Saturn Archives

November 22, 2016November 26, 2016 by Nancy Atkinson

Cassini Is About To Graze Saturn’s Rings In Mission Endgame

A lovely view of Saturn and its rings as seen by the Cassini spacecraft on Aug. 12, 2009. Credit: NASA/JPL-Caltech/Space Science Institute.

There is a Twitter-bot that randomly tweets out “NOOOOOOOO Cassini can’t be ending!” (with varying amounts of “O’s”). @CassiniNooo represents the collective sigh of sadness and consternation felt by those of us who can’t believe the the historic and extensive Cassini mission will be over in just a matter of months.

And next week is the beginning of the end for Cassini.

On November 30, Cassini will begin a phase of the mission that the science team calls “Cassini’s Ring-Grazing Orbits,” as the spacecraft will start skimming past the outer edge of the rings, coming within – at times — 4,850 miles (7,800 kilometers) of the rings.

“The scientific return will be incredible,” Linda Spilker, Cassini project scientist, told me earlier this year. “We’ll be studying things we just couldn’t do any other place.”

Between November 30, 2016 and April 22, 2017 Cassini will circle high over and under the poles of Saturn, diving every seven days for a total of 20 times through the unexplored region at the outer edge of the main rings.

During the close passes, Cassini’s instruments will attempt to directly sample the icy ring particles and molecules of faint gases that are found close to the rings. Cassini will also capture some of the best high-resolution images of the rings, and garner the best views ever of the small moons Atlas, Pan, Daphnis and Pandora, which orbit near the rings’ outer edges.

During the first two ring-grazing orbits, the spacecraft will pass directly through an extremely faint ring produced by tiny meteors striking the two small moons Janus and Epimetheus. Later ring crossings in March and April will send the spacecraft through the dusty outer reaches of the F ring.

“Even though we’re flying closer to the F ring than we ever have, … there’s very little concern over dust hazard at that range,” said Earl Maize, Cassini project manager at JPL.

Of course, the ultimate ‘endgame’ is that Cassini will plunge into Saturn with its “Grand Finale,” ending the mission on September 15, 2017. Since Cassini is running out of fuel, destroying the spacecraft is necessary to ensure “planetary protection,” making sure any potential microbes from Earth that may still be attached to the spacecraft don’t contaminate any of Saturn’s potentially habitable moons.

This graphic illustrates the Cassini spacecraft's trajectory, or flight path, during the final two phases of its mission. The view is toward Saturn as seen from Earth. The 20 ring-grazing orbits are shown in gray; the 22 grand finale orbits are shown in blue. The final partial orbit is colored orange. Image credit: NASA/JPL-Caltech/Space Science Institute — This graphic illustrates the Cassini spacecraft’s trajectory, or flight path, during the final two phases of its mission. The view is toward Saturn as seen from Earth. The 20 ring-grazing orbits are shown in gray; the 22 grand finale orbits are shown in blue. The final partial orbit is colored orange. Image credit: NASA/JPL-Caltech/Space Science Institute

To prepare for the Grand Finale, Cassini engineers have been slowly adjusting the spacecraft’s orbit since January of this year, doing maneuvers and burns of the engine to bring Cassini into the right orbit so that it can ultimately dive repeatedly through the narrow gap between Saturn and its rings, before making its mission-ending plunge. During some of those final orbits, Cassini will pass as close as 1,012 miles (1,628 kilometers) above the cloudtops of Saturn.

One question for Cassini’s engineering team is how much fuel is actually left in the tank for Cassini’s main engines, which do the majority of the work for orbit adjustments. Each time they’ve used the main engines this past year, the team has held their breath, hoping there is enough fuel.

One final burn of the main engine remains, on December 4. This maneuver is important for fine-tuning the orbit and setting the correct course to enable the remainder of the mission, said Maize.

“This will be the 183rd and last currently planned firing of our main engine,” he said. “Although we could still decide to use the engine again, the plan is to complete the remaining maneuvers using thrusters,” said Maize.

A montage of images from Cassini of various moons and the rings around Saturn. Credit: NASA/JPL-Caltech/Space Science Institute

When I visited with Maize and Spilker earlier this year, Spilker wistfully said that they had begun to experience some of the “lasts” of the mission — the final flyby of Enceladus and other moons. And there’s one big “last” coming up: on Nov. 29, 2016, Cassini will come within 6,800 miles (11,000 km) of Titan, the final flyby of this eerily Earthlike but yet totally alien moon.

This final flyby, named Flyby T-125 has two primary goals: Mapmaking of Titan’s surface, and enabling the change in Cassini’s orbit to begin the end of the mission. But it also might be the most daring and thrilling part of Cassini’s nearly 20-year mission.

