Figure: The Red Spider Nebula

Object name: NGC 6537, Red Spider Nebula

Huge waves are sculpted in this two-lobed nebula some 3000 light-years away in the constellation of Sagittarius. This warm planetary nebula harbours one of the hottest stars known and its powerful stellar winds generate waves 100 billion kilometres high. The waves are caused by supersonic shocks, formed when the local gas is compressed and heated in front of the rapidly expanding lobes. The atoms caught in the shock emit the spectacular radiation seen in this image.

This NASA/ESA Hubble Space Telescope image shows that the gas walls of the two lobed structures are not at all smooth, but rather are rippled in a complex way. These waves are driven by stellar winds radiating from the hot central star, much as a wind passing over a lake can generate waves on the water.

Credit: ESA & Garrelt Mellema (Leiden University, the Netherlands)

http://www.spacetelescope.org/images/html/heic0109a.html