Occultation of Saturn on Feb. 22, 2014 by Colin Legg
Or, more accurately, watch the Moon pass in front of Saturn. Either way you get the same result: a beautiful video of planetary motion in action!
On the morning of Saturday, Feb. 22, the Moon drifted in front of the planet Saturn from the point of view of certain locations on Earth. Luckily one of those locations was Perth, Australia, where astrophotographer Colin Legg happens to be, and thus we all get to enjoy the fantastic results of his photographic and astronomical acumen.
Check out the video below:
The occultation — as such events are called whenever one celestial object passes in front of, or “hides,” another (the root of the word means “to conceal”) — may make it look like a tiny Saturn is getting absorbed by a giant Moon. But (obviously) they are separated by a vast distance: at the time of the occultation, 9.658 AU, or about 1,444,816,000 kilometers (897.7 million miles).
These sort of events will become a bit more common as the Moon is “headed towards a ‘shallow’ year in 2015 relative to the ecliptic; it will then begin to slowly open back up and ride high around 2025,” according to a recent Universe Today article by David Dickinson.
For those of you interested, Colin lists his equipment as a Celestron C8, f/10, prime focus. His camera is a Canon 5D2, running Magic Lantern RAW video firmware in 3x crop mode @ 1880 x 1056 resolution. Footage was taken at 1/60 sec exposure, ISO 200, 10 fps.
An aurora around Saturn's north pole in 2013. Credit: NASA/ESA/University of Leicester and NASA/JPL-Caltech/University of Arizona/Lancaster University
Above is the latest rave-like video from NASA. While the images are reminiscent of what could play during an awesome Friday night party, what you’re actually seeing is a timelapse of auroras on Saturn. These pictures are pretty to look at, but they also tell us more about how the sun’s belches of stuff influence the magnetic field around the ringed gas giant.
“Saturn’s auroras can be fickle — you may see fireworks, you may see nothing,” stated Jonathan Nichols of the University of Leicester in England, who led the work on the Hubble Space Telescope images shown in the video. “In 2013, we were treated to a veritable smorgasbord of dancing auroras, from steadily shining rings to super-fast bursts of light shooting across the pole.”
The light show was captured by both the Saturn-orbiting Cassini spacecraft and the Earth-orbiting Hubble. Cassini managed to nab its images from three Saturn distances away (which is apparently an unusually close vantage point.) This location “provided a look at the changing patterns of faint emissions on scales of a few hundred miles (kilometers) and tied the changes in the auroras to the fluctuating wind of charged particles blowing off the sun and flowing past Saturn,” NASA stated.
Here are a few things scientists are learning (or hoping to learn soon) from the light show:
How auroras are formed. The Cassini images suggest that as magnetic field lines forge new links, this is where the storms are centered. This process happens on Earth, so it would make sense for it to happen elsewhere. Researchers also found that some of the auroras stick close to the orbital position of Mimas, suggesting that the moon may be influencing some of the storms (a process already known to happen with Enceladus).
The nature of Saturn’s atmosphere. While the answers are still forthcoming, scientists are examining why the top of Saturn’s atmosphere (and other gas giants) are warmer than would be expected given how far they are from the sun. “By looking at these long sequences of images taken by different instruments, we can discover where the aurora heats the atmosphere as the particles dive into it and how long the cooking occurs,” stated Sarah Badman, a Cassini visual and infrared mapping spectrometer team associate at Lancaster University, England.
What color the auroras are. Red on the bottom, and purple on the top, depending on how Saturn’s hydrogen is excited and what light it emits. (For reference, Earth’s is green on bottom and red at top due to excitement of nitrogen and oxygen).
Where charged particles around Saturn go. More data from the W.M. Keck Observatory and NASA’s Infrared Telescope Facility (both in Hawaii) could show “how particles are ionized in Saturn’s upper atmosphere,” NASA stated. Better yet, scientists can compare that information to the stuff gathered from outside of Earth’s atmosphere by Hubble and Cassini. This will allow them to see what distortions the ground-based observatories experienced due to Earth’s atmosphere, and improve the accuracy of the observations.
