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. 2007 June 18
Explanation: Exploring the myriad shapes found in the cosmic zoo
of planetary nebulae, some astronomers have focused on the
intriguing example of M2-9. About 2,100 light-years away and
over one light-year across, M2-9 is known as a twin jet or
butterfly nebula in reference to its striking bipolar symmetry.
Monitoring M2-9 over many years from ground based telescopes has
revealed the dramatic west to east (left to right) progression
of features illustrated in this collage. The apparent motion
could well be caused by an energetic rotating beam sweeping
across the nebular material. Astronomers argue that the beam is
collimated by interacting stellar winds in a double star system
at the center of M2-9. The binary system of a giant star and hot
white dwarf star orbit each other about once every 120 years.
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