Cassini’s Grand Finale (Why I Missed Wednesday’s APotW)

Hello! You’ll noticed that I skipped Astronomy Pictures of the Week on Wednesday. That… was on purpose.

Today was Cassini’s last day alive. This morning, Cassini plunged into Saturn, sending back some amazing data, but, in the process, ending its life.

Cassini was launched on October 15th, 1997. For two decades, Cassini revealed the wonders of the greatest planet and planetary system in our solar system to us. We learned so much.

But, now, it’s over…

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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.

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Astronomy Picture of the Week – Highlighting Titan’s Hazes

Back to Cassini’s Grand Finale… today we’re highlighting Titan

NASA’s Cassini spacecraft looks toward the night side of Saturn’s moon Titan in a view that highlights the extended, hazy nature of the moon’s atmosphere. During its long mission at Saturn, Cassini has frequently observed Titan at viewing angles like this, where the atmosphere is backlit by the Sun, in order to make visible the structure of the hazes.

Titan’s high-altitude haze layer appears blue here, whereas the main atmospheric haze is orange. The difference in color could be due to particle sizes in the haze. The blue haze likely consists of smaller particles than the orange haze.

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Astronomy Picture of the Week – Prometheus and the Ghostly F Ring

Cassini’s Grand Finale…

The thin sliver of Saturn’s moon Prometheus lurks near ghostly structures in Saturn’s narrow F ring in this view from NASA’s Cassini spacecraft. Many of the narrow ring’s faint and wispy features result from its gravitational interactions with Prometheus (86 kilometers, or 53 miles across).

Most of the small moon’s surface is in darkness due to the viewing geometry here. Cassini was positioned behind Saturn and Prometheus with respect to the sun, looking toward the moon’s dark side and just a bit of the moon’s sunlit northern hemisphere.

Also visible here is a distinct difference in brightness between the outermost section of Saturn’s A ring (left of center) and rest of the ring, interior to the Keeler Gap (lower left).

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

The view was acquired at a distance of approximately 680,000 miles (1.1 million kilometers) from Saturn. Image scale is 4 miles (6 kilometers) per pixel.

Click the image for the tif file…

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Astronomy Picture of the Week – Haze on the Horizon

Late on this one… by a week… I know why I’m missing these, too… real life has me extra stressed… 🙁

Anyways… here’s more from Cassini’s Grand Finale…

This false-color view from NASA’s Cassini spacecraft gazes toward the rings beyond Saturn’s sunlit horizon. Along the limb (the planet’s edge) at left can be seen a thin, detached haze. This haze vanishes toward the left side of the scene.

As usual… click on the image for the tif download…

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Astronomy Picture of the Week – Dawn’s Early Light

As usual until September, this is from Cassini’s Grand Finale

The light of a new day on Saturn illuminates the planet’s wavy cloud patterns and the smooth arcs of the vast rings.

The light has traveled around 80 minutes since it left the sun’s surface by the time it reaches Saturn. The illumination it provides is feeble; Earth gets 100 times the intensity since it’s roughly ten times closer to the sun. Yet compared to the deep blackness of space, everything at Saturn still shines bright in the sunlight, be it direct or reflected.

This view looks toward the sunlit side of the rings from about 10 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on Feb. 25, 2017 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 939 nanometers.

The view was obtained at a distance of approximately 762,000 miles (1.23 million kilometers) from Saturn. Image scale is 45 miles (73 kilometers) per pixel.

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Astronomy Picture of the Week – Small Wonders (Cassini’s Grand Finale)

(This is 30 minutes late because I was a couple days late with GGS.)

Still on the Grand Finale, and as I said when this started, I’ll be staying here until it’s over, because yes, I’m mourning the end of Cassini’s mission. It’s an image of three of Saturn’s smaller ring moons.

I hope you enjoy this one. As always, click on the image for the .tif download…

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Astronomy Picture of the Week – Northern Summer on Titan

Another one from Cassini’s Grand Finale. And yeah, I’m a day late.

NASA’s Cassini spacecraft sees bright methane clouds drifting in the summer skies of Saturn’s moon Titan, along with dark hydrocarbon lakes and seas clustered around the north pole.

Compared to earlier in Cassini’s mission, most of the surface in the moon’s northern high latitudes is now illuminated by the sun. (See here for a view of the northern hemisphere from 2007.) Summer solstice in the Saturn system occurred on May 24, 2017.

The image was taken with the Cassini spacecraft narrow-angle camera on June 9, 2017, using a spectral filter that preferentially admits wavelengths of near-infrared light centered at 938 nanometers. Cassini obtained the view at a distance of about 315,000 miles (507,000 kilometers) from Titan.

As usual, click on the image for the .tif download…

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Astronomy Picture of the Week – Puzzled Iapetus

Yet another one from Cassini’s Grand Finale. Yup, it’s still going

Iapetus is a world of contrast, with light and dark regions fitting together like cosmic puzzle pieces.

Cassini Regio on Iapetus (914 miles or 1,471 kilometers across) is covered in a layer of dark, dusty material creating a stark contrast to the much brighter region that surrounds it. This leads to the moon’s distinctive, two-toned appearance. To learn more about the cause of the contrast between regions, see Encountering Iapetus.

This view looks toward Saturn-facing hemisphere of Iapetus. North on Iapetus is up and rotated 20 degrees to the right. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 11, 2017.

The view was obtained at a distance of approximately 1.6 million miles (2.6 million kilometers) from Iapetus. Image scale is 9 miles (15 kilometers) per pixel.

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