Not bad work for a single music video, isn’t it? For more information on auroras on Saturn, check out these past Universe Today stories:
Saturn's F ring appears distorted in this October 2013 picture from the Cassini spacecraft. The twisting may be because the F ring is crashing repeatedly into a "single small object", NASA stated. Credit: NASA/JPL-Caltech/Space Science Institute
What’s up with this distortion? This picture from the Cassini spacecraft shows some kind of twist happening in the F ring of Saturn. Scientists in fact have seen other strange shapes in this delicate ring, indicating that something is disturbing it from time to time.
“Saturn’s F ring often appears to do things other rings don’t. In this Cassini spacecraft image, a strand of ring appears to separate from the core of the ring as if pulled apart by mysterious forces. Some ring scientists believe that this feature may be due to repeated collisions between the F ring and a single small object,” NASA stated this month.
There’s a debate in the scientific community about where the rings arose in the first place. “It’s been going back and forth for ages and it still goes back and forth. Are they old, or have they been there a long period of time? Are they new? I don’t know what to think, to be quite honest. I’m not being wishy-washy, I just don’t know what to think anymore,” Kevin Grazier, a planetary scientist with the Cassini mission for over 15 years, told Universe Today in December.
While this picture dates from October, you can check out Cassini images as they come in to NASA’s raw image database. Even in unprocessed form, the planet and its rings look beautiful — as you can clearly see in samples below.
The bulk of Saturn looms to the side of this shot of Saturn’s rings taken in February 2014 by the Cassini spacecraft. Credit: NASA/JPL/Space Science InstituteThe variety of Saturn’s rings is visible in this raw shot from the Cassini spacecraft taken in February 2014. Credit: NASA/JPL/Space Science InstituteAlthough Saturn’s rings look solid and substantial in images such as this, they are made up of many tiny, icy objects collecting as thin as 6.2 miles (10 kilometers) deep. Image taken by the Cassini spacecraft in February 2014. Credit: NASA/JPL/Space Science Institute
Shepherd moon Prometheus hovers just inside the reflective F ring
Lit by eerie, reflected light from Saturn’s F ring (and a casting a faint shadow through a haze of icy “mist”) Saturn’s moon Prometheus can be seen in the raw image above, captured by Cassini’s narrow-angle camera on Feb. 5 from a distance of 667,596 miles (1,074,392 km). It’s also receiving some light reflected off Saturn, which is off frame at the top (where the outermost edge of the A ring and the Keeler gap can be seen.)
As the potato-shaped Prometheus approaches the ring it yanks fine, icy material in towards itself, temporarily stretching the bright particles into long streamers and gaps and even kicking up bright clumps in the ring. It’s a visual demonstration of gravity at work! Watch an animation of this below, made from images acquired just before and after the one above:
Streamers and clumps created by the passing Prometheus on Feb. 5, 2014. (NASA/JPL/SSI. Animation by Jason Major.)
At its longest Prometheus is about 92 miles (148 km) across, but only 42 miles (68 km) in width. It circles Saturn in a wave-shaped, scalloping orbit once every 14.7 hours.
Comet Lovejoy still shows both an ion tail (blue) and dust tail in this photo taken Jan. 12 from Stixendorf, Austria. Credit: Michael Jaeger
My hands are still cold from the experience, but there’s no denying the pleasure I felt at seeing C/2013 R1 Lovejoy and C/2012 X1 LINEAR through the telescope this morning. Some comets fizzle, others fall apart, but these vaporous hunks have hung in there for months like steadfast friends that stick with you through hard times and good.While no longer visible with the naked eye, 50mm binoculars easily show it as a magnitude 7 fuzzy glow with a short, faint tail pointing up and away to the northwest. I had no difficulty seeing it even with a last quarter moon glaring in the south.
Comets Lovejoy and X1 LINEAR are neighbors in northern Ophiuchus this month and next. This map shows the sky facing east about 1 hour 45 minutes before sunrise shortly before the start of morning twilight. Tick marks show the comets’ position every 5 days. Click to enlarge. Detailed map below. Created with Chris Marriott’s SkyMap software.
