Behold: four of Saturn’s 82 true moons. Four you say? That’s right, four. To wit:
First — and farthest in the background — is Titan, the largest moon of Saturn and one of the larger moons in the Solar System. The dark feature across the top of this perpetually cloudy world is the north polar hood. The next most obvious moon is bright Dione, visible in the foreground, complete with craters and long ice cliffs. Jutting in from the left are several of Saturn’s expansive rings, including Saturn’s A ring featuring the dark Encke Gap. On the far right, just outside the rings, is Pandora, a moon only 80-kilometres across that helps shepherd Saturn’s F ring. The fourth moon? If you look closely inside Saturn’s rings, in the Encke Gap, you will find a speck that is actually Pan. Although one of Saturn’s smallest moons at 35-kilometres across, Pan is massive enough to help keep the Encke gap relatively free of ring particles. After more than a decade of exploration and discovery, the Cassini spacecraft ran low on fuel in 2017 and was directed to enter Saturn’s atmosphere, where it surely melted.
(Image: Cassini Imaging Team, ISS, JPL, ESA, NASA)
Behold: two gas giants passing in the night. What do you mean you missed it? To wit:
Two days ago Jupiter and Saturn passed a tenth of a degree from each other in what is known a Great Conjunction. Although the two planets pass each other on the sky every 20 years, this was the closest pass in nearly four centuries. Taken early in day of the Great Conjunction, the featured multiple-exposure combination captures not only both giant planets in a single frame, but also Jupiter’s four largest moons (left to right) Callisto, Ganymede, Io, and Europa — and Saturn’s largest moon Titan. If you look very closely, the clear Chilescope image even captures Jupiter’s Great Red Spot. The now-separating planets can still be seen remarkably close — within about a degree — as they set just after the Sun, toward the west, each night for the remainder of the year.
(Image: Damian Peach)
The approach of Mars is so over.
For the next two months, Saturn and Jupiter will take centre stage in the night sky, drawing closer to earth and appearing closer together. To wit:
…in mid-December, a Great Conjunction will occur — when the two planets will appear only 0.1 degrees apart — just one fifth the angular diameter of the full Moon. And this isn’t just any Great Conjunction — Saturn (left) and Jupiter (right) haven’t been this close since 1623, and won’t be nearly this close again until 2080. This celestial event is quite easy to see — already the two planets are easily visible toward the southwest just after sunset — and already they are remarkably close. Pictured, the astrophotographer and partner eyed the planetary duo above the Tre Cime di Lavaredo (Three Peaks of Lavaredo) in the Italian Alps about two weeks ago.
(Image: Giorgia Hofer)
Behold: a vast hexagonal cloud formation over Saturn’s northern hemisphere. First discovered by Voyager in the 1980s and subsequently observed by Cassini, nothing like it has been found elsewhere in the solar system. To wit:
Acquiring its first sunlit views of far northern Saturn in late 2012, the Cassini spacecraft’s wide-angle camera recorded this stunning, false-colour image of the ringed planet’s north pole. The composite of near-infrared image data results in red hues for low clouds and green for high ones, giving the Saturnian cloudscape a vivid appearance. This and similar images show the stability of the hexagon even 20+ years after Voyager. Movies of Saturn’s North Pole show the cloud structure maintaining its hexagonal structure while rotating. Unlike individual clouds appearing like a hexagon on Earth, the Saturn cloud pattern appears to have six well defined sides of nearly equal length. Four Earths could fit inside the hexagon. Beyond the cloud tops at the upper right, arcs of the planet’s eye-catching rings appear bright blue.
(Image: NASA, ESA, JPL, SSI, Cassini Imaging Team)
Those two dots visible between Saturn’s rings? That’s the Earth and the Moon. To wit:
Just over three years ago, because the Sun was temporarily blocked by the body of Saturn, the robotic Cassini spacecraft was able to look toward the inner Solar System. There, it spotted our Earth and Moon — just pin-pricks of light lying about 1.4 billion kilometers distant. Toward the right of the featured image is Saturn’s A ring, with the broad Encke Gap on the far right and the narrower Keeler Gap toward the center. On the far left is Saturn’s continually changing F Ring. From this perspective, the light seen from Saturn’s rings was scattered mostly forward , and so appeared backlit. After more than a decade of exploration and discovery, the Cassini spacecraft ran low on fuel in 2017 and was directed to enter Saturn’s atmosphere, where it surely melted.
