Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2023 November 26
A dark and jagged hill is shown strewn with rocks.
On the slope is a white foggy area that appears to 
emanate from a non-descript place on the rock face.
Please see the explanation for more detailed information.

A Dust Jet from the Surface of Comet 67P
Image Credit: ESA, Rosetta, MPS, OSIRIS; UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Explanation: Where do comet tails come from? There are no obvious places on the nuclei of comets from which the jets that create comet tails emanate. In 2016, though, ESA's Rosetta spacecraft not only imaged a jet emerging from Comet 67P/Churyumov-Gerasimenko, but flew right through it. Featured is a telling picture showing a bright plume emerging from a small circular dip bounded on one side by a 10-meter high wall. Analyses of Rosetta data shows that the jet was composed of both dust and water-ice. The rugged but otherwise unremarkable terrain indicates that something likely happened far under the porous surface to create the plume. This image was taken about two months before Rosetta's mission ended with a controlled impact onto Comet 67P's surface.

Tomorrow's picture: open space


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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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