... 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. Unusual Spiral Galaxy M66 . ... Spiral galaxy M66 is largest galaxy in the a group known as the Leo Triplet. ... Usually dense waves of gas, dust, and newly formed stars - called spiral density waves - circle a galactic center and create a symmetric galaxy. ... Early Microscopic Life on Mars? ...