Jewelbox open cluster (NGC4755)

Jewelbox open cluster (NGC4755)

Jun 06, 2021

The Jewelbox is an open star cluster about 6,440 light years away just under the Southern Cross (it sits just under beta-crucis) and contains about 100 stars.

Here it is just under beta crucis (beta crucis is in the lower left) - when you look up at the Sounthern Cross you can see a smudge just next to it:

Notice the colour of the stars? They are all bright white, but there's one that's red - hard to miss! Here's a close up from a couple of months back that I took with a Newtonian telescope:

There are 6 massive stars that form an 'A' asterism (a shape formed by stars), these are B-type stars, ie blue supergiants. That red one is a red supergiant, an M2 class - it has used up its hydrogen in its core and has started burning helium, surrounded by a core of hydrogen. When stars do this they have left the main sequence, or middle age, of their life and are beginning to get older. But this is a very young cluster, only about 14 million years old. The thing with massive blue stars is that they live fast and die young, and that red supergiant is the first to burn through its hydrogen. The other blue giants will follow it soon, maybe within a million years (or less?).

Just for kicks I'm going to share my first photo of this cluster taken in March 2021 with my first telescope. Be warned - it's very rough!

You can see from these images how much a difference a better quality telescope, dark skies and processing makes to really see the beauty that is always above our heads.

I hope you have enjoyed learning a bit about the Jewelbox cluster!

Clear skies!

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