All Eyes on Jupiter

Leigh Fletcher
Leigh Fletcher

What an incredible few hours it’s been for astronomers everywhere, as we witness a chance of a lifetime event: evidence of a space rock of some sort slamming into Jupiter. Images taken after the impact show the debris field and aftermath of a gigantic collision that occurred in the southern polar region of the enormous planet.

An extremely dedicated and meticulous team of amateur astronomers observe Jupiter’s changing cloud patterns on a regular basis, and it came as an amazing surprise when Anthony Wesley, near Canberra, Australia, reported his Sunday-morning (July 19, 2009) observations ( of a dark scar that bore all the hallmarks of the Shoemaker Levy 9 impacts at Jupiter in 1994. By an amazing coincidence, I was part of a team that had already been allocated time to observe Jupiter from the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Based on Anthony’s discovery, we were crowded around our computers at 3 a.m. PDT (with Anthony observing with us remotely from Australia) as the first near- and mid-infrared images started to come in… it was such an exciting moment, seeing the high altitude particles that had been lofted by the impact (they appear bright in the infrared). Anthony celebrated with us, but then the real work began. We celebrated and then rolled up our sleeves and began an exciting night of observations.

This image shows a large impact shown on the bottom left on Jupiter’s south polar region captured on July 20, 2009, by NASA’s Infrared Telescope Facility in Mauna Kea, Hawaii. Image credit: NASA/JPL/Infrared Telescope Facility

With the assistance of William Golisch at the IRTF, Glenn Orton and I viewed the impacts in as many wavelengths and spectra as we possibly could, as Jupiter rotated and carried the impact scar out of Earth’s view. We used these many views to show evidence for high temperatures at the impact location, and suggestions of ammonia and aerosols that had been carried high into the atmosphere. The observations were repeated again today, Tuesday morning, to track the shape and properties of the site. The scar is extremely large, almost as big as Earth and will continue to grow as Jupiter’s atmospheric winds and jet streams redistribute the material, and then, like Shoemaker-Levy 9, it will begin to fade in the coming weeks and months. Based on comparisons to SL-9, the impactor was likely to be small despite the large aftermath, maybe a few hundreds of metres across. Not only will this tell us a lot about impacts in the outer solar system, and how they contribute to the nature of the planets and icy moons, but they’ll also serve as a probe for the fundamental weather patterns in Jupiter’s high atmosphere.

Amateur observers continue to flood the Internet with new images of the dark spot at approximately 60 degrees south on Jupiter, and so far it looks as though the impact took place sometime in the 24 hours preceding Anthony’s discovery. The debris field now extends out to the west and northwest, with additional high-resolution images from the Keck telescope (Marchis, Wong, Kalas, Fitzgerald and Graham showing the detailed morphology of the impact region. The hard work continues today, as an international team of planetary astronomers scrambles for time on some of the world’s largest astronomical facilities.

Finally, it’s a shame but perhaps not surprising that we didn’t see the collision, or the impactor itself, given the great distance to Jupiter. Like throwing a rock in a pond, we’re seeing and analyzing the splash that it’s made, and we can’t yet infer many details about the rock itself - the detailed shape of the impact site could help determine the trajectory and energy of the collision. But it certainly made quite a splash, and we hope to learn a lot about Jupiter from this event!

Anthony’s discovery is truly astounding, as it united astronomers in looking again at the gas giant Jupiter. It’s overwhelming and spectacularly exciting to watch this event unfolding before our eyes!

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    25 Responses to “All Eyes on Jupiter”

  1. Luis Says:
    July 22nd, 2009 at 11:55 am

    Its amazing how this event has been unfolding — to see the remains of this impact on Jupiter. It is almost frightening to know that whatever it was that hit Jupiter was the size of Earth. Thanks for your hard work and for the information!

  2. Chris Jone Says:
    July 22nd, 2009 at 1:40 pm

    It is amazing, but the impacter was not the size of Earth. The article says it left a mark that size, but the object itself was probably a couple of hundred meters across.

    Fletcher says:
    Yes, that’s absolutely right. The debris field was on a huge scale, and similar to the scars left by the intermediate fragments of SL9, which were a few hundred metres in size at most. The debris is spread over an extremely large area, which we expect to grow and fade in the coming weeks as Jupiter’s strong atmospheric winds redistribute the material. The scar size depends on the impact direction, speed, and the physical properties of the impactor.

  3. Mike Salway Says:
    July 22nd, 2009 at 4:57 pm

    Great blog post, Leigh. My hearty congratulations to Anthony for his amazing discovery. I’m glad to have helped him spread the news early on Monday morning before boarding a flight to Melbourne :)

    His discovery gives us all hope and has given amateurs a renewed vigour to keep our eyes (and telescopes) on the skies - especially on Jupiter!

