famous comets - mr. hill's science websitemrscienceut.net/famouscomets.pdf · 2012-03-12 ·...

Names ____________________________________________________________

Famous Comets (an activity from NASA’s STARDUST Mission: Think SMALL in a Big Way Guide)

This activity has two parts. In the first part, you will research the significance of a specific comet. In the second part, you will write a story based on the facts surrounding your comet. You will work in teams of two to four students. Part, the First Comet Research Team Worksheet Team Roles Decide which team member will perform each of the following roles (if you don’t have four in your group, one or two members can do two jobs): Recorder: Records the results of the team’s research. Computer Operator: Uses the computer to navigate the Internet and print out

any essential materials. Literary Supervisor: Records team’s input for the story. Reporter: Presents the team’s story to the rest of the class.

Research Using the Internet, answer the questions on the next page. Have the recorder write down what the team learns. Each of the computers in the classroom has a folder called “Comets” with websites that will help you select your comet and find out more information about that comet. We have selected Comet _____________________________________________

1. What makes this comet unique? __________________________________________________________________ __________________________________________________________________ 2. How long is this comet’s period? __________________________________________________________________ __________________________________________________________________ 3. What major events in history have happened when the comet has appeared? __________________________________________________________________ __________________________________________________________________ 4. How did this comet change the way astronomers think about comets or the Solar System? __________________________________________________________________ __________________________________________________________________ 5. Who discovered the comet? From what country was the discoverer? Was the discoverer a professional or amateur astronomer? __________________________________________________________________ __________________________________________________________________ 6. Print out a picture of the comet. Label its coma, gas tail, dust tail, and nucleus (if visible). 7. What was the most recent great comet? __________________________________________________________________ __________________________________________________________________

8. What comets will appear in the night sky over the next three years? __________________________________________________________________ __________________________________________________________________ Part, the Second Using the information about your comet, you will write a story based on the facts surrounding your comet. Use the following writing prompts to help your team write a two-page story about your comet. Have the Literary Supervisor write the story as the rest of the team provides ideas and suggestions. Base your story on facts and science concepts. Here are some suggestions. Imagine you are a reporter writing a headline story about sighting this comet. Imagine that you belong to another culture in another century when your comet

appears. Describe what you see, what you think it is, and how you feel. Imagine you are an amateur astronomer watching the night sky when you think you

discover a comet. How do you feel? Whom do you tell? Imagine you are the comet. Talk about where you would travel during your entire

orbit. Think of your own story!

Illustrate your story with the photo you printed of your comet. Make sure that its parts are labeled.

On July 23, 1995, an unusually largeand bright comet was seen outside ofJupiter's orbit by Alan Hale of NewMexico and Thomas Bopp of Arizona.Careful analysis of Hubble SpaceTelescope images suggested that itsintense brightness was due to itsexceptionally large size. While thenuclei of most comets are about 1.6to 3.2 km (1 to 2 miles) across,Hale-Bopp's was estimated to be 40km (25 miles) across. It was visibleeven through bright city skies, andmay have been the most viewedcomet in recorded history. CometHale-Bopp holds the record for thelongest period of naked-eye visibility:an astonishing 19 months. It will notappear again for another 2,400 years.

COMET HALE-BOPP

COMET SWIFT-TUTTLE 1992

This comet was first seen in July 1862 byAmerican astronomers Lewis Swift andHorace Tuttle. As Comet Swift-Tuttle movescloser to the Sun every 120 years, it leavesbehind a trail of dust debris that provides theingredients for a spectacular fireworksdisplay seen in July and August. As Earthpasses through the remnants of this dusttail, we can see on a clear night the Perseidmeteor shower. Comet Swift-Tuttle is notedas the comet some scientists predictedcould one day collide with Earth because thetwo orbits closely intercept each other. Thelatest calculations show that it will pass acomfortable 24 million km (15 million miles)from Earth on its next trip to the inner SolarSystem.

COMET HYAKUTAKE

On January 30, 1996, Yuji Hyakutake(pronounced "hyah-koo-tah-kay"), anamateur astronomer from southernJapan, discovered a new comet usinga pair of binoculars. In the spring ofthat year this small bright comet with

Famous Comets! http://amazing-space.stsci.edu/resources/explorations/comets/lesson/facts...

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a nucleus of 1.6 to 3.2 km (1 to 2miles) made a close flyby of Earth —sporting one of the longest tails everobserved. The Hubble SpaceTelescope studied the nucleus of thiscomet in great detail. This is notComet Hyakutake's first visit to theinner Solar System. Astronomershave calculated its orbit and believe itwas here about 8,000 years ago. Itsorbit will not bring it near the Sunagain for about 14,000 years.

COMET HALLEY

Comet Halley is perhaps the most famouscomet in history. It was named after Britishastronomer Edmund Halley, who calculatedits orbit. He determined that the cometsseen in 1531 and 1607 were the sameobjects that followed a 76-year orbit.Unfortunately, Halley died in 1742, neverliving to see his prediction come true whenthe comet returned on Christmas Eve in1758. Each time this comet's orbitapproaches the Sun, its 15-km (9-mile)nucleus sheds about 6 m (7 yards) of iceand rock into space. This debris forms anorbiting trail that, when falling to Earth, iscalled the Orionids meteor shower. CometHalley will return to the inner Solar Systemin the year 2061.

COMET SHOEMAKER-LEVY 9

Between July 16 and July 22, 1994, more than 20 fragments of CometShoemaker-Levy 9 collided with the planet Jupiter. Astronomers Carolyn andEugene Shoemaker and David Levy discovered the comet in 1993. The HubbleSpace Telescope took many spectacular pictures of this event as the comet'spieces crashed into Jupiter's southern hemisphere. It was the first collision of twoSolar System bodies ever to be recorded. The impacts created atmosphericplumes many thousands of kilometers high that showed hot "bubbles" of gas withlarge dark "scars" covering the planet's sky.

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Capture the cosmos > Comets > Dig deeper (cont'd) > Fast Facts:Comet Hale-Bopp

Description Hale-Bopp has a very large nucleus.(Most comet nuclei measure only 1.6 to3.2 km, or 1-2 miles, in diameter.) Itcould be seen in the sky for a record 19months — from May 1996 to November1997 — and was visible through thebright skies of cities.

Age About the same age as the Sun: 4.5billion years

Location Outer solar system — Oort Cloud

Avg. distancefrom the Sun

It has a highly elongated orbit thattakes it very close to the Sun and thenflings it out into the outer solar system,well past the orbit of Pluto.

Diameter The diameter of the nucleus has beenestimated to be 40-80 km (25-50miles).

Mass Not determined

Orbitalperiodaround theSun

2,392 Earth years

(Image courtesyof AlessandroDimai)

Capture the cosmos > Comets > Dig deeper (cont'd) > Fast Facts:Comet Hale-Bopp

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HOMEWhat are Comets? Halley's Comet Comet Hale-Bopp

Shoemaker-LevyComet Ten Facts About Halley's Comet

The view of the night sky from Earth is very familiar. On a clear night, you know that you will be able to look into the skyand see the Moon and lots of stars. Sometimes though, the Moon and stars are joined by other objects. If you looked into thesky on an evening early in 1997, you may have been able to see what looked like a star which had been smudged. In fact,

this smudged star was a comet, one of the brightest comets visible from Earth for many years. It was named CometHale-Bopp and remained visible from Earth for 19 months, being at its brightest and clearest during the first half of 1997.

Comets are balls of ice, dust and gas which travel in elliptical orbits around the Sun. At their most distant, they are invisible.However, when they get closer to the Sun, they begin glowing, forming a coma and tails as dust and gas is burnt off the

comet. It is only when they have begun glowing that they become visible from Earth with telescopes. This means that theyusually only get discovered two or three months before they actually get close to Earth. However, Hale-Bopp was different. it

was discovered almost two years before it became a prominent feature in the night sky.

It was a summer's evening in July 1995 when two astronomers in different parts of America happened to be observing thesame part of the sky. Alan Hale is a professional astronomer and was working at his observatory in New Mexico on the

evening of 22nd July. He was actually observing other comets, but while waiting for one previously discovered comet to comeinto view, he turned his telescope to a group of stars called M70 (a globular cluster). At a similar time, Tom Bopp, an

amateur astronomer at a "star party" in Phoenix (a gathering for astronomers to observe the stars together!), was alsoobserving the M70 globular cluster. Both astronomers noticed a small fuzzy object in a place where there shouldn't be a

fuzzy object. Alan Hale suspected the object may be a comet, but had to check it hadn't already been discovered. He referredto his big comet catalogue and noticing it wasn't in there, he emailed the Central Bureau for Astronomical Telegrams. He

returned to his discovery and noticed that the object had moved against the starry backdrop, confirming that it definitely wasa comet. He then sent a second email. When Tom Bopp observed the object, he called over some friends. They watched theobject move against the stars in the background and, realising he had discovered a comet, Bopp also got in touch with theCentral Bureau for Astronomical Telegrams to inform them of this. Because both people discovered the comet at about the

same time, it was named after both of them, hence the name Comet Hale-Bopp.

When the comet was discovered, it was about as far away fromEarth as Jupiter is. The comet doesn't orbit on the same path as the

planets. In the diagram to the left, the orbits of the four innerplanets and Jupiter can be seen. The path that Hale Bopp takes canalso be seen.. Because Hale-Bopp was discovered when it was so faraway from Earth, there was a great deal of anticipation that when itgot closer, it would be very bright. Halley's Comet, which last visitedin 1986, has a nucleus of 20km. The nucleus of Hale Bopp is 40km,

much larger than most comets.