But still ….. NOOOOOO!

Keep track of Cassini’s latest endeavours at the Cassini website

November 3, 2016November 11, 2016 by Matt Williams

Beautiful Planetary Rings Are Dead Dwarf Planets! Dead Dwarf Planets!!!

This portrait looking down on Saturn and its rings was created from images obtained by NASA's Cassini spacecraft on Oct. 10, 2013. Credit: NASA/JPL-Caltech/Space Science Institute/G. Ugarkovic

In 1655, astronomer Christiaan Huygens became the first person to observe the beautiful ring system that surrounds Saturn. And while they are certainly the most spectacular, astronomers have since discovered that all the gas and ice giants of the Solar System (i.e. Jupiter, Saturn, Uranus and Neptune) have their own system of rings.

These systems have remained a source of fascination for astronomers, largely because their origins are still something of a mystery. But thanks to a recent study by researchers from the Tokyo Institute of Technology and Kobe University, the origins of these rings may be solved. According to their study, the rings are pieces of Dwarf Planets that got torn off in passing, which were then ripped to pieces!

This research could help to resolve many of the burning questions about the ring systems around our system’s giant planets, as well as details about the Solar Systems past. For the sake of their study – titled “Ring Formation around Giant Planets by Tidal Disruption of a Single Passing Large Kuiper Belt Object” – the Japanese team of researchers considered a number of factors.

The Kuiper Belt was named in honor of Dutch-American astronomer Gerard Kuiper, who postulated a reservoir of icy bodies beyond Neptune. The first Kuiper Belt object was discovered in 1992. We now know of more than a thousand objects there, and it's estimated it's home to more than 100,000 asteroids and comets there over 62 miles (100 km) across. Credit: JHUAPL — *The Kuiper Belt was named in honor of Dutch-American astronomer Gerard Kuiper, who postulated a reservoir of icy bodies beyond Neptune. Credit: JHUAPL*

First, they considered the diversity of the various ring systems in our Solar System. For instance, Saturn’s rings are massive (about 100,000 trillion kg!) and composed overwhelmingly (90-95%) of water ice. In contrast, the much less massive rings of Uranus and Neptune are composed of darker material, and are believed to have higher percentages of rocky material in them.

To shed some light on this, the team looked to the Nice Model – a theory of Solar System formation that states that the gas giant migrated to their present location during the Late Heavy Bombardment. This period took place between 4 and 3.8 billion years ago, and was characterized by a disproportionately high number of asteroids from Trans-Neptunian space striking planets in the Inner Solar System.

They then considered other recent models of Solar System formation which postulate that the giant planets experienced close encounters with Pluto-sized objects during this time. From this, they developed the theory that the rings could be the result of some of these objects getting trapped and ripped apart by the gas giants’ gravity. To test this theory, they performed a number of computer simulations to see what would happen in these instances.

As Ryuki Hyodo – a researcher at the Department of Planetology, Kobe University, and the lead author on the paper – told Universe Today via email:

“We performed two simulations. First, using SPH (Smoothed-particle hydrodynamics) simulations, we investigated tidal disruption of Pluto-sized objects during the close encounters with giant planets and calculated the amount of fragments that are captured around giant planets. We found enough mass/fragments to explain current rings is captured. Then, we performed the longer-term evolution of the captured mass/fragments by using N-body simulations. We found that the captured fragments can collide each other with destruction and form thin equatorial circular rings around giant planets.”

A composite image of Uranus in two infrared bands, showing the planet and its ring system. Picture taken by the Keck II telescope and released in 2007. Credit: W. M. Keck Observatory (Marcos van Dam) — *A composite image of Uranus in two infrared bands, showing the planet and its ring system. Credit: W. M. Keck Observatory (Marcos van Dam)*

The results of these simulation were consistent with the mass of the ring systems observed around Saturn and Uranus. This included the inner regular satellites of both planets – which would have also been the product of the past encounters with KBOs. It also accounted for the differences in the rings’ composition, showing how the planet’s Roche limits can influence what kind of material can be effectively captured.

This study is especially significant because it offers verifiable evidence for one of the enduring mysteries of our Solar System. And as Hyodo points out, it could come in mighty handy when it comes time to examine extra-solar planetary systems as well.

“Our theory suggested that, in the past, we had two possible epochs to form rings,” he said. “One is during the planet accretion phase and the other is during the Late heavy bombardment. Also, our model is naturally applicable to other planetary systems. So, our theory predicts that exoplanets also have massive rings around them.”

