Comet Shoemaker-Levy Homepage (JPL) Comet Shoemaker-Levy Collision with Jupiter July 16, 2014 Update: 20 years later Twenty years ago, Comet Shoemaker-Levy 9 (SL9) impacted Jupiter. I created this website in June 1994 on a voluntary basis, and it was my first public website. I was immensely interested in this unique comet since its discovery in 1993 - a comet that was not only captured into Jupiter orbit, but had broken up into several pieces which were about to hit Jupiter in July 1994. There were a lot of speculation about how the impacts would appear on Jupiter, and this website documents each impact as they occurred. Also note: back in 1994, websites were relatively unknown and somewhat of a novelty. This website became the first big Web event, and was key in raising the awareness of websites to the mainstream public, which we now take for granted today. Here's a good summary of the Comet Shoemaker-Levy 9 events published the "JPL Universe" on January 13, 1995.

Jupiter 1994 The Impact of Comet Shoemaker - Levy / 9 on Jupiter in July 1994 The Prediction This was billed as the astronomical event of the century, perhaps even the millennium, when, for the first time, mankind was to witness a comet crashing into a planet. Jupiter acts as a sort of cosmic vacuum cleaner, sweeping up into its gravitational field a proportion of comets that enter the inner Solar System. Indeed, some calculations suggest that the presence of Jupiter directly benefits life on Earth by collecting comets that could otherwise crash into Earth in "Dinosaur-killer" scale events. The comet, discovered in 1993 was named Shoemaker - Levy / 9, after its co-discoverers. When first discovered the comet presented a very puzzling sight, and was likened to a string of beads. It was quickly realised that the comet was in orbit around Jupiter, not the Sun. Its highly elliptical orbit had carried it so close to the planet in July 1992 (just 16,000 miles) that the tidal forces had torn the nucleus apart into many fragments.

Calculations working backwards in time suggested that the comet had been captured by Jupiter in the 1920s or 30s. Each orbit was slightly different, as the comet was pulled by Jupiter's Galilean moons each time it swung round the planet, and by the Sun and other planets as it wandered chaotically in a gravitational "no-mans-land" when far from Jupiter. Running the calculation forward it was realised that the next visit to Jupiter, in July 1994, would be its last. The individual fragments of SL/9, each following a slightly different orbit following its break-up two years earlier, would crash into Jupiter like machine-gun bullets. The first, named A was due to arrive on 16th July, and the last, W, on 22nd July. While their size and mass was not accurately known, their speed of 141,000 mph (63km per second) suggested that they would cause massive disruption on Jupiter as they plunged into the atmosphere and exploded. Unfortunately the impact point on Jupiter was just out of sight of the Earth, but the planet's fast rotation would carry it into view a few minutes later.

Telescopes on Earth and in space were therefore trained on Jupiter to record the unfolding drama... The Outcome The power and size of the explosions of most fragments far exceeded most predictions. Although the visible flashes were out of sight, in infra-red the huge mushroom clouds, some bigger than the entire Earth, could be seen rising up over the edge of Jupiter. The power of the biggest explosion, that of fragment G, was estimated at 250 million megatons of TNT, 17 billion times bigger than the bomb dropped on Hiroshima in 1945 (yield 15 kilotons). Even the biggest hydrogen bomb ever exploded by mankind, 50 megatons, is tiny by comparison. The picture right shows one such fireball rising on the lower left of the planet, and the sites of previous impacts still glowing hot in infra-red. For images of the event taken from the Hubble Space Telescope, the Galileo spacecraft that was on its way to Jupiter, and from large ground-based telescopes, visit Jet Propulsion Laboratory or National Space Science Data Center .

My Observations The devastation caused by these huge explosions was plain to see even in ordinary telescopes, as each impact point was marked by a black "hole" in the atmosphere. This was before the days of digital cameras, and with conventional photography at the telescope being a bit hit and miss, I decided to draw what I saw instead. The pictures below are the results at the eyepiece of my 8.75 inch telescope, which I set up my garden in Kettering. In each case, the picture has been turned round to give a view in keeping with those on the external websites, i.e. north to the top and east to the right. The impacts occur to the lower left (at a latitude of 44 degrees south on Jupiter) and the planet's rapid rotation brings them into view from left to right. To make it possible see how the impact sites changed over the course of a month I have initially stacked the pictures in sequence according to the approximate longitude of the centre of the disk. Jupiter's rotation period of just under 10 hours meant that at one time or another it was possible to view every part of Jupiter, though poor weather and other commitments some evenings meant that coverage of some longitudes was better than others.