(Image: NASA, ESA, JPL-Caltech, SSI, Cassini Imaging Team; Processing & License: Kevin M. Gill)
An image taken in Guatemala in late 2019. Lights from small towns are visible in the foreground behind the huge Pacaya volcano. But why does Saturn appear so big? To wit:
It doesn’t — what is pictured are foreground clouds on Earth crossing in front of the Moon. The Moon shows a slight crescent phase with most of its surface visible by reflected Earthlight known as ashen glow. The Sun directly illuminates the brightly lit lunar crescent from the bottom, which means that the Sun must be below the horizon and so the image was taken before sunrise.This double take-inducing picture was captured on 2019 December 24, two days before the Moon slid in front of the Sun to create a solar eclipse.
(Image: Francisco Sojuel)
An image of five Saturnine moons above the ring plane captured in 2011, by the Cassini spacecraft’s narrow-angle camera. To wit:
Left to right are small moons Janus and Pandora respectively 179 and 81 kilometres across, shiny 504 kilometre diameter Enceladus, and Mimas, 396 kilometres across, seen just next to Rhea. Cut off by the right edge of the frame, Rhea is Saturn’s second largest moon at 1,528 kilometres across. So how many moons does Saturn have? Twenty new found outer satellites bring its total to 82 known moons, and since Jupiter’s moon total stands at 79, Saturn is the Solar System’s new moon king. The newly announced Saturnian satellites are all very small, 5 kilometres or so in diameter, and most are in retrograde orbits inclined to Saturn’s ringplane.
(Image: Cassini Imaging Team, SSI, JPL, NASA )
Earlier this week, on its monthly trundle around the Earth, our moon passed directly in front of Saturn from the viewpoint of the Southern hemisphere.To wit:
The featured image from Sydney, Australia captured the pair a few minutes before the eclipse. The image was a single shot lasting only 1/500th of a second, later processed to better highlight both the Moon and Saturn. Since Saturn is nearly opposite the Sun, it can be seen nearly the entire night, starting at sunset, toward the south and east. The gibbous Moon was also nearly opposite the Sun, and so also visible nearly the entire night — it will be full tomorrow night. The Moon will occult Saturn again during every lap it makes around the Earth this year.
(Image: Peter Patonai)
Behold: two detailed views of Mimas, one of the major moons of Saturn. To wit:
Peering from the shadows, the Saturn-facing hemisphere of Mimas lies in near darkness alongside a dramatic sunlit crescent. The mosaic was captured near the Cassini spacecraft’s final close approach on January 30, 2017. Cassini’s camera was pointed in a nearly sunward direction only 45,000 kilometres from Mimas.
The result is one of the highest resolution views of the icy, crater-pocked, 400 kilometre diameter moon. An enhanced version better reveals the Saturn-facing hemisphere of the synchronously rotating moon lit by sunlight reflected from Saturn itself. Other Cassini images of Mimas include the small moon’s large and ominous Herschel Crater.
(Image: Cassini Imaging Team, SSI, JPL, ESA, NASA)
If you have a pair of those red-blue 3D specs, now’s the time to fish them out and float along beside Helene. To wit:
Appropriately named, Helene is one of four known Trojan moons, so called because it orbits at a Lagrange point. A Lagrange point is a gravitationally stable position near two massive bodies, in this case Saturn and larger moon Dione. In fact, irregularly shaped ( about 36 by 32 by 30 kilometers) Helene orbits at Dione’s leading Lagrange point while brotherly ice moon Polydeuces follows at Dione’s trailing Lagrange point. The sharp stereo anaglyph was constructed from two Cassini images captured during a close flyby in 2011. It shows part of the Saturn-facing hemisphere of Helene mottled with craters and gully-like features.
(Image: Cassini Imaging Team, ISS, JPL, ESA, NASA; Stereo Image by Roberto Beltramini)