A cloud of ionised hydrogen more than a hundred light years across with the characteristic red-pink colour of an H II region. In the centre of the nebula, pressure from the Rosette Cluster, C50, has created a darker region some thirty light years across, adding to the overall impression of a rosette shape.
The circular pocket in the centre of the Rosette Nebula is caused by the hundreds of newly-formed stars in the heart of the nebula, collectively known as the Rosette Cluster. Though there are estimated to be more than two thousand young stars in this central cluster, two of these are particularly massive - HD 46150 and HD 46223 - and these two have played a significant role in hollowing the interior regions of the surrounding Rosette Nebula. Imagery provided by Aladin sky atlas
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