At left, Photograph of Jupiter's enormous Great Red Spot in 1879 from Agnes Clerk's Book " A History of Astronomy in the 19th Century".
Watch out! One day it may just go away. Jupiter’s most celebrated atmospheric beauty mark, the Great Red Spot (GRS), has been shrinking for years. When I was a kid in the ’60s peering through my Edmund 6-inch reflector, not only was the Spot decidedly red, but it was extremely easy to see. Back then it really did span three Earths. Not anymore.
Drawing of Jupiter made on Nov. 1, 1880 by French artist and astronomer Etienne Trouvelot showing transiting moon shadows and a much larger Great Red Spot.
In the 1880s the GRS resembled a huge blimp gliding high above white crystalline clouds of ammonia and spanned 40,000 km (25, 000 miles) across. You couldn’t miss it even in those small brass refractors that were the standard amateur observing gear back in the day. Nearly one hundred years later in 1979, the Spot’s north-south extent has remained virtually unchanged, but it’s girth had shrunk to 25,000 km (15,535 miles) or just shy of two Earth diameters. Recent work done by expert astrophotographer Damian Peach using the WINJUPOS program to precisely measure the GRS in high resolution photos over the past 10 years indicates a continued steady shrinkage:
2003 Feb – 18,420km (11,445 miles)
2005 Apr – 18,000km (11,184)
2010 Sep – 17,624km (10,951)
2013 Jan – 16,954km (10,534)
2013 Sep – 15,894km (9,876)
2013 Dec – 15,302km (9,508) = 1.2 Earth diameters
Voyager 1 Jupiter time lapse animation, a reprocessed high-resolution view. Enlarge to full screen to see the GRS rotation best. Credit: NASA / JPL / Bjorn Jonsson / Ian Regan
If these figures stand up to professional scrutiny, it make one wonder how long the spot will continue to be a planetary highlight. It also helps explain why it’s become rather difficult to see in smaller telescopes in recent years. Yes, it’s been paler than normal and that’s played a big part, but combine pallor with a hundred-plus years of downsizing and it’s no wonder beginning amateur astronomers often struggle to locate the Spot in smaller telescopes . This observing season the Spot has developed a more pronounced red color, but unless you know what to look for, you may miss it entirely unless the local atmospheric seeing is excellent.
Reprocessed view by Bjorn Jonsson of the Great Red Spot made by Voyager 1 in 1979 reveals an incredible wealth of detail. The Spot is a vast, long-lived. hurricane-like storm located between opposing jet streams in Jupiter’s southern hemisphere. Click to enlarge. Credit: NASA/
Not only has the Spot been shrinking, its rotation period has been speeding up. Older references give the period of one rotation at 6 days. John Rogers (British Astronomical Assn.) published a 2012 paper on the evolution of the GRS and discovered that between 2006 to 2012 – the same time as the Spot has been steadily shrinking – its rotation period has spun up to 4 days. As it shrinks, the storm appears to be conserving angular momentum by spinning faster the same way an ice skater spins up when she pulls in her arms.
Drawings by Cassini of what is presumably the Great Red Spot from 1665 to 1677. South is up. In size and shape it greatly resembles the current Red Spot. (From Amedee Guillemin’s “Le Ciel” 1877)
Rogers also estimated a max wind speed of 300 mph, up from about 250 mph in 2006. Despite its smaller girth, this Jovian hurricane’s winds pack more punch than ever. Even more fascinating, the Great Red Spot may have even disappeared altogether from 1713 to 1830 before reappearing in 1831 as a long, pale “hollow”. According to Rogers, no observations or sketches of that era mention it. Surely something so prominent wouldn’t be missed. This begs the question of what happened in 1831. Was the “hollow” the genesis of a brand new Red Spot unrelated to the one first seen by astronomer Giovanni Cassini in 1665? Or was it the resurgence of Cassini’s Spot?
14-frame animation showing the circulation of Jupiter’s atmosphere spans 24 Jovian days, or about 10 Earth days. The passage of time is accelerated by a factor of 600,000. Credit: Voyager 1 / NASA
Clearly, the GRS waxes and wanes but exactly what makes it persist? By all accounts, it should have dissipated after just a few decades in Jupiter’s turbulent environment, but a new model developed by Pedram Hassanzadeh, a postdoctoral fellow at Harvard University, and Philip Marcus, a professor of fluid dynamics at the University of California-Berkeley, may help to explain its longevity. At least three factors appear to be at play:
* Jupiter has no land masses. Once a large storm forms, it can sustain itself for much longer than a hurricane on Earth, which plays itself out soon after making landfall.
* Eat or be eaten: A large vortex or whirlpool like the GRS can merge with and absorb energy from numerous smaller vortices carried along by the jet streams.