Click on each picture to take you to a full description of what is being seen and when it was made... Longitude (degrees west of Central Meridian) 305 Remember that Jupiter is a large planet, about 11 times the diameter of the Earth. Therefore the impact scars I recorded were huge, roughly the size of the Earth itself. This compares closely with the size of some of the observed fireballs created at the moment of impact. Although Jupiter does not have a solid surface, so the explosions took place entirely within the atmosphere, the scale of devastation has worrying implications should an asteroid or comet hit the Earth at a similar speed - an entirely possible event! 20 Jul 1994 Jupiter, with impact sites (left to right) from fragments Q1, D / G complex and L; 20 Jul 1994, 21:40UT Q crashed into Jupiter just 1h 25m before I drew this picture and is now coming into view on the left hand side of the disk.

The older scars of D (crashed 11:50UT on 17th) and G (07:30UT on 18th), which landed almost on top of each other so cannot be distinguished, and L (22:20UT on 19th),are much more obvious. The view of 25th July shows the same longitude but with additional scars caused by later impacts. System II longitude = 304 degrees. 22 Jul 1994 Jupiter, with impact sites (left to right) L and K / W / U complex; 22 Jul 1994, 21:00UT This view shows more eastern longitudes - whereas the scar from L is on the right of the 20th July picture, here it is on the left. The double scar to the right was caused by fragments K (10:20UT on 19th Jul), W (08:00UT on 22nd) and U (21:48 on 21st), which almost crashed into the same spot on Jupiter over a period of 2 days.

Two weeks later, on 8th August , this view remained almost unchanged. System II longitude = 220 degrees. 25 Jul 1994 Jupiter, with impact sites (left to right) H, Q1, R / S / D / G complex and L; 25 Jul 1994, 21:00 - 21:20UT This view corresponds almost exactly to that of 20th July but shows additional scars from later impacts. H (19:30UT on 18th) is visible to the extreme left, Q1 is now more visible, the D and G site has been joined by further impacts nearby of R (05:30UT on 21st) and S (15:15UT on 21st), and L is visible to the right much as before. No further view was obtained of this longitude, a shame given how many impacts were visible. System II longitude = 310 degrees.

28 Jul 1994 Jupiter, with impact sites (left to right) E, H, Q1 and R / S / D / G complex; 28 Jul 1994, 20:30 - 20:45UT This view is further west of 25th July - the R / S / D / G multiple impact site is disappearing off to the right hand side, and Q1 appears double now. H appears to be fading, but the scar from fragment E (15:12UT on 17th), which crashed 11 days previously, is still very prominent. System II longitude = 022 degrees. 29 Jul 1994 Jupiter, with impact sites (left to right) K / W / U complex and C; 29 Jul 1994, 20:30 - 20:45UT This view is further east of 22nd July - the K / W / U multiple impact site is to the left and still appears much as it did a week earlier, complete with an adjacent darkening of the South Temperate Belt.

A previously unseen scar C (07:12UT on 17th) is visible to the right. System II longitude = 172 degrees. 31 Jul 1994 Jupiter, with impact sites (left to right) K / W / U complex, C and E; 31 Jul 1994, 20:15 - 20:30UT This view lies between the longitudes seen on 28th and 29th July - the K / W / U multiple impact site is to the far left, C is to the right of centre but less visible than two days ago, and the scar of E is still clearly visible on the right despite being two weeks old. Amazingly they were still visible two and a half weeks later on 17th August . System II longitude = 122 degrees.

8 Aug 1994 Jupiter, with impact sites (left to right) S / G / D complex on extreme left, L and K / W / U complex; 8 Aug 1994, 20:00 - 20:15UT This view is almost exactly the same as that of 22nd July and shows that despite nearly two and a half weeks having elapsed the impact sites are still clearly visible. The S / G / D multiple impact site, seen almost edge on, appeared almost as a dent in the left hand side of the planet. System II longitude = 215 degrees. 13 Aug 1994 Jupiter, with impact sites (left to right) S / G / D complex, L and K / W / U complex; 13 Aug 1994, 20:00 - 20:15UT Jupiter has rotated 30 degrees to the right compared to the view of 8th August , so the S / G / D multiple impact site has moved further into view, but K / W / U is disappearing off to the right.