In the meantime, some might find the idea that ring systems are the corpses of Dwarf Planets troublesome. But I think we can all agree, a Soylent Green allusion might be just a bit over the top!

Further Reading: arXiv

November 1, 2016November 4, 2016 by Bob King

November Opens with a Splendid Gathering of Moon and Planets

Crescent Moon and flag. Credit: Bob King

Look how pretty. This will be the scene from your yard, apartment window or driving west along the freeway Tuesday evening about 45 minutes after sundown. Saturn and the Moon will be in conjunction about 3 degrees apart with Venus 6 degrees to the southeast of the crescent. Source: Stellarium — Look how pretty. This will be the scene from your yard, apartment window or driving west along a freeway Tuesday evening about 45 minutes after sundown. Saturn and the Moon will be in conjunction about 3 degrees apart with Venus 6 degrees to the southeast of the crescent. Source: Stellarium

I love easy and bright. While I often spend time seeking faint nebulae and wandering comets, there’s nothing like just looking up and seeing a beautiful scene aglow in the night sky. No binoculars or telescope needed. That’s exactly what will happen Tuesday November 2, when an attractive crescent Moon will join Saturn and Venus at dusk in the southwestern sky.

The supermoon of March 19, 2011 (right), compared to an average moon of December 20, 2010 (left). Note the size difference. Image Credit: Marco Langbroek, the Netherlands, via Wikimedia Commons. — The Supermoon of March 19, 2011 (right), compared to an average moon of December 20, 2010 (left). November’s Supermoon will be 14% bigger and 30% brighter than a regular Full Moon. Credit: Marco Langbroek / Wikimedia Commons

What a fine threesome they’ll make: Venus the white-hot spark shining at magnitude –4.0; Saturn a mellow magnitude +0.5, some 20 times fainter and the Moon a fingernail crescent above them both. The Moon will be just two days past apogee, the furthest point in its orbit from Earth. Does it look a little smaller than the usual crescent? If you’re a keen watcher of crescents, you just might notice the difference.

In less than two weeks, on November 14, the crescent will have waxed to full, swung around to the opposite end of its orbit, where it will be at perigee, its closest point to Earth. When a Full Moon occurs at perigee, we call it a Supermoon because it’s closer and correspondingly bigger and brighter than a typical Full Moon.

For a variety of reasons, the November Supermoon will come exceptionally close to Earth, the closest one in 70 years as a matter of fact. The last time Earth and Moon embraced each other so tightly was January 26, 1948, the year baseball great Babe Ruth died. But I’m getting ahead of myself. We’ll have much more on the Supermoon soon!

This photo shows the contrast between the bright, sunlit crescent and the ghostly earth-lit Moon. Several prominent craters are identified. Credit: Bob King

Tuesday night you have the pleasure of an eye-catching crescent filled with darkly luminous earthshine, sunlight reflected off our jolly blue and white globe into space that reflects from the Moon and back to Earth. Being twice reflected, the returning light is feeble, giving the Moon a haunted look.

The phases of the Moon and Earth are complementary; when one's a crescent, the other's nearly full. Credit: Bob King, Source: Stellarium — The phases of the Moon and Earth are complementary; when one’s a crescent, the other’s nearly full. Credit: Bob King, Source: Stellarium

Crescent phase is when earthshine is brightest. Why? Phases of Earth and Moon are complementary — when we see a crescent, an astronaut on the Moon would look back to see a nearly Full Earth in the sky. As you’ve already guessed, a Full Earth reflects a great deal more light than a half or crescent. Be sure to point your binoculars at the earth-lit Moon; the contrast of dusky earthlight adjacent to the sunlit crescent gives the scene a striking 3D look.

And if your glass can magnify ten times or more, you’ll get a sneak preview of several of the dark lunar seas or maria in the smoky light. Seas that will by and by ease into sunlight as the lunar terminator, the line separating day from night, rolls ever westward.

Through a small telescope, Venus appears three-quarters full in waning gibbous phase. Saturn's rings are still tipped wide open, and it's brightest moon, Titan, should be easy to spot Tuesday night in a small telescope. Source: Stellarium — Through a small telescope, Venus appears three-quarters full in waning gibbous phase. Saturn’s rings are still tipped wide open, and its brightest moon, Titan, should be easy to spot Tuesday night in a small telescope. Appearances are shown for Nov. 2. North is up and west to the right. Source: Stellarium

Have a small telescope? This may be one of your last easy chances at seeing the planet Saturn before it’s gobbled up by the western horizon. The ringed one has been sinking westward the past couple months and will soon be in conjunction with the Sun. I hate to see a good planet go, that’s why I’m happy to share that Venus will be with us a long, long time. Watch for this most brilliant of planets to rise higher in the southwestern sky as we approach Christmas and then swing to the north through early winter before dropping out of the evening sky in March 2017.