After discovery, the comet continued on its journey towards the Sun. As it got closer, its tail got larger and became easier tospot. On 20th May 1996, Terry Lovejoy of Queensland, Australia became the first person to spot the comet with the nakedeye. It would have still been very faint from Earth, but as the months went on, more and more people reported sightings ofthe comet without the assistance of a telescope or binoculars. Throughout the summer of 1996, Comet Hale-Bopp actuallybecame dimmer, leading scientists to believe that it had fizzled out. However, it began getting brighter again and in early1997, it was clearly visible from Earth. The comet came closest to Earth on 22nd March 1997 (at a distance of over 122million kilometres) and closest to the Sun on 1st April 1997. After reaching the Sun and going behind it the comet was

thrown back out and continued its journey away from the Sun, becoming less and less visible from Earth. It is estimated thatit will return in 2,300 years, in the year 4534! The comet would have last been visible 4,200 years ago. The reason its next

visit is sooner than its last visit is because in March 1997, Comet Hale-Bopp passed within the gravitational influence ofJupiter, shortening the length of time it takes to complete an orbit. The furthest the comet will go from the Sun now is 371AU (Astronomical Units). 1 AU is approximately the distance Earth is from the Sun, so Hale-Bopp will go 371 times as far

THE SOLAR SYSTEMCOMETSWhat are Comets?Halley's CometComet Hale-BoppShoemaker-LevyHalley's Comet FactsSTARS & GALAXIESASTEROIDSASTRONOMYSPACE EXPLORATIONSPACE A-ZASK AN ALIEN!SPACE QUIZUSEFUL RESOURCESSITE MAP

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from the Sun as Earth is.

Comet Hale-Bopp spent four months as a regular clear object in the night sky. it is estimated that 81% of Americans saw it,and the comet became the most photographed comet in the history of, er, comet photography. I suppose this isn't such agreat claim when you realise that the last great comet was in 1811 before cameras were even invented! The comet was

visible from Earth with the naked eye for a record breaking 19 months. The comet was very much a comet of the InternetBoom of the late 1990s. The fast increase in Internet users meant that people all over the world could share information

about sightings, pictures, etc. with each other. The original Comet Hale-Bopp website became NASA's first website to achieve1 million hits in one day. If only this website was around back then - it might have had a visit or two!

Comet Hale-Bopp also had a darker side. Throughout history, comets have been seen as omens; a sign that something wasgoing to happen. An early image of the comet was taken by an amateur astronomer which showed a mysterious object whichlooked like it was following the comet. This object didn't match up with any stars that should have been in the area, so theastronomer contacted a radio show stating that Hale-Bopp was being accompanied by a Saturn-Like Object. A cult callingthemselves Heaven's Gate believed that this Saturn-like object could be a UFO. 39 members of the cult killed themselves,believing that their spirits would be taken to another world by this UFO. That's what happens when you watch too much

X-Files! Analysis of the image proved that the object was in fact a star.

For most of us, Comet Hale-Bopp was simply a once-in-a lifetime opportunity to see a comet. It is now hundreds of millions ofmiles away from us and has much further to go before it even starts to return to our part of the Solar System. Of course,

there may be other comets about to visit us, and some may be even brighter than Hale-Bopp. Comets are mysteriousobjects. Unless they have been previously discovered and visit regularly (like Halley's Comet), we don't know they exist untilthey get very close to us. And even when they have been discovered, it isn't until they get even closer that we find out just

how spectacular it is.

What are Comets? Halley's Comet Comet Hale-Bopp

Shoemaker-Levy Comet Ten Facts About Halley's Comet

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March 29, 1996

I am a 45-year old amateur astronomer from Kagoshima, Japan. My name, Hyakutake, means "100 samurai,or chivalry," in Japanese. It is not a very common name in Japan.

I graduated from the Art Department at Kyushu Industry University, where I majored in photography.

I live in the village of Hayato, in the southernmost prefecture located 600 miles southwest of Tokyo on theisland of Kyushu. I lived in Fukuoka for many years, but moved to Kagoshima because the skies are muchclearer there.

I have been married for 15 years, and have two sons, ages 10 and 13. I am the only one in my family whosehobby is searching for comets. My younger son likes the television show, "The X-Files."

I've been interested in comets since I was 15 years old, after I heard of the Japanese Comet Ikeya-Seki whichappeared in 1965. My interest in astronomy has increased steadily since then. I wanted to discover a cometthat had a very far orbit.

Although I started searching for comets about seven years ago when I lived in Fukuoka, I have concentratedmy efforts more intensely since I moved to Kagoshima two years ago.

Since last July, I have been avidly searching the night sky for comets from 2 a.m. to 5 a.m., about four nightsa month. I want to continue searching for comets while my eyesight is reasonably good.

Many people have asked me how I discovered Comet Hyakutake. I live in the countryside and travel to arural mountain top area about 10 miles from my home to get a better view of the night sky. (Before I wasmarried, I enjoyed mountain climbing.)

Actually, I discovered two comets. I spotted the first one at 5:40 a.m. on December 26. I wasn't sure it was acomet, but I reported the sighting anyway. This first comet is still there, but it's not very bright.

A month later, I went back to the area to take photos of the first comet. I looked l up at the sky where itshould have been at that point in its path. However, that particular spot was filled with clouds. I tried to findan area in the sky that was unobscured. The clouds led me back to the same spot in the sky where I hadoriginally found the first comet, but it didn't make sense that it would be there. That is when I discovered thesecond Comet Hyakutake, the one the media now refers to as "The Comet of the Century."

I've been asked about 75 times how I felt when I discovered this comet. Actually, I was feeling a bit confused.My reaction was somewhat complicated, since I had originally intended to go to the viewing spot to take apicture of my first comet. I found the second comet in the same area as the first one, near the constellations ofLibra and Hydra.

How Comet Hyakutake B2 Was Discovered http://www2.jpl.nasa.gov/comet/hyakutake/disc2.html

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I discovered Comet Hyakutake at 4:50 in the morning, and usually a person can report a comet after 8 a.m.,but I decided to take some photos of the comet, using my camera with telephoto lenses, and got themdeveloped. It wasn't until 11 a.m. that I called the National Astronomy Observatory in Tokyo to report mynew comet.

I followed the formal procedure of gathering data and documenting my new comet discovery with photos.Then two other amateur astronomers in Japan recognized the comet.

It's interesting that my discovery wasn't reported very widely by the Japanese media until recently. The firstmedia reports were from London. Then the American press became very interested. Now the Japanese mediais covering the comet story. My wife can't make phone calls because the phone is always ringing.

I'm happy that this Comet Hyakutake was the second one I discovered, because it wasn't mere coincidence.This proved to me that my method of searching for comets is working, and I will continue to look for them.

I use high-powered, field binoculars with 6-inch lenses, mounted on a stand. This is the only equipment I own.

Comet Hyakutake has the longest tail that I have ever observed, although the new Hubble images show thatthis comet is breaking into fragments.

I am a bit perplexed by all the attention paid to me, when it is the comet that deserves the credit.

Comet 1996 B2 Hyakutake Home Page

How Comet Hyakutake B2 Was Discovered http://www2.jpl.nasa.gov/comet/hyakutake/disc2.html

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C/1996 B2 (Hyakutake)

Comet Hyakutake captured by the Hubble Space Telescope onApril 4, 1996, with an infrared filter.

Discovery and designationDiscovered by Yuji Hyakutake

Discovery date 31 January 1996[1]

DesignationsAlternate name(s)[note 1] Great Comet of 1996

Orbital characteristics[2]

Epoch 2450400.5

Ap 4367.87 AU

Peri 0.2301987 AU

Semi-major axis 2184.05 AU

Eccentricity 0.9998946

Orbital period 102070 a

Inclination 124.92246°

Longitude of ascending node 188.05766°

Argument of peri 130.17218°

Physical characteristicsDimensions 4.2 km[3]

Sidereal rotationperiod 6 hours

Absolute magnitude (H) ~5.3

1. ^ Minor Planet Designations (http://cfa-www.harvard.edu/iau/MPDes.html)

From Wikipedia, the free encyclopedia

Comet Hyakutake (Japanese

pronunciation: [çʲakɯ̥take], formally designatedC/1996 B2) is a comet, discovered on January 31,

1996,[1] which passed very close to Earth in Marchof that year. It was dubbed The Great Comet of1996; its passage near the Earth was one of theclosest cometary approaches of the previous 200years. Hyakutake appeared very bright in the nightsky and was widely seen around the world. Thecomet temporarily upstaged the much anticipatedComet Hale-Bopp, which was approaching the innerSolar System at the time.

Scientific observations of the comet led to severaldiscoveries. Most surprising to cometary scientistswas the first discovery of X-ray emission from acomet, believed to have been caused by ionised solarwind particles interacting with neutral atoms in thecoma of the comet. The Ulysses spacecraftunexpectedly crossed the comet's tail at a distance ofmore than 500 million km from the nucleus, showingthat Hyakutake had the longest tail known for acomet.

Hyakutake is a long-period comet. Before its mostrecent passage through the Solar System, its orbitalperiod was about 17,000 years, but the gravitationalinfluence of the giant planets has increased thisperiod to 72,000 years.

