| Emission nebula | |
|---|---|
| H II region | |
.jpg) Heart Nebula, with theFish Head Nebula on the top right corner,narrowband image captured on a 70 mm scope | |
| Observation data: J2000.0epoch | |
| Right ascension | 02h 33m 22s |
| Declination | +61° 26′ 36″ |
| Distance | 7500 ly |
| Apparent magnitude (V) | 18.3 |
| Apparent dimensions (V) | 150' x 150' |
| Constellation | Cassiopeia |
| Physical characteristics | |
| Radius | 165 ly |
| Absolute magnitude (V) | 6.5 |
| Designations | NGC 896,IC1805,Sh 2-190 |
| See also:Lists of nebulae | |
TheHeart Nebula (also known as theRunning Dog Nebula,Sharpless 2-190) is anemission nebula, 7,500light-years (2,300 pc) away fromEarth and located in thePerseus Arm of theGalaxy in the constellationCassiopeia. It was discovered byWilliam Herschel on 3 November 1787.[1] It displays glowing ionizedhydrogen gas and darkerdust lanes.[2]
The brightest part of the nebula (a knot at its western edge) is separately classified as NGC 896, because it was the first part of the nebula to be discovered. The nebula's intensered output and its morphology are driven by the radiation emanating from a small group of hot stars near the nebula's center. Thisopen cluster of stars, known asCollinder 26,Melotte 15, orIC 1805, contains a few bright stars nearly 50 times the mass of the Sun, and many more dim stars that are only a fraction of theSolar mass.[1]
The Heart Nebula is also made up of ionisedoxygen andsulfur gasses, which are responsible for the rich blue and orange colours seen in narrowband images. The nebula also spans almost 2degrees in the sky, covering an area four times that of thediameter of the full moon.[3]