Rising around 3 a.m., Lovejoy is best placed for viewing just before the start of dawn when it climbs to about 30 degrees altitude in Ophiuchus. Lucky for us, Lovejoy will spend the next few mornings very close to the easy naked eye star 72 Ophiuchi, located 3 fists held at arm’s length to the lower right of brilliant Vega. It’s not often that a fairly bright comet passes this close to a helpful guide star. Don’t miss this easy catch. Soon the moon won’t be any trouble either as it skedaddles eastward and dwindles to a crescent in the coming mornings.
This deeper map shows stars to about magnitude 8. Although both comets appear to be getting lower every morning, the westward seasonal drift of the stars will keep them in good view for the next few months. Click to enlarge. Created with Chris Marriott’s SkyMap software
Telescopic views of Lovejoy show a much diminished coma and tail compared to its heyday in early December. Still, the nucleus remains bright and very condensed within the 3′ diameter gauzy coma; a faint and silky tail 2/3 of a degree long flowed across the field of view of my 15-inch (37-cm) reflector like a bride’s train. According to the excellent Weekly Information about Bright Comets site maintained by Seiichi Yoshida, Lovejoy should glow brighter than magnitude 8, what I consider the “bright” comet cutoff, through early February. Given that Lovejoy remains the brightest predicted comet visible till summer, show it some love the next clear night.
Comet C/2012 X1 LINEAR shows a green coma from fluorescing gases and a short tail in this photo made on Jan. 15, 2014. Credit: Rolando Ligustri
If Lovejoy’s a fading celebrity, X1 LINEAR suffered a mid-life crisis and snapped out of it with a whole new attitude. Like Comet Holmes in 2007, it catapulted in brightness overnight in last October, blossoming from a 14th magnitude blip into a bright, expanding puffball briefly visible in ordinary binoculars. As expected, the comet soon faded. But on its return to obscurity, X1 surprised again, re-brightening and growing a short tail. Now it’s humming along at 9th magnitude thank you very much. You’ll find it gliding across northern Ophiuchus not far from Lovejoy (more about that in a minute).
Very different appearance of C/2012 X1 LINEAR during outburst on Oct. 21, 2013. Credit: Ernesto Guido, Martino Nicolini & Nick Howes
My binoculars won’t show the comet but a 6-inch telescope will do the trick. Overall weaker in appearance than Lovejoy, X1 LINEAR has a slightly larger, more diffuse coma, brighter core and a short, faint tail pointing to the northwest. The comet will remain a fine target for smaller scopes through early March when it’s predicted to glow between magnitude 8 and 9.
Comets Lovejoy and X1 LINEAR will be closest together on the morning of Feb. 6 CST. A plethora of deep sky objects near them will make for a complete morning’s worth of sky watching! Click to enlarge. Created with Chris Marriott’s SkyMap software
Looking at the maps, you’ll see that our two comets’ paths intersect. While they won’t overlap on the same morning, Lovejoy and X1 LINEAR will be in conjunction on Feb. 6 when they’ll be just 2 degrees apart. Get that camera ready! Guided telephoto and wide-field telescopes will be perfect for catching this unusual duet.
Before I sign off, don’t forget all the other good morning stuff: Mars hovers above Spica high in the south-southwestern sky, Saturn invites inspection in the southeast and Venus is back in view in the east-southeast 45 minutes before sunup. A delicate crescent moon shines near Venus on Jan. 28 and 29. Such riches.
An occultation occurs when one foreground celestial object completely obscures another. Technically, a total solar eclipse is an occultation of the Sun by the Moon, although it’s never referred to as such. The term finds modern usage mainly for the blocking of stars and planets by the Moon. Very occasionally, an asteroid or planet can occult a distant star as well.
And yes, the modern astronomical term “occultation” traces its hoary roots back to the days when astronomy was intertwined with the pseudoscience of astrology. To this day, the term still makes some folks wonder if astronomers are secretly casting horoscopes. Trust us, you’re still on a solid astronomical footing to use the term “occultation.”