* In the Hassanzadeh and Marcus model, as the storm loses energy, it’s rejuvenated by vertical winds that transport hot and cold gases in and out of the Spot, restoring its energy. Their model also predicts radial or converging winds within the Spot that suck air from neighboring jet streams toward its center. The energy gained sustains the GRS.
Feb. 1 photo of Oval BA, a.k.a. Red Spot Jr. It’s the first significant new red spot ever observed on Jupiter and located at longitude 332 degrees (Sys. II) The spot about half the width of the more familiar Great Red Spot. Credit: Christopher GoIf the shrinkage continues, “Great” may soon have to be dropped from the Red Spot’s title. In the meantime, Oval BA (nicknamed Red Spot Jr.) and about half the size of the GRS, waits in the wings. Located along the edge of the South Temperate Belt on the opposite side of the planet from the GRS, Oval BA formed from the merger of three smaller white ovals between 1998 and 2ooo. Will it give the hallowed storm a run for its money? We’ll be watching.
Time-lapse of Jupiter’s atmospheric motions centered on the Great Red Spot photographed by Paolo Porcellana. Each cylindrical/spherical map of the planet is a mosaic of 4-6 pictures made with 11 and 14-inch telescopes.
Special Guests: Stephen Pakbaz, designer of the LEGO Mars Rover Kit, and Ray Sanders from CosmoQuest, who is unboxing and building the kit as we hang out!
Astrophotographer Michael Phillips with the gear used to capture the Jupiter rotation animation. Credit-Michael Phillips
It’s always a thrill to watch the action at Jupiter, as its moons pass in front of and behind the gas giant planet. We wrote recently about this month’s opposition of Jove on January 5th, marking the start of the Jupiter evening viewing season for 2014.
Astrophotographer Michael A. Philips also recently undertook a challenging series of sequences of Jupiter and its moons Io and Ganymede, with stunning results. You can see the motion of Jupiter’s rotation, the Great Red Spot and even a bit of cloud swirl as Io disappears behind Jupiter and Ganymede begins to transit in front and cast a shadow back onto the Jovian cloud tops.
Concerning the capture, Michael wrote on his blog:
“This night was a lucky night. I had not looked at the weather forecast enough to know if it would be good or not. Cold temps aside, I decided earlier in the day to set up and go out with the 14” f/4.5 scope named Akule. As an added bonus, Mitchell Duke tipped me off to a transit of the Jovian moon, Ganymede.”
Note that Jupiter and its moons are currently casting their shadows nearly straight back from our perspective. Expect that to change, however, in the coming months,as Jupiter heads towards eastern dusk quadrature on April 1st and we see the action from a sideways angle. Watch the video in full screen mode and you’ll note that Mike captured some detail on the surface of Ganymede as well! Generally, at the eyepiece, the moons of Jupiter disappear entirely due to low contrast against the bulk of the planet, with only the black dot of the shadow seen… this video capture gives the ingress of Ganymede at the start of the transit a great 3-D appearance.
Webcam imaging of planets has really taken off in the past decade, with backyard astronomers now routinely capturing images that far surpass professional and textbook images from just a decade prior. Great images can be taken using nothing more than a telescope, a laptop, free image stacking software such as Registax, and a webcam converted to fit into an eyepiece holder… you may find that you’ve got the gear sitting around to image Jupiter, tonight.
Mr. Phillips rig, however, is a little more advanced. He notes in the description of the video that he’s using a Flea3 camera from PointGrey Research with a 5x Barlow lens yielding a 9200mm focal length. He’s also shooting at 120 frames per second, and taking successive red, green and blue images for 30 seconds. Finally, a derotation of Jupiter – yes, it really rotates that quickly, even in a short sequence – is accomplished using a sophisticated program named WINJupos.
Video stacking gives processors the ability to “freeze” and nab the best moments of seeing from thousands of frames. Some imagers hand select frames one by one, though many programs, such as Registax, use algorithms to nab the best frames from a preselected percentage of the total shot.
Local seeing conditions also play a key role in image capturing.
“I moved far away from the house as possible, and I think that helped some,” Michael noted. “I also started cooling the spit out of the mirror, aggressively. Even when cooled for a few hours in the winter, the heat in the Pyrex mirror comes back. I think there’s a small heat engine inside the beast!”
For best results, imagers tend to go after planets when they’re at their highest in the sky, and viewed through the least amount of turbulent atmosphere. This is when a planet is transiting the local north to south meridian, and when it’s at opposition, which Jupiter is this month. At opposition, a planet transits at local midnight. The same goes for the best opportunities for visual observing as well.
