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Chandra X-ray
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Titan: Saturn's largest moon and the only moon in the solar system with a thick atmosphere.
(Credit: NASA/CXC/Penn State/K.Mori et al.)

Caption: When Titan passed in front of the X-ray bright Crab Nebula on January 5, 2003, it gave astronomers a rare opportunity to study its X-ray shadow (inset). Chandra's precise measurement of Titan's shadow enabled astronomers to determine that its X-ray absorbing atmosphere has a height of about 550 miles (880 kilometers). This may have been the first transit of the Crab Nebula by Titan since the nebula was formed by a supernova that was observed to occur in the year 1054. The next similar conjunction will take place in the year 2267.

Scale: Inset is 16 arcsec per side; Crab Nebula is 134 arcsec per side

Chandra X-ray Observatory ACIS Image

CXC operated for NASA by the Smithsonian Astrophysical Observatory