Few details are visible on the Jupiter compared to earlier pictures because atmospheric turbulence spoilt the view. A view of similar longitudes on 23rd August proves that the impact sites are long-lived. System II longitude = 246 degrees. 14 Aug 1994 Jupiter, with impact sites (left to right) E, H, Q1, R and S / D / G complex; 14 Aug 1994, 20:00 - 20:15UT This view is of the same part of Jupiter as 28th July , but poor atmospheric conditions meant that I saw almost nothing. Although the impact sites are now starting to become more fuzzy as the debris is spread out by winds in Jupiter's atmosphere, another view of the same longitude on 19th August shows that they can still be seen. System II longitude = 036 degrees.

17 Aug 1994 Jupiter, with impact sites (left to right) K / W, C and E; 17 Aug 1994, 20:00 - 20:15UT This view is of the same part of Jupiter as 31st July , but again poor atmospheric conditions hampered visibility. The scars of K / W and C can still be seen as dark patches, though E, created nearly a month ago, is less visible now. System II longitude = 126 degrees. 19 Aug 1994 Jupiter, with impact sites (left to right) E and Q1; 19 Aug 1994, 19:15 - 19:45UT The same longitude as 14th August , but whereas I saw almost nothing that night, now the atmosphere was steady and I was able to see a lot of detail on Jupiter. Several giant storms show up as light ovals in the dark Equatorial Belts.The impact sites can still be seen although are definitely starting to become less well defined now, and by the 24th August are becoming harder to see.

System II longitude = 039 degrees. 23 Aug 1994 Jupiter, with impact sites (left to right) S / G / D, L and K / W; 23 Aug 1994, 19:00 - 19:15UT A view 25 degrees west of the view on 13th August , with the same sites visible but shifted to the right. A month has now elapsed since the last impacts, and, although the scars are more diffuse now, they are still visible. System II longitude = 270 degrees. 24 Aug 1994 Jupiter, with impact sites (left to right) E and Q1; 24 Aug 1994, 19:00 - 19:15UT A view 20 degrees west of the view on 19th August . The impact sites have almost disappeared now, but several other weather features, most notably the dark cloud in the Southern Temperate Zone adjacent to the white oval Southern Equatorial Belt, are similar to 5 days earlier. System II longitude = 060 degrees. So ended my run of observations.

As you can see from the times of each picture I had to progressively bring my observations forward as Jupiter set earlier each day. I eventually lost it in the evening twilight as the Sun caught up with Jupiter in mid September. By the time Jupiter re-emerged into the dawn sky in October little remained to be seen of the impacts, though big telescopes followed the evolution of the impact sites for several more months. Not having a convenient view to the East, I did not make any more drawings. Those that I did make while Jupiter was still in the evening sky serve as a record of an awesome event which, had it taken place on Earth, would have resulted in the extinction of almost every living thing. Let us hope that Jupiter continues to do a good job clearing the skies of dangerous comets!

This page last modified Comet Shoemaker-Levy 9's Epic Crash with Jupiter in Pictures Comet Shoemaker-Levy 9's Epic Crash with Jupiter in Pictures By Space.com Staff | July 18, 2014 11:00am ET MORE Comet Shoemaker-Levy 9 Fragments Credit: JPL/NASA/STScI In July 1994, the Comet Shoemaker-Levy 9 slammed into Jupiter after breaking apart into many pieces. Astronomers around the world watched the epic comet crash in real-time with telescopes and spacecraft. You can see some of those photos in this Space.com gallery. In This View: These repeated observations taken in July 1994 show how Jupiter sucked up the fragments of Comet Shoemaker–Levy 9 after their repeated impacts. David Levy and Shoemaker-9 Credit: Elizabeth Howell Amateur astronomer David Levy in front of the two "discovery" pictures of Shoemaker-Levy 9. Levy delivered a lecture to a branch of the Royal Astronomical Society of Canada in Ottawa, May 31, 2013. Comet Shoemaker-Levy 9 'String of Pearls' Credit: H.

Weaver (JHU), T. Smith (STScI), NASA Comet Shoemaker-Levy 9 was named for its co-discoverers, and because of its appearance was often referred to as the "string of pearls" comet. Comet Shoemaker-Levy 9 Scars Jupiter Credit: NASA/ESA Fragments of Comet Shoemaker-Levy 9 in July 1994 created dark clouds on Jupiter, visible even in small telescopes. Comet Shoemaker-Levy 9 Approaching Jupiter in 1994 Credit: NASA, ESA, H. Weaver and E. Smith (STScI) and J. Trauger and R. Evans (NASA's Jet Propulsion Laboratory) This composite photo shows Jupiter and comet Shoemaker-Levy 9 imaged by the NASA/ESA Hubble Space Telescope in 1994. Comet Shoemaker-Levy 9 Fragment W Impact With Jupiter Credit: NASA/JPL Galileo spacecraft caught these four images of Jupiter and the luminous night-side impact of fragment W of Comet Shoemaker-Levy 9 on July 22, 1994. Comet Impact Into Jupiter (Artist's Concept) Credit: © M.