1 Discovery2 Orbit3 The comet passes the Earth4 Perihelion and afterwards5 Scientific results

5.1 Spacecraft passes through the tail5.2 Composition5.3 X-ray emission5.4 Nucleus size and activity

6 References7 External links

Comet Hyakutake - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Comet_Hyakutake

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The comet was discovered on January 31, 1996,[1] by Yuji Hyakutake, an amateur astronomer from southern

Japan.[4] He had been searching for comets for years and had moved to Kagoshima Prefecture partly for thedark skies in nearby rural areas. He was using a powerful set of binoculars with 150 mm (6 inch) objective

lenses to scan the skies on the night of the discovery.[5]

This comet was actually the second Comet Hyakutake; Hyakutake had discovered comet C/1995 Y1 several

weeks earlier.[6] While re-observing his first comet (which never became visible to the naked eye) and thesurrounding patch of sky, Hyakutake was surprised to find another comet in almost the same position as the firsthad been. Hardly believing a second discovery so soon after the first, Hyakutake reported his observation to the

National Astronomical Observatory of Japan the following morning.[7] Later that day, the discovery wasconfirmed by independent observations.

At the time of its discovery, the comet was shining at magnitude 11.0 and had a coma approximately

2.5 arcminutes across. It was approximately 2 astronomical units (AU) from the Sun.[8] Later, a pre-discoveryimage of the comet was found on a photograph taken on January 1, when the comet was about 2.4 AU from the

Sun and had a magnitude of 13.3.[9]

When the first calculations of the comet's orbit were made, scientists realized that it was going to pass just

0.1 AU from the Earth on 25 March.[10] Only four comets in the previous century had passed closer.[11] CometHale-Bopp was already being discussed as a possible "great comet"; the astronomical community eventuallyrealised that Hyakutake might also become spectacular because of its close approach.

Moreover, the comet's orbit showed that it had last returned to the inner Solar System approximately

17,000 years earlier. Because the comet had probably passed close to the Sun several times before,[9] theapproach in 1996 would not be a maiden arrival from the Oort cloud, a place where comets with orbital periodsof millions of years come from. Comets entering the inner Solar System for the first time may brighten rapidlybefore fading as they near the Sun, as a layer of highly volatile material evaporates. This was the case withComet Kohoutek in 1973; it was initially touted as potentially spectacular, but only appeared moderately bright.Older comets show a more consistent brightening pattern. Thus, all indications pointed that Comet Hyakutakewould be bright.

Besides approaching close to the Earth, the comet would also be visible throughout the night to northernhemisphere observers at its closest approach because of its path, passing very close to the pole star. This wouldbe an unusual occurrence, because most comets are close to the Sun in the sky when the comets are at theirbrightest, leading to the comets appearing in a sky not completely dark.


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The comet on the evening of its closestapproach to Earth on 25 March 1996.

The SOHO satellite capturedthis image of Hyakutake as it

passed perihelion, with anascent coronal mass ejectionalso visible to the left of the

Sun.

Hyakutake became visible to the naked eye in early March 1996.By mid-March, the comet was still fairly unremarkable, shining at4th magnitude with a tail about 5 degrees long. As it neared itsclosest approach to Earth, it rapidly became brighter, and its tailgrew in length. By March 24, the comet was one of the brightestobjects in the night sky, and its tail stretched 35 degrees. The comet

had a notably bluish-green colour.[9]

The closest approach occurred on 25 March. Hyakutake wasmoving so rapidly across the night sky that its movement could bedetected against the stars in just a few minutes; it covered thediameter of a full moon (half a degree) every 30 minutes. Observersestimated its magnitude as around 0, and tail lengths of up to

80 degrees were reported.[9] Its coma, now close to the zenith forobservers at mid-northern latitudes, appeared approximately 1.5 to 2 degrees across, roughly four times the

diameter of the full moon.[9] Even to the naked eye, the comet's head appeared distinctly green, due to strongemissions from diatomic carbon (C2).

Because Hyakutake was at its brightest for only a few days, it did not have time to permeate the publicimagination in the way that Comet Hale-Bopp did the following year. Many European observers in particular

did not see the comet at its peak because of unfavourable weather conditions.[9]

After its close approach to the Earth, the comet faded to about 2ndmagnitude. It reached perihelion on May 1, 1996, brightening again andexhibiting a dust tail in addition to the gas tail seen as it passed the Earth.By this time, however, it was close to the Sun and was not seen as easily. Itwas observed passing perihelion by the SOHO Sun-observing satellite,which also recorded a large coronal mass ejection being formed at the sametime. Its distance from the Sun at perihelion was 0.23 AU, well inside the

orbit of Mercury.[12]

After its perihelion passage, Hyakutake faded rapidly and was lost tonaked-eye visibility by the end of May. Its orbital path carried it rapidly intothe southern skies, but following perihelion it became much less monitored.

The last known observation of the comet took place on November 2.[13]

Hyakutake had passed through the inner Solar System approximately17,000 years ago; gravitational interactions with the gas giants during its1996 passage stretched its orbit greatly, and fits to the comet's orbitpredicted it will not return to the inner Solar System again for approximately

72,000[9] to 114,000 years.[14]

Spacecraft passes through the tail


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The Ulysses spacecraft made an unexpected pass through the tail of the comet on May 1, 1996.[15] Evidence ofthe encounter was not noticed until 1998. Astronomers analysing old data found that Ulysses' instruments haddetected a large drop in the number of protons passing, as well as a change in the direction and strength of thelocal magnetic field. This implied that the spacecraft had crossed the 'wake' of an object, most likely a comet;the object responsible was not immediately identified.

In 2000, two teams independently analyzed the same event. The magnetometer team realized that the changes inthe direction of the magnetic field mentioned above agreed with the "draping" pattern expected in a comet's ion,or plasma tail. The magnetometer team looked for likely suspects. No known comets were located near thesatellite, but looking further afield, they found that Hyakutake, 500 million km away, had crossed Ulysses'orbital plane on April 23, 1996. The solar wind had a velocity at the time of about 750 km/s, at which speed itwould have taken eight days for the tail to be carried out to where the spacecraft was situated at 3.73 AU,approximately 45 degrees out of the ecliptic plane. The orientation of the ion tail inferred from the magnetic

field measurements agreed with the source lying in Comet Hyakutake's orbital plane.[16]

The other team, working on data from the spacecraft's ion composition spectrometer, discovered a sudden largespike in detected levels of ionised particles at the same time. The relative abundance of chemical elements

detected indicated that the object responsible was definitely a comet.[17]

Based on the Ulysses encounter, the comet's tail is known to have been at least 570 million km(360 million miles; 3.8 AU) long. This is almost twice as long as the previous longest-known cometary tail, thatof the Great Comet of 1843, which was 2.2 AU long.

Composition

Terrestrial observers found ethane and methane in the comet, the first time either of these gases had beendetected in a comet. Chemical analysis showed that the abundances of ethane and methane were roughly equal,which may imply that its ices formed in interstellar space, away from the Sun, which would have evaporatedthese volatile molecules. Hyakutake's ices must have formed at temperatures of 20 K or less, indicating that it

probably formed in a denser than average interstellar cloud.[18]

The amount of deuterium in the comet's water ices was determined through spectroscopic observations.[19] It

was found that the ratio of deuterium to hydrogen (known as the D/H ratio) was about 3 × 10−4, which

compares to a value in Earth's oceans of about 1.5 × 10−4. It has been proposed that cometary collisions withEarth might have supplied a large proportion of the water in the oceans, but the high D/H ratio measured inHyakutake and other comets such as Hale-Bopp and Halley's Comet have caused problems for this theory.


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Teaching tools > Comets > Overview: Comet Halley facts > FastFacts: Comet Halley

Description Halley is perhaps the most famouscomet in history. This is the comet thatproved correct Edmund Halley'sprediction that it would reappear. It isresponsible for depositing the debristhat, when falling through Earth'satmosphere, causes the Orionid meteorshowers.

Age About the same age as the Sun: 4.5billion years

Location Outer solar system — Kuiper belt

Avg. distancefrom the Sun

It has a highly elongated orbit thattakes it very close to the Sun and thenflings it out into the outer solar system,well past the orbit of Pluto.

Diameter The size of the nucleus has beenestimated to be 15 km x 7 km x 7 km(or 9 mi x 4 mi x 4 mi).

Mass 1.7 x 1015 kilograms

Orbitalperiodaround theSun

76 Earth years

(Image courtesyof NASA)

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Spacecraft that have visited Halley's Comet

Halley's [HAL-lee] Comet has been know since at least 240 BC and possibly since 1059 BC.Its most famous appearance was in 1066 AD when it was seen right before the Battle ofHastings. It was named after Edmund Halley, who calculated its orbit. He determined thatthe comets seen in 1531 and 1607 were the same object that followed a 76-year orbit.Unfortunately, Halley died in 1742, never living to see his prediction come true when thecomet returned on Christmas Eve 1758.

Halley's Comet put on bright shows in 1835 and in 1910. Then in 1984 and 1985, fivespacecraft from the USSR, Japan and Europe were launched to make a rendezvous withHalley's Comet in 1986. One of NASA's deep space satellites was redirected to monitor thesolar wind upstream from Halley. Only three comets have ever been studied by spacecraft.Comet Giacobini-Zinner was studied in 1985, Comet Halley in 1986, and CometGrigg-Skjellerup on July 10th, 1992. The nucleus of Halley is ellipsoidal in shape and measuresapproximately 16 by 8 by 8 kilometers (10 by 5 by 5 miles).

