As stars age, they throw off their outer layers. Sometimes a highly symmetric gaseous planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap971021.html http://www.seds.org/messier/planetar.html ] is created, as is the case in M2-9 [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1994ApJ%2E%2E%2E437%2E%2E281H&nosetcookie=1 ], also called the Butterfly. Most planetary nebulae [ http://www.noao.edu/jacoby/pn_gallery.html ] show this bipolar [ http://antwrp.gsfc.nasa.gov/apod/ap970914.html ] appearance, although some appear nearly spherical [ http://antwrp.gsfc.nasa.gov/apod/ap970331.html ]. An unusual characteristic of the Butterfly is that spots on the "wings"http://antwrp.gsfc.nasa.gov/apod/ap971021.html appear to have moved slightly over the years. The above picture [ http://spider.ipac.caltech.edu/staff/latter/ ] was taken in three bands of infrared light and computationally shifted into the visible. Much remains unknown about planetary nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap961203.html ], including why some appear symmetric [ http://antwrp.gsfc.nasa.gov/apod/ap970802.html ], what creates the knots of emission (some known as FLIERS [ http://antwrp.gsfc.nasa.gov/apod/ap961122.html ]), and how exactly stars create them.