./planetary/planetary_catseye.jpg Caption: The planetary nebula the Cat's Eye Nebula observed by the Hubble Space Telescope (HST).

    Features:

    1. The image is approximately true color???---but maybe a bit enhanced.

    2. 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.

    3. The green color is due to green forbidden lines of O III (i.e., doubly ionized atomic oxygen).

    4. 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.