CFHT, Current Image of the Week


January 31st, 2000

NGC 2244, A Stellar Cluster in the Rosette Nebula

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NGC 2244, A Stellar Cluster in the Rosette Nebula

Credit: Image courtesy of J.C. Cuillandre and G. Fahlman, CFHT

NGC 2244 is an open stellar cluster located 1600pc (5200 light years) away. It contains at least 17 OB stars, it 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.

For example, 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 ionisation 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.

Technical description: 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 Halpha emission, itself tracing the ionisation of the environment of the OB stars.

This image shows the full field of view available with the CFH12K. However, to keep the image at a reasonable size, it has been binned by a factor of 16 in each direction. Each pixel in this image is therefore the average of a square of 16 X 16 pixels in the original image.

This image is part of a set of 12 that make CFHT's Calendar for the year 2000.

next week: Uranus: The first ground based detection of the satellite Portia

editors: François Ménard & Jean-Charles Cuillandre
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CFHT is funded by the Governments of Canada and France, and by the University of Hawaii.