Halley's Comet Statistics

Perihelion distance: 0.587 AUOrbital eccentricity: 0.967Orbital inclination: 162.24°Orbital period: 76.0 yearsNext perihelion: 2061Diameter: 16 x 8 x 8 km

Animation of Halley's Comet

Animation of Halley's comet from Giotto pictures. (Courtesy A.Tayfun Oner)

Views of Halley's Comet

Comet Halley in False ColorThis image of Halley's Comets was taken during its 1986 appearance. False-color digital enhancement wasused to permit measurement of slight brightness differences. (Copyright Calvin J. Hamilton)

Giotto Mosaic of Halley's CometThis image is a mosaic of 8 images taken by the Giotto spacecraft during the Halley encounter on March 13,

Comet Halley http://www.solarviews.com/eng/halley.htm

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Brought to you by the National Earth Science Teachers Association

This image of the nucleus ofHalley's comet comes from theGiotto spacecraft.Click on image for full sizeJPL

Halley's comet

Halley's comet is named after Edmond G. Halley who was the first to suggest that comets werenatural phenomena of the solar system, in orbit around the Sun. He suggested that a certaincomet was a regular visitor, returning every 76 years, and was, in fact, the same one which hadbeen observed since 240 BC, but in particular in the years 1531, 1607, and 1682, dates which forhim were recent history. In 1682 he predicted the comet would return again in 1758, and sureenough, the comet arrived in March 1759. Halley's comet made a particularly brightappearance in 1910. It also was recorded in a famous ancient tapestry after its 1066appearance.

For hundreds of years humankind has wondered what the nucleus of Halley's comet was reallylike. This wonderful picture from the Giotto spacecraft gives us the answer. In this picture, theSun is on the left. Three jets can be seen blowing molecules toward the Sun. A crater can alsobe seen in the middle right. This image shows that evaporation occurs along specific portions ofthe comet. Data taken by a suite of spacecraft suggests that the comet is mostly made of ice.

Halley's comet is next scheduled to return in 2062.

Last modified December 6, 2000 by Jennifer Bergman.News Flash!

Halley's comet http://www.windows2universe.org/comets/Halleys_comet.html

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C/1975 V1 (West)

Discovery

Discovered by: Richard M. WestDiscovery date: August 10, 1975Alternatedesignations:

C/1975 V1, 1976 VI,1975n

Orbital characteristics A(http://www.minorplanetcenter.org/iau/Ephemerides

/Comets/)

Epoch: 2442840.5Aphelion distance: 13560 AUPerihelion distance: 0.58 AUSemi-major axis: 6,780.20 AUEccentricity: 0.99997Orbital period: 558,306.4201 aInclination: 43.0664°Last perihelion: February 25, 1976


There is another long-period comet West: C/1978 A1 (a.k.a. 1977 IX, 1978a).

Comet West formally designated C/1975 V1, 1976 VI, and1975n, was a spectacular comet, sometimes considered toqualify for the status of "great comet".

1 Discovery2 Breakup3 Nomenclature4 References

It was discovered photographically by Richard M. West, of theEuropean Southern Observatory, on August 10, 1975, andreached peak brightness in March 1976, attaining a brightness of-3 at perihelion. During peak brightness, observers reported thatit was bright enough to study during full daylight.

Despite its spectacular appearance, Comet West went largelyunreported in the popular media. This was partly due to therelatively disappointing display of Comet Kohoutek in 1973,which had been widely predicted to become extremelyprominent: scientists were wary of making predictions that mightraise public expectations.[1]

The comet has an estimated orbital period of 558,000 years.

During the passage of Comet West into the inner solar system, possibly for the first time in 500,000 years, itsnucleus was observed to split into four fragments as it passed within 30 million km of the Sun.

The first report of the split came around 7 March 1976 12:30UT, when reports were received that the comet hadbroken into two pieces. Astronomer Steven O'Meara, using the 9-inch Harvard Refractor, reported that twoadditional fragments had formed on the morning of 18 March.

The fragmentation of the nucleus was, at the time, one of very few comet breakups observed, one of the mostnotable previous examples being the Great Comet of 1882, a member of the Kreutz Sungrazing 'family' ofcomets. More recently, comets Schwassmann-Wachmann-3 (73/P), C/1999 S4 LINEAR, and 57/P duToit-Neujmin-Delporte, have been observed to disintegrate during their passage close to the Sun.

Comet West - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Comet_West

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2P/Encke

Discovery

Discovered by: Pierre Méchain

Discovery date: 1786

Alternatedesignations:

1786 I; 1795; 1805;1819 I; 1822 II; 1825 III;1829; 1832 I; 1835 II;1838; 1842 I; 1845 IV


/Comets/)

Epoch: September 22, 2006 (JD2454000.5)

Aphelion distance: 4.11 AU

Perihelion distance: 0.3302 AU

Semi-major axis: 2.2178 AU

Eccentricity: 0.8471

Orbital period: 3.30 a

Inclination: 11.76°

Last perihelion: 6 August 2010[1]

Next perihelion: 21 November 2013[1]


Comet Encke or Encke's Comet (official designation:2P/Encke) is a periodic comet that completes an orbit of thesun once every three years — the shortest period of anyknown comet. It was first recorded by Pierre Méchain in1786, but it was not recognized as a periodic comet until1819 when its orbit was computed by Johann Franz Encke;like Halley's Comet, it is unusual in being named after thecalculator of its orbit rather than its discoverer.

1 Discovery2 Characteristics3 Observations4 Meteor showers5 Effects on Earth6 Importance in the scientific history ofluminiferous aether7 See also8 References9 External links

As its official designation implies, Encke's Comet was thefirst periodic comet discovered after Halley's Comet(designated 1P/Halley). Its orbit was calculated by JohannFranz Encke, who, through laborious calculations was able tolink observations of comets in 1786 (designated 2P/1786B1), 1795 (2P/1795 V1), 1805 (2P/1805 U1) and 1818(2P/1818 W1) to the same object. In 1819 he published hisconclusions in the journal Correspondance astronomique,and predicted correctly its return in 1822 (2P/1822 L1).

The diameter of the nucleus of Encke's Comet is 4.8 km.[2]

Comets are in unstable orbits that evolve over time due to perturbations and outgassing. Given Encke's loworbital inclination near the ecliptic and brief orbital period of 3 years, the orbit of Encke is frequently perturbed

by the inner planets.[3]

Comet Encke - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Comet_Encke

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A Spitzer image of Encke and itsdebris trail in infrared light. Credit:(NASA/JPL-Caltech/University of

Minnesota)

A Han Dynasty silk comet atlas, featuring drawings ofcomets believed by Victor Clube and Bill Napier to be

related to the breakup of Encke's Comet in the past

The failed CONTOUR mission was launched to study this comet, and also Schwassmann-Wachmann 3.

On April 20, 2007, the tail of Comet Encke was observed to be temporarily torn off by magnetic field

disturbances caused by a Coronal Mass Ejection: a blast of solar particles from the sun.[4] The tail grew back

due to the continuous shedding of dust and gas by the comet.[5]

Comet Encke is believed to be the originator of several related meteorshowers known as the Taurids (which are encountered as the Northernand Southern Taurids across November, and the Beta Taurids in late

June and early July).[6][7]

Near-Earth object 2004 TG10 may be a fragment of Encke.[8]

More than one theory has associated Encke's Comet with impacts ofcometary material on Earth, and with cultural significance.

The Tunguska event of 1908, probably caused by the impact of acometary body, has also been postulated by Czechoslovakian astronomer

Ľubor Kresák as a fragment of Comet Encke.[9]

A theoryholds thatthe ancientsymbol of

the swastika appeared in a variety of cultures acrossthe world at a similar time, and could have beeninspired by the appearance of a comet from head on,as the curved jets would be reminiscent of theswastika shape (see Comets and the swastika motif).Comet Encke has sometimes been identified as thecomet in question. In their 1982 book CosmicSerpent (page 155) Victor Clube and Bill Napierreproduce an ancient Chinese catalogue of cometaryshapes from the Mawangdui Silk Texts, whichincludes a swastika-shaped comet, and suggest that some of the comet drawings were related to the breakup ofthe progenitor of Encke and the Taurid meteoroid stream. Fred Whipple in his The Mystery of Comets (1985,page 163) points out that Comet Encke's polar axis is only 5 degrees from its orbital plane: such an orientation isideal to have presented a pinwheel like aspect to our ancestors when Encke was more active.

Table of Contents

Comet IntroductionComet Historical Background

Comets

Comet 73P/Schwassmann -Wachmann 3

Comet BorrellyHalley's CometShoemaker-Levy 9

Shoemaker-Levy 9Background

Shoemaker-Levy 9 ImpactHubble PR - Collision Results

Comet LINEARComet P/Wild-2Comet Tempel 1Deep Impact Crash into Comet

Tempel 1Deep Impact Tells a Tale of

the Comet

Comet Information

Hale-Bopp Fails EmissionTests but Reveals CometOrigin

Kuiper Belt ObjectsComets Beyond NeptuneComet TutorialMake a Comet NucleusComet Space Exploration

ChronologyComet Image/Animation

Gallery

Contents | What's New | Image Index | Copyright | Puzzles | Posters | Search |

NASA's Hubble Space Telescope isproviding astronomers with extraordinaryviews of comet 73P/Schwassmann-Wachmann 3, which is falling apart rightbefore our eyes. Recent Hubble imageshave uncovered many more fragmentsthan have been reported by ground-basedobservers. These observations provide anunprecedented opportunity to study thedemise of a comet nucleus.

Amateur and professional astronomersaround the world have been tracking foryears the spectacular disintegration of

73P/Schwassmann-Wachmann 3. As it plunges toward a June 6th swing aroundthe Sun, the comet will pass Earth on May 12th, at a distance of 7.3 million miles,or 30 times the distance between Earth and the Moon.