Shadow transits of Jupiter’s moons are also just plain fun to watch. In an often unchanging universe, they offer a chance to see something unfolding in real time. Jupiter has the fastest rotation of any planet at 9.9 hours, and the large Galilean moons of Io, Europa, Ganymede and Callisto are tidally locked in their rotation, keeping one hemisphere permanently turned towards Jupiter like the Moon does orbiting the Earth. The inner three moons also keep a 1:2:4 orbital resonance, assuring you’ll never see more than three of the four Galilean moons transiting from your line of sight at once. You can see two of the inner three moons, plus Callisto in transit, but never all four at the same time! A triple transit last occurred on October 12th, 2013, and will next occur for observers in eastern Europe and Africa this year on June 3rd.
We’re also currently in the midst of a series of shadow transits for the outermost Galilean moon Callisto, which end in July 2016. Can you identify the different moons by the size and hue of shadows they cast? Sky & Telescope publishes a great table for the ingress and egress of Jupiter’s moons. You can also check them out using the freeware program Stellarium.
The double shadow transit of February 6th as seen at 11:22 UT. Created by the author using Starry Night Education software.
Can’t wait that long? A double shadow transit involving Europa and Callisto occurs in just a few weeks for western North America from 10:20 UT-12:44UT on the morning of February 6th, a chance for another stunning animation sequence…
Gorgeous shot of the Moon-Jupiter conjunction on January 14, 2014 and a beautiful lunar halo, as seen from Ankara, Turkey. Credit and copyright: M. Ra?id Tu?ral
Last night, the Moon and Jupiter snuggled up together in the evening sky, passing within 4°51′ of each other. Folks in Ankara, Turkey got an added benefit to the conjunction, a gorgeous lunar halo. This shot by M. Rasid Tugral is just lovely. The duo stayed together through the night, and you MUST see below for another awesome view of the conjunction at dawn as seen from Pennsylvania in the US:
The morning’s setting Moon and Jupiter, on January 15th, 2014. Photo taken near White Haven, Pennsylvania. Credit and copyright: Tom Wildoner.
So many things make this such a great photo: the conjunction, of course, but the colors, the shadow of the photographer, and the landscape all combine for a simply stunning image.
Thanks to both of our photographers for sharing, and you can always see more great astrophotos at our Flickr page.
If you’re looking for more conjunctions with the Moon, there are a couple coming up: On Wednesday, Jan 22, 2014 mars will be near the Moon, and on Saturday January 25, 2014 the Moon will meet up with Saturn. Find out more at In-The-Sky.org.
Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.
This colorized composite shows more than half of Earth’s disk over the coast of Argentina and the South Atlantic Ocean as the Juno probe slingshotted by on Oct. 9, 2013 for a gravity assisted acceleration to Jupiter. The mosaic was assembled from raw images taken by the Junocam imager. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
Juno Portrait of Earth
This false color composite shows more than half of Earth’s disk over the coast of Argentina and the South Atlantic Ocean as the Juno probe slingshotted by on Oct. 9, 2013 for a gravity assisted acceleration to Jupiter. The mosaic was assembled from raw images taken by the Junocam imager. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
See below a gallery of Earth from Juno[/caption]
During a crucial speed boosting slingshot maneuver around Earth on Oct. 9, NASA’s Jupiter-bound Juno probe snapped a dazzling gallery of portraits of our Home Planet over the South American coastline and the Atlantic Ocean. See our mosaics of land, sea and swirling clouds above and below, including several shown in false color.
But an unexpected glitch during the do or die swing-by sent the spacecraft into ‘safe mode’ and delayed the transmission of most of the raw imagery and other science observations while mission controllers worked hastily to analyze the problem and successfully restore Juno to full operation on Oct. 12 – but only temporarily!
Because less than 48 hours later, Juno tripped back into safe mode for a second time. Five days later engineers finally recouped Juno and it’s been smooth sailing ever since, the top scientist told Universe Today.
“Juno is now fully operational and on its way to Jupiter,” Juno principal investigator Scott Bolton told me today. Bolton is from the Southwest Research Institute (SwRI), San Antonio, Texas.
“We are completely out of safe mode!”
NASA’s Juno probe captured the image data for this composite picture during its Earth flyby on Oct. 9 over Argentina, South America and the southern Atlantic Ocean. Raw imagery was reconstructed and aligned by Ken Kremer and Marco Di Lorenzo, and false-color blue has been added to the view taken by a near-infrared filter that is typically used to detect methane. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
With the $1.1 Billion Juno probe completely healthy once again and the nail-biting drama past at last, engineers found the time to send the stored photos and research data back to ground station receivers.
“The science team is busy analyzing data from the Earth flyby,” Bolton informed me.
The amateur image processing team of Ken Kremer and Marco Di Lorenzo has stitched together several portraits from raw images captured as Juno sped over Argentina, South America and the South Atlantic Ocean and within 347 miles (560 kilometers) of the surface. We’ve collected the gallery here for all to enjoy.
