NGC 2903

(Captured on 21 Feb 2009 with a Mallincam Hyper Color Plus) 

Our February Challenge presented a fairly easy target for small to mid-sized scopes. NGC 2903 is a bright face-on galaxy in the constellation Leo. It was discovered by William Herschel on 16 November 1784. It is amazing that Charles Messier missed this galaxy since two of the comets he discovered passed quite close to it.  

It should have appeared somewhat like the image above in 8 to 12-inch scopes. At 9pm in mid-February, it was located almost due east at 43 degrees above the horizon. To find it, all you had to do was locate the tip of the Sickle's blade, 3rd-magnitude Epsilon Leonis. From Epsilon Leonis, you would locate orange 4th-magnitude Lambda  to the WSW (toward the Zenith) and drop down southwest almost 1.5 degrees.

Location of NGC 2903

Our challenge for NGC 2903 was to:

- Locate the galaxy without electronic aid (Star hop to it) - describe your technique 

- Determine the type of galaxy it is

- Determine and describe the location of NGC 2905 within the galaxy - you may need a medium scope to see it

- Describe the galaxy's core and halo 

- Describe the galaxy's arms 

Observations, Sketches, and Photos 

Roger Ivester - LVAS Member from Boiling Springs, NC

Observations using a 10” reflector at 142X in a moderately light polluted backyard from the foothills of western North Carolina, presents NGC-2903 as bright, very elongated with a brighter core. The orientation is NNE-SSW. The texture of this galaxy is very uneven with mottling noted. Conditions on this night didn’t allow the observation of the bright patch just north of the central region for certain. This bright patch carries the designation of NGC-2905. Please see sketch using 142X with a field of 0.46° / 28' arc minutes. The sketch was made using a white charcoal pencil on black card stock.

Fred Rayworth - LVAS Member from Las Vegas, NV 

I first observed NGC-2903 in 1984 with his home-built 8” f/9.44 Newtonian.  I was even able to see it through streetlights in the neighborhood near Torrejon Air Base, Spain where I lived at the time.  For this challenge, I observed from Valley of Fire State Park Visitor’s Center.  The skies were iffy at best.  Though I could see all the brightest stars in Leo, when I looked through the eyepiece, the background was not black, and everything in that part of the sky appeared dim and unremarkable.

It was a nice, medium-sized oval that appeared mostly round and face-on, but had a slight oval appearance to it.  It had a concentrated center with just a touch of lumpiness.  I noticed no significant stars in or around the galaxy and saw no distinctive sign of NGC-2905.  With the very bright background, the galaxy appeared drab as if I was looking at it through a heavy haze from downtown Las Vegas (even though Las Vegas was a good 30 miles in the opposite direction, as the crow flies).

Rob Lambert - LVAS Member from Las Vegas, NV 

I first observed NGC-2903 on February 21, 2009 and then again almost a year later on February 13, 2010. Using my Mallincam VSS astro-video camera, I observed this month’s challenge object through my Orion ST120 and 10” LX200GPS. The ST120 with focal reduction to f/2.5 presents a 1.5° FOV at 32X. The LX200 with focal reduction to f/3.2 presents a 0.5° FOV at 100X and at f/5.0 presents a 0.3° FOV at 160X. Although the skies were clear at the Valley of Fire observing site just outside of Las Vegas, the transparency wasn’t all that great due to the recent rains and higher than normal humidity in the air. In the accompanying images, north is toward the bottom right corner with west toward the bottom left corner.

Through the ST120 at approximately 32X, NGC-2903 hints at being a barred spiral with a counterclockwise rotation. It has an obvious bright core with somewhat less brighter bars extending NNE and SSW from the core. The NNE bar appears to be brighter than the opposite bar and may be the location of the star forming region known as NGC-2905. At this lower magnification, there wasn’t much detail to be seen in the spiral arms.

At 100X in the LX200, NGC-2903 presents a very bright elongated irregular core and mottled halo with more detail in its spiral arms and bar. The central bar cuts diagonally across the galaxy’s NNE-SSW axis at almost a 45° angle. The northern bar has a large bright nodule at the end of it and two smaller ones that follow the curve of the spiral. It must be this area that is the star forming region recognized as NGC-2905. The southern bar appears to have only one smaller bright nodule near the end of the arm. The galaxy has two distinct major arms radiating from each end of the bar.

At 160X, a couple of fainter minor arms squeezed in between the two major ones begin to become more distinct. All of the arms are more tightly wound than in other spiral galaxies the group has observed. They are fairly distinct closer in to the body of the galaxy, but become diffuse and faint as they extend away from the galaxy. The arms are more prominent on the east side of the galaxy than on the west.

On the next trip to a dark site, I'll see if less focal reduction will reveal more distinction in the minor arms of the galaxy.

