NARRATOR: The biggest things
in space are gargantuan beasts. Each one is a heavyweight. In its galactic division. LAURA DANLY: The universe is
an unimaginably large place. It's so big, it's really
hard for human beings to actually comprehend
things of these size scales. NEIL DEGRASSE TYSON: On
Earth, and in the universe, size matters, but it
matters in different ways. NARRATOR: In space, bigger
is not necessarily better. And oftentimes, the winners
live large and die young. [music playing] They're the Mount
Everests of the cosmos. Astronomers aim their telescopes
at them like paparazzi, eager to capture images
of their every movement. They are the biggest
things in the universe, and their sizes are
truly mind-boggling. NEIL DEGRASSE TYSON:
The good thing about being huge in the universe
is that the universe is even huger than you are, so
there's plenty of space to stretch out and
get your size measured among intelligent civilizations
that are having a look. MATT MALKAN: The first
thing you find out when you start
studying astronomy is how darn big everything is. Almost everything
you're studying is so far beyond any
kind of human scale that we're ever going to
encounter in our normal lives. [music playing, explosions] NARRATOR: The universe is
brimming with gigantic objects. Within our own
solar system, Earth is the fifth biggest planet. But it's 100 million
billion times smaller than the
largest stuff in space. So what holds that coveted
title as the biggest thing in the universe? Most astronomers agree
it's the cosmic web, an endless scaffolding of
superclusters of galaxies surrounded by dark matter, an
invisible and mysterious form of matter that accounts for
90% of the universe's mass. LAURA DANLY: The largest
thing in the universe, you might even wonder
if it's a thing at all. It's a web of dark
matter that fills the volume of the universe. Dark matter is this matter
that we can't even see. It doesn't emit any light. But it is filled
throughout the universe, and there's structure in it. MICHELLE THALLER: Dark matter is
something much more mysterious than most people know. Literally, the stuff that
makes me up, dark matter isn't made of that. I don't think you
could smell it. I don't think you
could touch it. It simply has
gravitational attraction. NARRATOR: The cosmic
web of dark matter becomes visible when looking
at the objects that fill it. MICHELLE THALLER:
This cosmic web really is almost like a
three-dimensional spider's web. At the very center
of all the vortexes, there are the
superclusters, clusters of thousands of galaxies. And then filaments
of galaxies connect them all the way across
the volume of the universe. LAURA DANLY: The deepest,
strongest gravity at the intersections of
these web-like structures is where all the gas falls. And that's where galaxies form,
clusters of galaxies form. NARRATOR: But just how
big is the cosmic web? [music playing] If the Milky Way galaxy
were the size of a poppy seed, then the observable universe,
everything we can see, would be about the volume
of the Rose Bowl Stadium. Now, that entire volume is
filled with the cosmic web, superclusters linked together
from one side of the universe to the other. NARRATOR: The origins of the
cosmic web remain uncertain, but scientists think its initial
seeds were planted in the Big Bang, the beginning
of the universe. During the Big Bang
explosion, the whole universe blew up, essentially, and
expanded very rapidly. So the cosmic
matter web contains all of the original matter that
was created during the Big Bang just blown up into the
very, very large structures that we see today. [music playing] NARRATOR: Scientists
are actively trying to map out
the cosmic web, which spans the entire universe. LAURA DANLY: One way is to
look at hot X-ray-emitting gas and how it's contained
by the gravity present in the dark matter. Another way is to
look at something called gravitational
lensing, where light is bent by the
gravity of the cosmic web. And so we're able to sort of see
the outlines of that cosmic web by the way it distorts the
light that's behind it. NARRATOR: The cosmic web
basically contains everything in the universe. But some scientists question
whether it's technically the largest object, because
the web isn't continuously connected throughout space. AMY MAINZER: The cosmic
matter web is not actually the largest gravitationally
bound object in the universe. Because all the
matter in the universe has expanded so vastly,
the force of gravity is not enough to keep
it together in one area, whereas superclusters
of galaxies are actually gravitationally
bound, meaning that they have enough mass to produce enough
gravity to hold them together over the passage of time. [music playing] NARRATOR: Astronomers
don't have a firm estimate, but the cosmic web could be
made up of hundreds of thousands of supercluster complexes. These are mega collections
of galaxies, gravitationally bound, up to hundreds of
millions of light years across. LAURA DANLY: The universe
