NGC 6621/6622 - Arp 81

Object: NGC 6621 and 6622 galaxy pair in Draco at a distance 85 Mpc (277 Mly). Field is 11.5' x 9.5' with North up and East to the left.

The grazing collision between the two spiral galaxies has been characterized as a strong and recent interaction (~100 My), as opposed to a similar grazing encounter in NGC 5754 that is now well developed. The bright bluish double knot seen in the overlap region between the galaxies is a 13000 ly wide massive starburst of young hot stars induced by the collision. The pink knot near the nucleus of NGC 6621 is very large HII emission nebula, perhaps in a pre-starburst stage.

NGC 6621 the larger of the pair is type Sb pec, 14m, size 1.9' x 0.7'.
NGC 6622 is type Sa, 14m, size 0.5' x 0.4'.

Subimages Clear: 17 x 1200 sec (5.7 hrs), Final star FWHM~2"
Subimages RGB: 6,9,10 x 1200s binned 2x2 (2/3/3 hrs)
Scope: Celestron C11XLT EFL=2935 mm (f/10.5 effective)
Mount: Losmandy G11 with Gemini L4
Camera: SBIG ST8XME+CFW10 (0.63"/pixel) set to -30C
Guiding: Self-guide, ExpTime=1 sec for C, 2 sec for RGB, dithered
Acquisition and processing: MaxIm DL/CCD v4.5
Imaged on: Aug 22, Sept 19, Nov 10, Nov 17 2007 and Aug 27, Sept 2 2008.