WEBVTT

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- IN THE PAST, COMETS HAVE
SOMETIMES GOTTEN A BAD RAP.

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A LOT OF PEOPLE TEND
TO BE SUPERSTITIOUS ABOUT THEM,

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BLAMING UNFORTUNATE EVENTS

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AND NATURAL DISASTERS
ON THEIR PRESENCE.

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HOWEVER, NASA SAYS
THERE IS NOTHING TO FEAR.

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AS A MATTER OF FACT,
NASA IS QUITE EXCITED

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ABOUT COMETS
AND WHAT THEY CAN TEACH US.

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FIND OUT ABOUT THESE FROZEN
MYSTERIES NEXT ON "REAL WORLD."

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COMETS ARE COSMIC SNOWBALLS
MADE UP OF FROZEN GASES,

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ROCK, AND DUST, AND WHEN THEY
GET CLOSE ENOUGH TO THE SUN,

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ALL THOSE ICES BEGIN
TO SUBLIMATE, OR BURN OFF,

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AS A DUSTY GAS
AND CAN EVEN CREATE

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A TEMPORARY ATMOSPHERE
AROUND THE COMET CALLED A COMA.

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SOLAR WINDS BLOW
THOSE GASES AWAY FROM THE SUN,

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CREATING
THOSE FAMOUS COMET TAILS,

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BUT WHAT'S SO INTERESTING
ABOUT A BIG CHUNK OF ICE

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AND ROCK HURTLING THROUGH SPACE?

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- COMETS ARE THE LEFTOVERS
OF THOSE ICY CHUNKS,

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THOSE ICY BITS THAT WENT
INTO MAKING UP THE PLANETS,

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SO ONE OF THE GREAT REASONS
TO STUDY THEM

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IS THAT WE WOULD REALLY LIKE
TO KNOW HOW MUCH

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OF THE VARIOUS PARTS
OF WHAT WENT INTO

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MAKING PLANETS ENDED UP
ON THE EARTH,

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HOW MUCH ENDED UP ON MARS,

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HOW MUCH ENDED UP ON VENUS,

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AND DOES THAT HELP EXPLAIN

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WHY THE DIFFERENT PLANETS
ARE SO DIFFERENT?

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- JUST AS NO TWO PLANETS
ARE EXACTLY ALIKE,

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NO TWO COMETS ARE ALIKE EITHER.

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COMETS COME IN DIFFERENT SIZES

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AND ARE MADE UP
OF DIFFERENT MATERIALS.

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ALTHOUGH THE COMET'S COMA
AND TAIL ARE FASCINATING TO SEE,

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SCIENTISTS DETERMINE
THE SIZE OF A COMET

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BY MEASURING THE DIAMETER
OF ITS NUCLEUS.

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THE DIAMETER
IS THE DISTANCE ACROSS

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A SPHERE
RIGHT THROUGH THE MIDDLE.

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BECAUSE OF SOLAR RADIATION,

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COMETS LOSE MASS
AS THEY ORBIT THE SUN.

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THIS MASS LOSS CAN TELL US
A LOT ABOUT THE LIFE OF A COMET

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AND WHERE IT MIGHT
HAVE COME FROM.

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- EVERY TIME A COMET
COMES IN NEAR THE SUN,

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IT'S GONNA LOSE SOME MASS.

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SO THE LIFETIME OF A COMET,

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HOW LONG IT'S ACTUALLY
GONNA SURVIVE AS AN ENTITY

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IN THE SOLAR SYSTEM
DEPENDS ENTIRELY

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ON HOW MUCH MASS IT LOSES EVERY
TIME IT COMES AROUND THE SUN.

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SOME COMETS COME IN
SO CLOSE TO THE SUN,

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THEY LOSE SO MUCH MASS
THAT THEY DON'T EVEN SURVIVE

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THE TRIP AROUND THE SUN.

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WHEREAS OTHERS,
LIKE THE FAMOUS HALLEY'S COMET,

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CAN SURVIVE MANY, MANY TRIPS
AROUND THE SUN

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BECAUSE THEY DON'T
LOSE NEARLY AS MUCH MASS.

