Episode 1 | 54m 41s | Video has closed captioning.
In this show, scientists around the world follow a once-in-a-lifetime event, the path of the sun-grazing comet ISON. The comet, somewhere between one and 10 kilometers in diameter, is currently just beyond the orbit of Jupiter. As it races past Earth toward the sun, it will likely develop a tail to light up the night skies.
Aired: 11/20/13
Expired: 03/16/15
RIGHT NOW A CITY-SIZED CHUNK OF ICE AND ROCK
IS HURTLING TOWARDS THE SUN.
[Explosions]
THIS IS COMET ISON.
ASTRONOMERS AROUND THE WORLD ARE TRACKING IT
AS IT BLAZES BRIGHTER.
We've amassed the most technologically advanced
armada of spacecraft in human history.
IT PRESENTS THE OPPORTUNITY OF A LIFETIME...
I feel like a little kid when these things happen.
...TO ANSWER MIND BOGGLING QUESTIONS...
This is going to give us a picture of this comet
like we've never seen before.
...AND LEARN MORE ABOUT OUR WORLD.
WHAT'S MORE,
COMET ISON COULD SHINE SPECTACULARLY IN OUR SKIES.
It could be brighter than the full Moon.
People are talking about comet of the century
even comet of the millennium.
It's a really exciting time.
NOW ALL EYES ARE ON ISON
FOR WHAT MAY BE AN INCREDIBLE COMET ENCOUNTER.
Comet Encounter is made po SEPTEMBER 21ST, 2012.
AS DARKNESS FALLS,
ASTRONOMERS AROUND THE GLOBE TURN THEIR TELESCOPES SKYWARD.
[Hum of machinery]
FOR MOST IT'S A ROUTINE NIGHT OF OBSERVING.
BUT THEY ARE ABOUT TO DISCOVER SOMETHING NEVER SEEN BEFORE...
...AN INSIGNIFICANTLY SMALL POINT OF LIGHT.
BUT A CLOSER LOOK REVEALS IT'S NO ORDINARY STAR.
IT'S A NEW COMET.
IT LIES ALMOST 600 MILLION MILES AWAY
FAR OUT IN THE DEPTHS OF THE SOLAR SYSTEM.
IT'S A CHUNK OF ROCK AND ICE AS BIG AS A CITY.
THEY USUALLY LIE BEYOND THE REALM OF THE PLANETS.
BUT THIS ONE IS HEADED THIS WAY.
AS IT APPROACHES THE SUN
IT HAS THE POTENTIAL TO BECOME A STUNNING LIGHT
IN THE NIGHT SKY.
FOR ASTRONOMERS, FINDING A NEW COMET IS AN EXCITING EVENT.
BUT THIS COMET IS EXTRAORDINARY.
THIS IS ISON.
Comet ISON is really important
because we saw it first all the way out at 6 AU,
6 times further from the Sun than the Earth is.
ISON'S UNUSUAL - IT'S MUCH BRIGHTER THAN MOST COMETS,
SO IT'S VISIBLE FROM MUCH FURTHER AWAY.
Comet ISON being discovered so far out of the solar system
means that it's obviously a very active object
and that naturally makes it more interesting
right from the word go.
FOR MANY ASTRONOMERS ISON IS A ONCE IN A LIFETIME OPPORTUNITY.
STUDYING IT COULD HELP ANSWER SOME FUNDAMENTAL QUESTIONS.
WHERE DO COMETS FROM?
WHAT ARE THEY MADE OF?
AND MOST IMPORTANTLY, HOW WILL THEY AFFECT PLANET EARTH?
[Control] ...two, one, zero.
TODAY SCIENTISTS HAVE LAUNCHED A HUGE COORDINATED EFFORT
TO VIEW ISON IN UNPRECEDENTED DETAIL.
We've amassed what is the single largest
and most technologically advanced armada of spacecraft
in human history.
And we are turning those spacecraft to look at the comet
over the next few months.
AND FROM EARTH IT HAS THE POTENTIAL
TO BLAZE IN OUR NIGHT SKY.
ISON could be a spectacular naked eye comet.
It could be brighter than the full Moon.
People are talking about comet of the century
even comet of the millennium.
It's a really exciting time.
TODAY ISON'S IMMINENT ARRIVAL IS AWAITED WITH EAGER ANTICIPATION.
BUT COMETS HAVEN'T ALWAYS BEEN GREETED WITH SUCH ENTHUSIASM.
[Explosion]
TURN BACK THE CLOCK JUST A FEW HUNDRED YEARS
AND THE REACTION IS VERY DIFFERENT.
THROUGHOUT HISTORY
THE SUDDEN APPEARANCE OF COMETS SENT PEOPLE RUNNING FOR COVER.
FOR ASTRONOMER FRANCISCO DIAGEO THEIR TERRIFYING ACCOUNTS
GIVE AN INSIGHT INTO HOW OUR ANCESTORS VIEWED THE SKY.
In the old times
people realized that the sky is moving
in a very orderly way
and they were developing calendars
and ways of predicting all these motions of stars and planets
and the Sun and the Moon.
But suddenly, out of nowhere we have these apparitions,
the comets will come very fast,
against all these orderly motions
that were so predictable.
It must have been terrifying.
EVEN MEN OF SCIENCE, THE ASTRONOMERS OF THE TIME,
THOUGHT COMETS WERE THE HARBINGERS OF DOOM.
There is a quote by an astronomer in the 1600s,
"As often as any comet
or blazing star appears in the world,
we may assuredly pronounce to the inhabitants of the Earth
much sorrow and affliction,
unusual storms and tempests,
corruptive and infectious air,
plague and famine,
all tending to the mortality and destruction of humanity."
That is amazing.
UNEXPLAINABLE BY SCIENCE
AND FLOUTING THE LAWS OF THE CLOCKWORK COSMOS,
MOST THOUGHT THAT COMETS MUST BE SIGNALS FROM THE GODS.
