The Cat's Eye Nebula
(NGC 6543) is one of the best known planetary
nebulae in the sky.

Its haunting symmetries are seen
in the very central region of
this stunning false-color picture, processed to reveal the
enormous but extremely faint halo of gaseous material, over three
light-years across, which surrounds the brighter,
familiar
planetary nebula.

Made with data from the
Nordic Optical Telescope in the
Canary Islands,
the composite picture shows extended emission from the nebula.

Planetary
nebulae have long been appreciated as a final phase
in the life of a sun-like star.

Only much more recently however, have some planetaries 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.

Related Skylook Posts:

• Wide Angle: The Cat’s Paw Nebula
• The Cat’s Eye Nebula from Hubble
• NGC 7635 The Bubble Nebula

Have you ever seen a halo around the Sun?

This fairly common sight occurs when high thin clouds containing millions of tiny
ice crystals cover much of the sky.

Each
ice crystal acts like a
miniature lens.

Because
most
of the crystals have a similar elongated
hexagonal
shape, light entering one crystal face and exiting
through the opposing face refracts 22
degrees,
which corresponds to the radius of the Sun halo.

A similar Moon halo
may be visible during the night.

Pictured above, a nearly complete
sun halo was photographed high above the ancient
Bayon temple in
Angkor,
Cambodia.

Exactly how
ice-crystals form in clouds remains under
investigation.

Related Skylook Posts:

• A Sun Halo Beyond Stockholm
• The Belt of Venus Over Mercedes Argentina
• Red Aurora Over Australia

Related Skylook Posts:

• A Sun Halo Over Cambodia
• In Through and Beyond Saturn’s Rings
• Sangstar1 Lunar Eclipse from Greenvale Thursday June 16-06-2011

Globlular
star clusters roam the halo of our Milky Way Galaxy.

Gravitationally
bound, these spherical groupings of
typically several hundred thousand stars are ancient,
older than the stars of the galactic disk.

In fact, measurements of globular cluster
ages constrain
the age of the Universe (it must be older than the stars in it!) and
accurate cluster distance determinations
provide a rung on the astronomical distance ladder.

Globular star cluster
NGC 6934
itself lies about 50,000 light-years away in the constellation
Delphinus.

At that distance,
this sharp
image from Hubble's Advanced Camera for Surveys spans
about 50 light-years.

The cluster stars are estimated to be some 10
billion years old.

Related Skylook Posts:

• CygnusX The Inner Workings of a Nearby Star Factory
• Bright Star Regulus near the Leo I Dwarf Galaxy
• Chasing Carina