Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
 Explanation: 
What causes unusual knots of gas and dust in 
planetary nebulae?  
Seen previously in the 
Ring Nebula, the 
Helix 
Nebula, and 
NGC 2392, 
the knots' existence was not predicted previously 
and still not well understood.  
Pictured above is a 
     
 Authors & editors: 
Robert Nemiroff
(MTU) &
Jerry Bonnell (USRA)
 Tomorrow's picture: MAP the Universe
 
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NASA Technical Rep.: 
Jay Norris.
Specific rights apply.
A service of:
LHEA at
NASA /
GSFC
&
NASA SEU Edu. Forum
&
Michigan Tech. U.