The comet is currently comprisedof a chain of over three dozenseparate fragments, namedalphabetically, stretching acrossseveral degrees on the sky. (TheSun and Moon each have anapparent diameter of about 1/2 of adegree.) Ground-based observershave noted dramatic brighteningevents associated with some of the

fragments (as shown in the bottom frame) indicating that they arecontinuing to break-up and that some may disappear altogether.

Hubble caught two of the fragments, B and G, (top frames)shortly after large outbursts in activity. Hubble also photographed fragment C (not shown), which was lessactive. The resulting images reveal that a hierarchical destruction process is taking place, in which fragments arecontinuing to break into smaller chunks. Several dozen "mini-fragments" are found trailing behind each mainfragment, probably associated with the ejection of house-sized chunks of surface material that can only bedetected in these very sensitive and high-resolution Hubble images.

Comet 73P/Schwassmann-Wachmann 3 http://www.solarviews.com/eng/wachmann.htm

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Sequential Hubble images of the B fragment, taken a few days apart, suggest that the chunks are pushed downthe tail by outgassing from the icy, sunward-facing surfaces of the chunks, much like space-walking astronautsare propelled by their jetpacks. The smaller chunks have the lowest mass, and so are accelerated away from theparent nucleus faster than the larger chunks. Some of the chunks seem to dissipate completely over the course ofseveral days.

Deep-freeze relics of the early solar system, cometary nuclei are porous and fragile mixes of dust and ices. Theycan be broken apart by gravitational tidal forces when they pass near large bodies (for example, CometShoemaker-Levy 9 was torn to pieces when it skirted near Jupiter in 1992, prior to plunging into Jupiter'satmosphere two years later). They can also fly apart from rapid rotation of the nucleus, break apart because ofthermal stresses as they pass near the Sun, or explosively pop apart like corks from champagne bottles due to theoutburst of trapped volatile gases.

"Catastrophic breakups may be the ultimate fate of most comets," says planetary astronomer Hal Weaver of theJohns Hopkins University Applied Physics Laboratory, who led the team that made the recent Hubbleobservations and who used Hubble previously to study the fragmentations of comets Shoemaker-Levy 9 in1993-1994, Hyakutake in 1996, and 1999 S4 (LINEAR) in 2000. Analysis of the new Hubble data, and datataken by other observatories as the comet approaches the Earth and Sun, may reveal which of these breakupmechanisms are contributing to the disintegration of 73P/Schwassmann-Wachmann 3.

German astronomers Arnold Schwassmann and Arno Arthur Wachmann discovered this comet during aphotographic search for asteroids in 1930, when the comet passed within 5.8 million miles of the Earth (only 24times the Earth-Moon distance). The comet orbits the Sun every 5.4 years, but it was not seen again until 1979.The comet was missed again in 1985 but has been observed every return since then.

During the fall of 1995, the comet had a huge outburst in activity and shortly afterwards four separate nucleiwere identified and labeled "A", "B", "C", and "D", with "C" being the largest and the presumed principalremnant of the original nucleus. Only the C and B fragments were definitively observed during the next return,possibly because of the poor geometry for the 2000-2001 apparition. The much better observing circumstancesduring this year's return may be partly responsible for the detection of so many new fragments, but it is alsolikely that the disintegration of the comet is now accelerating. Whether any of the many fragments will survivethe trip around the Sun remains to be seen.

Besides Weaver, the other members of the Hubble observing team are: Carey Lisse (JHU/APL), Philippe Lamy(Laboratoire d'Astronomie Spatiale, France), Imre Toth (Hungarian Academy of Sciences), William Reach(IPAC/Caltech), and Max Mutchler (STScI). Z. Levay (STScI)

Additional Image of Comet Borrelly

A Million Comet PiecesThis infrared image from NASA's Spitzer Space Telescope shows the brokenComet 73P/Schwassman-Wachmann 3 skimming along a trail of debris leftduring its multiple trips around the sun. The flame-like objects are the comet'sfragments and their tails, while the dusty comet trail is the line bridging thefragments.

Comet 73P /Schwassman-Wachmann 3 began to splinter apart in 1995 duringone of its voyages around the sweltering sun. Since then, the comet has

continued to disintegrate into dozens of fragments, at least 36 of which can be seen here. Astronomers believethe icy comet cracked due the thermal stress from the sun.

The Spitzer image provides the best look yet at the trail of debris left in the comet's wake after its 1995 breakup.


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The observatory's infrared eyes were able to see the dusty comet bits and pieces, which are warmed by sunlightand glow at infrared wavelengths. This comet debris ranges in size from pebbles to large boulders. When Earthpasses near this rocky trail every year, the comet rubble burns up in our atmosphere, lighting up the sky inmeteor showers. In 2022, Earth is expected to cross close to the comet's trail, producing a noticeable meteorshower.

Astronomers are studying the Spitzer image for clues to the comet's composition and how it fell apart. LikeNASA's Deep Impact experiment, in which a probe smashed into comet Tempel 1, the cracked Comet73P/Schwassman-Wachmann 3 provides a perfect laboratory for studying the pristine interior of a comet.(Courtesy NASA/JPL-Caltech)

Hubble Provides Spectacular Detail of a Comet's BreakupHubble Space Telescope is providing astronomers with extraordinary views ofComet 73P/Schwassmann-Wachmann 3. The fragile comet is rapidly disintegratingas it approaches the Sun. Hubble images have uncovered many more fragments thanhave been reported by ground-based observers. These observations provide anunprecedented opportunity to study the demise of a comet nucleus. The comet iscurrently a chain of over three dozen separate fragments, named alphabetically,stretching across the sky by several times the angular diameter of the Moon. Hubblecaught two of the fragments (B and G) shortly after large outbursts in activity.Hubble shows several dozen "mini-comets" trailing behind each main fragment,

probably associated with the ejection of house-sized chunks of surface material. Deep-freeze relics of the earlysolar system, cometary nuclei are porous and fragile mixes of dust and ices that can break apart due to thethermal, gravitational, and dynamical stresses of approaching the Sun. Whether any of the many fragmentssurvive the trip around the Sun remains to be seen in the weeks ahead. (Courtesy NASA, ESA, JHU/APL, STScI)

Comet 73P/Schwassmann-Wachmann 3 - Fragment B: Apr. 18, 2006Hubble Space Telescope Advanced Camera for Surveys image of Comet73P/Schwassmann-Wachmann 3 fragment B on April 18, 2006. (Courtesy NASA,ESA, JHU/APL, STScI)




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Comet 73P/Schwassmann-Wachmann 3 - Fragments B, GGround-based color composite image of Comet 73P/Schwassmann-Wachmann3 fragments B and G on April 21, 2006 made with a 8" f/1.5 Schmidt Camera.(Courtesy M. J�ger and G. Rhemann)

Comet Introduction

Views of the Solar System copyright © 1995-2006 by Calvin J. Hamilton. All rights reserved. PrivacyStatement.


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Table of Contents

Comet Shoemaker-Levy 9 (This Page)IntroductionViews of Shoemaker-Levy 9

Shoemaker-Levy 9 ImpactShoemaker-Levy 9 Image IndexHubble Press Release on the SL-9 Collision ResultsComet Tutorial

Links to other Comet Shoemaker-Levy Home Pages

Comet Shoemaker-Levy 9 Impact from JPLEffelsberg Radio Observations of the Great Comet CrashComet Shoemake-Levy 9 page from SEDS

Introduction

Comet Shoemaker-Levy 9 was the ninth short-periodic comet discovered by Eugene and Carolyn Shoemaker and David Levy. It wasfirst detected on a photograph taken on the night of March 24, 1993, with the 0.4-meter Schmidt telescope on Palomar Mountain inCalifornia. The magnitude of the comet's brightness was reported as 14, more than a thousand times too faint to be seen with thenaked eye. The existence of this object was soon confirmed by James V. Scotti of the Spacewatch program at the University ofArizona.

Through the observations and efforts of Brian G. Marsden and other astronomers, the comet's orbit was demonstrated to be aroundJupiter and that it had made a very close approach to Jupiter on July 7, 1992. During this close approach, the unequal Jupitergravitational attractions on the comet's near and far sides broke the fragile object apart. On March 27, an image was taken with the2.2-m telescope on Mauna Kea in Hawaii that showed as many as 17 separate sub-nuclei strung out like pearls on a string 50 arcseconds long. An early image taken by Scotti on March 30 is shown below.

Early Shoemaker/Levy 9 Image

On July 1, 1993 an image was taken with the Hubble Space Telescope (HST) that clearly shows at least 15 individual fragments inone image frame of the train.

Comet Shoemaker-Levy 9 http://www.solarviews.com/eng/levy.htm

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Early HST Image

Since it was not at all obvious where the center of mass of this new comet lay, most observers were using the position of whatappeared to be the center of the train. This made an accurate orbit (or orbits) difficult to determine; however, after numerousobservations of the comet, astronmers determined that the comet had passed within 96,000 kilometers (60,000 miles) of the center ofJupiter or 25,000 kilometers (16,000 miles) from the cloud tops during the July 8, 1992, approach. They also determined that it wouldagain pass within 25,000 kilometers (16,000 miles) of the center of Jupiter, on July 19, 1994. This distance was less than the radius ofJupiter. In other words, the comet, or at least parts of it, could very well hit Jupiter.

Shoemaker-Levy 9 had been in a rapidly changing orbit around Jupiter for some time before this, probably for at least severaldecades. It did not fragment during earlier approaches to Jupiter because these were made at much greater distances than the 1992approach. The comet's previous approaches to Jupiter probably came no closer than 9 million kilometers (5.6 million miles).

