Astronomy Picture of the Day
January 19, 2014

Surrounded by the Darkness...
Surrounded by the Darkness...

Credits: NASA/JPL-Caltech/Space Science Institute and Dr Paolo C. Fienga/LXTT/IPF, for the additional process. and color.

The NASA - Cassini Spacecraft's Narrow Angle Camera captured Saturn's tiny irregular moon Janus, surrounded by the vast, cold and dark expanse of the Outer Solar System. Janus (that is approx. 111 miles - or about  178,6 Km - across) shares an orbit with another small moon: Epimetheus; the two Celestial Objects (as you should since we wrote this information in the past) change, roughly every four years, their Orbital Positions (in other words: Janus and Epimetheus - which are only separated by a little less than 50 Km (such as approx. 31 miles) - as they approach each other, they also exchange a little momentum and trade orbits. This means that the Inner Body becomes the Outer one, while the Outer one moves in to the Inner position).

This view looks toward the Saturn-facing Side of Janus; North is up and rotated 38° to the left. The image was taken in Visible Light, with the NASA - Cassini Spacecraft's Narrow Angle Camera, on September 10, 2013. The frame was acquired at a distance of approximately 621.000 miles (such as about 999.400 Km) from Janus. The Original Raw Image scale was 3,7 miles (such as approx. 5,95 Km) per pixel, but the proportions, here, have substantially changed, since the image was magnified in order to allow the Viewers to see more details of the visible Surface of Janus.

This frame (which is an Original NASA - CASSINI Spacecraft's b/w and NON Map-Projected image published on the NASA - Planetary Photojournal with the ID n. PIA 17146) has been additionally processed, contrast enhanced, magnified to aid the visibility of the details, Gamma corrected and then colorized - according to an educated guess (or, if you wish, an informed speculation) carried out by Dr Paolo C. Fienga - in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Cassini Spacecraft and then looked outside, towards the Saturnian moon "Janus"), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among other things, the existence of different Elements (Minerals) present on the Surface of Janus, each having a different Albedo (---> Reflectivity) and Chemical Composition.

Note: it is possible (but we, as IPF, have no way to be one-hundred-percent sure of such a circumstance), that the actual luminosity of Janus - as it is in this frame - would appear, to an average human eye, a little bit lower than it has been shown (or, better yet: interpreted) here.

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