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Catalogue and alternative designations RCW 87 and RCW 88


Type Emission Nebulas 
Position 15 05 18, -57 31 12 (RCW 87)
Constellation Circinus
Camera and Telescope STXL6303 and 36.8 cm Ritchey Chretien
Focal Ratio F9
Exposure Details HaRGB using Astrodon series 2 filters.  Nine hours of hydrogen alpha (3nm filter) and 4 hours 30 minutes RGB.
Description (Description adapted from Galaxy Map entry) RCW 87 is on the right and RCW 88 is partially obscured on the left.

There are wildly varying distance estimates for RCW 87.
According to a 1987 paper from the Georgelins, RCW 87, 88 and 89 are part of the same structure located at a distance of 3000-4000 pc, most likely closer to 3000 pc. RCW 87 and 88 are HII regions.
According to a 2006 paper, RCW 87 may contain one of the most massive young star clusters (10300 solar masses) known in the Milky Way.  is about 20-25 million years old, has a distance of 7600 parsecs, and its brightest members have evolved into red supergiants.

According to one 2011 paper, RCW 87 is much closer at 1230 pc. A second 2011 paper gives a 2700 pc kinematic estimate.

RCW 87 appears to be immersed in a larger diffuse nebula that includes IRAS 14597-5728, sometimes called the Black Widow nebula because of its appearance in infrared. However, Avedisova places IRAS 14597-5728 in a separate star formation region.
You can see the full extent of RCW 87 in this Spitzer infrared image