They were seeing, I suppose, a kind of a message,
a kind of warning from gods and goddesses.
So God, in the case of where we are here,
is trying to tell us something bad is going to happen.
MANY SAW THEM AS THE PORTENTS OF WAR.
PERHAPS THE MOST FAMOUS IS ILLUSTRATED HERE
ON THE BAYEUX TAPESTRY,
AN EMBROIDERED CLOTH
DEPICTING THE NORMAN CONQUEST OF ENGLAND IN 1066.
This is a small part of the huge Bayeux Tapestry.
In this part we see King Harold, recently crowned,
and here on the left we see a crowd
terrified of pointing at the sky.
What's in the sky?
A bright comet.
And bright comets are not very good.
They bring bad omens and certainly, a few months later,
Harold was going to be defeated by the Normans
at the Battle of Hastings.
THE SUPERSTITIOUS LINK
BETWEEN OUR EARTHLY FORTUNES AND COMETS
IS FOUND IN CIVILIZATIONS AROUND THE WORLD.
And I have a vivid example of this
that came from my home country, Mexico,
with the conquest of the Aztec empire.
Just a couple of decades after the discovery of the Americas,
several hundred soldiers with a man, Cortez, came to Mexico
and just before that there was a comet in the sky.
And that comet was seen by the Emperor Moctezuma,
the Emperor of the Aztecs.
and the quote says:
"The appearance of the comet terrified them exceedingly.
The superstitious Moctezuma consulted his astrologers
but they could give him no satisfactory explanation."
IT'S EASY TO DISMISS OUR ANCESTORS' FEARS,
BUT TODAY SCIENTISTS KNOW A COMET COULD POSE
A REAL THREAT TO HUMANITY.
FEBRUARY 15TH 2013.
THE WORLD GETS A SPECTACULAR REMINDER
OF HOW VULNERABLE WE ARE TO IMPACTS FROM SPACE.
A CHUNK OF ROCK OVER 50 FEET ACROSS HURTLES TOWARDS EARTH
NEAR THE RUSSIAN CITY OF CHELYABINSK.
THE METEORITE ITSELF HURTS NO ONE
AS IT DISINTEGRATES IN THE ATMOSPHERE.
BUT MINUTES LATER...
[Explosion]
[Glass shatters and debris crashes]
THE POWERFUL SHOCKWAVE IT CREATES SHATTERS WINDOWS,
INJURING OVER A THOUSAND PEOPLE.
The Chelyabinsk meteorite was a small object
but even being such a small object
it caused a lot of damage.
AT AROUND 3 MILES ACROSS,
ISON IS HUNDREDS OF TIMES LARGER THAN THE CHELYABINSK METEORITE.
SOMETHING THIS LARGE SLAMMING INTO THE EARTH
WOULD DO MUCH MORE THAN SHATTER WINDOWS.
IT COULD BE DEVASTATING.
[Rumble of explosion]
OUR FIRST LINE OF DEFENSE AGAINST A COMET IMPACT
IS GARETH WILLIAMS AT THE MINOR PLANETS CENTER.
GARETH'S JOB IS TO CALCULATE WHERE ISON IS HEADING
AND HOW CLOSE IT WILL COME TO EARTH.
The Minor Planet Center is responsible
for keeping track of asteroids, comets and natural satellites,
particularly those that can come very close to us,
or even hit us.
We want to be aware, if and when that is going to happen.
WITH THE HELP OF POWERFUL COMPUTERS
GARETH STARTS CALCULATING THE COMET'S ORBIT.
BUT JUST DAYS AFTER ITS DISCOVERY,
THAT'S EASIER SAID THAN DONE.
The problem with any object for which
you've only got observations over the course of an hour
it's very hard to get a general orbit,
to say with certainty this is the orbit.
GARETH TURNS TO THE GLOBAL COMMUNITY OF ASTRONOMERS
FOR MORE OBSERVATIONS OF ISON.
BUT AFTER HOURS OF NUMBER CRUNCHING
HE IS STILL NOT SURE IF THE COMET WILL STRIKE US OR NOT.
Even three days after discovery, I could easily fit
more than 600 different, wildly different orbits.
IT'S HARDLY A PRECISE ANSWER.
WHAT'S ALARMING IS THAT SOME OF THE ORBITS
BRING ISON DANGEROUSLY CLOSE TO EARTH.
BUT GARETH HAS A FINAL PLAN
HE HOPES WILL HELP REFINE HIS CALCULATIONS.
We can look in the past,
we may have received observations from an observer
who didn't realize that he had an interesting object.
THE COMPUTERS STORE A BACK CATALOG
OF THOUSANDS OF SIGHTINGS OF CELESTIAL OBJECTS.
IT'S JUST POSSIBLE
THAT ISON MIGHT HAVE BEEN SEEN AND LOGGED BEFORE.
THIS COULD BE THE BREAKTHROUGH GARETH'S LOOKING FOR.
We use a computer program that takes those 600 orbits
and compares them to all the unidentified observations
saying, "Does this observation fit this orbit?"
GARETH'S IN LUCK.
COMET ISON WAS LOGGED TWICE BEFORE.
NOW HE CAN FINALLY NARROW DOWN THE 600 ORBITS TO ONE.
One of the orbits of ISON produces two matches
amongst the unidentified observations
and it's a really interesting orbit.
GARETH'S CALCULATIONS REVEAL
ISON'S ORBIT TAKES IT ALMOST 40 MILLION MILES FROM EARTH.
SO WE'RE SPARED FROM ARMAGEDDON...
THIS TIME.
BUT ISON MIGHT BE ON A PATH TO ITS OWN DESTRUCTION.
ON NOVEMBER 28TH 2013 IT WILL HURTLE PAST
ONE OF THE HARSHEST ENVIRONMENTS IN THE SOLAR SYSTEM...
...THE SUN.