Thank you Venus for lighting our path on the snowy nights that lie ahead!

*** If you’d like learn more about how to find the planets, check out my new book, Night Sky with the Naked Eye. It covers all the wonderful things you can see in the night sky without special equipment. The book publishes on Nov. 8, but you can pre-order it right now at these online stores. Just click an icon to go to the site of your choice – Amazon, Barnes & Noble or Indiebound. It’s currently available at the first two outlets for a very nice discount:

October 28, 2016 by Matt Williams

If it Wasn’t Already Strange Enough, now Saturn’s Hexagon Storm is Changing Color

Saturn makes a beautifully striped ornament in this natural-color image, showing its north polar hexagon and central vortex (Credit: NASA/JPL-Caltech/Space Science Institute)

Ever since the Voyager 2 made its historic flyby of Saturn, astronomers have been aware of the persistent hexagonal storm around the gas giant’s north pole. This a six-sided jetstream has been a constant source of fascination, due to its sheer size and immense power. Measuring some 13,800 km (8,600 mi) across, this weather system is greater in size than planet Earth.

And thanks to the latest data to be provided by the Cassini space probe, which entered orbit around Saturn in 2009, it seems that this storm is even stranger than previously thought. Based on images snapped between 2012 and 2016, the storm appears to have undergone a change in color, from a bluish haze to a golden-brown hue.

The reasons for this change remain something of a mystery, but scientists theorize that it may be the result of seasonal changes due to the approaching summer solstice (which will take place in May of 2017). Specifically, they believe that the change is being driven by an increase in the production of photochemical hazes in the atmosphere, which is due to increased exposure to sunlight.

Natural color images taken by NASA's Cassini wide-angle camera, showing the changing appearance of Saturn's north polar region between 2012 and 2016.. Credit: NASA/JPL-Caltech/Space Science Institute/Hampton University — Natural color images taken by NASA’s Cassini wide-angle camera, showing the changing appearance of Saturn’s north polar region between 2012 and 2016.. Credit: NASA/JPL-Caltech/Space Science Institute/Hampton University

This reasoning is based in part on past observations of seasonal change on Saturn. Like Earth, Saturn experiences seasons because its axis is tilted relative to its orbital plane (26.73°). But since its orbital period is almost 30 years, these seasons last for seven years.

Between November 1995 and August 2009, the hexagonal storm also underwent some serious changes, which coincided with Saturn going from its Autumnal to its Spring Equinox. During this period, the north polar atmosphere became clear of aerosols produced by photochemical reactions, which was also attributed to the fact that the northern polar region was receiving less in the way of sunlight.

However, since that time, the polar atmosphere has been exposed to continuous sunlight, and this has coincided with aerosols being produced inside the hexagon, making the polar atmosphere appear hazy. As Linda J. Spilker, the Cassini mission’s project scientist, told Universe Today via email:

“We have seen dramatic changes in the color inside Saturn’s north polar hexagon in the last 4 years. That color change is probably the result of changing seasons at Saturn, as Saturn moves toward northern summer solstice in May 2017. As more sunlight shines on the hexagon, more haze particles are produced and this haze gives the hexagon a more golden color.”

This diagram shows the main events of Saturn's year, and where in the Saturnian year the Voyager 1 and Cassini missions occurred. Credit: Ralph Lorenz — *Diagram showing he main events of Saturn’s year, and where in the Saturnian year the Voyager 1 and Cassini missions occurred. Credit: Ralph Lorenz*

All of this has helped scientists to test theoretical models of Saturn’s atmosphere. In the past, it has been speculated that this six-sided storm acts as a barrier that prevents outside haze particles from entering. The previous differences in color – the planet’s atmosphere being golden while the polar storm was darker and bluish – certainly seemed to bear this out.

The fact that it is now changing color and starting to look more like the rest of the atmosphere could mean that the chemical composition of the polar region is now changing and becoming more like the rest of the planet. Other effects, which include changes in atmospheric circulation (which are in turn the result of seasonally shifting solar heating patterns) might also be influencing the winds in the polar regions.

Needless to say, the giant planets of the Solar System have always been a source of fascination for scientists and astronomers. And if these latest images are any indication, it is that we still have much to learn about the dynamics of their atmospheres.

“It is very exciting to see this transformation in Saturn’s hexagon color with changing seasons,” said Spilker. “With Saturn seasons over 7 years long, these new results show us that it is certainly worth the wait.”

