Super Star Cluster Westerlund 1 in Near Infrared
This image shows the compact young star cluster Westerlund 1 which is located some 15,000 light years away in the central galactic bar of our Milky Way galaxy. The cluster is heavily obscured by interstellar dust and therefore appears only as a faint group of deeply reddened stars in optical images. However, in the infrared part of the spectrum the cluster shines brightly and reveals its true nature as a rare super star cluster; a very massive and luminous star cluster thought to be the precursor of a future globular cluster.
Westerlund 1 contains one of the largest known stars, Westerlund 1-26, a red hypergiant with a diameter 1500 times larger than that of the Sun. Based on stellar evolution models, the cluster is estimated to be very young in astronomical terms - only 4-5 million years old.
The infrared region seems largely unexplored by amateur astronomers. But by using a filter that only allows infrared light (>700nm) through, amateur astronomers are able to capture images of otherwise hidden features such as Westerlund 1.
Effectively the band observed is 700-1100nm since the sillicon CCD chip is not responsive to wavelengths longer than that, and this band is called NIR (Near Infrared). One issue arising from this technique is that the NIR band does not have a colour as such, since it lies outside the visible light spectrum. So in this image I have blended the red channel with NIR data which nicely brings brings the cluster to life with an impressive pinkish hue.
Date: 28th June 2017
Exposure: NIR+LRGB: 60:60:25:25:25 mins, total 3 hours 15 mins @ -25C
Telescope: Homebuilt 12.5" f/4 Serrurier Truss Newtonian
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2
Taken from my observatory in Auckland, New Zealand