Heart nebula

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Heart nebula
IC1805 -- H-alpha + RGB.jpg
Observational Data
Designation IC 1805
Sharpless 2-190
Right ascension 02h 33m 22s[1]
Declination +61° 26′ 36″[1]
Constellation Cassiopeia
Type of object Emission nebula
Dimensions 150 x 150'[1]
Magnitude Apparent Mag: +18.3[1]
Absolute Mag: +6.5[1]
Redshift -0.000159±0.000060[2]
Distance from Earth 7,500 ly[1]
Radial velocity -47.64±18.09 km/s[2]
Proper motion RA: -1.89 mas/yr[2]
Dec.: -2.01 mas/yr[2]

The Heart nebulae (IC 1805, Sharpless 2-190) is an emission nebula in the constellation of Cassiopeia,[1] Also known as the "Running Dog nebula," it is well known for its intense red color and dust lanes that produce its distinctive heart shape. It forms a famous pair with the Soul nebula, called the Heart and Soul nebula. These two nebulae are in fact connected via a bridge of gas. With its high magnitude +18.3, the nebula is hard to observe with small telescopes. It is best seen through astrophotography, making it a popular target for astrophotographers. The nebula is located close to Maffei 1 and Maffei 2, the two brightest galaxies in the Maffei Group. The brightest part of the nebula is classified as NGC 896 in the New General Catalogue as it was discovered before the whole nebula was observed.[3]

Properties and Structure

Lying around 7,500 light years away, the nebula appears to have dimensions of 150x150 arcminutes on the night sky.[1] This is around 5 times the diameter of a full Moon and corresponds to physical size of around 100 light years across.[4] The nebula is located in the Perseus arm of the Milky Way. The system is also thought to have once contained a microquasar.

The red color of the nebula comes from a particular excitation of the hydrogen gas in the nebula and is common to many emission nebulae. Radiation emitted by a small open star cluster (designated Melotte 15) excites the surrounding hydrogen gas which then produces the characteristic red color when the atoms de-excite. The stars in this cluster are blue supergiant stars. Extremely luminous in nature, these stars are situated in the centre of the nebula and have a mass around 50 times that of the Sun.[1] The cluster also contains less massive and fainter stars.


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Heart Nebula from constellation-guide.com
  2. 2.0 2.1 2.2 2.3 IC 1805 from simbad.u-strasbg.fr/simbad
  3. Star-Speckled Heart Nebula Glows Red in Lovely Deep-Space Photo from space.com
  4. IC 1805: The Heart Nebula from apod.nasa.gov