The dark spot at the bottom of the frame is the Rosetta spacecraft’s shadow on Comet 67P/Churyumov-Gerasimenko, which it has been orbiting since last August. The spacecraft was only 4 miles (6 km) from the comet when this image was acquired on February 14, 2015. Image via ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
On February 14, 2015, the Rosetta spacecraft made a close flyby of Comet 67P/Churyumov-Gerasimenko. The spacecraft not only passed closer to a comet than any spacecraft had before, but it also became part of a unique space geometry. For a short time during the maneuver – as the spacecraft swept in closest to 67P – the sun, the spacecraft and the comet were almost perfectly aligned. Thus – although the resulting images are of high scientific value – they don’t appear as dramatic as some earlier Rosetta images of the comet, because few shadows can be seen. But there is one exception: as a side-effect of this exceptional geometry, we can see Rosetta’s shadow on the surface of the comet, surrounded by a bright halo-like region.
The images were acquired by OSIRIS, the scientific imaging system on board the Rosetta spacecraft. They have a resolution of 11 centimeters per pixel.
The shadow seen on the comet’s surface is Rosetta’s penumbra. Such penumbras occur when an object is illuminated by an extended light source like the sun. Image via ESA
Bottom line: The Rosetta spacecrft caught its own shadow encircled in a wreath of light, on the icy surface of Comet 67P/Churyumov-Gerasimenko, on February 14, 2015.
Deborah Byrd (asteroid 3505 Byrd) helps edit EarthSky.org and is a frequent host of EarthSky videos. Deborah created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Prior to that, she had worked for the University of Texas McDonald Observatory since 1976, and created and produced their Star Date radio series. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named in her honor in 1990, a Public Service Award from the National Science Board in 2003, and the Education Prize from the American Astronomical Society in 2020. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.
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