THE COUNTDOWN TO ITS SUN-GRAZING ENCOUNTER HAS BEGUN.
[Car starts]
FOR ASTRONOMER KARL BATTAMS
ISON's NEWLY CALCULATED ORBIT IS KEY TO UNDERSTANDING
WHAT THE FUTURE HOLDS IN STORE FOR THE COMET.
The predicted orbit for ISON
means that it's a sun-grazing comet
and as the name implies
that means that this little ball of ice and rock
is gonna go flying right through the solar atmosphere
and it's almost literally gonna graze the surface of the Sun.
ISON WILL SKIM INCREDIBLY CLOSE OVER THE SUN'S SURFACE.
And this certainly has some very interesting
and very exciting consequences.
FIRST THERE'S THE SUN'S SEARING HEAT.
The comet is gonna be experiencing
incredible amounts of solar radiation.
THEN THERE'S ITS IMMENSE GRAVITATIONAL PULL.
When something like a comet is very close to the Sun
it actually gets elongated, it get's stretched.
FINALLY IT'LL BE TRAVELING AT AN INCREDIBLE SPEED -
FAST ENOUGH TO FLY FROM NEW YORK TO LA IN UNDER 20 SECONDS.
We've got this extreme environment
that this tiny delicate little ball of ice
is gonna be flying through.
PASSING SO PERILOUSLY CLOSE TO THE SUN COULD DESTROY ISON.
BUT IT MIGHT ALSO PROVIDE A SPECTACULAR SIGHT.
SEEN FROM EARTH ISON COULD APPEAR AS
THE COMET OF THE CENTURY IN OUR SKIES.
JANUARY 2013 - ISON IS ALMOST 500 MILLION MILES FROM THE SUN.
SCIENTISTS HAVE DISCOVERED IT'S ON COURSE
FOR AN INCREDIBLY CLOSE ENCOUNTER.
BUT FOR ASTRONOMER CAREY LISSE,
ISON'S ORBIT HELPS SOLVE ANOTHER PUZZLE -
WHERE THE COMET CAME FROM.
In front of me is a model of the solar system.
In it you can see that there are thousands of known comets.
If we look at the comets most of the comets seem to be going
in the plane of the solar system
moving the same way that the planets do around the Sun,
almost like grooves in a record.
But ISON is not that kind of comet,
ISON is coming from a very different orbit
that is not flat at all with respect to the solar system.
It's coming from very far north at a very steep angle
to the flat plane of the solar system.
We know that Ison is a different kind of comet.
ITS ORBIT REVEALS IT HAS A UNIQUE PATH.
SOME COMETS ORBIT THE SUN TIME AND TIME AGAIN.
BUT ISON WILL SWING BY JUST ONCE
BEFORE HEADING OUTWARDS NEVER TO RETURN.
So to see where these comets come from
we have to step way, way back,
we have to really take a big view of the solar system.
ISON comes from much, much farther away,
ten to a hundred to a thousand times farther away,
in a region that extends half-way to the next star,
it's what we call the Oort Cloud,
it's a giant sphere of comets,
extends half-way to the next star around the Sun.
THE OORT CLOUD IS THOUGHT TO CONTAIN
UP TO 2 TRILLION ICY COMETS.
BUT WERE DID COMETS LIKE ISON COME FROM?
ASTRONOMERS LIKE AMY MAINZER THINK THE ANSWER LIES
WITH THE FORMATION OF THE PLANETS.
When the solar system first formed
about four and a half billion years ago
it started off as a cloud of gas and dust
that collapsed to form a disc.
And you can imagine just like this sugar,
all these little grains of dust
circled throughout the solar system,
spread in roughly a disc shape around the forming Sun,
which you might imagine to be here in the middle of the table.
Now eventually, under the influence of gravity,
some of these little grains of dust
are gonna start to stick together
some of them starting to form little lumps
like these right here.
Some of the larger of these lumps are gonna stick together
to form the planets.
MOST OF THESE CHUNKS SMASHED TOGETHER,
BUT SOME WERE FLUNG OUTWARDS TO FORM THE OORT CLOUD.
And these can scatter really violently
into the outer parts of the solar system
where they're going to stay
in the deep-freeze of Outer Space
for billions of years in some cases.
And one of these little chunks is Comet ISON.
IT'S AN AMAZING REVELATION.
ISON IS A PRISTINE PIECE OF ROCK AND ICE
LEFT OVER FROM THE FORMATION OF THE SOLAR SYSTEM.
AND CONTAINED WITHIN THIS TIMECAPSULE
LIE CLUES TO HOW OUR PLANET EVOLVED.
ISON IS SPEEDING EVER CLOSER TOWARDS THE SUN,
PULLED IN BY ITS IMMENSE GRAVITY.
BUT WHAT SENT IT TUMBLING IN
FROM THE VERY EDGE OF THE SOLAR SYSTEM?
So if we take a step back
from the Oort Cloud surrounding our Sun,
we see that our solar system is just one star
among hundreds of billions of stars
that make up this giant collection
that we call the Milky Way galaxy.
GALAXIES AREN'T STATIC.
OVER HUNDREDS OF MILLIONS OF YEARS
THEY ROTATE.
If we speed up time
and we look at this giant pinwheel
we call the Milky Way galaxy,
we realize that all the stars in it
rotate around a common center,
the same way that the planets in our solar system
rotate around the Sun.
And every now and then,
as this Milky Way galaxy is rotating,
we pass by another star
and that star comes close enough
to actually perturb the comets in our Oort Cloud.
THE EXTRAORDINARY CONCLUSION IS THE GRAVITY OF ANOTHER STAR
PUSHED ISON OUT OF THE OORT CLOUD.
Millions of years ago, close to the dawn of Man,
ISON was perturbed by a passing star
and started falling in towards the inner solar system
towards the Sun, so we could see it today.