Showalter This artist's concept shows comet Shoemaker-Levy 9 streaking towards Jupiter in July 1994. The comet's dust cloud created a rippling wake in Jupiter's ring. Image released March 31, 2011. Shoemaker-Levy-9 Impacts on Jupiter Credit: NASA This graphic shows fragments of comet Shoemaker-Levy-9 smashing into Jupiter’s southern hemisphere, an event which lasted for almost six days in 1994. Hubble Space Telescope Image of Comet Shoemaker-Levy 9 Credit: H. Weaver This Hubble Space Telescope image shows the "string of pearls" comet, Shoemaker-Levy 9, in March, 1994, four months before its collision with Jupiter. previous | next Cosmic Impact: Comet Shoemaker-Levy 9 crashes into Jupiter - YouTube Cosmic Impact: Comet Shoemaker-Levy 9 crashes into Jupiter Want to watch this again later? Sign in to add this video to a playlist. Need to report the video? Sign in to report inappropriate content. Rating is available when the video has been rented. This feature is not available right now. Please try again later.

Uploaded on Apr 3, 2009 Spectacular images of Jupiter during and after impacts, when over twenty fragments of Comet Shoemaker-Levy 9 smashed into the planet in July 1994. Category Comet Shoemaker-Levy 9 | astronomy | Britannica.com Comet Shoemaker-Levy 9 comet Comet Shoemaker-Levy 9, comet whose disrupted nucleus crashed into Jupiter over the period of July 16–22, 1994. The cataclysmic event, the first collision between two solar system bodies ever predicted and observed, was monitored from Earth-based telescopes worldwide, the Hubble Space Telescope and other Earth -orbiting instruments, and the Galileo spacecraft, which was en route to Jupiter. Fragments of Comet Shoemaker-Levy 9 lined up along the comet’s orbital path, in a composite of … NASA/STScI/H.A. Weaver and T.E. Smith On March 25, 1993, a previously unknown comet positioned close to Jupiter was discovered by Eugene and Carolyn Shoemaker and David Levy in photographs taken by using the 18-inch (46-cm) Schmidt telescope at Palomar Observatory in California .

Its appearance was very unusual—it comprised at least a dozen active cometary nuclei lined up like glowing pearls on a string. As the nuclei spread farther apart, a total of 21 fragments were seen. An analysis of their common orbit revealed that the original comet had been revolving about the Sun and had been captured into orbit around Jupiter, most probably around 1929. It had passed only 0.31 Jupiter radii, about 22,100 km [13,800 miles], above the cloud tops of Jupiter’s atmosphere on July 8, 1992. At that distance, tidal forces from the giant planet’s gravity broke the original nucleus (estimated to be 1.6 km [1 mile] in diameter) into many pieces. The resulting 21 nuclei followed a highly eccentric two year orbit around Jupiter. Gravitational perturbations by the Sun then changed the orbit and lowered the perijove (point of closest approach to Jupiter) to less than the planet’s radius, causing the 21 nuclei to impact Jupiter in July 1994.

The train of fragments from Shoemaker-Levy 9 smashed into Jupiter’s atmosphere with a velocity of 221,000 km (137,300 miles) per hour beginning on July 16, 1994. They all hit on the unobservable night side beyond the limb of Jupiter as seen from Earth. Fortunately, NASA’s Galileo spacecraft, then en route to Jupiter, was in a position to see the night side and observed the impacts directly. For Earth-based observers, the planet’s 9.92-hour rotation period quickly brought each impact site into view. Separated in time by an average of seven to eight hours, each fragment plunged deep into the Jovian atmosphere, exploding with tremendous energy and creating a bubble of super-hot gas called a “fireball.” As the fireball rose back out of the Jovian atmosphere, it deposited dark clouds of ejecta on top of the Jovian clouds. aligned along a zone near latitude 44° S. Those clouds were composed of fine organic cometary dust and dust from the fireball burning in Jupiter’s atmosphere.

