Astronomy Picture of the Week – Saturn-lit Tethys

Here’s a pretty cool image

Cassini gazes across the icy rings of Saturn toward the icy moon Tethys, whose night side is illuminated by Saturnshine, or sunlight reflected by the planet.

Tethys was on the far side of Saturn with respect to Cassini here; an observer looking upward from the moon’s surface toward Cassini would see Saturn’s illuminated disk filling the sky.

Tethys was brightened by a factor of two in this image to increase its visibility. A sliver of the moon’s sunlit northern hemisphere is seen at top. A bright wedge of Saturn’s sunlit side is seen at lower left.

Saturn-Lit Tethys

Saturn-Lit Tethys

This view looks toward the sunlit side of the rings from about 10 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on May 13, 2017.

The view was acquired at a distance of approximately 750,000 miles (1.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 140 degrees. Image scale is 43 miles (70 kilometers) per pixel on Saturn. The distance to Tethys was about 930,000 miles (1.5 million kilometers). The image scale on Tethys is about 56 miles (90 kilometers) per pixel.

I would like to take this moment to remind everyone that Cassini will take it’s final journey into the clouds of Saturn on September 15. Specifically it will happen on September 15, 2017, at around 6:32 am Eastern Standard Time, with the Earth receiving the last signal from Cassini at 7:55 am EST.


  1. StevoR says

    You may well already have seen these but just in case :

    That effect gets magnified many times when the backdrop is space exploration. Cassini’s success in the harshest of places feels like extreme loyalty and heroism, and for some, its final journey like a suicide. It doesn’t matter that machines can’t feel – we do it for them.

    Yeah, not ashamed to say I’m going to get misty eyed when Cassini mergers into Saturn becoming part of the world she’s orbited for so long too.

    Article linked there from :|NSNS|2017-GLOBAL-inlinelink&utm_medium=ILC&utm_source=NSNS&utm_campaign=inlinelink

    website-y thingamajig which also has a countdown clock and oodles of great Cassini articles there. (2 hours 28 minutes to go as of right now.)

    Also live (or once live?) Cassini press conference -- hour long -- here :

    with lots of the scientists, engineers and people who made Cassini so splendidly successful.

  2. StevoR says

    .. And its gone.

    Vale Cassini your molecules now part of the butterscotch planet you showed us so well -- and thankyou to all those who made her possible.

    One superluminous (beyond the merely brilliant) little robot -- and her crew of thousands of individual people that built and designed and flew and taught and learned and brought so many so much wonder, joy, beauty and knowledge.

    Never forgotten, so much seen and learnt and to be remembered so happily.

  3. says

    SteveoR… I’m sorry to say that I wasn’t able to watch it live. I was sick last night and had to sleep… didn’t wake up until 10:30 am EDT. I’m even sadder because I missed it.

    However, I’ve got a post about it going up in about 30 minutes or so.

Leave a Reply