David Blanchette - LVAS Member from Las Vegas, NV

A 12 minute exposure of NGC-2903 is attached.  No stacking, just some contrast adjustment. Taken through 12" Meade LX200, f/6.3 focal reducer.  I did try without the focal reducer, but the seeing really wasn't up to it (see Daves NGC-2903.jpg).

Dr. James Dire - LVAS Friend from North Carolina 

NGC-2903 is a fine barred spiral galaxy located to the west of the sickle of Leo. The galaxy is 1.5° due south of the 4th mag. red star Lambda Leonis. This 9th mag. galaxy measures 11.8 by 5.1 arcminutes. The image shown here was taken with an Orion 190mm f/5.3 Maksutov-Newtonian using an SBIG ST-2000XCM CCD camera. The exposure was 40 minutes. Even with this short focal length, the galaxies central bar is quite apparent. As usual for barred spiral galaxies, the spiral arms tend to originate at the ends of the bar. There are roughly two spiral arms coming from each end of the bar, however only one spiral arm from each end appear distinct and wrapped 180° around the galaxy. The galaxy lies 34 million light years away. It has significant star formation occurring in the spiral arms as evident by the abundant number of short-lived blue giant stars and bright red hydrogen gas regions.

Frank Barrett - LVAS Friend for North Carolina 

On Feb 19, 2010, I took this photo of NGC-2903 from my observatory in Gastonia, NC. I used a Meade 10” LX200R, with a 2800mm focal length, at f/11. The exposure was four hours of luminance along with three hours of color using an SBIG STL-11000M camera. My mount is a Losmandy G11 with an Ovision worm upgrade (see Franks NGC-2903.jpg) 

Other Published Observations from Notable Astronomers  

"...NGC 2903, a barred spiral galaxy similar in size and shape to our Milky Way... is faintly visible through a 50-millimeter finder. With my 4.1-inch (105mm) refractor at 87x, this is a very nice galaxy about 8' by 4' in angular size. The outer halo is faint, but there is considerable brightening toward the center. Some dark patches in the oval core hint at spiral structure, and a stellar spot can be seen south of center. A bright patch in the galaxy's northeastern spiral arm bears its own designation, NGC 2905. You'll probably need at least an 8-inch scope to catch sight of NGC 2905." (Sue French, Celestial Sampler, Sky Publishing Corp., 2005)

NGC-2903 is a big 9^th mag. spiral about 4° SW of Epsilon Leonis.  It seems distinctly oval, but not as much as the catalog dimensions 11' x 4.6' suggest.  At mag. 9, it should be visible even in a good 2” finder.  Long exposure photographs show it as a single galaxy, but this object's ownership of two NGC numbers, 2903 and 2905, is a reminder that early visual observers thought otherwise.  In his Cycle of Celestial Objects, Smyth tells us that William Herschel described it in 1784 as "a double nebula, each having a seeming nucleus, with their apparent nebulosities running into each other."  William's son, John, and Smyth had some difficulty in making this out with his 6” refractor.  "The upper or south part is better defined than the lower, it requires, however, the closest attention and most patient watching, to make it a bi-central object."  It would be interesting to view NGC-2903 with a long-focus instrument at medium to high magnification, gradually reducing the aperture until the object becomes nearly invisible in the hope of inducing the "double" appearance.  “I myself have never been able to see such an appearance, despite experiments with various apertures.  Has any reader of this column observed NGC-2903 as double?”. 

He always wondered why Charles Messier missed this galaxy, especially since he catalogued fainter ones in nearby Virgo.  Ron Morales of Tucson, Arizona, found it "easy and impressive" as seen with an 8” reflector.  California amateur Tokuo Nakamoto reports seeing a faint oval halo surrounding the "much brighter" center of NGC-2903 with his 14” reflector.  Years ago in Kansas, Walter viewed the galaxy with a 10” reflector at 120X.  The arms were rather ill-defined, but several knots of material dotted the extensions around the core.  These knots were bright clouds of ionized hydrogen (called H-II regions) similar to the Orion Nebula within our own galaxy.  Photographers might try recording NGC-2903 with a series of exposures.  Long ones should show the galaxy's arms in all of their splendor, but shorter exposures may better reveal the knots and the nucleus.  Astronomers have identified over 70 such glowing clouds within NGC-2903.  In the 1960's he saw several of them with the 20” Clark refractor at Connecticut's Wesleyan University.  They gave the galaxy a mottled appearance. (Walter Scott Houston with selections and commentary by Stephen O'Meara, Deep-Sky Wonders, Sky Publishing Corp.)

One of the best galaxies missed by Messier and a fine sight in small telescopes.  "Elongated, faint, with a double nucleus," thus the dual designation NGC-2903-5 that's sometimes given.  Actually a star cloud lying just 1' N of the nucleus.  But it's not exactly an obvious object in average backyard scopes. (James Mullaney, Celestial Harvest)