About one-third of the fragments produced little or no observable effects, suggesting that their nuclei were very small, probably less than 100 metres (330 feet) in diameter. Jupiter’s southern hemisphere, showing several dark scars created by collisions of fragments of … NASA/Hubble Space Telescope Comet Team Similar Topics Biela’s Comet Astronomers labeled the individual fragments with capital letters in order of arrival. Fragment G, with an estimated diameter of 350–600 metres (1,100–2,000 feet), was probably the largest and heaviest. It left a multiringed black cloud larger than Earth’s diameter. Its impact delivered energy equivalent to at least 48 billion tons of TNT —many times the yield of the world’s supply of nuclear weapons. The dark clouds glowed warmly in infrared images of Jupiter as they slowly expanded and cooled over a few days, and they remained visible for weeks. They faded slowly and eventually disappeared. Shoemaker-Levy 9 - Student Encyclopedia (Ages 11 and up) Shoemaker-Levy 9 is a comet that broke into 21 fragments, each of which smashed into Jupiter in July 1994.

The bombardment, which took place within the span of a week, caused blazing fireballs to break out on the surface of Jupiter and roiled the dense Jovian atmosphere into dark storms, one of them as large as Earth. The impacts-some of which had an explosive power equivalent to between 6 million and 250 million megatons of TNT-left numerous large, dark scars on the surface of Jupiter. Fragments G and H were the largest and most destructive. They were each about 1.5 miles (2.4 kilometers) in diameter, and both traveled at a speed of approximately 130,000 miles (209,000 kilometers) per hour. Article Contributors Shoemaker-Levy 9: Comet's Impact Left Its Mark on Jupiter Shoemaker-Levy 9: Comet's Impact Left Its Mark on Jupiter By Elizabeth Howell, Space.com Contributor | February 19, 2013 02:35pm ET MORE Comet Shoemaker-Levy 9 experienced one of the most spectacular ends that humans ever witnessed. Several months after its discovery, pieces of the comet smashed into the planet Jupiter. The collision produced scars that were visible from Earth in small telescopes.

"This is the first collision of two solar system bodies ever to be observed, and the effects of the comet impacts on Jupiter's atmosphere have been simply spectacular and beyond expectations," NASA wrote on a website describing the comet . Jupiter vacuumed up the pieces of the disrupted comet Shoemaker–Levy 9 in 1994, but the impacts were a reminder of the danger faced by Earth. Credit: JPL/NASA/STScI The comet, which struck Jupiter in 1994, brought the dangers of asteroid and comet collisions with Earth to the public fore. In the late 1990s, Hollywood unleashed two blockbuster films – "Armageddon" and "Deep Impact" – on the theme of large objects threatening Earth. After the release of these films, Congress authorized NASA to seek more near-Earth objects (NEOs) to better monitor those that come cruising close to our planet. [ Related: Meteor Blast over Russia Feb. 15, 2013: Complete Coverage ] The first known Jupiter-orbiting comet The comet was first spotted in March 1993 by three veteran comet discoverers: Eugene and Carolyn Shoemaker, and David Levy.

The group had collaborated several times before and discovered several other comets, which is why this comet was called Shoemaker-Levy 9. A March circular from the International Astronomical Union Central Bureau for Astronomical Telegrams contained a casual reference to the comet's position: "The comet is located some 4 degrees from Jupiter, and the motion suggests that it may be near Jupiter's distance." As the months progressed, it was clear that the comet was actually orbiting Jupiter and not the sun. Astronomer Steve Fentress suggested the comet broke up on July 7, 1992, when it whipped by Jupiter roughly 74,600 miles (120,000 km) above its atmosphere. (Accounts vary, with some sources saying the comet passed as close as 15,534 miles, or 25,000 km.) But the comet was probably orbiting Jupiter for decades before that, perhaps as early as 1966 when it got captured by the massive planet's gravity. Further orbital calculations showed the comet would actually crash into Jupiter in July 1994.

The spacecraft Galileo, scheduled to orbit Jupiter, was still en route to the planet at the time and would not be able to get a close-up view. Observatories around the world, however, prepared to turn their attention to the planet, expecting a spectacular show. The orbiting Hubble Space Telescope also was tapped to observe the encounter. "For comet experts and planetary specialists around the world, this may be the most important event of their careers, because of the discoveries they may make about the nature of comets and the makeup of Jupiter's atmosphere and magnetosphere," NASA wrote prior to the event . "This knowledge may help them explain similar high-energy events on Earth." Watching the fireworks The collisions ended up being a multi-day extravaganza. From July 16 to 22, 1994, 21 separate fragments of the comet smashed into Jupiter's atmosphere, leaving blotches behind. Although all of the collisions took place on the side of Jupiter facing away from Earth, they generally occurred fairly close to the morning "terminator", or the location on Jupiter that was shortly moving within sight of Earth. This meant that telescopes saw some impact sites just minutes after the event.

