Curious Cometary Knots in the Helix Nebula
Explanation:
What causes unusual knots of gas and dust in
planetary nebulas?
Seen also in the
Ring Nebula, the
Dumbbell Nebula and the
Eskimo Nebula,
the knots' existence was not initially predicted and their origins
are still not well understood.
Pictured above is a fascinating image of the
Helix Nebula by the
Hubble Space Telescope
showing tremendous detail of its mysterious gaseous knots.
The above cometary knots have masses similar to the Earth but have radii typically
several times the orbit of Pluto.
One hypothesis
for the fragmentation and evolution of the knots includes existing gas being
driven out
by a less dense but highly energetic
stellar wind
of the central evolving star.
The
Helix Nebula
is the closest example of a
planetary nebula
created at the end of the
life of a Sun-like star.
The
Helix Nebula, given a technical designation of NGC 7293, lies about 700
light-years
away towards the
constellation of
Aquarius.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
