp features normally too red [ http://www.ipac.caltech.edu/Outreach/Edu/infrared.html ] to be seen. Anyone with a good pair of binoculars [ http://www.birdwatching.com/optics/binoculars1.html#How Binoculars Work ], however, can see this Whirlpool [ http://heritage.stsci.edu/public/2001apr/table.html ] toward the constellation [ http://www.physics.csbsju.edu/astro/asp/constellation.faq.html ] of Canes Venatici [ http://www.astronomical.org/constellations/cvn.html ]. M51 is a spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] of type Sc [ http://www.astr.ua.edu/preprints/white/gal_tuningfrk.html ] and is the dominant member of a whole group of galaxies [ http://www.seds.org/messier/more/m051gr.html ]. Astronomers speculate that M51 [ http://heritage.stsci.edu/public/2001apr/supplemental.html ]'s spiral structure [ http://www.ifa.hawaii.edu/~barnes/ast626_97/tss.html ] is primarily due to its gravitational interaction with a smaller galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap980710.html ] just off the top of this image.