Several portraits showing the swirling clouds and land masses of the Earth’s globe have already been kindly featured this week by Alan Boyle at NBC News and at the Daily Mail online.
NASA’s Juno probe captured the image data for this composite picture during its Earth flyby on Oct. 9 over Argentina, South America and the southern Atlantic Ocean. Raw imagery was stitched by Ken Kremer and Marco Di Lorenzo in this view taken by a near-infrared filter that is typically used to detect methane. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
Raw images from the Junocam camera are collected in strips – like a push broom. So they have to be carefully reconstructed and realigned to match up. But it can’t be perfect because the spacecraft is constantly rotating and its speeding past Earth at over 78,000 mph.
So the perspective of Earth’s surface features seen by Junocam is changing during the imaging.
And that’s what is fascinating – to see the sequential view of Earth’s beautiful surface changing as the spacecraft flew over the coast of South America and the South Atlantic towards Africa – from the dayside to the nightside.
This composite shows more than half of Earth’s disk over the coast of Argentina and the South Atlantic Ocean as the Juno probe slingshotted by on Oct. 9, 2013 for a gravity assisted acceleration to Jupiter. The mosaic was assembled from raw images taken by the Junocam imager. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
It’s rare to get such views since only a few spacecraft have swung by Earth in this manner – for example Galileo and MESSENGER – on their way to distant destinations.
Coincidentally this week, the Cygnus cargo carrier departed the ISS over South America.
Fortunately, the Juno team knew right from the start that the flyby of Earth did accomplish its primary goal of precisely targeting Juno towards Jupiter – to within 2 kilometers of the aim point, despite going into safe mode.
“We are on our way to Jupiter as planned,” Juno Project manager Rick Nybakken, told me in a phone interview soon after the flyby of Earth. Nybakken is from NASA’s Jet Propulsion Lab in Pasadena, CA.
“None of this affected our trajectory or the gravity assist maneuver – which is what the Earth flyby is,” he said.
Juno swoops over Argentina
This reconstructed day side image of Earth is one of the 1st snapshots transmitted back home by NASA’s Jupiter-bound Juno spacecraft during its speed boosting flyby on Oct. 9, 2013. It was taken by the probes Junocam imager and methane filter at 12:06:30 PDT and an exposure time of 3.2 milliseconds. Juno was flying over South America and the southern Atlantic Ocean. The coastline of Argentina is visible at top right. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer
It also accelerated the ships velocity by 16,330 mph (26,280 km/h) – thereby enabling Juno to be captured into polar orbit about Jupiter on July 4, 2016.
Dayside view of a sliver of Earth snapped by Juno during flyby on Oct. 9, 2013. This mosaic is stitched from raw image data captured by methane near-infrared filter on Junocam imager at 11:57:30 PDT. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
The safe mode did not impact the spacecraft’s trajectory one smidgeon!
It was likely initiated by an incorrect setting for a fault protection trigger for the spacecraft’s battery when Juno was briefly in an eclipse during the flyby.
Nybakken also said that the probe was “power positive and we have full command ability,” while it was in safe mode.
Safe mode is a designated fault protective state that is preprogrammed into spacecraft software in case something goes amiss. It also aims the craft sunwards thereby enabling the solar arrays to keep the vehicle powered.
False-color composite of a sliver of Earth snapped by Juno during flyby on Oct. 9, 2013. This mosaic is stitched from raw image data captured by methane near-infrared filter on Junocam imager at 11:57:30 PDT. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
The Earth flyby maneuver was necessary because the initial Atlas V rocket launch on Aug. 5, 2011 from Cape Canaveral Air Force Station, FL was not powerful enough to place Juno on a direct trajectory flight to Jupiter.
As of today, Juno is more than was 6.7 million miles (10.8 million kilometers) from Earth and 739 million miles (7.95 astronomical units) from Jupiter. It has traveled 1.01 billion miles (1.63 billion kilometers, or 10.9 AU) since launch.
With Juno now on course for our solar system’s largest planet, there won’t be no any new planetary images taken until it arrives at the Jovian system in 2016. Juno will then capture the first ever images of Jupiter’s north and south poles.
We have never seen Jupiter’s poles imaged from the prior space missions, and it’s not possible from Earth.
During a year long mission at Jupiter, Juno will use its nine science instruments to probe deep inside the planet to reveal its origin and evolution.
“Jupiter is the Rosetta Stone of our solar system,” says Bolton. “It is by far the oldest planet, contains more material than all the other planets, asteroids and comets combined and carries deep inside it the story of not only the solar system but of us. Juno is going there as our emissary — to interpret what Jupiter has to say.”
Based on what we’ve seen so far, Junocam is sure to provide spectacular views of the gas giants poles and cloud tops.
