Globular Cluster NGC 1851

NGC 1851 is a massive globular cluster located in the Southern constellation of Columba. It is one of the largest deep sky object in Columba spanning 11 arc minutes of sky. It is an unusual cluster speculated to be a product of the merger of two individual clusters. It has been known to have a bimodal horizontal branch in the H-R diagram.

In this color-composite image, the blue and red colors are the UVIT images in FUV and NUV filters respectively. The blue dots in the image are the Blue horizontal branch stars mostly distributed in the 2.4 arcmin radius of the cluster. These stars have evolved off the red-giant branch phase and are now burning helium in their cores.

Full resolution image [437 KB]
Credits: UVIT Team/ISRO/CSA