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- FROM TIME TO TIME, A COMET
IS IN JUST THE RIGHT PLACE

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IN OUR SOLAR SYSTEM
THAT HUMANS CAN LOOK UP

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AND SEE A BRIGHT OBJECT
IN THE SKY.

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ONE COMET THAT HAS NASA LOOKING
TO THE SKY IS COMET ISON.

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- AND THIS IS PROBABLY COMET
ISON'S FIRST TRIP PAST THE SUN.

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IT'S A YOUNG COMET.

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WE SPEAK OF THEM AS BEING YOUNG
BECAUSE THEY'VE ONLY BEEN

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PAST THE SUN ONCE OR MAYBE
A COUPLE OF TIMES.

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THIS IS PROBABLY COMET ISON'S
ONLY TRIP PAST THE SUN.

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IT'S ON WHAT WE CALL
A HYPERBOLIC TRAJECTORY,

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WHICH MEANS THAT AFTER
IT GOES AROUND THE SUN,

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WE'RE ACTUALLY GONNA LOSE IT
FROM THE SOLAR SYSTEM.

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IT'S GONNA BE COMPLETELY EJECTED
FROM THE SOLAR SYSTEM

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AND GO WANDERING AROUND
THROUGH INTERSTELLAR SPACE.

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SO COMET ISON CAME
FROM VERY FAR OUT

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IN THE OUTER, OUTERMOST REGIONS
OF THE SOLAR SYSTEM.

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IT'S COME IN.

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THIS IS ITS 15 SECONDS OF FAME,

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AND THEN IT'S GONNA
BE GONE FOREVER,

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SO IT'S VERY INTERESTING
TO STUDY THESE OBJECTS,

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BECAUSE WE DON'T GET
VERY MANY OPPORTUNITIES.

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- THIS COMET HAS SPENT
THE LAST FEW MILLION YEARS

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COMING TO US FROM THE FAR
REACHES OF THE OORT CLOUD,

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WHERE IT HAS BEEN IN DEEP FREEZE
FOR BILLIONS OF YEARS.

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BUT AS THE COMET GETS CLOSER
TO THE SUN,

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IT WILL BOIL AND EVAPORATE
AND LOSE MUCH OF ITS MASS

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AS THE MATERIAL
FROM THE BEGINNING OF TIME

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STREAMS ACROSS THE SOLAR SYSTEM.

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NASA HAS USED SEVERAL
OF THE TOOLS IN ITS BAG

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TO GET A BETTER LOOK
AT THE HEAVENLY PHENOMENON.

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SPACECRAFT LIKE DEEP IMPACT,
SPITZER, SWIFT,

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AND EVEN
THE HUBBLE SPACE TELESCOPE

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HAVE OBSERVED COMET ISON
AND HAVE GIVEN US

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SOME PRETTY INTERESTING PICTURES
OF THIS UNIQUE COMET.

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BUT THAT'S NOT ALL.

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NASA INTENDS TO OBSERVE
COMET ISON

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WITH ALL AVAILABLE TOOLS
AT THEIR DISPOSAL,

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INCLUDING SOHO, STEREO,

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SDO, CHANDRA SPACE TELESCOPE,

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MESSENGER, THE INTERNATIONAL
SPACE STATION,

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MARS RECONNAISSANCE ORBITER,

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AND EVEN THE MARS
CURIOSITY ROVER.

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COMET ISON WILL HELP
SCIENTISTS GATHER

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THE MOST COMPREHENSIVE
PACKAGE OF DATA

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EVER COLLECTED
ABOUT A SINGLE COMET.

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WHO KNOWS WHAT WE'LL LEARN,
BUT JUST WATCHING A COMET

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ISN'T ENOUGH FOR NASA OR OUR
INTERNATIONAL PARTNERS IN SPACE.

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THE EUROPEAN SPACE AGENCY
HAS LAUNCHED A COMETARY FIRST.

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THE ROSETTA SPACECRAFT
WILL RENDEZVOUS WITH A COMET

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AND LAND ROBOTIC INSTRUMENTS
ON THE SURFACE.

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NASA HAS SEVERAL INSTRUMENTS
ABOARD ROSETTA,

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INSTRUMENTS
THAT WILL HELP US UNDERSTAND

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HOW A COMET DEVELOPS
ITS COMA AND TAILS,

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HOW A COMET'S CHEMICALS
INTERACT WITH EACH OTHER

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AND WITH THE SUN,

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AND HOW THE COMET WAS FORMED
IN THE FIRST PLACE.