IT'S AN INCREDIBLE THOUGHT -
WE'RE ABLE TO WITNESS THE FINAL STAGE
OF ISON'S INWARD JOURNEY,
A JOURNEY THAT BEGAN WHEN HUMANS FIRST WALKED THE EARTH.
APRIL 10TH 2013 -
COMET ISON IS MOVING CLOSER.
IT NOW LIES WITHIN THE ORBIT OF JUPITER.
IT'S CLOSE ENOUGH FOR BONNIE MEINKE
AND THE TEAM AT THE SPACE TELESCOPE SCIENCE INSTITUTE
TO CAPTURE DETAILED IMAGES -
USING THE HUBBLE SPACE TELESCOPE ORBITING ABOVE THE EARTH.
[Meinke] Hubble's designed to look at small things,
distant things, faint things,
and that's what Comet ISON is at this point.
It's just a small hunk of ice
out there in the far solar system.
THE IMAGES OF ISON REVEAL SOMETHING INTRIGUING.
[Meinke] What we're seeing with Hubble
is that Comet ISON is developing a coma
and that's a huge layer,
kind of like an atmosphere around the nucleus of the comet.
It's full of gases,
and they're raging like a snowstorm around this nucleus.
ISON IS ERUPTING CLOUDS OF GAS IN A PROCESS CALLED SUBLIMATION.
I'm going to show you how that works
with some dry ice and some water.
So we have our dry ice in a bowl,
our cryo-gloves for safety
and we can put those on,
pick up a small piece of dry ice
and we'll place that in the water.
AS THE DRY ICE HITS THE WARMER WATER
A CHEMICAL REACTION OCCURS -
THE ICE TURNS STRAIGHT FROM A SOLID
INTO CARBON DIOXIDE GAS,
CAUSING IT TO FIZZ VIOLENTLY.
AMAZINGLY, COMET ISON IS UNDERGOING THE SAME REACTION.
This is exactly what happens with comets
as they come into the inner solar system and warm up
as they get closer to the Sun.
All of that solid ice begins to sublimate and form a coma.
AS IT CONTINUES TO HEAT UP,
THE REACTION INTENSIFIES.
So you can see the, the chunk of ice is now beginning to spin
and that's because gas is coming off in different directions.
BUT WHAT'S EXCITING ABOUT ISON
IS JUST HOW MUCH GAS ITS ICY NUCLEUS IS RELEASING.
[Meinke] Hubble is showing us
that the whole coma is about the size of the United States
but if you move all that away
you can see that the nucleus is tiny,
only about the size of Manhattan.
That tells us that this comet is raging.
EVEN IN THE FREEZING DEPTHS OF SPACE
ISON IS VIOLENTLY REACTING TO THE HEAT OF THE SUN.
MOST COMETS OUT HERE ARE USUALLY INACTIVE.
So if comet ISON at this point
is able to create such a huge coma
out of a very tiny nucleus
this bodes well for its future.
Hopefully it'll continue to get brighter and brighter.
ISON IS STILL SEVEN MONTHS AWAY FROM ITS ENCOUNTER WITH THE SUN
AND BRIGHTENING AS IT COMES CLOSER.
BUT JUST HOW BRIGHT IT WILL BECOME
IS ANYONE'S GUESS.
If I was a betting man I guess on a scale of 1 to 10
in terms of how bright and spectacular
Comet ISON is going to be,
right now I'd put it at maybe a 7 or an 8.
I would probably say that it'll be somewhere around a 5.
If I was a betting woman
I would probably guess that ISON may not live up to expectations.
Comets are like cats,
they all have tails and they do whatever they were going to do.
WE'RE ABLE TO SEE ISON
BECAUSE OF SUNLIGHT REFLECTED FROM GASES AND DUST
THAT MAKE UP ITS COMA.
BUT AS IT CONTINUES TO WARM UP, SOMETHING INCREDIBLE HAPPENS.
ITS GASES START TO GLOW WITH A LIGHT OF THEIR OWN.
THIS GIVES ASTRONOMERS A UNIQUE OPPORTUNITY
TO SEE WHAT ISON IS MADE OF.
IT'S SIMILAR TO WHAT WE SEE WITH EVERYDAY STREET SIGNS.
THEIR TUBES ARE FILLED WITH GASES LIKE NEON.
ELECTRICITY PASSING THROUGH THE TUBE ENERGIZES THE GAS -
CAUSING IT TO GLOW BRIGHTLY.
So here I have a lamp that is filled with gas
that I'm gonna make glow when I click the switch on.
And it is emitting light,
the same way that gases in a comet's coma emit light.
And it looks to you like it's a reddish orange glow.
IN FACT THE ORANGE LIGHT EMITTED
IS MADE OF A NUMBER OF DIFFERENT COLORS MIXED TOGETHER.
When I hold this film up in front of it,
you're going to see that light
split into many, many, many different lines.
Mostly red and orange, a little bit of green.
The exciting and fascinating thing is
that I can tell you that this must be neon atoms in that tube.
EVERY GAS PRODUCES ITS OWN UNIQUE PATTERN OF LINES
WHEN IT GLOWS -
THESE ARE CALLED SPECTRA.
LIKE A BARCODE IN A SUPERMARKET -
IF YOU CAN IDENTIFY THE SPECTRA
YOU CAN IDENTIFY WHICH GASES ARE GLOWING.
AND THAT'S INCREDIBLY HELPFUL WHEN STUDYING ISON.
So if I know what this is doing in the lab
and then I go and I look at a comet
and I see these four lines,
I know that there is neon in the comet.
And seeing the glow of the atoms and the molecules in its coma,
we can tell you what's there
and we can tell you how much is there.
IT'S A POWERFUL TECHNIQUE CALLED SPECTROSCOPY
AND OVER THE COMING MONTHS IT WILL PROVIDE ASTRONOMERS
WITH A DETAILED BREAKDOWN OF ISON'S CHEMICAL COMPOSITION.
