Expert: Steve Nelson - 5/22/2009

Question
Hi Steve,
I recently saw an amazing photo of the Cat's Eye Nebula and read that it is considered to be one of the least understood and amazing phenomena so far photographed in space (Mind you, the magazine I saw it in was over 5 years old, so things may have changed). Could you tell me what exactly the Cat's Eye Nebula is (e.g. is it a star) and is it true that it is one of the least understood phenomena in space and, if so, why? What is so unique about it and, if we understood it better what could it tell us or give us an insight into (i.e. what would it's legacy be if it's mystery was unravelled)?
Finally, is it also true that the Cat's Eye Nebula is dying and, if so, does that make it less significant a discovery?
I am really intrigued about this because there is just something quite incredible about that photo that I can't quite put my finger on!
Thanks for your time
Gary

Answer
First, keep in mind that I'm not an astronomer.  The physics of what's going on inside is part of my field, not the structures themselves that are out there.

The wikipedia page on the subject is actually quite good:  
http://en.wikipedia.org/wiki/Cat's_Eye_Nebula

All nebulae are subject to gravitational collapse.  Does that make them less significant?  No!  The fact that such nebulae can collapse to form stars and planets makes them *more* significant.  There's a central star in this nebula, ejecting material (unknown if the system is binary or not).  Therefore it's reasonable to assume that there are probably planets either formed or forming around it.  If the world worked like Star Trek and we could go there this type of system would be one of the first places I'd start looking for habitable planets in their early stages of formation.

The real mystery to astronomers (and I leave the details of this question to them) is the abundances of various elements formed by nuclear reactions in the nebula's stars.  Given nuclear reaction rates that we measure  in the lab (that is my field) and extrapolate to star-temperatures, astrophysicists run simulations of the stars to determine how a particular type of star will evolve over its lifetime.  Their simulations and observations, properly done, should match.  When they don't, we figure out what's causing the mismatch...that's how discoveries are made, the process of figuring out things that don't make sense at first.  This nebula apparently has atomic abundances that are hard to measure, the different types of measurements themselves disagree.  So it's an astronomer you need for a more detailed answer on measurement techniques.  Another mystery is exactly what caused the structures you see in it, which there's yet to be a definitive answer for.