From CFHT's Astronomy Picture of the Week
NGC 2244 is an open stellar cluster located 1600 pc (5200 light years) away. It contains at least 17 OB stars and is an OB-association. Some of them are visible as bright objects at the center (slightly to the top and right) of this CFH12K image. O and B stars are massive, about 20 times more so than our sun, or even more. They drive powerful stellar winds and shine brightly in the ultraviolet. Because of that these stars, although fairly rare, have a strong impact on their environment. The combined stellar wind of the cluster's OB stars is presently blowing the dust and gas away from the center of NGC 2244 at a velocity of about 20 km/sec and the empty cavity near the OB stars may already be visible on the image. The wave of expanding material is expected to trigger events of extensive star formation as the gas and dust is compressed. Their strong ultraviolet flux is also responsible for the propagation of an ionization front that will also help trigger star formation. This large UV Flux is responsible for the illumination of the bright extended reddish features seen in the image.
On this image North is up and East to the left. It is a color-composite made of 8-minute frames that were obtained in three different filters: B, V and R. The reddish nebulosity traces mostly Ha emission, itself tracing the ionization of the environment of the OB stars.
Image Title: NGC 2244, A Stellar Cluster in the Rosette Nebula
Photograph by J.C. Cuillandre and G. Fahlman, CFHT
The text is based on accompanying on-line materials.
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Last Modified On: Tuesday, December 19, 2000