The Snake Nebula in Ophiuchus.

What slithers there? The dark curly lanes visible in part of the constellation Ophiuchus belong to the Snake Nebula. The Snake Nebula is a series of dark absorption clouds . Interstellar dust grains - composed predominantly of carbon - absorb visible starlight and reradiate much of it in the infrared . Infrared is a band of light so red humans can't see it. This absorption causes stars in the background to be blocked from our view - and hence the appearance of noticeable voids on the sky.