Thursday, May 09, 2013
Image: The Iris nebula in the Cepheus constellation
The Iris reflection nebula is surrounded by a dark nebula. The dark nebula is a huge amount of interstellar dust hiding the stars behind it. The few stars being visible to our human eyes "in" the dark nebula region are obviously between us and the nebula. The blue-greenish reflection nebula is caused by the light of a hot star called SAO 19158, that illuminates the dust clouds around it. Only IR (infrared) light can penetrate the thick dust clouds, that means an infrared photo should show more stars in the dark nebula region.