By December 9 1993, the probability of impact for all the large fragments of Shoemaker-Levy 9 was calculated to be greater than99.99%. The fragments would hit over a period of several days, centered on July 19, on the night side of Jupiter. Unfortunately, thiswas the back side of Jupiter as viewed from Earth. The impact site would be close to the limb of Jupiter, near 75° from the midnightmeridian and only a few degrees beyond the dark limb as seen from Earth.

The disruption of a comet into multiple fragments is an unusual event, the capture of a comet into an orbit about Jupiter is even moreunusual, and the collision of a large comet with a planet is an extraordinary, millennial event.

Views of Shoemaker-Levy 9

HST 1993 MosaicThis high resolution image is a mosaic of images taken by the Hubble Telescope on January 24-27, 1994.Twenty nuclei are visible with one slightly outside of the field-of-view (to the right). Each nucleus has its owncoma and tail. The fourth nucleus from the left (the first bright one) is apparently starting to separate into at

least two pieces. (Courtesy NASA/JPL)

HST ImagesThese images were taken with the Hubble telescope's new camera's on January 24-27, 1994. In the upperimage, 20 nuclei are visible with one slightly outside of the field-of-view (to the right). Each nucleus has its owncoma and tail. The fourth nucleus from the left (the first bright one) is apparently starting to separate into atleast two pieces. The width and height of this image project to distances of 605,000 kilometers (376,000 miles)and 126,500 kilometers (78,600 miles), respectively, at the comet.

The lower left and right parts of the screen show the region near the brightest nucleus at higher resolution. To the left is the newimage from the corrected camera, while the image to the right shows old data from the aberrated camera. (Courtesy NASA/JPL)

Depictions of the Shoemaker-Levy 9 CollisionIn this series of depictions, comet Shoemaker-Levy 9 impacting Jupiter is shown from three differentperspectives: at left, from the viewpoint of Earth; center, from the Voyager 2 spacecraft in the outer reachesof the solar system; and, at right, from Jupiter's south pole. For visual appeal, most of the large cometaryfragments are shown close to one another in this image. At the time of Jupiter impact, the fragments will be

separated from one another by several times the distances shown. (Courtesy NASA/JPL)

Additional Shoemaker-Levy 9 Depictions

Viewpoint from the Earth.Viewpoint from Voyager 2.Viewpoint from Juipter's South Pole.

Comet Halley's Comet Shoemaker-Levy 9 Impact

Comet Shoemaker-Levy 9 http://www.solarviews.com/eng/levy.htm

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Table of Contents

IntroductionTable of Fragment Impacts and TimesViews of Shoemaker-Levy 9 / Jupiter Impact

Introduction

Fragments of comet P/Shoemaker-Levy 9 collided with Jupiter on July 16-22, 1994. Theresults were spectacular. At least 20 large fragments impacted the planet at 60 kilometers(37 miles) per second, causing plumes thousands of kilometers high. They left hot bubblesof gas in the atmosphere and great dark scars which lasted for months after the collision.The largest fragments were estimated at 2 kilometers (1.2 miles) in diameter.

The fragments impacted Jupiter at approximately 45° south latitude and 6.5° longitude fromthe limb, and 15° from the dawn terminator just out of view of the Earth. Eleven minutesafter impact, the point in the atmosphere where the impact occurred would rotate across thelimb and 14 minutes later would cross the dawn terminator. The fragments were moving atan angle of 83° from the Jovian north to south axis and struck the cloud tops at about 45°.The following table lists the impact times as seen from the Earth, calculated by DonYeomans and Paul Chodes.

Table of Fragment Impacts and Times.

FragmentDate(July)

PredictedImpact Time(HH:MM:SS)

AcceptedImpact Time

& 1-sigma error

A 16 20:00:40 20:11:00 (3 min)

B 17 02:54:13 02:50:00 (6 min)

C 17 07:02:14 07:12:00 (4 min)

D 17 11:47:00 11:54:00 (3 min)

E 17 15:05:31 15:11:00 (3 min)

F 18 00:29:21 00:33:00 (5 min)

G 18 07:28:32 07:32:00 (2 min)

H 18 19:25:53 19:31:59 (1 min)

J 19 02:40 Missing since 12/93

K 19 10:18:32 10:21:00 (4 min)

L 19 22:08:53 22:16:48 (1 min)

M 20 05:45 Missing since 7/93

N 20 10:20:02 10:31:00 (4 min)

O 20 15:16:20 15:23:00 (7 min)

P1 20 16:30 Missing since 3/94

Q2 20 19:47:11 19:44:00 (6 min)

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Q1 20 20:04:09 20:12:00 (4 min)

R 21 05:28:50 05:33:00 (3 min)

S 21 15:12:49 15:15:00 (5 min)

T 21 18:03:45 18:10:00 (7 min)

U 21 21:48:30 21:55:00 (7 min)

V 22 04:16:53 04:22:00 (5 min)

W 22 07:59:45 08:05:30 (3 min)

Views of Shoemaker-Levy 9 / Jupiter Impact

Galileo Image of Impact WThese four images of Jupiter and the luminous night-side impact of fragment W of Comet Shoemaker-Levy 9were taken by the Galileo spacecraft on July 22, 1994. The spacecraft was 238 million kilometers (148 millionmiles) from Jupiter at the time, and 621 million kilometers (386 million miles) from Earth. The spacecraft was

about 40 degrees from Earth's line of sight to Jupiter, permitting this direct view. The first image, taken at an equivalent time to 8:06:10Greenwich Mean Time (1:06 a.m. Pacific Daylight Time), shows no impact. In the next three images, a point of light appears, brightensso much as to saturate its picture element, and then fades again, seven seconds after the first picture. The location is approximately44 degrees south as predicted; dark spots to the right are from previous impacts. Jupiter is approximately 60 picture elements indiameter. (Courtesy NASA)

Impact of H-fragment observed at La SillaThis image was obtained with the TIMMI instrument at the European Southern Observatory's 3.6-metertelescope on July 18, 1994, 20:11 UT. It shows the rising plume above the impact site of fragment H of cometShoemaker-Levy 9. The image was made in the 9.1 - 10.4 micron band in the far-infrared region. The surfacebrightness of this plume was about 50 times that of the Jupiter disk. The temperature was measured as morethan 300 K. (Courtesy European Southern Observatory)

HST UV Image of Impacts H, Q1, R, D, G, L, B, N & Q2This ultraviolet image shows Jupiter's atmosphere at a wavelength of 2550 Angstroms after many impacts byfragments of comet Shoemaker-Levy 9. The most recent impactor is fragment R which is below the center ofJupiter (third dark spot from the right). This photo was taken by the Hubble Space Telescope at 3:55 EDT onJuly 21, about 2.5 hours after R's impact. A large dark patch from the impact of fragment H is visible rising onthe morning (left) side. Proceeding to the right, other dark spots were caused by impacts of fragments Q1, R, Dand G (now one large spot), and L, with L covering the largest area of any seen thus far. Small dark spots fromB, N, and Q2 are visible with careful inspection of the image. The spots are very dark in the ultraviolet because

a large quantity of dust is being deposited high in Jupiter's stratosphere, and the dust absorbs sunlight. (Courtesy Hubble SpaceTelescope Comet Team)

HST Image of Impacts E/F, H, N, Q1, Q2, R and D/GImage of Jupiter with the Hubble Space Telescope Planetary Camera. Eight impact sites are visible. From left toright are the E/F complex (barely visible on the edge of the planet), the star-shaped H site, the impact sites fortiny N, Q1, small Q2, and R, and on the far right limb the D/G complex. The D/G complex also shows extendedhaze at the edge of the planet. The features are rapidly evolving on time scales of days. The smallest featuresin this image are less than 200 kilometers (124 miles) across. (Courtesy Hubble Space Telescope Comet Team)

HST Image of Impacts D and GThis image of Jupiter shows the impact sites of fragments "D" and "G" from Comet Shoemaker-Levy 9. Thelarge feature was created by the impact of fragment "G" on July 18, 1994 at 3:28 a.m. EDT. It entered Jupiter'satmosphere from the south at a 45-degree angle, and the resulting ejecta appears to have been thrown backalong that direction. The smaller feature to the left of the fragment "G" impact site was created on July 17, 1994,at 7:45 a.m. EDT by the impact of fragment "D". The "G" impact has concentric rings around it, with a central

dark spot 2,500 kilometers (1,550 miles) in diameter. This dark spot is surrounded by a thin dark ring 7,500 kilometers (4,661 miles) indiameter. The dark thick outermost ring's inner edge has a diameter of 12,000 kilometers (7,460 miles) - about the size of the Earth.(Courtesy Hubble Space Telescope Comet Team)

HST Views of Comet Fragment G Impact ZoneThis image shows two views of the impact zone on Jupiter of fragment G of Comet Shoemaker-Levy 9. Theimage on the left was made in green light. The image on the right is the same field taken through a methanefilter. These images were obtained by the Hubble Space Telescope in the early morning of July 18, 1994. Theimpact site is visible as a complex pattern of circles seen in the lower left of the partial planet image. The smalldark feature to the left of the pattern of circles is the impact site of fragment D. The dark, sharp ring at the siteof the fragment G impact is 80% of the size of the Earth. (Courtesy Dr. Heidi Hammel, Massachusetts Institute

of Technology/NASA HST)


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HST G Plume ImageThese images taken by the Hubble Telescope show the G impact site through methane, red, green, blue andviolet filters. (Courtesy Hubble Space Telescope Comet Team)