SPECTROSCOPY HAS ALLOWED SCIENTISTS LIKE LEWIS DARTNELL
TO BUILD UP A CHEMICAL PROFILE OF COMETS -
AND IT'S REVEALED SOME STARTLING RESULTS.
What we've discovered more recently
is a lotof other very intriguing chemistry,
a lot of very exciting molecules
that are mixed into their recipe alongside the ice.
And I thought this would be a really good place
to look into how we can actually make a comet.
What are the ingredients that go into the recipe?
So let's put in a good glug of some water in there.
Er, there's also other simple compounds like ammonia,
and I've got some smelling salts
that I'm going to drip into our mixture there.
And as well as the simple compounds,
the water and ammonia,
the surprising thing about comets is
they have a bit of more complex chemistry to it,
an organic compound.
So there's things like sugar
which is one of the components of DNA.
So let's put some sugar in.
We've also got some amino acids, the Lego bricks,
the building blocks, the proteins in our body...
I'm now going to add some frozen carbon dioxide.
This is dry ice.
So I'm going to pour some of that in,
give this a good mix to stir all that together.
And the final ingredient I'm going to add
is this ground up charcoal.
It's basically some pure carbon.
So let's sprinkle some of the charcoal on there.
So if I pull out this comet that we've made here,
you can see it really is like a dirty lump of ice,
a very mucky snowball...
ISON IS A TIME CAPSULE.
LOCKED IN IT IS THE CHEMISTRY THAT EXISTED
WHEN OUR SOLAR SYSTEM AND EARTH FORMED.
What really excites me personally about these comets
is what they can teach us about the kind of primordial chemistry
that would have been around in the early solar system.
And ISON in particular is unique
because it's falling into the inner solar system
for the first time.
THE CHEMICAL INFORMATION SCIENTISTS GLEAN FROM ISON
COULD PROVIDE ANSWERS
TO ONE OF THE GREATEST MYSTERIES OF OUR PLANET.
COMETS HAVE LONG BEEN MYSTERIOUS OBJECTS.
BUT AS SCIENCE HISTORIAN PATRICIA FARA KNOWS,
THEIR GHOSTLY APPARITIONS HELPED PROVE
ONE OF THE MOST IMPORTANT SCIENTIFIC THEORIES OF ALL TIME.
THE EVIDENCE LIES IN A BOOK OVER THREE HUNDRED YEAR OLD
AT CLARE COLLEGE
AT THE UNIVERSITY OF CAMBRIDGE, IN ENGLAND.
[Woman] This book is Isaac Newton's Principia
and it's the single most important book
in the history of science.
It's in this book that he describes gravity
as a force that holds the Universe together.
IT'S OFTEN SAID NEWTON HIT UPON HIS THEORY OF GRAVITY
WHILE WATCHING AN APPLE FALL FROM A TREE.
BUT THE TRUTH IS VERY DIFFERENT.
Towards the end of 1680, a new comet appeared in the sky
and many people were absolutely terrified,
but for Newton this was a new opportunity.
It was a challenge to try and work out what was happening.
NEWTON WAS THINKING HOW GRAVITY MIGHT EXPLAIN
THE ELLIPTICAL ORBITS OF THE PLANETS AROUND THE SUN.
BUT THE MOVEMENT OF COMETS REMAINED MYSTERIOUS.
COULD THEY ALSO BE EXPLAINED BY GRAVITY?
NEWTON SETS ABOUT MEASURING THE 1680 COMET
AS IT SLOWLY MOVES ACROSS THE SKY
UNTIL IT'S LOST IN THE GLARE OF THE SUN.
[Fara] He's showing the time the comet appears,
where it is with respect to the Sun,
the longitude and the latitude of the comet.
WHAT HE SEE'S NEXT INTRIGUES HIM MORE.
Then a few months later, beginning of 1681,
there's another comet in the sky,
so Newton tracks that.
And it's on the other side of the Sun,
so Newton starts thinking,
well is it really another comet
or has this comet somehow come back again?
So this is a diagram that Newton drew
to explain the observations of the comet that he'd made.
And there it is - observations in November,
then it goes round the back of the Sun,
reappears in December,
and here it is, coming up to January 1681 and February,
and off it goes.
NEWTON REALIZES SOMETHING ASTONISHING -
THE COMETS OF 1680 AND 1681 ARE IN FACT THE SAME COMET,
ONE THAT'S FOLLOWED AN ELLIPTICAL PATH AROUND THE SUN.
FROM HIS OBSERVATIONS NEWTON MAKES A BOLD PREDICTION -
COMETS, LIKE THE PLANETS
MUST BE CONTROLLED BY THE SAME INVISIBLE FORCE - GRAVITY.
BUT IT TAKES A FORTUITOUS MEETING
WITH ASTRONOMER EDMOND HALLEY
TO INSPIRE NEWTON TO FINALLY PROVE THE THEORY.
HALLEY HAS ALSO BEEN STUDYING
THE ORBITS OF PLANETS AND COMETS.
USING MATHEMATICS, HE THINKS HE CAN EXPLAIN THEIR MOTIONS,
BUT HE NEEDS SOME HELP.
So he went up to Cambridge to seek advice
from the great Isaac Newton.
HALLEY ASKS NEWTON WHAT SHAPE A COMET'S ORBIT WOULD BE -
USING HIS FORMULA.
BASED ON HIS RECENT OBSERVATIONS,
NEWTON'S QUICK TO OFFER AN ANSWER.
And so Newton said it's obvious, it's an ellipse.
And Halley said, well how do you know that?
And Newton said, well 'cause I've calculated it.
So Halley said, well, could I see the calculation?
BUT NEWTON'S HESITANT.
HE HADN'T QUITE FINISHED THE MATHEMATICAL PROOF
TO SHOW THAT THE PATHS OF COMETS AROUND THE SUN
WERE ELLIPTICAL IN SHAPE.
So Newton sort of shuffled round on his desk and said,
mmm, can't quite find it just now.
