Image Credit & Copyright: John H.
Moore; Annotation: Judy Schmidt
Explanation:
How many different astronomical phenomena have come together to create the
above vista? Several. First, in the foreground, is Crater Lake -- a caldera
created by volcanism on planet Earth about 7,700 years ago. Next, inside the
lake, is water. Although the origin of the water in the crater is melted
snowfall, the origin of water on Earth more generally is unclear, but possibly
related to ancient Earthly-impacts of icy bodies. Next, the green glow in the
sky is airglow, light emitted by atoms high in the Earth's atmosphere as they
recombine at night after being separated during the day by energetic sunlight.
The many points of light in the sky are stars, glowing by nuclear fusion. They
are far above the atmosphere but nearby to our Sun in the Milky Way Galaxy.
Finally, the bright arch across the image is the central band of the Milky Way,
much further away, on the average, than the nearby stars, and shaped mostly by
gravity. Contrary to appearances, the Milky Way band glows by itself and is not
illuminated by the airglow. The above image is a six-frame panorama taken
during about two weeks ago in Oregon, USA.
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