TV Series | The Universe | Contents page
In the beginning there was darkness...And then... BANG!
Giving birth to an endless expandingexistence of time, space and matter.
Now see further than we've ever imagined,beyond the limits of our existence,
in a place we call...THE UNIVERSE
Are there planets beyondour solar system?
It's a question few have dared to probe.
The origin of hunting forplanets started, really,
from the lunatic fringe of science.
Now, hundreds of these exoticworlds have been found.
Could any of them be home to alien life?
Right now, the sort of planetswe're discovering are kind of...
You would be incinerated immediately
before you had a chance to reallysort of groove on your surroundings.
But some planets hold more promise.
I'm so excited about Gliese 436,I'm almost jumping out of my clothes.
Could we be on the vergeof finding another Earth?
We still don't know whether our Earthis a commonly occurring planet
or a one-in-a-billion freak.
Cutting-edge science, strangeworlds, and wild weather,
as we travel the Universe insearch of "alien planets".
Lurking in the constellation Pegasus,50 light-years from Earth,
is a monstrous planet.
A superheated gas giantalmost as massive as Jupiter,
whipping around its starin a little over four days.
It's called "51 Pegasi b" and in 1995,
it became the first planetdetected orbiting an alien sun.
It was a landmark discovery,
but just a stepping stoneon an even greater quest
to find a planet that looksmore like our own.
The ultimate but elusivegoal for astronomers
is to find another Earth.
What we're after is the appreciation
of where our Earth fits in, in thegrand context of our Universe.
And we'd love to be ableto find other Earths.
But Earths are so undetectable,
little chunks of rock thatdon't emit much light.
How common might Earth-likeplanets be in the Universe?
Even if only one percent of all starswere circled by a planet like our own,
that would still mean there are billionsof other Earths waiting to be discovered.
We are almost sure
that rocky Earth-like planetsexist in abundance out there,
but how Earth-like?
There are still open questionsabout the uniqueness of our Earth,
and we don't know whetherour Earth is unusual or not.
It's an extremely profound and,I think, disturbing question.
In the realm of alien planets,
there is a wide rangeof imaginable worlds.
We might find ocean worlds,completely covered in water,
frigid ice planets,
mars-like worlds, but perhapswith thick atmospheres
fed by massive active volcanoes,
and even planets withtwo suns in their skies.
There may be planets that humanswould find hospitable,
and others on which humanswouldn't dare tread
that could still be hometo other types of creatures.
Perhaps the major lessonwe've learned so far
from looking the planets around the stars
is that nature can make a lot moreplanets that we can dream of.
Finding just one othertruly Earth-like planet
would hint that Earths arecommon in the Universe.
And if Earths are common, thenperhaps life, too, is widespread.
But of the over 200 alienplanet detected so far,
most of them seem uttlerlyhostile to life as we know it.
So far, we found sortof three kinds of worlds.
One kind are the planets that are reallyclose to the star that they orbit,
and they're totally baked to death.
Then there are the ones that are quitefar away, and they're pretty cold.
And then there are the onesin the highly eccentric orbits
which sometimes get close to thestar and sometimes far away.
So they're alternately very hot
So far, we definitely haven't foundany worlds with jungles and forests.
Indeed, we haven't found any worlds
that are square smack in thehabitable zone where there's
liquid water on the surfaceand other nice conditions.
Our frame of reference for what weconsider to be a nice planet is this one.
We like it quite a bit.
We've got breathable air, it's a pleasanttemperature, and there is water.
And even in our own solar systemwe don't see a lot of planets like that.
Right now the sort of planets we'rediscovering are kind of monsters.
In other words, they're extremes.
So is the Earth, with its rocky surface,oceans, and abundant life,
just a planetary wonder withno close kin in the cosmos?
The early discoveries of alien planethave yet to answer that question,
but they have brought legitimacy towhat once seemed like a futile quest.
While many believe there hadto be other worlds out there
in the vastness of the Universe,
locating them was widely consideredbeyond the reach of modern science.
Only a few decades ago,
an astronomer hunting for theseso-called "extrasolar planets",
was taken about as seriouslyas someone searching for UFOs.
The search for planets, as itstarted in the 1980s and 1990s,
was considered off of the beatentrack of standard science.
In the early '80s, astronomer GeoffMarcy's career was going nowhere.
His research into the magnetic fieldsof stars had reached a dead end,
and he was beginning to questionhis own abilities as a scientist.
When I first began thinkingabout looking for planets,
it was in a time in my careerwhen I thought it was over.
I thought there were... There's no hopefor me as a scientist, and I thought
the best shot I had going out in flames
was to try an experiment that everybodythought would never work...
Namely, looking for planetsaround other stars.
And most people thought wewould never find any planets.
Before Geoff Marcy, hiscollaborator, Paul Butler,
and a handful of pioneeringastronomers around the globe
could begin the searchfor alien planets,
they had to first perfectmethods for finding them.
Stars are easy to locateusing conventional telescopes,
but to find a planet takessome ingenuity and patience.
Unlike the stars they orbit, planetsare small and emit very little light.
Even the giant ofour solar system, Jupiter,
is a thousand timesless massive than the Sun
and 10 billion times fainter.
A huge difficulty in taking a pictureof a planet around a star is that
the planet is extremely, extremelyfaint compared to the star.
The star is so brightit almost completely obscures
the much, much dimmer planet.
Blinded by starlight,planet hunters realized
that even if they couldn't seea planet directly,
they should still be ableto detect its gravitational effect
on the star it orbits.
A star with no planets should driftsmoothly through the sky,
while one with planets should exhibita telltale gravitational wobble.
We often say that planetsorbit the sun or other stars,
but that's not exactly true:the planets and the stars
orbit their common center of massor center of gravity.
And this center of massisn't halfway between them.
Just like on a seesaw,the more massive object
must be closer to the center of massto bring balance to the system.
TV Series | The Universe | Contents page