Unfortunately, the January 25thoccultation of Saturn by the Moon will only grace part of Antarctica, southern Argentina and Chile, and the Falkland Islands post-sunrise. The rest of us still will see a very photogenic pass of Saturn near the waning crescent Moon on the morning of Saturday, January 25th. The Moon will pass just about a degree — two times its apparent width — south of Saturn for northern hemisphere observers.
The footprint for the January 25th occultation of Saturn by the Moon. dashed lines indicate where the events occurs in the daytime sky. (Created using Occult 4.0.11 software)
Both the Moon and Saturn will reside in the astronomical constellation of Libra this weekend during closest passage. The pair will rise around 2 AM local. After their brief tryst, the Moon will head towards New on January 30th while Saturn will continue to rise successively earlier as its heads towards opposition and the start of evening Saturn observing season on May 10th, 2014.
January 2014 is also notable for having two New Moons, an occurrence informally known as a Black Moon. This occurs again this year in March, and February 2014 is devoid of a New Moon. February is the only month that can be “missing a Moon phase” as it’s the only one shorter the synodic period of 29.5 days, in which the Moon returns to like phase.
Saturn as imaged by the author in 2012.
In the telescope, Saturn will present a +0.8 magnitude disk 16” across (38” with rings from tip-to-tip). Saturn’s rings are tipped open to our line of sight by about 22 degrees in 2014, and are widening towards a maximum of 27 degrees in 2016 through 2017. If you have an equatorial telescope with tracking capability, it may be possible this weekend to follow Saturn up into the daytime sky. Though Saturn isn’t quite bright enough to see in the daytime unaided, it might just be possible to spy using binoculars on the 25th using the nearby crescent Moon as a guide. Saturn is a tough daytime target to be sure, but it’s not impossible to acquire with a little skill and patience.
The current cycle of occultations of Saturn began on December 1st, 2013 and ends on November 22nd, 2014. The cycle will move progressively northward through the year.
The Moon and Saturn put on a repeat performance over almost the same exact location (this time in darkness) on April 17th, 2014, and the best event in the cycle for North America will be the August 31st daytime occultation of Saturn by the waxing crescent Moon.
Now for the wow factor of what you’re seeing. On Saturday morning, the Moon is just over 371,000 kilometres distant, or a little over a light second away. Saturn is over four thousand times more remote at just over 10.1 astronomical units (AUs) distant, which works out to 1.5 billion kilometres, or over 83 light minutes away. And although the Moon is over a 112 times larger in apparent diameter than Saturn as seen from the Earth, the globe of Saturn is actually over 34 times bigger.
Saturn and the Moon crossing the local meridian shortly after sunset on January 25th. Created using Starry Night Education Software.
And though we’ve been to the Moon lots since the dawn of the Space Age, only two spacecraft (Voyagers 1 and 2) have made brief flybys of the ringed world, and only one – Cassini – has orbited it. Note that China’s Chang’e-3 lander and rover are about to experience their second sunset this weekend as well from the lunar surface since landing on the Moon last month.
And although lots of planets get occulted by the Moon in 2014, no stars brighter than +1st magnitude lie in its path. In fact, the next cycle of bright star occultations by the Moon doesn’t resume until the Moon meets Aldebaran in January 29th, 2015.
There are, however, over a 100 lesser events involving the Moon occulting naked eye stars worldwide in 2014. Two such events occur this week as well, when the 48% illuminated Moon occults the +4.5th magnitude star Lambda Virginis for west-central South America on the morning of January 24th, and the occultation of the +2.8th magnitude star Alpha Librae (Zubenelgenubi) for central Asia on January 25th.
Don’t miss these celestial events, and be sure to send those pics in to Universe Today… there’s something for everyone happening in the sky this week worldwide!
Cassini narrow-angle camera image of Janus from Sept. 10, 2013 (NASA/JPL-Caltech/SSI)
One of 62 moons discovered thus far orbiting giant Saturn, Janus is a 111-mile (179-km) -wide pockmarked potato composed of rock and ice rubble. The image above shows Janus as seen with Cassini’s narrow-angle camera on September 10, 2013, from a distance of 621,000 miles (1 million km), floating against the blackness of space.
