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Caption: The
planetary nebula
the
Cat's Eye Nebula
observed by the
Hubble Space Telescope (HST)
.
Features:
The image is approximately
true color
???---but maybe a bit enhanced.
The
Cat's Eye Nebula
is ∼ 1 kpc (3000 ly) away in
constellation
Draco
. It is one of the most complex of
planetary nebulae
and is estimated to be only about 1000 years old.
The green color is due to green
forbidden lines
of
O III
(i.e., doubly ionized atomic
oxygen
).
The
Cat's Eye Nebula nucleus
(i.e., its
planetary nebula nucleus (PNN)
) is in the transition phase from
asymptotic giant branch (AGB) star
to
white dwarf
. Currently, it has
mass
≅ 1.06
M_☉
. If it continues losing
mass
at its current
stellar mass loss rate
and it reaches its
white dwarf
state with
mass
≅ 0.6
M_☉
(which the mean
white dwarf
mass
:
Wikipedia: White dwarf: Composition and structure
), it will take ∼ 1.3*10**6 yr to reach the
white dwarf
state (
Bianchi et al. 1986, p. 234
).
Credit/Permission:
NASA
,
1994
/
Public domain
.
Download site:
ESA: Images
.
Image link:
Itself
.
Local file:
local link: planetary_nebula_cats_eye.html
.
File:
Post-main-sequence file
:
planetary_nebula_cats_eye.html
.