HST A, C and E Impact SitesThis Hubble image of Jupiter was obtained with a filter at 336 nm (near-ultraviolet light) at 18:42 UT on 17 July1994. Three impact sites (from left to right: C, A, and E) are visible as dark spots across the lower portion of theimage. All other features in this picture are characteristic of Jupiter's normal state. The feature created by theimpact of A is 23 hours old in this image. The C and E features are 12 and 5 hours old, respectively. Io is seenon the left as a dark spot in the northern hemisphere, and the Great Red Spot is visible on the right limb.(Courtesy Hubble Space Telescope Jupiter Imaging Team)

Evolution of the G Impact SiteThis mosaic of Hubble images shows the evolution of the G impact site on Jupiter. The images from lower rightto upper left show: the impact plume at 07/18/94 07:38 UT (about 5 minutes after the impact); the fresh impactsite at 07/18/94 at 09:19 UT (1.5 hours after impact); the impact site after evolution by the winds of Jupiter (left),along with the L impact (right), taken on 07/21/94 at 06:22 UT (3 days after the G impact and 1.3 days after theL impact); and further evolution of the G and L sites due to winds and an additional impact (S) in the G vicinity,taken on 07/23/94 at 08:08 UT (5 days after the G impact). (Credit: R. Evans, J. Trauger, H. Hammel and theHST Comet Science Team and NASA)

IRTF Infrared Image of Q & R ImpactsThis is a 2.07 micron image of Jupiter taken on the NASA Infrared Telescope Facility, Mauna Kea, Hawaii, at08:54 on July 21, 1994. Io, the closest of the jovian moons, can be seen crossing the planet in the northwest ofthe image (top right). The Great Red Spot is visible in the south east of the planet. At the collision latitudes, theimpact due to Fragment Q is just setting on the west. Just to the east of it, the R Fragment impact site showsup very brightly. Another four impact sites form a chain of spots behind R. (Courtesy NASA IRTF CometScience Team)

Comet SL9 Background Kuiper Belt Objects

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Was it a comet or an asteroid? Scientists are debating that question as they continue topore over Hubble Space Telescope imaging and spectroscopic data gleaned in the wake ofthe spectacular July 1994 bombardment of Jupiter by comet P/Shoemaker-Levy 9. Theirinitial findings, combined with results from other space-borne and ground-based telescopes,shed new light on Jupiter's atmospheric winds, its immense magnetic field, the mysteriousdark debris from the impacts, and the composition of the doomed comet itself.

The Last Days Of The Comet

Before the comet impact, there was a great deal of speculation and prediction aboutwhether the 21 nuclei would survive before reaching Jupiter, or were so fragile thatgravitational forces would pull them apart into thousands of smaller fragments. Hubblehelped answer this question by watching the nuclei until about 10 hours before impact.

HST's high resolution images show that the nuclei, the largest of which were probably a fewkilometers across, did not break up catastrophically before plunging into Jupiter'satmosphere. This reinforces the notion that the atmospheric explosions were produced bysolid, massive impacting bodies. HST's resolution also showed that the nuclei werereleasing dust all along the path toward Jupiter, as would be expected from a comet. Thiswas evident in the persistence of spherical clouds of dust surrounding each nucleusthroughout most of the comet's journey. About a week before impact, these dust cloudswere stretched out along the path of the comet's motion by Jupiter's increasingly stronggravity.

Was P/Shoemaker-Levy 9 A Comet Or An Asteroid?

At present, observations seem to slightly favor a cometary origin, though an asteroidal origincannot yet be ruled out. The answer isn't easy because comets and asteroids have so muchin common: they are small bodies; they are primordial, having formed 4.6 billion years agoalong with the planets and their satellites; either type of object can be expected to be foundin Jupiter's vicinity. The key difference is that comets are largely icy while the asteroids arevirtually devoid of ice because they formed too close to the Sun.

What Is That Dark Stuff Made Of?

The HST Faint Object Spectrograph (FOS) detected many gaseous absorptions associated with the impact sites and followed theirevolution over the next month. Most surprising were the strong signatures from sulfur-bearing compounds like diatomic sulfur (S2),carbon disulfide (CS2), and hydrogen sulfide (H2S). Ammonia (NH3) absorption also was detected. The S2 absorptions seemed tofade on timescales of a few days, while the NH3 absorptions at first got stronger with time, and finally started fading after about onemonth. During observations near the limb of Jupiter, the FOS detected emissions from silicon, magnesium and iron that could onlyhave originated from the impacting bodies, since Jupiter itself normally does not have detectable amounts of these elements.

Swept Across Jupiter

Observations made with HST's Wide Field Planetary Camera-2, a week and a month after impact, have been used to make globalmaps of Jupiter for tracking changes in the dark debris caught up in the high-speed winds at Jupiter's cloudtops. This debris is a

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natural tracer of wind patterns and allows astronomers a better understanding of the physics of the Jovian atmosphere. The highspeed easterly and westerly jets have turned the dark "blobs" originally at the impact sites into striking "curly-cue" features. Althoughindividual impact sites were still visible a month later despite the shearing, the fading of Jupiter's scars has been substantial and itnow appears that Jupiter will not suffer any permanent changes from the explosions.

Hubble's ultraviolet observations show the motion of very fine impact debris particles now suspended high in Jupiter's atmosphere.The debris eventually will diffuse down to lower altitudes. This provides the first information ever obtained about Jupiter's high altitudewind patterns. Hubble gives astronomers a "three dimensional" perspective showing the wind patterns at high altitudes and how theydiffer from those at the visible cloudtop level. At lower altitudes, the impact debris follows east-west winds driven by sunlight andJupiter's own internal heat. By contrast, winds in the high Jovian stratosphere move primarily from the poles toward the equatorbecause they are driven mainly by auroral heating from high energy particles.

Piercing Jupiter's Magnetic Field

About four days before impact, at a distance of 2.3 million miles from Jupiter, nucleus "G" of comet P/Shoemaker-Levy 9 apparentlypenetrated Jupiter's powerful magnetic field, the magnetosphere. (Jupiter's magnetosphere is so vast, if visible from Earth, it would beabout the size of the full Moon.)

Hubble's Faint Object Spectrograph (FOS) recorded dramatic changes at the magnetosphere crossing that provided a rareopportunity to gather more clues on the comet's true composition. During a two-minute period on July 14, HST detected strongemissions from ionized magnesium (Mg II), an important component of both comet dust and asteroids. However, if the nuclei wereice-laden - as expected of a comet nucleus - astronomers expected to detect the hydroxyl radical (OH). Hubble did not see OH,casting some doubt on the cometary nature of comet P/Shoemaker-Levy 9. Eighteen minutes after comet P/Shoemaker- Levy 9displayed the flare-up in Mg II emissions, there was also a dramatic change in the light reflected from the dust particles in the comet.

New Auroral Activity

HST detected unusual auroral activity in Jupiter's northern hemisphere just after the impact of the comet's "K" fragment. This impactcompletely disrupted the radiation belts which have been stable over the last 20 years of radio observations.

Aurorae, glowing gases that create the northern and southern lights, are common on Jupiter because energetic charged particlesneeded to excite the gases are always trapped in Jupiter's magnetosphere. However, this new feature seen by Hubble was unusualbecause it was temporarily as bright or brighter than the normal aurora, short-lived, and outside the area where Jovian aurorae arenormally found. Astronomers believe the K impact created an electromagnetic disturbance that traveled along magnetic field lines intothe radiation belts. This scattered charged particles, which normally exist in the radiation belts, into Jupiter's upper atmosphere.

X-ray images taken with the ROSAT satellite further bolster the link to the K impact. They reveal unexpectedly bright X-ray emissionsthat were brightest near the time of the K impact, and then faded.

The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) forNASA, under contract with the Goddard Space Flight Center, Greenbelt, Md. The Hubble Space Telescope is a project of internationalcooperation between NASA and the European Space Agency (ESA).

Donald SavageHeadquarters, Washington, D.C.September 29, 1994(Phone: 202/358-1547) Jim ElliottGoddard Space Flight Center, Greenbelt, Md.(Phone: 301/286-6256) Ray VillardSpace Telescope Science Institute, Baltimore, Md.(Phone: 410/338-4514) RELEASE: 94-161

Comet Shoemaker-Levy 9

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109P/Swift-Tuttle

Discovery

Discovered by: Lewis SwiftHorace Parnell Tuttle

Discovery date: July 16, 1862

Alternatedesignations:

1737 N1; 1737 II; 1862O1;1862 III; 1992 S2; 1992XXVIII


/Comets/)

Epoch: October 10, 1995 (JD2450000.5)

Aphelion distance: 51.225 AU

Perihelion distance: 0.9595 AU

Semi-major axis: 26.092 AU

Eccentricity: 0.9632

Orbital period: 133.28 a

Inclination: 113.45°

Last perihelion: December 11, 1992

Next perihelion: July 12, 2126


Comet Swift-Tuttle (formally designated as 109P/Swift-Tuttle)is a comet that was independently discovered by Lewis Swift onJuly 16, 1862 and by Horace Parnell Tuttle on July 19, 1862.

The comet made a return appearance in 1992, when it wasrediscovered by Japanese astronomer Tsuruhiko Kiuchi and

became visible with binoculars.[1] Its solid nucleus is about 27kilometers (16.8 miles) across, considerably larger than the10 km object hypothesized to have wiped out the dinosaurs in

the Cretaceous–Paleogene extinction event.[2]

It is the parent body of the Perseid meteor shower, perhaps thebest known shower and among the most reliable in performance.[3]

An unusual aspect of its orbit is that it is presently captured intoa 1:11 orbital resonance with Jupiter; it completes one orbit for

every 11 of Jupiter.[4]

The comet is on an orbit which puts it close to the Earth and the

Moon.[5] Upon its 1992 rediscovery, the comet's date ofperihelion passage was off from the then-current prediction by 17 days. It was then noticed that, if its nextperihelion passage (August 14, 2126) was also off by another 15 days, the comet would very likely strike theEarth or Moon. Given the size of the nucleus of Swift-Tuttle, this was of some concern. This prompted amateurastronomer and writer Gary W. Kronk to search for previous apparitions of this comet. He found the comet wasmost likely observed by the Chinese in 69 BC and AD 188, which was quickly confirmed by Brian G.