    Orton says:
    Good post from Mike Salway who is another one of the cadre of the world’s talented Jupiter observers. I should note that, in fact, there aren’t all that many of us who track the time evolution of phenomena in the planets in the professional community, either (see the web pages for the International Outer Planet Watch:

  4. Duane Williams Says:
    July 22nd, 2009 at 5:05 pm

    I have seen news reports that say the scar is the size of Earth and reports that say it’s the size of the Pacific Ocean. Which is closest to the truth?

  5. James Rexford Says:
    July 22nd, 2009 at 5:45 pm

    I think they are saying that the scar, the impact result, is currently the size of the Earth. But the object which hit Jupiter would have been much smaller. That is still cool though, and actually more frightening if you think about it.

  6. Tina Louise Says:
    July 22nd, 2009 at 6:23 pm

    Fascinating and so well shared, thank you.

  7. Asher Arbit Says:
    July 22nd, 2009 at 9:19 pm

    Let’s nip this false rumor in the bud. Whatever hit Jupiter was “maybe a few hundreds of metres across” - not the size of Earth as you wrote! It is the cloud of debris that is the size of Earth - and expanding.

  8. Kevin Says:
    July 22nd, 2009 at 10:40 pm

    I was thrilled to note the “aussie” contribution to the Jupiter bang, being so close to the 40th anniversary of the moon landing where the “aussies” also made a significant contribution to that event.

  9. naav Says:
    July 23rd, 2009 at 1:01 am

    Actually, if you read carefully, only the scar is the size of Earth, (”The scar is extremely large, almost as big as Earth”), the object itself is estimated to be small (”Based on comparisons to SL-9, the impactor was likely to be small despite the large aftermath, maybe a few hundreds of metres across.”).

  10. asim Says:
    July 23rd, 2009 at 9:25 am

    i m surprised that how JPL missed the event.why such a earthy size opportunity never came to NASA Observation! thanks mr. Anthony

    Orton says:
    Asim. Neither NASA nor JPL is capable of observing everything in the sky. There is a program to search for asteroids whose orbits will intersect the Earth’s, but not at Jupiter. In fact, it’s unlikely this object could have been seen, given that it may have been at most a half kilometer in size. For Shoemaker-Levy 9, we were both lucky and the disruption of the comets left a lot of very shiny material around it which made it easier to see.

  11. Tom Says:
    July 23rd, 2009 at 1:25 pm

    Can you see this on any on-line telescope? If so, do you have any links so the masses can observe this. I’m happy WE have an atmosphere to shield us from these type of events. To all those looking in the skies for debris of this type, on course to/from anywhere, I applaud you, keep up the great work. Even better, perhaps the Gov. could pass a little more funding in that direction.

  12. denise Says:
    July 23rd, 2009 at 2:05 pm

    It almost looks like it’s in the same place when Comet Shoemaker-Levy hit the planet. But it still is awesome that something either a comet or an asteriod that big can make an inpact for all to see.

    Orton says:
    Denise. It hit quite a bit further south than the Shoemaker-Levy 9 fragments, almost at 60 deg S latitude.

  13. Patrick Says:
    July 24th, 2009 at 7:58 am

    Since the time span between the SL9 impact and this most recent one is basically less than the blink of an eye on an astronmical scale - could there be any link between the two? Maybe a known or unknown object in the outer solar system has gravitationally flung a few more impactors towards the inner solar system? Many thanks to Jupiter for being our goalie!

  14. Jim Stryder Says:
    July 24th, 2009 at 8:30 am

    Sounds a lot like a piece of SL-9 from 1994. We always talk about meteor showers from Comet Halley and others, that have debris leftover from their passage. Even though the fragments that hit Jupiter in 1994 apparently were all “seen”, perhaps they all were “not” seen! A slight shift in orbit, or re-direction following the SL-9’s breakup could have left a rouge piece or more on a prolonged tour until now!

  15. BobK Says:
    July 24th, 2009 at 3:07 pm

    I agree with Patrick, but…

    Is it possible that this could perhaps actually -have been- a part of SL-9 - one
    that somehow got detached from the rest of the “train”. Similar to how
    outgassing from a comet causes dust grains from it to spread out along the
    orbital path of the parent comet to create meteor showers? Could this
    have been a piece of SL-9 whose orbit was delayed just enough that it went
    around Jupiter rather than participating in the main event? (Only to impact
    a few years later?)

    The timing (and impact placement) of this object seems suspiciously close
    to SL-9 - on the cosmic scale, anyways. The picture of this impact makes it
    look like it’s very close to the same latitude. Assuming it’s in the same
    hemisphere(didn’t Sl-9 impact in Jupiters southern hemisphere?)

    Orton says:
    Patrick, Jim, BobK. I suspect that the only link between this and the SL9 fragments is the voracious appetite of Jupiter, the great gravitational vacuum cleaner in that part of the solar system! SL9 fragments impacted from the south; this was from the east.

  16. Paul atkinr Says:
    July 25th, 2009 at 6:04 am

    Makes me happy to know that jupiter is our vaccum cleaner of space 1-0 to the big ball of gas thumbs up .

