The Southern Pleiades (IC 2602) in Carina
April 2021 - Picture of the Month
It was time for another open cluster and Marco's image of IC 2602 caught my eye with its light haze of nebulosity and punchy crisp stars.
IC 2602 isn't a rich cluster with about 60 members spread over its 100 arc-minute diameter. This is a binocular object and the 5th and 6th magnitude main members are easily observed in any small instrument, or naked eye. However, most of the members are fainter than those of the Pleiades in Taurus.
What isn't fainter is that central star, Theta Carinae. It's a large (around 15 solar masses) blue star that appears to be significantly younger, at a tenth of the age, than open cluster of which it's a member. The reason for this is that it's a blue straggler: a star that has been rejuvenated by the transfer of mass from a neighbouring star. These aren't common in open clusters so this is a special star worthy of featuring itself.
Right below Theta Carinae (to the south) you can see a faint condensation of stars on the border of the image. This is another open cluster called Melotte 101 which is much further away than IC 2602: around 6500 light-years rather than 540. It adds some stardust sparkle to the field of view.
James Whinfrey - Website Administrator.