Jupiter's bright surface was now dotted with smudges from where the comet smashed through the atmosphere. Astronomers using Hubble were surprised to see "sulfur-bearing compounds" such as hydrogen sulfide, as well as ammonia, as a result of the collision. A month after the collision, the sites were noticeably faded, and Hubble scientists declared that Jupiter's atmosphere would have no permanent change from the impacts. "Hubble's ultraviolet observations show the motion of very fine impact debris particles now suspended high in Jupiter's atmosphere," NASA added in a release . "The debris eventually will diffuse down to lower altitudes. This provides the first information ever obtained about Jupiter's high altitude wind patterns." Ripple effects The impact scars disappeared many years ago, but at least one group of scientists has recently detected a change in Jupiter's environment because of Shoemaker-Levy 9. When Galileo arrived at Jupiter, the spacecraft imaged ripples in Jupiter's main ring in 1996 and 2000. Also, the entire ring tilted in 1994 by about 1.24 miles (two kilometers) following the impact.

In 2011 – nearly two decades after the impact – the Pluto-bound New Horizons spacecraft still was detecting disturbances in the ring, according to a paper in the journal Science. "Impacts by comets or their dust streams are regular occurrences in planetary rings, altering them in ways that remain detectable decades later," the researchers wrote in their abstract . Political effects also came to pass in the decades after Shoemaker-Levy 9, as politicians sought to figure out how many large extraterrestrial objects lurk near Earth. In 1998, Congress mandated that NASA seek out at least 90 percent of the asteroids near the planet that are 0.62 miles (1 kilometer) in diameter. Seven years later, representatives refined the search to order that by 2020, NASA find 90 percent of NEOs that are 459 feet (140 meters) wide or larger – a threshold considered to pose a large threat to Earth. [ Video: NEOs: The Video Show ] As of 2011, NASA had found more than 90 percent of the biggest asteroids lurking near Earth, the agency announced.

A survey using the Wide-field Infrared Survey Explorer suggested that there were actually fewer asteroids lurking near our planet than previously feared. "Astronomers now estimate there are roughly 19,500 – not 35,000 – mid-size near-Earth asteroids. Scientists say this improved understanding of the population may indicate the hazard to Earth could be somewhat less than previously thought," NASA wrote. "However, the majority of these mid-size asteroids remain to be discovered." — Elizabeth Howell, SPACE.com Contributor Comet Shoemaker-Levy 9 Comet Shoemaker-Levy 9 The Great Comet Crash of 1994 Image taken by Mats Lindgren at the European Southern Observatory in Chile. Image taken on March 28, 1993, just 4 days after it was discovered. On the night of March 24, 1993, Eugene and Carolyn Shoemaker and David Levy discovered a strange looking comet from a photograph taken from the 0.4 meter Schmidt telescope in Palomar Observatory in Califonia. The comet was named Comet Shoemaker-Levy 9 after the discoverers, the ninth comet discovered by this team.

The comet was very elongated, and it turned out that comet had been pulled apart due to tidal forces from an extremely close flyby of Jupiter on July 8, 1992. Twenty-one separate fragments were eventually identified. By April 5, 1993, enough observations of the comet have been made to better define the comet's orbit, and it was surprisingly found to be in orbit around Jupiter. By May 25, additional observations helped refined the orbit further, and a exciting new development came forth: Comet Shoemaker-Levy 9 could possibly impact Jupiter in July 1994! By June 1993, the comet's orbit was well determined and the impacts into Jupiter would definitely occur. Hubble image taken in May 1994. The fragments were named from the letters of the alphabet in the order they would impact on Jupiter. With one year's advance notice, astonomers and observatories made plans to observe this unique event. This would mark the first time that a collision between two solar system bodies would be observed.

Most astronomers downplayed the event to the public, mainly due to past disappointments with a couple of expected bright comets in the previous two decades that did not live up to expectations. Astronomers noted that the impacts were very unusual, but they warned that the effects of the impacts of the comet would probably not be visible to Earth except by the largest telescopes. Also, the impacts would occur on the night side of Jupiter, out of direct view from Earth. The 21 fragments would hit Jupiter over a one week period starting on July 16, 1994, and everyone waited anxiously for that day to arrive. Calar Alto Observatory image of the first impact - July 16, 1994 The first image of the comet collision to appear on the Internet When the first impact hit (called Fragment A), a plume sighting from the impact was reported by Calar Alto Observartory in the Canary Islands and the South African Astronomical Observatory (SAAO). The Calar Alto and SAAO images of the plume were quickly placed on the Internet just a few hours after they were taken.