R. G. French (Wellesley College) et al., NASA, ESA, and The Hubble Heritage Team (STScI/AURA) — *The seasons on Saturn, visualized with images taken by the Hubble Heritage Team. Credit: R. G. French (Wellesley College) et al./NASA/ESA/Hubble Heritage Team (STScI/AURA)*

It also shows that Cassini, which has been in operation since 1997, is still able to provide new insights into Saturn and its system of moons. In recent weeks, this included information about seasonal variations on Titan, Saturn’s largest moon. By April 22nd, 2017, the probe will commence its final 22 orbits of Saturn. Barring any mission extensions, it is scheduled enter into Saturn’s atmosphere (thus ending its mission) on Sept. 15th, 2017.

Further Reading: NASA/JPL/Caltech

August 22, 2016 by Bob King

5 Days, 2 Spectacular Conjunctions

Two planets close and up close. This is the view through a telescope during the extremely close conjunction of Jupiter and Venus on August 27. Credit: Stellarium

Saturn, Mars and Antares are shown on Sunday night August 21 two nights before their lineup. Mars is still far and away the brightest object in the bunch at magnitude -0.5. Details: 35mm lens, f/2.8, ISO 400, 10 seconds. Credit: Bob King — Saturn, Mars and Antares are shown on Sunday night August 21 two nights before their lineup. Mars is still the brightest of the bunch at magnitude –0.5. It will with Saturn at +0.4 and Antares at +1.0. Details: 35mm lens, f/2.8, ISO 400, 10 seconds. Credit: Bob King

Conjunctions of bright planets make for jewelry in the sky. This week, get ready for some celestial shimmer. If you’ve been following the hither and thither of Mars and Saturn near Antares this summer, you know these planets have been constantly on the move, creating all kinds of cool alignments in the southern sky.

On Tuesday night (August 23) the hopscotching duo will fall in line atop Antares in the southwestern sky at nightfall. Mars will sit just 1.5° above the star and Saturn 4° above Mars. Viewed from the Americas and Europe, the line will appear slightly bent. To catch them perfectly lined up, you’ll have to be in central Asia on the following evening, but the view should be pleasing no matter where you live.

This will be the scene facing south at nightfall from the central U.S. on Tuesday night August 23. The two planets and star form a compact gathering that's sure to grab your attention. Credit: Stellarium — This will be the scene facing southwest at nightfall from the central U.S. on Tuesday night August 23. The two planets and star form a compact gathering that’s sure to grab your attention. The moment of conjunction between Mars and Saturn occurs at 11:00 UT (7 a.m. Eastern Aug. 24), but they’ll be below the horizon at that time for the Americas and Europe. Credit: Stellarium

Nice as it is, the Mars-Saturn-Antares lineup is only the warm-up for the big event: the closest conjunction of the two brightest planets this year. On Saturday evening, August 27, Venus and Jupiter will approach within a hair’s breadth of each other as viewed with the naked eye — only 0.1° will separate the two gems. That’s one-fifth of a full moon’s width! While Mars and Saturn will be a snap to spot low in the southwestern sky during their conjunction, Venus and Jupiter snuggle near the western horizon at dusk.

Look for Venus and Jupiter right next to each other 4 degrees (about three fingers held together horizontally) above the western horizon about a half-hour after sunset on August 27. Map: Bob King; source: Stellarium — Look for Venus and Jupiter right next to each other 4° (about three fingers held together horizontally) above the western horizon about a half-hour after sunset on August 27. This map shows the view from across the central U.S. at about 40°N latitude. The two planets will be closest at 22:00 UT (6 p.m. Eastern, 7 p.m. Central, 8 p.m. Mountain and 9 p.m. Pacific). Map: Bob King; source: Stellarium

To make sure you see them, find a place in advance of the date with a wide open view to the west. I also suggest bringing a pair of binoculars. It’s so much easier to find an object in bright twilight with help from the glass. You can start looking about 25 minutes after sunset; Venus will catch your eye first. Once you’ve found it, look a smidge to its lower right for Jupiter. If you’re using binoculars, lower them to see how remarkably close the two planets appear using nothing but your eyeballs. Perhaps they’ll remind you of a bright double star in a telescope or even the twin suns of Tatooine in Star Wars.

