The Pleiades is one of the brightest and closest open clusters. This cluster also known as the Seven Sisters and M45. The Pleiades contains over 3,000 stars, is about 400 light years away, and only 13 light years across. This image is a composite of 20 photos. Total exposure: 2h 30min
The Horsehead Nebula is one of the most famous nebulae on the sky. The horse-head feature is dark because it is really an opaque dust cloud that lies in front of the bright red emission nebula. Like clouds in Earth's atmosphere, this cosmic cloud has assumed a recognizable shape by chance. After many thousands of years, the internal motions of the cloud will alter its appearance. The emission nebula's red color is caused by electrons recombining with protons to form hydrogen atoms. Also visible in the picture are blue reflection nebulae that preferentially reflect the blue light from nearby stars.