The Calar Alto images were taken in the infrared, and there was no doubt of the first impact - showing a huge explosion off the side of Jupiter. The Hubble Space Telescope also took images of the impact, but it took longer to download the images from the spacecraft down to Earth. During a live NASA press conference, Eugene and Carolyn Shoemaker had mentioned the possible plume sigthings and were anxiously awaiting the Hubble image, unaware that images confirming the impacts were already on the Internet. When the Hubble images did arrive, a joyous Heide Hammel ran onto the stage with the good news. Hubble had also detected the plume, and showed the impact site on Jupiter as it rotated into view - a feature that appeared as a black eye on the top of the Jovian cloudtops. The first impact was more visible than what everyone had imagined, and everyone then knew they were in for a week long extravaganza for the remaining impacts. Comet fever had set in. Spectacular image taken from the Mount Stromlo and Siding Observatory in Australia on July 18, 1994. Fragment G was one of the larger fragments of the comet.

Everyone around the world with a telescope were now viewing Jupiter in earnest. The impact sites were visible even fom the smallest amature telescopes. A Internet frenzy ensued as hundreds of images were made available on the World Wide Web. The 21 impacts were happening around the clock, so someone around the world was able view each impact. The plumes were particularly prominent in the infrared, often oversaturating the infrared detectors, but displaying spectacular images of the impact. By sheer coincidence, the Galileo spacecraft, enroute to Jupiter, was in position to view the impact sites directly and took the only direct measurements of the comet collisions. Image showing the impact of Fragment W taken by the Galileo spacecraft on July 22, 1994. It was all over by July 22, 1994, and everyone drew a big excited sigh of relief. Estimates of the fragment sizes ranged from 1 to 2 km for the larger pieces. Water was detected at the impact sites. The comet collision was a once-in-a-lifetime event, and perhaps a once-in-a-millennium event. The show put on by Comet Shoemaker-Levy 9 was tuly spectacular and beyond everyone's expectations.

Ron Baalke, STARDUST Webmaster, ron@jpl.nasa.gov Last Updated Wednesday, 07-Jun-2000 13:50:34 PDT Top 20 Comet Shoemaker-Levy Images Top 20 Comet Shoemaker-Levy Images Here are the most popular images at the JPL Comet Shoemaker-Levy home page during the month of July 1994, when the comet was impacting Jupiter. The total access count for each image is listed. Top 20 Images Comet Crashes Into Jupiter In Dazzling, Galactic Show - NYTimes.com Comet Crashes Into Jupiter In Dazzling, Galactic Show By MALCOLM W. BROWNE Published: July 17, 1994 The first of 21 huge fragments of Comet Shoemaker-Levy 9 blasted its way into the depths of Jupiter's atmosphere yesterday, exploded with a bright flash and hurled a white-hot plume of gas high above the giant planet, leaving a huge, circular wound in Jupiter's dense cloud cover.

The show last night was so spectacular it could be seen even by amateur astronomers with small telescopes, despite the fact that all the comet fragments were striking the far side of Jupiter, out of direct sight of Earth. The splintered comet's first huge chunk, Fragment A, hit the Jovian cloud tops shortly after 4 P.M. (Eastern time) yesterday. At the Wise Observatory in Israel, Dr. James Scotti and his team from the University of Arizona saw a flash at the edge of the planet at 4:04 P.M. At 4:18 P.M., a huge plume came into view as Jupiter rotated, bringing the impact site into view. Within hours, observatories in many parts of the world were transmitting electronic images and reports of their observations of the first cometary impact. The view was generally best for observatories in the Southern Hemisphere, particularly the European and American observatories in Chile, because for those observatories Jupiter is farther above the horizon than in the Northern Hemisphere. Spectacular pictures also came from the Hubble Space Telescope, in orbit.

At the Space Telescope Science Institute in Baltimore, astronomers toasted each other with champagne as computers churned out fresh images of Jupiter from the space telescope, vividly showing the planet's new dark blemish -- a giant region where clouds were disrupted and churned by Fragment A. "My God, look at that!" exclaimed Dr. Heidi Hammel of the Massachusetts Institute of Technology, a leader of one of the teams observing Jupiter with the Hubble Space Telescope. "And Fragment A wasn't even one of the biggest fragments -- it was just the first of 21! This is going to be a great week." Dr. Hal Weaver of the space telescope group estimated Fragment A was a mile in diameter. Fragment G, due to arrive Monday, is believed to be several times larger. Even amateur astronomers were filing detailed reports of their observations with Dr. Brian G. Marsden, director of the Central Bureau for Astronomical Telegrams in Cambridge, Mass., whose organization is the international clearinghouse for astronomical discoveries. Among the amateurs reporting the sighting of a large spot created by the fall of Fragment A were Jeff Beisch, Carl Hernandez and Don Parker of Miami, using a telescope only 16 inches in diameter -- small, by professional standards.

