NGC 4449, also known as Caldwell 21, is an irregular galaxy located 12.5 million light-years away in the constellation Canes Venatici. It's part of the M94 Group (or Canes Venatici I Group), a galaxy group close to the Local Group. With an apparent magnitude of +9.4, it's within binocular range but challenging. The galaxy is much easier to spot with telescopes and a rewarding object due to its unusual appearance.
NGC 4449 is intrinsically similar in size and brightness to the Large Magellanic Cloud (LMC), but unlike the Large Magellanic Cloud, it's a starburst galaxy with a high rate of active star formation. It's believed that the current widespread starburst was triggered by interaction or merging of NGC 4449 with a smaller companion or companions. As a result, it contains numerous HII regions and several large star clusters, which contain thousands of young, hot blue stars.
William Herschel discovered the galaxy on April 27, 1788. It's best seen from Northern Hemisphere latitudes during the months of March, April and May.
NGC 4449 is located 3 degrees northwest of Chara (β CVn - mag. +4.2). It has a high surface brightness and therefore, under dark skies, can be spotted with 7x50 or 10x50 binoculars. With binoculars, averted vision is recommended, although at best the galaxy appears as only a tiny diffuse glow. Through a small 100mm (4-inch) telescope, an odd rectangle shape of light with a bright centre is revealed. A 250mm (10-inch) scope at high powers shows several foreground stars along the main axis of the galaxy, with knotty HII regions visible at the northern edge. In total, the galaxy spans 6.2 x 4.4 arc minutes of apparent sky, which corresponds to a spatial diameter of 20,000 light-years.
NGC 4449 Data Table
|Object Type||Irregular Galaxy|
|Distance (light-years)||12.5 Million|
|RA (J2000)||12h 28m 11s|
|DEC (J2000)||+44d 05m 36s|
|Apparent Size (arc mins)||6.2 x 4.4|
|Number of Stars||15 Billion|
|Notable Feature||Member of the M94 Group|