Marsden.[6] This information and subsequent observations have led to recalculation of its orbit, which indicates

the comet's orbit is very stable, and that there is absolutely no threat over the next two thousand years.[7]

Astronomers believe that in the 2126 pass it will likely be a great naked-eye comet like Hale-Bopp.[1]

A close encounter with Earth is predicted for the comet's return to the inner solar system in the year 4479,around Sept. 15; the closest approach is estimated to be 0.03-0.05 AU, with a probability of impact of

1 × 10−6.[4] Subsequent to 4479, the orbital evolution of the comet is more difficult to predict; the probability of

Earth impact per orbit is estimated as 2 × 10−8.[4] As the largest Solar System object that makes repeated close

passes of Earth, and which does so at a relative velocity of 60 km/s,[2][8] leading to an estimated impact energy

of ~27 times that of the K-T impactor,[9] Comet Swift-Tuttle has been described as "the single most dangerous

object known to humanity".[8]

^ a b Britt, Robert (2005-08-11). "Top 10 Perseid Meteor Shower Facts" (http://www.space.com/spacewatch/050811_perseid_facts.html) . Space.com. http://www.space.com/spacewatch/050811_perseid_facts.html. Retrieved

1.

109P/Swift-Tuttle - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/109P/Swift-Tuttle

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G A R Y W. K R O N K ' S C O M E T O G R A P H Y

Past, Present, and Future Orbits by Kazuo Kinoshita

Copyright © 1992 by Herman Mikuz (Crni Vrh Observatory, Slovenia)

This image was obtained on 1992 December 15, with 3.5/250mm lens, CCD, and narrow-band H2O+ filter, centered at620nm (FWHM=10nm). The field of view is 2.9x1.9 degrees. (The webmaster has inverted the image to betterrepresent the appearance of the comet.)

Lewis Swift (Marathon, New York, USA) discovered this comet in Camelopardalis on 1862 July 16, while examining thenorthern sky with his 11.4-cm Fitz refractor. He described the comet as a somewhat bright telescopic object, but did notreport it since he thought he was observing the comet Schmidt had found on July 2. Without knowledge of Swift'sobservation, Horace Parnell Tuttle (Harvard College Observatory, Cambridge, Massachusetts, USA) independentlydiscovered this comet on July 19.19 and noted it was heading northward. He then made an official announcement. WhenSwift heard of Tuttle's find, he immediately realized the comet seen on July 16 was not Schmidt's and made hisannouncement to get credit for his first comet discovery.

There were several independent discoveries. Thomas Simons (Dudley Observatory, Albany, New York, USA)independently discovered the comet on July 19.30. He remarked, "When first seen it appeared as a nebula considerablycondensed at the centre, the light being intense enough to be easily observed when the wires of the micrometer wereilluminated." Antonio Pacinotti and Carlo Toussaint (Florence, Italy) found the comet on July 22. Schjellerup (Copenhagen)found this comet in Camelopardalis on the night of July 26/27. He described it as a bright nebulosity with a very slowmovement. On July 27.98, Schjellerup and d'Arrest confirmed the discovery with a large refractor. Schjellerup remarked,"The comet is rather bright, the nucleus equalled a star of 7th magnitude." He added that at a magnification of 226x theysaw a distinct extension in the direction of the sun, while the surrounding nebulosity was 3 arc minutes across. On

C&MS: 109P/Swift-Tuttle http://cometography.com/pcomets/109p.html

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September 1, John Tebbutt (Windsor, New South Wales) independently discovered this comet, not yet having received anotification of its prior discovery. With a 3.25-inch telescope, he noted the comet's nucleus was badly defined and did notadmit accurate determinations of position.

J. F. Julius Schmidt (Athens, Greece) made numerous observations of the comet from 1862 August to September. Heexamined his magnitude estimates of the comet's nucleus and determined that, on the average, maximum light occurredevery 2.691Â±0.269 days, while minimum light occurred every 2.711Â±0.284 days.

The earliest orbits were computed at the end of July and in early August. These were parabolic orbits indicating aperihelion date of 1862 August 22 to 24. During the next few years several astronomers computed elliptical orbits indicatingan orbital period between 120 and 125 years, with the first attempt at a definitive orbit coming in 1889 when F. Hayndetermined the orbital period as 119.64 years. During 1971, B. G. Marsden and Zdenek Sekanina took 212 positionsobtained during the period of 1862 July 22 to October 22, applied perturbations by all nine planets, and determined theorbital period as 119.98 years. A couple of years later, Marsden looked at the possibility of trying to link Swift-Tuttle to anearlier comet. He found two in the 18th century that looked promising--1737 (Kegler) and 1750 (Wargentin). The 1750comet appeared at just about the right time expected for Swift-Tuttle if that comet's motion was integrated back from 1862.The problem, however, was that it was moving too fast. The 1737 comet actually exhibited a motion consistent for whatwould have been expected for Swift-Tuttle if the perihelion date had fallen on June 15 of that year; however, as Marsdenpointed out, the main point this identity "is that the comet's osculating period would have to have been some 10 yr longerthan is indicated by the observations in 1862." Marsden made two predictions for a forthcoming return. First, using thedefinitive orbit of Sekanina and himself, he suggested a perihelion date of 1981 September 16.93. Second, he suggested thatif the link to the comet of 1737 was valid, the comet would likely return to perihelion on 1992 November 25.85.

Minor searches for the comet began in 1980, which was within the error range given by calculations, and more rigoroussearches were conducted in 1981 and 1982, but nothing was found.

Tsuruhiko Kiuchi (Japan) discovered a comet on 1992 September 26.76 and reported it to the National AstronomicalObservatory (Tokyo). He said it was magnitude 11.5. H. Kosai of that observatory subsequently reported it to the (CentralBureau for Astronomical Telegrams) and suggested it might be comet Swift-Tuttle. Several observers were able to confirmthe comet within the next 24 hours and the indicated direction and rate of motion was consistent with what would beexpected for Swift-Tuttle. Brian G. Marsden (Central Bureau) was not able to do a precise linkage between the 1862 and1992 positions, but he did provide an orbit that adequately represented all available positions. It indicated a perihelion dateof 1992 December 12.29, a perihelion distance of 0.959 AU, and an orbital period of 135.29 years.

Observations made within the first days following the recovery revealed the comet's actual magnitude was near 9 and thatthe coma diameter was about 4 arc minutes.The comet steadily brightened during the following weeks. It surpassedmagnitude 8.5 shortly after October began and had climbed to 6.0 by the beginning of November. A faint tail over a degreelong was already visible on photographs after mid-October and this continued to brighten during the following weeks. Bymid-November it was possible to see over 2 degrees of tail with binoculars. Along other lines of observation, astronomersreported that observations during the first half of November were revealing the production rates of various gases, of whichOH, Methanol, CS, and water were among the first identified.

The comet surpassed magnitude 5.0 right at mid-November and continued brightening. The ion tail was 6.7 degrees longon November 23 when Herman Mikuz (Slovenia) imaged it with 10-minute exposure CCD frames. Most interesting was areport by L. Jorda and J. Lecacheux (Paris-Meudon) and F. Colas (Observatoire de Paris) that observations of a nuclear jetwith the 1.05-m telescope and CCD camera at Pic du Midi over the period of November 20-26 indicated a probable nuclearrotation period of 2.9 days. Compare this to the periodicity earlier noted by Schmidt in the brightness of the nucleus back in1862. As November came to a close brightness estimates were still at 5.0 and the comet showed no sign of fading until justbefore mid-December.


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Copyright © 1992 by Gerald Rhemann

This image was obtained on 1992 November 24.74 UT with the171/200/257mm Schmidt camera. Exposure time was 10minutes and the photographic emulsion was KodakEktachrome 100. The comet's total magnitude was then about5.0. (The image has been cropped by the webmaster to savespace.)

By early December of 1992 it was becoming obvious that independent orbital calculations by Marsden and Donald K.Yeomans which attempted to fit the 1862 and 1992 observations were becoming increasing further off the mark inpredicting the motion of this comet. Marsden attempted a nongravitational solution and managed the best fit of the availablepositions, but noted large discrepancies in the positions of 1862 October. Interestingly, this new orbit allowed twoprediscovery images to be located. The first was found by R. Haver (Cima Ekar) on a plate exposed with a 0.4-m f/2.5Schmidt on 1992 January 3.08. The comet was described as stellar with a magnitude of 17.5. The second was found by L.Kohoutek (Calar Alto) on a plate exposed on January 7.09 with a 0.8-m Schmidt. He estimated the magnitude as 18. Aroundthis time, Gary Kronk (Troy, Illinois, USA) announced the liklihood that comets reported by the Chinese in -68 and +188were good candidates for Swift-Tuttle. Independent computations by Marsden and G. Waddington (Oxford University)confirmed the links and noted a purely gravitational solution worked better to fit the apparitions. In addition, it was realizedthat no favorable apparitions would have occurred following 188 until 1737.

The comet was last seen on 1995 March 29.48, by observers at Siding Spring Observatory (Australia).

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