They described the new spot as bluish in color. Huge though it is by terrestrial standards -- probably more than 1,000 miles across -- it is dwarfed by Jupiter "Great Red Spot," a feature of the Jovian atmosphere that is as big as Earth. 'Not a Dud' The effects of the cometary impacts on Jupiter were registered not only in visible light but also by ultraviolet and infrared emissions. The 90-inch telescope operated by the University of Arizona at Kitt Peak detected a strong disruption of Jupiter's aurora after the impact. The aurora on Jupiter, as on Earth, is caused by the impact of charged particles from space bombarding the atmosphere. "At any rate," Dr. Weaver said, "Comet Shoemaker-Levy 9 is not a dud, as some of us had feared. There were signs last week that it was being stretched apart, as if the fragments were breaking up and dispersing, but tonight we've seen that this is not the case." The impacts, which will continue until Friday, afford astronomers an unprecedented chance not only to study the composition of a comet and its behavior when captured by a planet, but also to gauge the structure of Jupiter itself.

This huge planet, the largest in the solar system, is blanketed with an atmosphere so thick and heavy that the hydrogen of which it mainly consists is crushed to metallic form at great depths. Dr. Hammel and other scientists hope to detect and measure seismic waves created by the cometary blasts as the waves pass through the planet. Careful analysis of their size and frequencies may give physicists a kind of X-ray revealing details of Jupiter's inner structure. Obstacles to Observation The only chance of photographing the impacts themselves lay with a Jupiter-bound spacecraft, Galileo, that is far enough along on its journey to see the impact area on the back side of Jupiter. But Galileo is still more distant from Jupiter than is Earth from the sun -- much too distant to see impact details. Moreover, Galileo's main antenna is inoperable, and it will take an auxiliary antenna some two months to transmit Galileo's first comet picture to Earth. Some theorists, including Dr. Paul W. Chodas and Dr. Donald K. Yeomans of the Jet Propulsion Laboratory in Pasadena, Calif., had predicted since the comet was discovered last year that it would release energy equivalent to hundreds of billions of tons of TNT when its components hit Jupiter.

But other experts predicted that the comet fragments would disperse before impact and have virtually no observable effects. The comet, discovered on March 25, 1993, was named for its discoverers, Dr. Eugene Shoemaker (then with the United States Geological Survey), his wife, Dr. Carolyn Shoemaker of Northern Arizona University, in Flagstaff, and David Levy, an amateur astronomer. Astronomers surmise that after spending millions or billions of years in orbit around the sun, the comet was captured by Jupiter's gravity in the early 1970's. It was spotted only after the Jovian gravitation gently pulled it apart some time in 1992. Last week, Dr. Willy Benz, an astronomer at the University of Arizona, reported calculations showing that Comet Shoemaker-Levy 9 was probably a "rubble pile" of "hundreds if not thousands" of small snowballs before it broke up. These tiny fragments were held together over the eons by their own mutual gravitation, he said, but were gently nudged apart in 1992 by Jupiter's gravity when the comet drifted to close to the planet.

Difficulties and Disruptions This is likely to mean, Dr. Benz predicted, that the comet's crash into Jupiter will be "less spectacular than the media would like to have it," but that there was still a chance for gaining useful scientific information. But observations will not be easy during the coming week. At a crucial point during the impact of Fragment B, the orbiting telescope will pass into a region of intense radio noise called the South Atlantic Anomaly, disrupting signals in the instrument's sensitive detectors. The Hubble telescope team hoped for better luck with Fragment C, which was scheduled to hit Jupiter early today. Many astronomers were pinning their greatest hopes on Fragment G, which is generally believed to be the biggest one and will hit Jupiter at 3:28 A.M. on Monday, while Hawaii and other major observing centers are in darkness. Among the telescopes that will concentrate on Fragment G is the Keck Telescope atop Mauna Kea mountain on the island of Hawaii -- the largest and most powerful telescope in the world. "We'll be taking pictures of Jupiter every four seconds that could be combined to make a kind of movie," said Dr. Imke de Pater, a Dutch astronomer who leads one team at the Keck Observatory.

Question: What was Shoemaker-Levy 9, that crashed into Jupiter in 1994?
Answer: Comet