MyCn18: An Hourglass Planetary Nebula
The sands of time are running out for the central star
of this hourglass-shaped
planetary nebula.
With its nuclear fuel
exhausted, this brief, spectacular, closing phase of a Sun-like star's life
occurs as its outer layers are ejected - its
core becoming a cooling, fading
white dwarf.
In 1995, astronomers used the
Hubble Space Telescope
(HST) to make a series of
images of planetary nebulae,
including the one above.
Here, delicate rings of colorful glowing gas
(nitrogen-red,
hydrogen-green, and
oxygen-blue) outline the tenuous walls of the
hourglass.
The unprecedented sharpness of the HST images has revealed
surprising details of the nebula ejection process
that are
helping to resolve
the outstanding mysteries
of the complex shapes and symmetries of planetary nebulas.