These tadpole‐like structures have been found in the Helix nebula, the closest planetary nebula to Earth—450 light‐years away. With the aid of Wide Field Planetary Camera 2 on the Hubble Space Telescope, C. Robert O’Dell and Kerry P. Handron of Rice University observed 313 of the well‐resolved structures, which they call cometary knots; their glowing heads and wispy tails resemble comets. O’Dell and Handron estimate that the entire nebula has 3500 of them.

This content is only available via PDF.
You do not currently have access to this content.