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- WE HAVE VISITED COMETS WITH
LITTLE FLYBY KINDS OF PROBES,

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BUT THIS IS THE FIRST ATTEMPT

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TO ACTUALLY NOT ONLY GO INTO
ORBIT AROUND THE COMET NUCLEUS

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AND OBSERVE IT VERY CLOSELY,
BUT ALSO TO LAND ON THE SURFACE,

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AND SO IT'S GONNA PROVIDE US,
REALLY,

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THE MOST IN-DEPTH UNDERSTANDING
OF WHAT COMETS ARE MADE OF

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AND HOW THEY BEHAVE
AND WHAT THEIR DYNAMICS ARE

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AND HOW THEY EVOLVE OVER TIME.

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ONE OF THE BIGGEST CHALLENGES,
ACTUALLY,

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HAS BEEN THE DURATION
OF THIS MISSION.

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BECAUSE WE'RE TRYING
TO CATCH UP WITH A COMET,

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IT'S NOT JUST STRAIGHTFORWARD.

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YOU CAN'T JUST DRIVE
TO THE COMET.

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YOU'VE GOT TO SYNC UP YOUR ORBIT
WITH THE COMET

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SO AS IT'S GOING AROUND THE SUN,
YOU JOIN UP WITH IT--

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SMOOTHLY, BECAUSE WE DON'T
WANT TO FLY PAST IT REAL FAST.

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WE ACTUALLY WANT
TO GO INTO ORBIT AROUND IT,

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SO WE HAVE TO SMOOTHLY
CATCH UP WITH IT.

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AND THAT'S NOT EASY.

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COMETS TEND
TO BE GOING PRETTY QUICKLY.

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THEY'RE ON RATHER ODD ORBITS

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COMPARED TO THINGS
LIKE THE EARTH,

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AND SO ROSETTA'S TRAJECTORY
HAS TAKEN IT PAST THE EARTH

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A COUPLE OF TIMES.

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IT'S TAKEN A ZING PAST--
A SLING PAST MARS,

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AND WE'VE BEEN USING
THESE PLANETARY ENCOUNTERS

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TO SYNC UP THE ORBIT
WITH THE COMET.

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- SO WHILE YOU'RE WAITING
FOR NEWS ABOUT THE COMET ISON

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OR THAT NEXT
EXCITING COMET MISSION,

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CHECK OUT COMET QUEST, A GAME
CREATED BY NASA'S SPACE TEAM.

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JUST LIKE
THE REAL ROSETTA MISSION,

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YOU CAN HITCH A RIDE ON A COMET
AS IT JOURNEYS TOWARDS THE SUN,

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AND JUST LIKE NASA,
YOU MAY HAVE TO USE

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A LITTLE BIT OF MATH
TO MEET THE CHALLENGE.

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I'M DIEGO, AND SEE YOU
NEXT TIME ON "REAL WORLD."

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- AND NOW FOR AN UPDATE
ABOUT COMET ISON.

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AS NASA DETERMINES
THE FINAL STATUS OF ISON,

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MOST AGREE THAT THE COMET
WAS DESTROYED

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AS IT ROUNDED THE SUN,
LEAVING BEHIND

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ONLY PIECES OF RUBBLE,

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BUT EVEN THOSE DUSTY FRAGMENTS
HAVE A STORY TO TELL.

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COMET ISON, WHICH BEGAN
ITS JOURNEY FROM THE OORT CLOUD

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SOME 3 MILLION YEARS AGO,

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MADE ITS CLOSEST APPROACH
TO THE SUN ON NOVEMBER 28, 2013.

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REGARDLESS OF ITS FATE,

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COMET ISON DID NOT
DISAPPOINT RESEARCHERS.

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OBSERVATORIES AROUND THE WORLD
AND IN SPACE

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GATHERED THE LARGEST SET OF
COMET OBSERVATIONS OF ALL TIME,

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WHICH SHOULD PROVIDE ENOUGH DATA
FOR PROFESSIONAL

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AND AMATEUR ASTRONOMERS
TO STUDY FOR YEARS TO COME.