This is Westserlund 1, also known as the Ara Cluster – this is the wide field view:

The colors in this image are great – blue, red, and yellow stars throughout, plus the presence of some darker regions of dust.

This is the closeup view of Westerlund 1:

Westerlund 1 is one of two objects in the Milky Way that appear to be globular clusters but are in fact young super clusters made up of young stars. The other such object is NGC 1850.

Westerlund 1 was discovered relatively recently, in 1961, but was not studied due to the presence of dust and gas between us and Westerlund 1. The dust and gas are from the Milky Way itself.

Upon closer inspection, it was found that this super cluster contains one of the largest known stars, called Westerlund 1-26, having a size estimated at between 3.6 and 16.6 billion times the size of our Sun!

All of the stars in this supercluster have been studied now and are made up of yellow hypergiants, blue supergiants, red hypergiants, or Wolf-Rayet stars (Wolf-Rayet stars are unusual because they appear to be made up of helium, nitrogen, carbon, silicon, and oxygen; most other stars are made up of hydrogen).

Acquisition and Processing Details

I acquired this image using Slooh’s Chile Two telescope and the image is made up of the following exposures:

  • Luminance: 7 x 50 sec, binned 3×3
  • Red: 4 x 50 sec, binned at 3×3
  • Green: 4 x 50 sec, binned at 3×3
  • Blue: 4 x 50 sec, binned at 3×3

I processed this image in PixInsight and Photoshop. In Photoshop, I resized the image, added the logo and extracted the closeup view.