Here's what the two planets will look like through a telescope at medium and high magnification, when both will comfortably fit into the same field of view. Stellarium — The two planets will be only 6 arc minutes apart Saturday evening and easily fit in the same field of view of a telescope at high magnification. Jupiter’s four brightest moons will be obvious. If you’re patient and wait for the air to settle, you’ll be able to make out Venus’s waxing gibbous phase. Credit: Stellarium

Have a small telescope? Take it along — Jupiter and Venus are so close together that they easily fit in the same high magnification field of view. Jupiter’s four brightest moons will be on display, and Venus will look just like a miniature version of the waxing gibbous moon. Rarely do the sky’s two brightest planets nearly fuse, making this a not-to-miss event.

Venus and Jupiter do a little square dance over the nights of August 26-28. Jupiter is headed westward toward conjunction with the sun, while Venus is moving away from the sun from our perspective. Stellarium — Venus and Jupiter do a little square dance over the nights of August 26-28. Jupiter is headed westward toward conjunction with the sun, while Venus is moving away from the sun in the opposite direction from our perspective. Credit: Stellarium

If cloudy weather’s in the forecast that night, you can still spot them relatively close together the night before and night after, when they’ll be about 1° or two full moon diameters apart. I get pretty jazzed when bright objects approach closely in the sky, and I’m betting you do, too.

I also don’t mind being taken in by illusion once in a while. During a conjunction, planets only appear close together because we view them along the same line of sight. Their real distances add a dose of reality.

On Saturday evening Venus will be 143 million miles (230 million km) away vs. 592 million miles (953 million km) for Jupiter. In spite of appearing to almost touch, Jupiter is more than four times farther than the goddess planet.

The showpieces in this week's conjunction parade: Jupiter, Venus, Mars and Saturn. Credit: NASA/ESA — The showpieces in this week’s conjunction parade: Jupiter, Venus, Mars and Saturn. Credit: NASA/ESA

That distance translates to the chill realm of the giant gaseous planets where sunlight is weak and ice is common. Try stretching your imagination that evening to sense as best you can the vast gulf between the two worlds.

You might also try taking a picture of them with your mobile phone. I suggest this because the sky will be light enough to get a hand-held photo of the scene. Photos or not, don’t miss what the planets have in store for earthlings this week.

May 26, 2016May 26, 2016 by David Dickinson

A Lord of Rings: Saturn at Opposition 2016

Saturn 2016 — Saturn in early May 2016. Image credit: Efrain Morales.

They’re back. After a wintertime largely devoid of evening worlds, the planets are once again in the evening sky. First Jupiter, then Mars have crossed opposition over the past few months, and now Saturn is set to take center stage later next week, reaching opposition at 7:00 Universal Time (UT) on the night of June 2/3^rd. This places the ringed world in a position of favorable evening viewing, rising in the east as the Sun sets in the west, and riding highest near local midnight across the meridian.

Opposition 2016 sees the planet Saturn looping through the southern realm of the constellation Ophiuchus, making a retrograde run this summer at the Scorpius border before looping back and resuming eastward motion. That’s right: Saturn currently occupies the dreaded ‘13^th house,’ of Ophiuchus, for all you Snake-Bearers out there. Saturn is currently at bright as it can be, at magnitude +0.04.

Saturn rising on the night of June 2nd. Image credit: Starry Night Education Software.

Saturn reaches opposition once every 378 days, as it orbits the Sun at a leisurely pace every 29.5 years. 2016 and the next few oppositions sees Saturn ‘bottoming out,’ sitting around -20 degrees south. Saturn won’t peek northward across the celestial equator again until March 2026. This places the 2016 appearance of Saturn high in the sky south of the equator, transiting about 30 degrees above the southern horizon around midnight for folks observing around 40 degrees north latitude. Saturn also begins looping towards the star-rich region of the galactic equator for a crossing it late next year in December 2017. Saturn sits 9 Astronomical Units (AU) or 1.4 billion kilometers distant on June 3^rd, a slightly larger distance than usual, owing to the fact that the planet is headed towards aphelion on April 17^th, 2018.

The waxing gibbous Moon passes 3.2 degrees north from Saturn on Sunday, June 19^th, just a day before reaching Full.

Watch for a sudden brightening of the planet in early June, known as an ‘opposition surge’ due to what is known as the Seeliger effect. This is a coherent back-scattering of light, focusing it similar to highway retro-reflectors shining your headlights back at you at night. In this case, the Sun is the ‘headlight,’ and the millions of snowball moonlets hiding their shadows from view reaching 100% illumination are the highway retro-reflectors. The effect is subtle, to be sure, but serves to raise the brightness of the planet by about half a magnitude. This should be apparent in an animation sequence shot before, during and after over the span of a about a week. Any takers?

Almost there... the widening tilt of Saturn's rings. image credit and copyright: Andrew Symes (@failedprotostar). — Almost there… the widening tilt of Saturn’s rings. image credit and copyright: Andrew Symes (@failedprotostar).

