NGC 2903: Spiral Galaxy in Leo
April 2011 :
To the deep-sky aficionado, spring means one thing – galaxies. Dozens of these island universes are within the grasp of small-aperture telescopes, while a 10-inch Dob can corral thousands. The constellation Leo is home to some of the brighter spring galaxies, including five listed in the Messier Catalog. One, however, escaped the eye of the French comet-hunter, even though it’s visible in binoculars from dark-sky locations. What Messier missed, William Herschel found. In 1784, during one of his all-sky surveys, he came upon a smudge of light 1½° south of lambda (?) Leonis in the “Sickle” of Leo. To him, the object seemed double, so he catalogued the pair as H I 56 and H I 57 - number 56 and 57 in category I (Bright Nebulae). Their modern-day designations are NGC 2903 and 2905.
Like our Milky Way, NGC 2903 is a spiral galaxy intersected by a central bar. NGC 2905 is a stellar knot in one of the galaxy’s spiral arms. NGC 2903 appears to be slightly more than half the size of the Milky Way and lies between 20 and 25 million light-years away.
I first viewed NGC 2903 in April, 1977 after reading about it in Walter Scott Houston’s “Deep Sky Wonders” column. Houston described it as a 9th magnitude galaxy with 11’ by 4.6’ dimensions, adding that NGC 2903 should be visible in a 2-inch finder. Here was a deep-sky target I could observe with the only telescope I owned at the time - a 3-inch f/10 reflector. Sure enough, that little scope and a 30X eyepiece brought NGC 2903 to light. With little effort, I was able to make out a definite nebulous patch, slightly oval in shape. I saw no evidence of NGC 2905.
NGC 2903 appears on the lists of both the Saguaro Astronomy Club’s 110 best NGC and the RASC’s finest NGC Objects. Check it out for yourself and see if it belongs on your list of favorites.
Your comments on this column are welcome. E-mail me at gchaple@hotmail.com.
