On February 11, 2010, when NASA’s Solar Dynamics Observatory (SDO) was launched into space, its path took it directly through an atmospheric optical phenomenon known as a sundial. In the video above, you can hear observers gasping in surprise as the rainbow-colored sundial disappears as the spacecraft travels through that part of the atmosphere. It was a promising start for a spacecraft that contributed to our understanding of our local star. And the launch also brought to light a new form of ice halo and taught those who love and study aerial optics new insights into how shock waves interact with clouds.
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A sundog is a bright rainbow-colored patch in the sky formed by the refraction of sunlight from plate-shaped ice crystals drifting from the sky like leaves fluttering from trees. Les Cowley of the Atmospheric Optics website explained what happens in the video in a post on Science @ NASA:
When the rocket entered the cirrus, shock waves rippled through the cloud, destroying the alignment of the ice crystals. This extinguished the sundial.
In this simulation, the sun is surrounded by a 22-degree halo and flanked by sundials. Read more at Les Cowley’s Atmospheric Optics.
In the video, watch out for the luminous column of white light that appears next to the Atlas V rocket that powered SDO’s 2011 launch. While Cowley and other celestial optics experts understood why the sundial disappeared, they didn’t understand the events that followed, especially that white light column. Cowley said:
A luminous column of white light appeared next to the Atlas V and followed the rocket into the sky. We had never seen anything like it.
View bigger. | When the Solar Dynamic Observatory (bright stripe in the lower left quadrant of the photo) was launched from Cape Canaveral on February 11, 2010, its launch enabled optical experts to discover a new form of ice halo. Image via NASA / Goddard / Anne Koslosky.
Cowley and colleague Robert Greenler were initially unable to explain this column of light. Then they realized that the plate-shaped ice crystals were organized by the shock wave of the Atlas V. Cowley explained:
The crystals are tilted between 8 and 12 degrees. Then they rotate so that the main axis of the crystal describes a conical movement. Toy tops and gyros will do. The Earth does it once every 26,000 years. The movement is ordered and precise.
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Incidentally, NASA’s Solar Dynamics Observatory has been observing the sun for eleven years now. It’s one of the many observatories that monitor our sun, part of NASA’s Living with a Star program. The video below highlights some of SDO’s achievements over the past decade.
In short, on February 11, 2010, a solar observatory launched into space tore apart a sundial, creating a new ice halo that astounded scientists.
Via Science @ NASA
Via Les Cowley’s atmospheric optics
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