And speaking of the rings, here’s another reason to check out Saturn this opposition 2016 season. The tilt of rings is about 26 degrees wide as seen from our Earthly perspective… about as wide as they can be. Saturn’s rings were last edge on in 2009, and reach a maximum width of 27 degrees on October 16^th, 2017 before slowly heading towards edge on again in 2025.

The path of Saturn through the last half of 2016. Image credit: Starry Night Education software.

At the eyepiece, Saturn shows a yellowish disk 18” extended to 43” across if you count the rings. Crank up the magnification to over 100x under good seeing, and the black thread of the Cassini division jumps into view. Saturn has 62 moons in all, with +9^th magnitude Titan being the brightest. You’re looking at the most distant surface outpost of humanity, the site of the 2005 landing of the European Space Agency’s Huygens lander. Six moons are readily visible in a small telescope, while the fainter moons Hyperion and Phoebe present a challenge to owners of extreme light buckets. Also, as Saturn heads past opposition and towards eastern quadrature 90 degrees from the Sun on September 2^nd, 2016, watch for the shadow of the bulk of the planet, cast back across the rings.

A sampling of the Moons of Saturn. Image credit: Stellarium.

We never miss a chance to observe Saturn if it’s above the horizon. Saturn is a sure-fire crowd-pleaser for any sidewalk astronomy session, and no one forgets their first glimpse of the glorious ringed world. You can just imagine how much consternation this bizarre-looking planet must have caused Galileo. You can tell just how primitive his first telescope was, as his sketches show off Saturn as more of a two-handled ‘coffee cup’ in appearance. Christaan Huygens first deduced something of the true nature of Saturn’s rings in 1655, correctly claiming that they are physically separated from the disk.

Don’t miss Saturn at opposition next week!

May 11, 2016May 15, 2016 by Evan Gough

New Composite Image Of Saturn’s Polar Vortex Mesmerizes

This image of Saturn's southern polar vortex reveals previously unseen detail of the giant storm. Image: NASA/JPL/Space Science Institute

Atmospheric features on our Solar System’s gas giants dwarf anything similar on Earth. Earth’s atmosphere spawns hurricanes as larger as 1500 km in diameter. But on Saturn, a feature called the southern polar vortex has an eye that is 8,000 km across, or two thirds the diameter of the entire Earth.

A new high-resolution of Saturn’s southern polar vortex captured by the Cassini probe is ten times more detailed than any previous picture, and reveals details that were previously unseen. The image, which is a composite of two images taken by Cassini in July 2008, was captured when the spacecraft was 392,000 km from Saturn, and 56º below the plane of Saturn’s rings. Despite the distance and position, the image still has a resolution of 2 km per pixel.

Previous images of the vortex revealed clouds of immense proportions ringing the edge of the vortex, but showed the vortex itself to be clear. This is similar to a hurricane on Earth, where the eye itself is clear, but is ringed by wall-clouds of towering heights. This new image shows cloud formations within the vortex itself. The vortex is punctuated with wispy white cloud formations, and a smaller vortex at 10:00 within the larger formation.

The clouds inside the vortex are more than just pretty curiosities, of course. They are deep convective structures welling up from deep within Saturn’s atmosphere, and they form their own distinctive ring. This is all the more interesting because the eye of the vortex itself is generally clear, and is considered by scientists to be an area of downwelling.

The convection on display in Saturn’s southern polar vortex is an important clue to understanding how Saturn transfers energy through its atmosphere. On Earth, hurricanes are caused by warm water, and they move across the surface of the ocean as the warm water does.

Saturn, of course, has no liquid ocean, and the vortex is powered by warm atmospheric gases from deeper in Saturn. As they rise and cool they condense into clouds. The vortex also remains stationary, rather than following a warm mass of water. It’s locked into position over Saturn’s south pole.

Cassini’s narrow angle camera captured this new image, using a combination of two spectral filters. One was sensitive to wavelengths of polarized visible light centered at 617 nanometers, and the other to infrared light centered at 750 nanometers.

These two previously released infrared images of Saturn show the entire south polar region with the hurricane-like vortex in the center. The top image shows the polar region in false color, with red, green, and blue depicting the appearance of the pole in three different near-infrared colors (NASA/JPL/University of Arizona)

Cassini is a joint mission of NASA, the ESA, and the Italian Space Agency. It was launched in 1997, and has had its mission extended to September 2017. Cassini will end its mission in what the team operating Cassini is calling a Grand Finale. This will be a series of deep dives between Saturn and its rings, and will end with the spacecraft plunging into Saturn’s atmosphere.

