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.
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.
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.