The Heart of the Heart: Melotte 15...

Star Cluster Melotte 15

Object: Melotte 15
Type: Open star cluster 
Constellation: Cassiopeia
Distance: 6000 light years

Date: 19th January 2020

Equipment: ATIK 460EX with EFW2, Skywatcher f5.5 Esprit 100 ED refractor, Avalon Linear mount, guiding with Lodestar X2/PHD

Subframes: 12 x 600s H-alpha, 1 x 600s OIII, no flats/darks (hot pixel removal in Astroart)

Stellarium map showing location of Melotte 15

Melotte 15 is an open cluster of stars, containing a few bright stars nearly 50 times the mass of our Sun and many more dim stars that are only a fraction of our Sun's mass.

It lies in the distant Perseus arm of our Milky Way galaxy at the centre of the Heart Nebula (IC 1805, Sharpless 2-190). Its stars provide the source of radiation that causes the surrounding clouds of hydrogen gas to fluoresce.

Across the region are strewn dark bands of dust, which are believed to be the birthplace of new stars.  Melotte 15 itself is a relatively young star cluster, estimated to be around 1.5 million years old.


I had previously imaged this part of the sky back in November 2007 as a wide field mosaic of two frames using a 135mm camera lens: the image below shows Melotte 15 in relation to the surrounding extensive nebulosity in the area.

Nebulae in the region of Melotte 15

The main image is a work in progress: clouds rolled in before I could get any RGB or more than one frame of OIII data!  Below is the stack of the 12 x 600s H-alpha frames, which gives a better idea of the detail in the region.

Melotte 15 in H-alpha light.