Lunar Transit of the Sun
Yesterday, Nov. 22nd, the Moon passed in front of the sun off-center,
producing a beautiful partial eclipse. No one on Earth saw it, because the
lunar transit was visible only from Earth orbit. More than 22,000 miles above the
planet's surface, NASA's Solar Dynamics Observatory (SDO) snapped this picture:
Using a bank of 16-megapixel cameras, SDO observed the event at multiple
extreme ultraviolet wavelengths. Scan the edge of the Moon in the 171 Å
high-resolution image, shown below. The little bumps and irregularities you see
are lunar mountains backlit by solar plasma:
Beyond the novelty of observing an eclipse from space, these images have
practical value to the SDO science team. The sharp edge of the lunar limb helps
researchers measure the in-orbit characteristics of the telescope--e.g., how
light diffracts around the telescope's optics and filter support grids. Once
these are calibrated, it is possible to correct SDO data for instrumental
effects and sharpen the images even more than before.
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