Soul and Heart Nebulae - October 2013

About the image…

Image title – Soul and Heart Nebulae in Hα.
Taken at – Observatorio del Teide (Tenerife – Spain; 16º 30' 35" W, 28º 18' 00" N).
Telescope – Takahashi FSQ-106ED, f/3.6.
Instrument – SBIG STL-11000 CCD camera.
Exposure –  Twelve 900s images in Hydrogen alpha.
Image size – 5.1º x 3.2º.
Images taken and reduced by –
 Jorge A. Pérez Prieto and Pedro A. González Morales.
Text  Jorge A. Pérez Prieto and Pablo Rodríguez-Gil.

This romantic name coins this magnificent pair of emission nebulae in the constellation Cassiopeia, in the Perseus arm of our Galaxy, located about 7,500 light years away from Earth. This dense region of ionised hydrogen plasma forms a huge nebular complex about 600 light-years across. The Heart (IC 1805 or Sh2-190), to the right of the image, covers more than two degrees on the sky and displays numerous interstellar dust dark regions, which absorb the visible light emitted by the nebula. NGC 896, a bright area of ​​very active star formation (top right corner) was the first part of the nebula to be discovered. The centre of the heart harbours Melotte 15, an open cluster of O and B giant stars whose radiation pushes the gas and dust and make the nebula shine.

The Soul (Sh2-199) can be found just to the left of the Heart. It's somewhat smaller and shines due to the presence of several young open clusters in its core, especially IC 1848 or W5, which is identified as a radio source, and CR634 to the east (left) of the nebula. The Soul has an approximate size of 140 light years and also shows the typical cavities carved by the radiation of the energetic stars inside.

This month's AIM covers a very large sky area, equivalent to ten full moons in its large side. It was taken through a hydrogen alpha filter that is only transparent to light with wavelength around 656.3 nm, and isolates the light emitted by the hydrogen content of the nebulae due to excitation by ultraviolet light from the massive stars.