is organized hierarchically. Stars make up galaxies,
galaxies make up clusters, clusters make up superclusters. You could draw an analogy that
a cluster might be the North American continent,
and a supercluster might be the association of
cities on the North American continent, cities in
the European content, cities on the Asian
continent, et cetera. [music playing] NARRATOR: The current record
holder for the largest supercluster of galaxies
is called the Shapley Supercluster. This dense region of galaxies
is 400 million light years long. So it would take the fastest
interplanetary spacecraft trillions of years
to travel across it. The Shapley Supercluster
spans several constellations, and is almost 650 million
light years from our Milky Way galaxy. [music playing] I have here a
small toy boat which is a replica of the Queen
Mary, which you can see here behind me. And this little toy is
about 4,000 times smaller than the real Queen Mary. If you could just imagine
that our own Milky Way galaxy that we live in is the
same size as this toy boat, then one of the most massive
superclusters that we know about, the Shapley Supercluster,
would be the same size as the Queen Mary. So the Shapley Supercluster
would be about 4,000 times larger than our own Milky Way. It's one of the most
massive things we know about in the entire universe. [music playing] NARRATOR: Astronomers have
known about superclusters since the 1950s, but now,
they've determined their origin through recent measurements
of the cosmic microwave background, which is
actual radiation left over from the Big Bang. It's been concluded that
all superclusters, including the Shapley Supercluster,
originated during the formation of the universe over
13 billion years ago. AMY MAINZER: As the universe
evolves and expands, gravity is an attractive
force, so any region that has a little extra density there
attracts more matter and more matter. So Shapley is a cluster that
basically had the accumulation of many other little
galaxies falling into it, and that's why it's
gotten so big over time. NARRATOR: Incredibly, scientists
think the Shapley Supercluster may maybe even bigger
than it appears. In fact, we may only be seeing
a small fraction of what's really contained within
the Shapely Supercluster. When the Wide-Field Infrared
Survey Explorer launches, we should be able to see
about 10 times farther away, and hopefully, we'll be able
to see the rest of the Shapley Supercluster, see if it is
even more massive than what we already know about. NARRATOR: Superclusters
of galaxies will stay together over time
because they're gravitationally bound. AMY MAINZER: Gravity is
holding them together. So even though the universe
is expanding over time, those superclusters of
galaxies will stay together, and they'll always keep
orbiting each other. [music playing] NARRATOR: We humans also live
in a supercluster complex, but it's less than half the
size, and about 10 times less massive than the
Shapley Supercluster. LAURA DANLY: Our Milky Way as
part of a small little cluster called the local group, which is
part of a larger cluster called the Virgo Cluster, sort of
on the outskirts of that. So it's like your home address. You live on this street, in
this town, in this state, in this country. Similarly, the Milky Way has its
larger and larger associations of which it's a part. NARRATOR: Superclusters
of galaxies are the most crowded
neighborhoods in space, but they surround
equally big regions where almost nothing exists. These bare spots
are called voids. LAURA DANLY: Voids are
the opposite of clusters. If clusters are where
all the galaxies are, voids are where all
the galaxies aren't. And you do see this
kind of frothy, web-like structure
of clusters and voids and clusters and voids. So it's kind of like cities
and countryside, cities and countryside. [music playing] NARRATOR: The largest
confirmed void in the universe remains Bootes. Named after the constellation
where it resides, this near empty space is
a whopping 250 million light years across. That's equal to 2,500 Milky Way
galaxies placed side by side. BOB BRITT: Look out into
the cosmos in any direction and you'll see something. You'll see stuff. You'll see galaxies. You'll see gas, dust,
you'll detect dark matter. Everywhere you look,
there's something. Yet, here's this giant
hole with nothing in it. [music playing] NARRATOR: The Bootes void,
which was discovered in 1981, is almost completely
devoid of galaxies. A new way to search
for even larger voids may be possible by
precise measurements of the temperatures of the
cosmic microwave background radiation. Subtle cold spots
in this radiation could locate the directions
of large, distant voids. [music playing] MATT MALKAN: The story
of their formation is basically the reverse
of how superclusters form. The voids must have started
out, in the first microsecond of the Big Bang, as slightly
low density regions. But with time, they became
less and less dense. All of the matter flowed away