Despite its apparent isolation in the image above, though, Janus isn’t alone. It shares its orbit around Saturn with its slightly smaller sister moon Epimetheus, and they regularly catch up to each other — and even switch places.
Janus and Epimetheus: Saturn’s “dancing moons” (NASA/JPL/SSI)
Janus and Epimetheus travel in nearly the same track, about 94,100 miles (151,500 km) out from Saturn. They occasionally pass each other, their gravity causing them to switch speeds and positions as they do; Janus goes faster and higher one time, slower and lower the next – but the two never come within more than about 6,200 miles of each other.
The two moons switch positions roughly every four years.
This scenario is referred to in astrophysics as a 1:1 resonance. Astronomers were initially confused when the moons were discovered in 1966 as it wasn’t known at the time that there were actually two separate moons in a single orbit. (This wasn’t confirmed until Voyager 1’s visit to Saturn in 1980.) It’s been suggested that Janus and Epimetheus will eventually come to orbit a single Lagrangian point around Saturn instead of trading places… in about another 20 million years.
The view above looks toward the Saturn-facing side of Janus. Covered in both dark and light colored material, Janus’ surface is thought to be coated with a layer of fine dust that slides down its steeper slopes, revealing the brighter ice beneath.
Cassini image of Janus from April 2010 (NASA/JPL-Caltech/SSI)
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)
Cassini couldn’t make it to the mall this year to do any Christmas shopping but that’s ok: we’re all getting something even better in our stockings than anything store-bought! To celebrate the holiday season the Cassini team has shared some truly incredible images of Saturn and some of its many moons for the world to “ooh” and “ahh” over. So stoke the fire, pour yourself a glass of egg nog, sit back and marvel at some sights from a wintry wonderland 900 million miles away…
Thanks, Cassini… these are just what I’ve always wanted! (How’d you know?)
Saturn’s southern hemisphere is growing more and more blue as winter approaches there — a coloration similar to what was once seen in the north when Cassini first arrived in 2004:
Saturn’s southern hemisphere images from a million miles away (Credit: NASA/JPL-Caltech/Space Science Institute)
(The small dark spot near the center right of the image above is the shadow of the shepherd moon Prometheus.)
Titan and Rhea, Saturn’s two largest moons, pose for Cassini:
Rhea (front) and Titan, images by Cassini in June 2011 (Credit: NASA/JPL-Caltech/Space Science Institute)
The two moons may look like they’re almost touching but in reality they were nearly half a million miles apart!
Titan’s northern “land of lakes” is visible in this image, captured by Cassini with a special spectral filter able to pierce through the moon’s thick haze:
Titan images by Cassini on Oct. 7, 2013 (Credit: NASA/JPL-Caltech/Space Science Institute)
The frozen, snowball-like surface of the 313-mile-wide moon Enceladus:
Enceladus: a highly-reflective and icy “snowball in space” (Credit: NASA/JPL-Caltech/Space Science Institute)
(Even though Enceladus is most famous for its icy geysers, first observed by Cassini in 2005, in these images they are not visible due to the lighting situations.)
Seen in a different illumination angle and in filters sensitive to UV, visible, and infrared light the many fractures and folds of Enceladus’ frozen surface become apparent:
View of the trailing face of Enceladus (Credit: NASA/JPL-Caltech/Space Science Institute)
Because of Cassini’s long-duration, multi-season stay in orbit around Saturn, researchers have been able to learn more about the ringed planet and its fascinating family of moons than ever before possible. Cassini is now going into its tenth year at Saturn and with much more research planned, we can only imagine what discoveries (and images!) are yet to come in the new year(s) ahead.
“Until Cassini arrived at Saturn, we didn’t know about the hydrocarbon lakes of Titan, the active drama of Enceladus’ jets, and the intricate patterns at Saturn’s poles,” said Linda Spilker, the Cassini project scientist at NASA’s Jet Propulsion Laboratory. “Spectacular images like these highlight that Cassini has given us the gift of knowledge, which we have been so excited to share with everyone.”