To see a gallery of Cassini images, go here.

At Universe Today, we’ve written about Saturn’s polar vortices before. Have a look:

Violent Polar Cyclones on Saturn Imaged in Unprecedented Detail by Cassini

Hexagonal Structure at Saturn’s North Pole

April 27, 2016December 5, 2021 by Matt Williams

How Do We Terraform Saturn’s Moons?

The moons of Saturn, from left to right: Mimas, Enceladus, Tethys, Dione, Rhea; Titan in the background; Iapetus (top) and irregularly shaped Hyperion (bottom). Some small moons are also shown. All to scale. Credit: NASA/JPL/Space Science Institute

Continuing with our “Definitive Guide to Terraforming“, Universe Today is happy to present our guide to terraforming Saturn’s Moons. Beyond the inner Solar System and the Jovian Moons, Saturn has numerous satellites that could be transformed. But should they be?

Around the distant gas giant Saturn lies a system of rings and moons that is unrivaled in terms of beauty. Within this system, there is also enough resources that if humanity were to harness them – i.e. if the issues of transport and infrastructure could be addressed – we would be living in an age a post-scarcity. But on top of that, many of these moons might even be suited to terraforming, where they would be transformed to accommodate human settlers.

As with the case for terraforming Jupiter’s moons, or the terrestrial planets of Mars and Venus, doing so presents many advantages and challenges. At the same time, it presents many moral and ethical dilemmas. And between all of that, terraforming Saturn’s moons would require a massive commitment in time, energy and resources, not to mention reliance on some advanced technologies (some of which haven’t been invented yet).

February 3, 2016February 3, 2016 by Jason Major

Saturn’s Rings Continue to Surprise Scientists

Composite image of a backlit Saturn, made from Cassini images acquired on July 19, 2013. Saturn's B ring appears darkest and densest here. (NASA/JPL-Caltech/Space Science Institute)

If you try to apply simple common sense to how Saturn’s rings really work you’re going to be sorely mistaken: the giant planet’s signature features run circles around average Earthly intuition. This has been the case for centuries and is still true today after recent news from Cassini that the most opaque sections of rings aren’t necessarily the densest; with Saturn looks literally are deceiving.

Continue reading “Saturn’s Rings Continue to Surprise Scientists”

November 30, 2015December 23, 2015 by Nancy Atkinson

Enceladus, the Jet-Powered Water World

The crescent of Saturn's moon Enceladus hangs above the planet's rings in this image from the Cassini spacecraft. Water jets that spew from the moon’s south pole region are also visible. Credit: NASA/JPL-Caltech/Space Science Institute

I don’t think I’ll ever tire of seeing pictures of Saturn’s moon Enceladus, with those captivating water jets and plumes at its South Pole. And this new images from the Cassini mission is just stunning – and intriguing. Carolyn Porco, the Cassini imaging team lead described the image on Twitter: “Be moved by crescent Enceladus with its ghostly geysers floating above Saturn’s glowing rings.”

There are over 100 geyser jets of varying sizes near Enceladus’s south pole spraying water vapor, icy particles, and organic compounds out into space. Enticingly, this distant and small moon (313 miles or 504 kilometers across) has a global subsurface ocean of liquid water, as tidal forces from Enceladus’ orbital relationship to Saturn and another moon, Dione heats the interior.

Liquid water and the observation of organic chemicals in the plumes of Enceladus make this moon of high astrobiological interest to scientists. In a 2014 paper by Porco and astrobiologist Chris McKay, the due wrote that Enceladus’ “steady plume derives from a subsurface liquid water reservoir that contains organic carbon, biologically available nitrogen, redox energy sources, and inorganic salts. … No other world has such well-studied indications of habitable conditions.”

While the rings of Saturn are also beautiful, they are they are frozen and geologically dead. “The small ring particles are too tiny to retain internal heat and have no way to get warm,” the Cassini imaging team explained on the CICLOPS website.

This image was taken in July of 2015, and was not part of two close flybys of Enceladus in October of this year. Project scientist Linda Spilker hinted there might be some new discoveries from those flybys (see images here and here), as she said, “Cassini’s stunning images are providing us a quick look at Enceladus from this ultra-close flyby, but some of the most exciting science is yet to come.”

This beautiful view of Enceladus and Saturn’s rings looks toward the unilluminated side of the rings from about 0.3 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 29, 2015.

The view was acquired at a distance of approximately 630,000 miles (1.0 million kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase angle of 155 degrees. Image scale is 4 miles (6 kilometers) per pixel.

See a larger version of this image here from NASA.