into the sheets and filaments, leaving the voids emptier
and emptier of matter, until today, there's
almost nothing but a few little dwarf galaxies
in some of these voids. NARRATOR: Voids and
superclusters are just some of the big things contained
in the even larger structure called that cosmic web. But the web also holds other
immense objects, including colossal bubbles that might hold
missing clues to the formation of galaxies. [music playing] The universe is packed
with monstrous things. Researchers have recently
discovered giant clouds of gas that resemble something
out of a horror movie. These mysterious objects are
called Lyman-alpha blobs. My personal favorite biggest
objects in the universe are the Lyman-alpha
blobs, unpredicted, unexpected phenomenon where
you're catching a galaxy in the first phases of its
formation and collapse. A Lyman-alpha blob is very
much like this expanding soap bubble, except in the
case of the soap bubble, it's the air which
is making it fill up. A Lyman-alpha blob is
expanding because of heat. A lot of energy has been
injected into this gas to make it heat up, and when you
put all that energy into a gas, it inevitably tends to
puff up and expand exactly like an expanding bubble. In the case of a
Lyman-alpha blob, it's being puffed up
by heat, and maybe also by the
ultraviolet radiation from the newly formed stars. [music playing] NARRATOR: The largest
known Lyman-alpha blob is a colossal amoeba-shaped
structure that resembles a giant green jellyfish. It's 200 million
light years wide and it's located in the
constellation Aquarius. AMY MAINZER: When we're looking
at the Lyman-alpha blob, we're seeing gas that's sort
of spread amongst these very first stars and galaxies. It's kind of an
amorphous shape of about 30 separate little
blobs inside of it. It's very large
and very massive. The whole structure is
about 3,000 times the size of our own Milky Way galaxy. NARRATOR: The Keck and
Subaru telescopes in Hawaii contain special filters that are
able to see this faraway blob which spreads out
along curvy tentacles. Scientists estimate that the
largest Lyman-alpha blob was formed about 12 billion years
ago, almost two billion years after the Big Bang. The observational technique
we use to see that gas, it refers to a very
specific color of light, emission of light that's
called Lyman-alpha. So you hear a phrase
Lyman-alpha blob, because if you take
an image of the sky through a filter that gives you
only that Lyman-alpha light, that very special
wavelength of light, you'll see a little
blob on the sky. [music playing] NARRATOR: Lyman-alpha
blobs are perhaps precursors to the galaxy
clusters we see today. Within these gigantic bubbles
may exist cocoons that will one day spawn new galaxies. The Lyman-alpha blobs are
probably a fairly special, short-lived phase in the
evolution to creating a galaxy. I do expect that most of them
are going to collapse and form young galaxies in the next
100 million years or so of their lives. So it's a special phase just
when a galaxy is beginning to pull itself together. The search in the universe
for Lyman-alpha blobs is just beginning. We'll undoubtedly find
many more of them, and even perhaps some
larger ones in the future. Stay tuned. NARRATOR: Lyman-alpha
blobs may hold the answers to the formation of
individual galaxies, which are gravitationally bound
systems containing stars, gas, dust, and dark matter. At least 100 billion
single galaxies exist in the
observable universe. They range in size from 10,000
to millions of light years across. NEIL DEGRASSE TYSON: Galaxies,
these titanic collections of stars, I think
of them as cities, having been born in one myself. Not only a galaxy, but
also, an actual city, a native of New York where
everyone is crowded together. Galaxies are sort of how
matter has organized itself in the universe. [music playing] NARRATOR: In the competition
for largest single galaxy in the universe, sizing up
a winner is challenging. MATT MALKAN: The
problem in saying, what's the largest galaxy, is
in deciding where they end. Galaxy does not
have a sharp edge. It just gets thinner and
thinner as you go further out. It's exactly
analogous to saying, where's the end of a very
large metropolitan area? Where's the end of Los Angeles? You can go out 50 miles and
you'll still find a fairly high density of suburbs. The suburbs of a big
galaxy like the Milky Way extend out very, very far,
more than 100,000 light years. And wi8th a giant
galaxy, those suburbs extend out hundreds of
thousands of light years. [music playing] NARRATOR: Since scientists
can't determine a clear width, several galaxies share
the title as biggest. They're called Cluster
Diffuse or CD galaxies. And they sit in the centers
of rich clusters of galaxies. MICHELLE THALLER: If you
think about the cosmic web as being sort of like a
three-dimensional spiderweb, well, then the spiders lurking
in the middle of the web are these monstrous CD
galaxies, as we call them. These galaxies could have