So then Halley went away and then we assume
that Newton locked himself away for the next few days
and thought and scribbled, and eventually
he came up with nine pages of manuscript notation,
proving that the orbits were ellipses.
THE MANUSCRIPT IS A REVELATION.
HALLEY REALIZES IF NEWTON'S ORBITAL THEORY IS RIGHT -
MAYBE THERE ARE OTHER COMETS
THAT HAVE COME BACK MORE THAN ONCE IN THE PAST.
So Halley went one step further,
he started collecting historical records
of comets that appeared in the past,
and what he noticed was
that several of them had the same sort of pattern.
IN PARTICULAR THREE COMETS SEEN IN 1531, 1607, AND 1682.
HALLEY THEN MAKES THE BIGGEST BET IN THE HISTORY OF ASTRONOMY.
NOT ONLY DOES HE SUGGEST THEY'RE THE SAME COMET,
REAPPEARING EVERY 75 YEARS OR SO,
BUT HE BOLDLY PREDICTS THE COMET WILL RETURN AGAIN IN 1758.
AS THE YEAR APPROACHES THE EXCITEMENT BUILDS.
[Fara] If I were an astronomer at that time
I would have looked at the sky every night
and I would have thought
am I going to be the first person to see this comet,
is it really coming back?
ON CHRISTMAS DAY 1758 HALLEY'S COMET RETURNS!
IT'S PREDICTED APPEARANCE
SPECTACULARLY VINDICATES NEWTON'S THEORY OF GRAVITY.
He might well have watched apples fall from a tree,
but what was much more significant
is that he watched a comet flying through the sky
in 1680 and 1681.
And it was that comet that inspired him
to formulate the great mathematical law of gravity
that ties the Universe together.
SADLY NEITHER NEWTON NOR HALLEY
LIVE TO WITNESS THE RETURNING COMET,
BUT THEIR INTEREST IN THESE FIERY APPARITIONS
CHANGES THE WAY WE UNDERSTAND THE UNIVERSE FOREVER.
[Fara] From then on
it was absolutely impossible for astrologers to say
that the appearance of a comet
heralds some incredibly significant disaster.
From then on the comets were part of the Universe,
they had been taken in
within the clockwork mechanism of nature.
ASTRONOMERS HAVE LEARNT A GREAT DEAL MORE ABOUT COMETS
SINCE NEWTON AND HALLEY.
THEY FORMED BILLIONS OF YEARS AGO
DURING THE FORMATION OF THE SOLAR SYSTEM.
THEY LIE BEYOND THE ORBIT OF THE PLANETS.
AND THEIR ICY CENTERS CARRY A COCKTAIL OF CHEMICALS.
NOW ISON HERALDS AN EXCITING NEW CHAPTER
IN OUR UNDERSTANDING OF COMETS.
BUT DESPITE ALL WE'VE LEARNT,
COMETS CAN STILL CAST DARK SPELLS.
When Halley's Comet appeared in 1910
we knew a lot of things about comets.
ASTRONOMERS PREDICTED THAT DURING THIS APPARITION
HALLEY WOULD COME VERY CLOSE TO THE EARTH.
The orbits of the comet and the Earth were in such a way
that the Earth was going to go through the tail of the comet.
BUT THEY DISCOVER SOMETHING ELSE THAT CAUSES PANDEMONIUM.
HALLEY'S TAIL CONTAINS TRACES OF CYANOGEN,
THE MAIN INGREDIENT IN CYANIDE -
A DEADLY, POISONOUS GAS.
This gas was gonna contaminate the atmosphere of the Earth
and that caused mass hysteria.
THE NEWSPAPERS LEAP ON THE STORY.
MANY FEAR DEATH BY ASPHYXIATION,
THERE'S PANIC BUYING OF GAS MASKS,
AND RESIDENTS IN CHICAGO SEAL THEIR DOORS AND WINDOWS.
And in effect, yes,
the Earth went through the tail of the comet
but tails of comets are very, very thin,
the possibility of contamination is negligible.
BUT MORE RECENTLY
COMET ENCOUNTERS HAVE RESULTED IN DEADLY CONSEQUENCES.
SPRING 1997.
THE EARTH IS TREATED TO A SPECTACULAR COMET,
ONE OF THE BRIGHTEST IN MANY YEARS -
HALE BOPP.
And it came very slowly
because it was quite far away from the Sun,
and it moved very slowly and it stayed for weeks actually
and you could see it all the time.
BUT FOR A GROUP OF PEOPLE IN SAN DIEGO
HALE-BOPP TRIGGERS A SINISTER SERIES OF EVENTS.
If I would title this tape, it would be,
"Last Chance to Evacuate Planet Earth
"Before It Is Recycled".
THE HEAVENS GATE CULT THINKS
THAT HALE BOPP SIGNALS THE END OF THE EARTH.
TO ESCAPE THE MEMBERS BELIEVE THEY MUST BOARD A SPACECRAFT
CONCEALED BEHIND THE COMET'S TAIL.
BUT THE TRIP REQUIRES A GRISLY SACRIFICE.
THE MEMBERS OF THE CULT COMMIT MASS SUICIDE.
IN ALL 39 BODIES ARE DISCOVERED.
So I find amazing to realize
that people still got this reaction to...
to these apparitions of comets in the sky.
OCTOBER 2ND 2013
JUST OVER A YEAR AFTER ITS DISCOVERY
ISON IS NOW WITHIN 200 MILLION MILES OF THE SUN.
NOW THE COMET IS CLOSE ENOUGH FOR ASTRONOMERS ON EARTH
TO GET THEIR FIRST DETAILED LOOK AT ITS COMPOSITION.
ASTRONOMER ADAM MCKAY IS TRAVELLING TO AN OBSERVATORY
IN THE MOUNTAINS OF NEW MEXICO
ON HIS WAY TO OBSERVE COMET ISON.
