NGC 5822, NGC 5823

NGC 5823 is an open star cluster with dual celestial citizenship. Although its center lies within the constellation Circinus, its northermost stars extend into Lupus, the Wolf.

NGC 5823 lies about halfway between α Cen and ζ Lup, in a dense, patchy region of the Milky Way. It is a binocular object about 1-1/4° south of the 5th-magnitude cluster NGC 5822 in Lupus, which is about 3 magnitudes brighter and an impressive 40' across.

NGC 5823 has an visual magnitude of 7.9, and an apparent diameter of 12 arc minutes. While some 10th magnitude field stars may hint at resolution, NGC 5823's true members are magnitude 13 and fainter. In a 4" scope at 25x, the cluster looks boxy; at 72x the cluster's main stars trace a tulip-like figure, with a C-shaped curve opening northeast at the base. NGC 5823 contains 103 members within a 12' wide area, which extends 12 light years across in space.

The visual confusion presented by these two clusters suggests that they might be physically related, but in fact they are not. At a distance of 3,400 light years, the fainter NGC 5823 is nearly twice as far away (NGC 5822's distance is about 1,800 light years.) NGC 5823 is also a bit older, with an age of 600 to 800 million years - about the same as the Hyades.