Halo of the Cat's Eye
From NASA’s Astronomy
Picture of the Day
Its haunting symmetries are seen in
the very central region of this
tantalizing image, processed to reveal the enormous but extremely faint
halo of gaseous material, about 6 light-years across,
which surrounds the brighter, familiar planetary nebula.
Made with narrow and broadband data the composite picture
shows the remarkably strong extended emission from twice ionized oxygen atoms
in blue-green hues and ionized hydrogen and nitrogen in red.
Planetary
nebulae have long been appreciated as a final phase in the
life of a sun-like star. But recently many planetaries have been found
to have halos like this one, likely formed of material shrugged off during
earlier active episodes in the star's evolution.
While the planetary nebula phase is
thought to last for around 10,000 years, astronomers estimate the age of the outer filamentary
portions of this halo to be 50,000 to 90,000 years.