So, we're heading up to Apache Point Observatory
to use the 3.5 meter telescope there
to obtain the specter of Comet ISON.
PERCHED HIGH IN THE SACRAMENTO MOUNTAINS
APACHE POINT IS TREATED TO SOME OF THE DARKEST SKIES
IN THE UNITED STATES.
Every observation for a comet is unique.
It's changing its distance from the Sun and the Earth,
and that really makes every observation very important.
ADAM'S ONE OF THE FIRST ASTRONOMERS
TO USE SPECTROSCOPY WITH AN EARTH-BASED TELESCOPE
TO OBSERVE ISON'S COMA,
THE GASEOUS ATMOSPHERE SURROUNDING ITS ICY NUCLEUS.
One of the things we're really hoping to measure
from the spectra we get tonight
is the water production rate of Comet ISON.
OVER THE NEXT FEW HOURS HE TRACKS ISON -
ANALYZING ITS GLOWING GASES.
So here's the spectrum of Comet ISON
that we were just able to obtain.
Basically the actual spectrum is all these bright rows
that you see here going across.
ISON'S SPECTRA MIGHT NOT LOOK LIKE MUCH,
BUT WITH A TRAINED EYE
ADAM MAKES AN IMPORTANT DISCOVERY.
One of the things we're really interested in
is this bright spot right here.
And that corresponds to atomic oxygen
that is present in the comet.
OXYGEN IS ONE OF THE TWO ELEMENTS THAT MAKE UP WATER -
AND ADAM'S DISCOVERY SUGGESTS
THE NUCLEUS OF ISON IS GUSHING WATER VAPOR
AS IT CONTINUES TO WARM UP.
This is one of the very first detections of water
in this comet.
IT MEANS THAT WHEN ISON FORMED
WATER MUST HAVE BEEN PRESENT.
This is material that,
as the solar system formed 4.6 billion years ago,
it gets incorporated into comets
and has basically been locked in a time capsule ever since.
THE DISCOVERY THAT ISON CONTAINS WATER
ADDS WEIGHT TO AN INCREDIBLE THEORY
THAT MIGHT ANSWER ONE OF THE BIGGEST MYSTERIES
ABOUT OUR OWN PLANET.
[Dartnell] There's a lot of water in the world today.
But what we think is that the early Earth
was created as quite a dry world.
So the question is, where did that water come from?
THE ANSWER MAY LIE WITH COMETS LIKE ISON.
The chances of the Earth being hit by a comet today
are thankfully quite slim.
But it wasn't always like that.
And billions of years ago in the early solar system
when our world was first formed,
the rate of comets pummeling down
onto the surface of the inner planets
would have been much, much higher.
THE EVIDENCE FOR THESE CATACLYSMIC COLLISIONS
IS CLOSER THAN YOU THINK.
THE MOON'S ANCIENT SURFACE
PRESERVES THE SCARS OF CRATERS AND VAST IMPACT BASINS -
MANY FORMED AROUND 4 BILLION YEARS AGO
WHEN COMET IMPACTS WERE FAR MORE FREQUENT.
The Moon is like a pristine record
of what would have been happening back on the Earth
at the same time,
but the dynamic surface of our world
has erased any evidence that that period once happened.
THE EARTH WAS ALSO SUBJECTED TO THIS INTENSE BOMBARDMENT
THOUGHT TO HAVE LASTED FOR MILLIONS OF YEARS.
ASTRONOMERS CALCULATE
AN AVERAGE SIZED COMET CARRIES MILLIONS OF TONS OF WATER.
MANY THOUSANDS OF THEM IMPACTING EARTH
MIGHT HAVE DELIVERED THE OCEANS THAT COVERS OUR WORLD TODAY.
[Rumble of explosion]
BUT SPECTROSCOPY REVEALS SOMETHING EVEN MORE INTRIGUING.
COMETS CARRY MOLECULES NECESSARY FOR LIFE.
What's even more incredible
is these comets are full, we now realize,
of organic compounds,
the building blocks of life on Earth.
Not only would they have been delivering water
to fill our oceans
and give the wet stuff for life to get started in,
but they would have been helping build up this reservoir
of the building blocks for life as well.
IT'S ONLY A THEORY, BUT IT'S A PROFOUND THOUGHT -
WE MAY OWE OUR EXISTENCE TO COMETS LIKE ISON.
NOVEMBER 19TH 2013 -
ISON IS ABOUT TO EXPERIENCE THE MOST PERILOUS PART
OF ITS FOUR AND A HALF BILLION-YEAR LIFE.
STREAKING PAST MERCURY
IT'S JUST DAYS AWAY FROM ITS SUN-GRAZING ENCOUNTER.
[Mainzer] Sun-grazing comets like to live dangerously.
And it's an open question as to whether or not
something this cold and icy
can survive a passage by the Sun.
THE NEXT WEEK WILL BE MAKE OR BREAK FOR THE COMET.
WILL IT BE DESTROYED BY THE FEROCITY OF THE SUN,
OR WILL IT SURVIVE?
[Explosions]
THE IMMENSE POWER OF OUR SUN IS FORCE TO BE RECKONED WITH.
SOLAR SCIENTIST ALEX YOUNG
AT NASA'S GODDARD SPACE FLIGHT CENTER
KNOWS ISON IS IN FOR THE RIDE OF ITS LIFE.
These images are showing us
the surface of the Sun
and its outer atmosphere called the corona
in extreme ultra-violet light.
THE CORONA IS HEATED TO OVER 2 MILLION DEGREES
AND TWISTED BY SUPER STRONG MAGNETIC FIELDS.
COMETS VENTURE HERE AT THEIR PERIL.
[Young] You can see here these lines,
which are tracing out magnetic fields.
This is what ISON will be passing through.
THE MAGNETIC FIELDS CAN TWIST AND VIOLENTLY SNAP
CAUSING EXPLOSIVE SOLAR FLARES.
