NGC 4755 – The Jewel Box

NGC 4755
By Scott Mellish

NGC 4755 “The Jewel Box”
Open Cluster
Crux
18/03/10
Ilford NSW Australia
56cm f5 Dobsonian
Field: 27′
Magnification: 149x
Sky Quality Meter reading: 21:46

There was a bit of haze around while I was out observing, along with intermittent thin cloud so I decided to stick with something bright.

I have sketched NGC 4755 a number of times, but I have to say that a sketch can never do justice to this very beautiful object.

With this sketch I put in an extra effort to try and get as accurate a representation as I could.

The “Jewel Box” was discovered by Nicolas Louis de Lacaille when he was in the southern hemisphere during the years 1751-53

John Hershel was suitably impressed when he observed the cluster and wrote the following description-

“this cluster, though neither a large nor a rich one, is yet and extremely brilliant and beautiful object when viewed through an instrument of sufficient aperture to show distinctly the very different colour of its constituent stars, which give it the effect of a superb piece of fancy jewellery”

NGC 4755 contains some of the most luminous supergiant stars within the Milky Way ranging from around 83 000 to 75 000 times the brightness of the Sun. The central orange coloured star in the sketch is a massive red supergiant about equal to Betelguese.

One really has to look at this object through a telescope to really enjoy the visual treat of this exquisite open cluster.

Scott Mellish.