The full mosaic from the Cassini imaging team of Saturn on July 19, 2013... the "Day the Earth Smiled"
Just to demonstrate how far-reaching that Saturn snapshot of Earth this year was, the Skopje Astronomical Society (from Macedonia) made a video celebrating “The Day The Earth Smiled”, when the Cassini spacecraft looked at Earth on July 19 and thousands of people made pictures and video showing what they were doing at that time.
Watch the video, then look at some stunning pictures of Saturn below the jump.
Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute. Assembled by Gordan Ugarkovic.
Mosaic of Saturn seen in eclipse in September 2006. Earth is the bright dot just inside the F ring at upper left. (CICLOPS/NASA/JPL-Caltech/SSI)A false-color view of Saturn’s storm, as seen through Cassini’s wide-angle camera. The blue bands at the edge are Saturn’s rings. Credit: NASA/JPL-Caltech/SSISaturn, its rings and three moons are visible in this image from Cassini. Credit: NASA/ESA
A white storm in Saturn’s northern hemisphere, as seen on Dec. 14, 2010. Credit: Anthony Wesley
At Saturn, NASA's Cassini spacecraft snapped pictures showing a high-resolution view of a hexagon-shaped jet stream. Credit: NASA/JPL-Caltech/SSI/Hampton
A raging hurricane is creating a “suck zone” at Saturn’s north pole. The handy Cassini spacecraft recently captured a bunch of images of the six-sided jet stream surrounding the storm, which mission managers then put together into an awesome animation showing the wind currents shifting. (You can see the animation below the jump.)
The feature is pretty in a picture, but NASA has a special interest because there is nothing else like this anywhere in our solar system, the agency stated. The immense storm stretches 20,000 miles (30,000 kilometers) across with winds whipping in its jet stream at 200 miles per hour (322 kilometers per hour). And despite all the turbulence, the storm is staying put at the north pole for reasons scientists are still trying to understand.
“The hexagon is just a current of air, and weather features out there that share similarities to this are notoriously turbulent and unstable,” said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena. “A hurricane on Earth typically lasts a week, but this has been here for decades — and who knows — maybe centuries.”
An animation of Cassini Saturn images showing a hexagonal jet stream surrounding a storm at the north pole. Credit: NASA/JPL-Caltech/SSI/Hampton University
Cassini has been orbiting Saturn since 2004, but it’s only since last year that it’s been able to peer at the hexagon with much success. That’s because the angle of the sun is finally favorable to peer at the storm. This has allowed scientists, for example, to look at the types of particles inside. They discovered that the jet stream is a sort of barrier around the storm, delineating a location with a lot of small haze particles and few large haze particles. (It’s the opposite outside of the jet stream). Scientists said it looks like the Antarctic ozone hole on Earth.
“The Antarctic ozone hole forms within a region enclosed by a jet stream with similarities to the hexagon,” NASA stated.
“Wintertime conditions enable ozone-destroying chemical processes to occur, and the jet stream prevents a resupply of ozone from the outside. At Saturn, large aerosols cannot cross into the hexagonal jet stream from outside, and large aerosol particles are created when sunlight shines on the atmosphere. Only recently, with the start of Saturn’s northern spring in August 2009, did sunlight begin bathing the planet’s northern hemisphere.”
Should Cassini have enough funding to function for a few more years, scientists are eager to watch as Saturn gets to its summer solstice in 2017 and the lighting gets even better around the north pole.
NASA also held an interesting Google+ Hangout yesterday (Nov. 4) about Saturn and the Cassini mission that featured Carolyn Porco, director of the Cassini Imaging Team and the Cassini Imaging Central Laboratory for Operations (CICLOPS). The whole video below is worth a watch, but here’s a little tidbit to let you know some of what was talked about:
“If you took all the mass of Saturn’s rings and recomposed it into a moon, it would be no bigger than Enceladus, so it’s a big spectacle coming from little mass,” Porco said. “The main rings are very thin, only about 30 feet [9 meters] thick, no bigger than about 2 stories in a modern day building. Despite the fact they are about 280,000 km [174,000 miles] across.”