You see these bright flashes here,
these are solar flares
that are releasing huge amounts of energy.
AS ISON PASSES AROUND THE SUN
IT WILL FEEL THE FULL FORCE OF THE SOLAR MAELSTROM.
Standing on the surface of ISON
you would be feeling all of this material
that's boiling away, blasting out into space
you would be feeling the intense radiation from the Sun,
the unbelievable gravitational forces pulling underneath you,
magnetic fields slamming into you,
just an incredibly harsh and hostile environment.
BUT FRUSTRATINGLY FROM EARTH
WATCHING ISON DURING THE MOST EXCITING PART OF ITS JOURNEY
WILL BE IMPOSSIBLE.
It's going to be so close to the Sun,
and the Sun is a brilliant white ball in the sky
when we look at it from Earth.
SO KARL WILL COMMANDEER TWO SOLAR SATELLITES
THAT CAN HELP.
ONE - CALLED SOHO -
CARRIES A SPECIAL TELESCOPE KNOWN AS A CORONAGRAPH.
So, the Coronagraph telescopes can see Comet ISON
because they actually place a solid disc
in front of the Sunitself
so that blinding light from the Sun
is prevented from reaching us.
LOOK AT AN ONCOMING CAR AT NIGHT
AND ITS DIFFICULT TO SEE THE DRIVER
IN THE GLARE OF THE HEADLIGHTS.
If you block out that headlight with your hand,
then you can see the fainter stuff around,
you can recognize the driver.
So it's the same principle that we apply
with the Coronagraph telescopes
for seeing the comet for example.
This is a Coronagraph image from the ESA NASA SOHO satellite
and what we're seeing here
is the faint atmosphere around the Sun
where the Sun has actually been blocked by this solid disc.
So we get to see these coronal streamers, for example.
We see stars moving across the images.
BLOCKING OUT THE SUN'S BLINDING LIGHT
KARL CAN STUDY COMETS LIKE ISON AS THEY PLUNGE INWARDS.
So here we have a sun-grazing comet
that's flying into the solar atmosphere.
We lose sight of it as it disappears behind this disc.
It will have gone very close to the solar surface,
but it would have vaporized before it got to that point.
SOHO HAS SEEN MANY SUN-GRAZING COMETS.
BUT ONLY ONE HAS EVER ROUNDED THE SUN AND ESCAPED INTACT.
COMET LOVEJOY.
LOVEJOY PUT ON A SPECTACULAR DISPLAY IN OUR SKIES IN 2011.
BUT THE MOST INCREDIBLE VIEW
CAME FROM NASA'S SOLAR DYNAMICS OBSERVATORY -
OR SDO FOR SHORT.
SDO SEES WAVELENGTHS OF LIGHT INVISIBLE TO OUR EYES.
IT ALLOWS ASTRONOMERS
TO PEER DIRECTLY INTO THE SUN'S ATMOSPHERE.
So in this SDO image of the Sun,
what we're seeing here is Comet Lovejoy
flying in, actually flying behind the Sun,
through the solar corona,
and in this case it actually survives
and comes out the other side!
This is exactly what we wanna see with Comet ISON.
NOVEMBER 28TH 2013.
THIS WILL BE D-DAY FOR COMET ISON -
ITS ENCOUNTER WITH THE SUN.
AND FOR OUR SCIENTISTS,
IT'S THE DAY THEY'LL LEARN ISON'S FATE.
THEY'VE NARROWED IT DOWN TO A NUMBER OF LIKELY SCENARIOS.
So there are several things that could happen to comet ISON
on its passage in towards the Sun.
ONE SCENARIO DEALS WITH THE INTENSE SOLAR RADIATION.
This is a big risk for a comet because if those ices,
if too many of those get vaporized away,
the comet is just going to fall apart.
It's going to dissipate into its constituent parts
and just fade away of sight.
IF THIS HAPPENS WE'LL LOSE SIGHT OF ISON FOREVER.
ANOTHER SCENARIO DEALS WITH THE SUN'S IMMENSE GRAVITY.
The gravitational pull of the Sun
is going to stretch the comet
and if the comet is just not structurally strong enough
it could just get completely ripped apart.
THAT'S WHAT HAPPENED TO COMET SHOEMAKER-LEVY 9 IN 1994
WHEN IT STRAYED TOO CLOSE TO JUPITER.
THE GIANT PLANET'S GRAVITY TORE IT INTO 21 FRAGMENTS.
IF THE SUN DOES THE SAME TO ISON -
WE COULD BE TREATED TO A SPECTACULAR SIGHT ON EARTH.
BUT THERE IS HOPE FOR ISON...
So the final scenario for Comet ISON
is that actually survives.
It flies past the Sun,
it goes through the million degrees solar corona
and it comes back out the other side in one piece.
WHICH MEANS WE MIGHT GET TO SEE ISON AGAIN,
BLAZING IN OUR SKIES IN DECEMBER.
Any one of these scenarios is possible,
and it may be we get a combination of a couple of them.
THE WAIT IS ALMOST OVER -
JUST DAYS FROM NOW ISON'S FATE WILL BE DETERMINED -
THEN WE'LL ALL KNOW THE FINAL CHAPTER
IN THE LIFE OF THIS INCREDIBLE COMET.
[Mainzer] So all eyes are on ISON right now,
everybody's watching,
we really want to know what's going to happen to this comet.
I feel like a kid when these sort of things happen.
I have a feeling that it's going to break up,
but when a comet breaks up it's still spectacular!
If you're able to see this comet and see it in the sky
that's a memory that will live with you forever.
I want huge flare-ups,
I want it to be bright and brilliant.
If it's gonna go out, I really want it to go out with a bang.
Comet Encounter is made poss To learn more about this program
visit pbs.org.
This program with updated footage of the comet
is available on DVD.
To order visit shoppbs.org or call 1-800-playpbs.
The original version
is also available for download on iTunes.
