For the sake of simplicity...

This is what a comet looks like:

Hale Bopp: [link to www.exploratorium.edu]

Comet schematics: [link to burro.astr.cwru.edu]

Comet C2012 S1 ISON: [link to i.space.com]

CS3 Filtered ISON: [link to img11.imageshack.us]

Chandra X-ray Neutron Star w/comet tail: [link to web.archive.org]

Original Source of Image: [link to web.archive.org]

Also, all of this shit is scrubbed off of the net, well most. The stuff using webarchive has been removed.