Except for the rings Nebula (M57) is probably the most famous
celestial band. Its classic appearance is understood to be due
to perspective - our view from planet Earth looks down the
center of a roughly barrel-shaped cloud of glowing gas. But
expansive looping structures are seen to extend the Ring
Nebula's familiar central regions in intriguing composite of
ground based and Hubble Space Telescope images with narrowband
image data from Subaru. Of course, in this well-studied example
of a nebula, the glowing material does not come from planets.
Instead, the gaseous shroud represents outer layers expelled
from the dying, sun-like star at the nebula's center. Intense
ultraviolet light from the hot central star ionizes atoms in the
gas. Ionized oxygen atoms produce the characteristic greenish
glow and ionized hydrogen the prominent red emission. The
central ring of the Ring Nebula is about one light-year across
and 2,000 light-years away. tonight's shooting stars it shines
in the northen constellation Lyra.