WLM (DDO 221, Wolf–Lundmark–Melotte)

Telescope: Planewave 17" CDK Reflector, 2912mm FL
Camera: FLI ProLine PL16803, 4096 x 4096 pixels
Exposure: 12 x 3 minutes. The object's low surface brightness limits noise reduction. Processed with PixInsight.
Location: Siding Springs Observatory, Australia (Elevation 3720')
Image Center (J2000): RA 0h 01m 58s, Dec -15° 27' 27"

An isolated, small, irregular galaxy at mag 11.1. One of the faintest dwarf irregular galaxies in the Local Group. Not recognized as a galaxy until 1926. Only 1 known globular cluster. Its proximity and low dust allow its brightest stars to be resolved in this image. In support of other measurements, resolution into stars at around 18th magnitude suggests WLM is relatively near. Most stars across the face are foreground stars but in this image 21 stars in WLM including 1 Cepheid variable can be identified. The galaxy looks unusual since images of spiral galaxies are familiar but this type of galaxy is probably more common.
Raw data for this image can be downloaded.


WLM (DDO 221, Wolf–Lundmark–Melotte), An isolated, small, irregular galaxy at mag 11.1. One of the faintest dwarf irregular galaxies in the Local Group. Not recognized as a galaxy until 1926. Only 1 known globular cluster. Its proximity and low dust allow its brightest stars to be resolved in this image. In support of other measurements, resolution into stars at around 18th magnitude suggests WLM is relatively near. Most stars across the face are foreground stars but in this image 21 stars in WLM including 1 Cepheid variable can be identified. The galaxy looks unusual since images of spiral galaxies are familiar but this type of galaxy is probably more common., acquired with a remote telescope at Siding Springs Observatory, Australia (Elevation 3720')

Object Label Identifier Notes
Galaxy G1 GALEXASC J000129.37-152753.4 Galaxy, mV=16.74, 0.5' x 0.4'
Galaxy N [SC85b] N Galaxy, mV=18.83
Galaxy PGC 912947 PGC 912947 Galaxy, mV=16.29, 0.9' x 0.2'
Globular Cluster D [SC85b] D Globular cluster, mV=16.06, only known globular cluster of WLM
Star 04 [SC85b] 4 Red supergiant, mV=18.98
Star 06 [SC85b] 6 Red supergiant, mV=18.23
Star 09 [SC85b] 9 mV=19.31
Star 10 [SC85b] 10 Bright blue star, mV=18.20
Star 12 [SC85b] 12 mV=20.03
Star 14 [SC85b] 14 mV=20.05
Star 15 [SC85b] 15 mV=18.13
Star 21 [SC85b] 21 mV=19.9
Star 22 [SC85b] 22 Brightest blue star, mV=17.97
Star 23 [SC85b] 23 mV=18.38
Star 26 [SC85b] 26 mV=19.3
Star 27 [SC85b] 27 mV=18.81
Star 30 [SC85b] 30 Bright blue star, mV=18.38
Star 31 [SC85b] 31 mV=18.42
Star 35 [SC85b] 35 Bright blue star, mV=18.39
Star 37 [SC85b] 37 mV=19.66
Star 42 [SC85b] 42 mV=19.77
Star 45 [SC85b] 45 mV=19.41
Star 51 [SC85b] 51 mV=19.79
Star 55 [SC85b] 55 mV=19.6
Star 58 [SC85b] 58 mV=20.48
Star V12 [SC85b] V12 Cepheid variable, mV=18.98

Click on the plate solved image to display annotations. 4' across WLM is about 3,500 light years.

Identifier [SC85b] is Sandage, Carlson "The brightest stars in nearby galaxies", Astron. J., 90, 1464-1473 (1985).
Stars highlighted are spectroscopically confirmed members of WLM from "A survey of Local Group galaxies currently forming stars", Astron. J., 133, 2393-2417 (2007).