NGC 2403 is an intermediate spiral galaxy located in the faint northern constellation of Camelopardalis. This superb mag. +8.4 object is about 10 Million light-years distant and is an outlying member of the M81 group of galaxies that also includes M81 "Bode's Galaxy" and M82 "the Cigar Galaxy". Since it's relatively near and almost face-on from our perspective, NGC 2403 displays intricate details in its spiral arms especially through large amateur scopes.

NGC 2403 was discovered on November 1, 1788 by William Herschel and is best seen from northern latitudes during the months of January, February and March. It's number 7 in the Caldwell catalogue.

NGC 2403 (credit - NASA, ESA, Filippenko (Univ. of California), Challis (Harvard-Smithsonian Center for Astrophysics), et al.)

Finder Chart for NGC 2403 (credit - freestarcharts)

Finder Chart for NGC 2403 - pdf format (credit - freestarcharts)

The galaxy is located in the southeastern corner of Camelopardalis not far from the Ursa Major and Lynx borders. In a barren region of sky, it's positioned between two 6th magnitude stars. Almost 8 degrees southeast of NGC 2403 is star Muscida (ο UMa - mag. +3.4).

The structure of NGC 2403 resembles that of M33 "the Pinwheel Galaxy" in Triangulum. Both galaxies are spatially similar in size, appear almost face-on from our perspective and contain numerous HII star-forming regions, although M33 is more than three times closer to us than NGC 2403.

Through 7x50 binoculars, NGC 2403 appears as a faint patch of nebulous light. With an 80mm (3.1-inch) scope, it displays a bright core surrounded by an oval fuzz without detail. A larger 200mm (8-inch) scope reveals mottling and on good nights part of the brighter northern spiral arm can be seen. In addition, averted vision reveals numerous bright and dark regions. On closer inspection, the bright nucleus appears slightly oval shaped. In very large instruments, for example 400mm (16-inch) reflectors, the spiral arms are much easier to distinguish.

There are more than 100 known emission nebulae in NGC 2403's spiral arms; some span up to 800 light-years are visible in large backyard scopes. In total, the galaxy spans 21.9 × 12.3 arc minutes of apparent sky.

NGC 2403 is a wonderful spiral that's the brightest galaxy in the northern section of sky not included in the Messier catalogue. It has a spatial diameter of 65,000 light-years and is estimated to contain about 50 billion stars. To date, three supernovae have been reported, SN 1954J, SN 2002kg and SN 2004dj.

NGC 2403 Data Table

Object TypeIntermediate Spiral Galaxy
Distance (light-years)10 Million
Apparent Mag.8.46
RA (J2000)07h 36m 51s
DEC (J2000)65d 36m 09s
Apparent Size (arc mins)21.9 × 12.3
Radius (light-years)32,500
Number of Stars50 Billion
Notable FeatureIs an outlying member of the M81 Group

Sky Highlights - March 2017

Comet 41P/Tuttle-Giacobini-Kresak now visible with binoculars as it heads towards perihelion

Mercury heading towards greatest elongation east

Minor Planet
Vesta now visible with binoculars and small telescopes.

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for March 2017

Northern Hemisphere
West:- Venus (mag. -4.8 to -4.1 - first half of month), Mars (mag. +1.3 to +1.5), Uranus (mag. +5.9), Mercury (mag. -1.5 to -0.4 - second half of month)
Southeast:- Jupiter (mag. -2.3 to -2.5)
Southwest:- Jupiter
Southeast:- Saturn (mag. +0.5)

Southern Hemisphere
West:- Venus (first half of month), Mars, Uranus
North:- Jupiter
East:- Saturn
West:- Jupiter
Northeast:- Saturn
East:- Neptune (mag. +8.0 - second half of month)

Deep Sky
Naked eye / binoculars:-
Melotte 111 - Mel 111 - The Coma Star Cluster (Open Cluster)
Messier 44 - M44 - The Praesepe (Open Cluster)

Messier 67 - M67 - Open Cluster
Messier 51 - M51 - The Whirlpool Galaxy (Spiral Galaxy)
Messier 97 - M97 - The Owl Nebula (Planetary Nebula)
Messier 101 - M101 - The Pinwheel Galaxy (Spiral Galaxy)
Messier 65 – M65 – Spiral Galaxy
Messier 66 - M66 - Intermediate Spiral Galaxy
Messier 95 - M95 - Barred Spiral Galaxy
Messier 96 - M96 - Intermediate Spiral Galaxy
NGC 4244 - Spiral Galaxy
NGC 4565 - Needle Galaxy - Spiral Galaxy

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