NASA's Solar Dynamics Observatory, best known for its mind-blowing
photos and videos of the sun, started life as a rainbow
As the rocket carrying the sun
observer climbed into orbit, it produced shock waves that destroyed
a small splotchy-shaped rainbow and created a new,
never-before-seen form of ice halo.
Ice halos are rings and arcs of light that appear when sunlight
is deflected through ice crystals. On the morning of February 11,
2010, when SDO launched from Cape Canaveral, hexagonal plate-shaped
ice crystals drifting downward created a sundog, a fragment of a
rainbow that can often be found on either side of the morning sun
on chilly days.
As SDO passed the sundog, it erased it. Shortly after, a column
of white light appeared next to the rocket and followed it into the
Astronomers knew what happened to the sundog: Shock waves from
the rocket destroyed the alignment of ice crystals, which in turn
destroyed the rainbow. But the white column was a mystery.
"We'd never seen anything like it," said retired physicist and
atmospheric-optics expert Les Cowley in an explainer at Science@NASA.
Now, a year later, Cowley and retired physicist Robert Greenler of the University of
Wisconsin-Milwaukee think they know what happened. Rather than
scrambling the ice crystals, the shock wave from the rocket
organised them into an array of tiny spinning tops.
The hexagonal ice crystals are tilted between 8 and 12 degrees,
Cowley said. The crystals then wobble in an ordered, precise motion
so that an imaginary line running through their centre traces out a
cone shape. This motion, called precession, shows up in a variety of spinning
bodies, from toy tops to planets.
"This could be the start of a new research field -- halo
dynamics," Cowley said.
Cowley and Greenler's simulations show that the white column
that followed SDO to orbit was part of a larger oval that would have surrounded the
ascending rocket if the crystals and shock waves had covered a
Watch a video of the