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Four Moons in One Frame

With bonus rings.

Another great picture from the Cassini Probe, taken from Astronomy Picture of the Day for 4/4/2021.

Four Saturnian Moons

The most obvious moon is the bright Dione, hovering on the centre of the frame, with shadowy but much larger Titan in the background. Titan is the tenth largest object in the Solar System bigger than the planet Mercury.

To the extreme right of the rings is Pandora, a moon which shepherds Saturn’s F ring.

Just in the gap in the rings (the Encke gap) is Pan, only 35 kilometres across but which keeps the gap free of ring particles.

Astronomy Picture of the Day (APOD)

Astronomy Picture of the Day was 20 years old on Jun 16th. It has been on a bit of a roll recently.

The Pinwheel Galaxy (Jun 14th):-

Pinwheel Galaxy

The Black Eye galaxy (Jun 18th):-

the black eye galaxy

On 23rd Jun there was this star bubble round Sharpless 2-308:-

Star Bubble

This is a picture of Zeta Ophiuchi (Jul 5th) which is travelling to the left at 24 kilometres per second thus causing the bow-shock in the interstellar dust as shown:-

Zeta Ophiuchi

The next day gave us this picture of clouds near Rho Ophiuchi

Clouds near Rho Ophiuchi

Then Jul 8th had this stunning scene of Dione, Saturn and Enceladus (Saturn is visible only as a faint arc and its rings are edge-on):-

Dione

Fly-over Ceres, Jun 10th, a composite of still pictures:-

It’s exciting times for NASA as New Horizons is getting very close to Pluto. See yesterday’s picture:-

5 million miles from Pluto

Wonderful stuff.

Titan and Dione

Another fantastic photo from Astronomy Picture of the Day (5/1/12) taken by the Cassini spacecraft.

This clearly shows that the moons orbit in the same plane as Saturn’s rings (whose shadows are cast on the main planet in the background.) In this view the two moons are 900,000 kiolmetres apart from each other, Dione nearer to Saturn, with the edge of the rings another 300,000 kilometres beyond Dione.

Also obvious is Titan’s atmosphere which makes its edges appear fuzzy.

Titan and Dione

4 Saturnian Moons

Astronomy Picture of the Day for 26/10/11 was this stunning view of four of Saturn’s moons, one (Dione) pictured in relief against the background of another (Titan.)

Saturn’s rings jut into the picture and the shepherd moon, Pandora, can be seen as an extended bright blur beyond their tips. In the ring gap (the Encke Gap) you can just make out an inner shepherd moon, Pan, whose presence keeps the gap free of ice particles.

This sort of image is just brilliant. It gives me the famous “sense of wonder” associated with Science Fiction.

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