  17. Salvador Mtz B Says:
    July 25th, 2009 at 8:08 am

    Amazing discovery.
    I wish you more discoveries like this. waiting for your reporting

  18. John Turner Says:
    July 25th, 2009 at 1:30 pm

    Another possibility it that it was a minor moon of Jupiter, so small that not even Voyager or Galileo photo surveys detected it, deorbiting and then exploding in Jupiter’s atmosphere. Jupiter has an extensive family of satellites beyond the Galilean moons, many in backwards, elliptical and/or inclined orbits. We likely haven’t catalogued a tenth of what’s out there.

    To fit this hypothesis the object would have to be small and monolithic, able to resist the Roche-limit stresses that would pulverize a larger or less well integrated object (such as Shoemaker-Levy 9) before it neared the atmosphere. I would predict a low water and low carbon-monoxide content for such an object.

  19. J. David Osorio Says:
    July 25th, 2009 at 6:16 pm

    I completely agree with Jim Stryder. Assuming the same speed of SL9, 60km/s, the Sun-Jupiter distance ~8×10^11m, and a perfect circular orbit, it would take the comet/asteroid ~2.3yr to return to Jupiter.

  20. Emiliano Guevara Says:
    July 25th, 2009 at 10:17 pm

    I think that this could be volcanic activity at the core, perhaps the core of the planet is not so deep after all the red spot has been there for long time and this perhaps is some sort of mountain feature that blocks the normal planetary flow of gases and that’s why is there for long time.

  21. Martin Bradshaw Says:
    August 6th, 2009 at 12:37 pm

    My brain goes addled when considering how a solid object can hit a gaseous planet without just passing through. If a gas were so dense, how can it not be a solid? Am I missing something?

  22. Jim Stryder Says:
    August 14th, 2009 at 8:36 am

    Emiliano, Jupiter is not volcanic, nor is the Great Red Spot a mountain.

    The GRS having been there for now, what some 300 years or so. When you look at the dynamics of its movements, and how it more or less pushes everything out of its path, it seems as if it has a mind of its own! Ever since the earlier flybys of the 70’s and 80’s, and even with Galileo which orbited Jupiter, the GRS remains one of the solar system’s biggest mysteries!

    What makes it tick, how does it get its energy, what is its energy source, etc? Being very similiar to a terrestrial hurricane, yet no “eye” at the center of its circulation!

    If anything, when Galileo released its probe into Jupiter back in 1995 , they should have targeted it into the GRS!

  23. Lyle Evans Says:
    October 24th, 2009 at 1:11 am

    My name is Lyle Evans and im an writing about an observation i made in a photograph of the rich galaxy cluster catalogued as Cl 0024+17 from your web site titled ( Hubble finds ghostly ring of dark matter ) i have found three identical galaxies in this photograph. Here is a link to the enlarged photograph in the very center of this photo there is a very small galaxy with two areas of dark cloud like strutcers in its center. An just below the center to the right is the same galaxy a bit larger. And again the same galaxy is just above the center and to the left and again a bit larger. The two outside galaxies are reversed of each other and the upper one is slightly over lapped by another galaxy . i know of the gravitational lensing effect but i have never seen triples in different sizes or inverted of each other. Can you please tell me if my observation is correct. Thank You Lyle Evans

    JPL astronomer Dan Coe responds:

    Hi Lyle,

    Yes, these are in fact all multiple images of a blue ring galaxy being lensed by the galaxy cluster CL0024. In all, there are five multiple images of this ring galaxy: the small (demagnified) central image and four strongly magnified images at about 10:30, 11:00, 11:30, and 4:30 (in terms of orientations on a clock face). And, yes, every other image is “flipped” relative to the next.

    Is it just a coincidence that this *ring* galaxy is being lensed by a galaxy cluster hosting a *ring* of dark matter? Probably, as the ring galaxy and galaxy cluster, while very close to one another in these Hubble ACS images, are actually separated by millions of light years along our line of sight.

    A recent analysis led by Adi Zitrin of Tel Aviv University looked more deeply at the ACS images of CL0024 and found 33 multiple images of 11 lensed background galaxies (shown here )!

    Thanks for your question,
    Dan Coe

  24. seks za darmo Says:
    June 28th, 2010 at 8:08 am

    I like your post. Your blog is fantastic.

  25. Jerome Says:
    October 29th, 2010 at 7:44 pm

    i was always amazed by outer space. i always wanted to see something much closer but due to resource limits, i cant. are there anymore pics on other planets? jupiter’s shot is really good, but it would be wonderful if you have saturn’s as well. sometimes is watch the stars with a toothbrush in my mouth. nice work.

    JPL responds:


    Thanks so much for your comment. You can find hundreds of images of planets, galaxies and other space images in our Planetary Photojournal. Or, if you own an iPhone, iPad or iPod Touch, you can download our Space Images app for free in iTunes. Hope that helps!

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