A very young, infrared cluster (identified in SIMBAD as " NGC3576 IR Cluster") is on the western side of the HII region, including a number of massive young stellar objects (YSOs).

John Herschel discovered NGC 3581 = h3326 on 14 Mar 1834 in an HII complex and noted "a * 12m, with a fan nebula attached. Place by direct observation." Joseph Turner sketched the group of nebulae on 19 May 1876 using the Great Melbourne Telescope (plate IV.35 at www.docdb.net/history/texts/1885osngmt________e/lithograph_m_4_35.php). He shows the nebula tapering at the southwest end to a brighter star or knot.

400/500mm - 18" (7/7/02 - Magellan Observatory, Australia): NGC 3581 is the brightest section of this complex and has sharply defined borders running SW-NE and NW-SE, meeting at a right angle about 1' WNW of mag 9.2 SAO 251313. The overall size is ~2'x1.5' with an irregular surface brightness. NGC 3581 is just disconnected from NGC 3582, which is close NE.

Notes by Steve Gottlieb