masses that are, in some cases, maybe 10 times or 20 times
the mass of our own Milky Way. LAURA DANLY: These CD galaxies
are the largest galaxies in the universe. For example, IC 1102 sits in
the center of a galaxy cluster called Abell 2029, and it's
6 million light years across. Compare that to our
own Milky Way, that's 100,000 light years across. It's a really big galaxy. It's 60 times the
size of our Milky Way. [music playing] NARRATOR: CD galaxies are
elliptically shaped, as opposed to a disk structure
like our Milky Way. This is because they've achieved
their size by bulking up on other galaxies
through galaxy mergers. LAURA DANLY: You may have heard
the phrase galaxy cannibalism, where one galaxy eats another. That goes on all the time
in clusters of galaxies. So sitting usually
down at the very center of a massive cluster
you'll find one big galaxy. MICHELLE THALLER: These
CD galaxies have so much mass that they are the 800
pound gorilla wherever they are. You see little galaxies
maybe orbiting around them, but basically, it's eaten
up everything nearby. [music playing] NARRATOR: The
largest galaxies may be 6 to 20 million light
years across, however, there are other
objects even larger. They're called radio lobes. Stretching out from both
sides of the galaxy, these immense
structures are actually hurling jets of
charged particles that emit radio waves. So we're here in this
auto body shop, where I'm going to use these two
torches to simulate radio jets coming out of opposite
sides of an accretion disk swirling around a
supermassive black hole. So in the visible, you see a
small blue flame coming off of the torch, but
in the infrared, you can see that the
heat from the torch extends much, much further out. Similarly, with the radio jets,
what you see in the optical is actually quite different from
what you see in radio waves. MICHELLE THALLER: A typical lobe
might be 160,000 light years as the lobe spreads out on
both sides of the galaxy. That's about twice the size of
the Milky Way galaxy's disk. NARRATOR: Astronomers think
radio lobes are powered by supermassive black
holes located in quasars. These are the luminous centers
of most active galaxies. MATT MALKAN: The
Jets of radio energy that come from a
giant black hole and make these enormous radio
lobe structures are very closely related to quasars. In fact, in some cases, you
can see a low power quasar in the center of the
galaxy, and then it's surrounded by these giant
lobes to either side. They've been blasted out by very
high energy jets of electrons that are basically moving at
almost the speed of light. And they are
blasted out probably from the north and south poles
of a spinning black hole. MICHELLE THALLER:
The radio lobes depend on matter going
down the black hole. As matter goes down the
black hole, some of it gets accelerated up
into these lobes. So the size of the
lobes has something to do with the history of how
much matter the black hole was actually fed on. And so over time
they'll change size. NARRATOR: Radio telescopes
had surveyed the universe and determined the
largest known radio lobe. Undeniable record holder is
located in the galaxy named 3C 236, which is in the
constellation Leo Minor. Its jets span 40 million
light years across. Scientists don't understand
why some active galaxies formed these jets and others don't. But one thing's certain, radio
lobes will not last forever, perhaps for only a
few million years. AMY MAINZER: So just as this
torch will eventually run out of gas and shut itself off,
the Jets from a radio galaxy will eventually die as well. When the black hole
has consumed all of the material in its
immediate vicinity, there'll be nothing left
of the accretion disk to get shot out along
the magnetic field lines, and the jet will die. NARRATOR: If black
holes are the producers of these gigantic
radio lobes, then what is the largest black
hole in the universe? Scientists are currently
placing bets on the winner. When it comes to the biggest
things in the universe, some black holes earn a
place in the record books. A black hole is a region of
space where the pull of gravity is so immense that nothing
can escape it, not even light. There are billions upon
billions of these black monsters prowling the universe. They come in two
size categories. Most of them are the
stellar mass black holes, which are about 5 to 100
times the mass of our Sun. And then there are the
supermassive black holes that are millions to billions
of times the mass of the Sun. NEIL DEGRASSE TYSON: We have
the supermassive black holes, the kind that we
seem to be finding in the centers of every galaxy
where we've had the resources to look. Havoc is wrought
upon your environment if you are a star
orbiting close to one of these supermassive
black holes in the centers of these galaxy. [music playing] NARRATOR: Black holes are
not physically large regions, but when measuring
their mass, they become top competitors in the
galactic heavyweight division. AMY MAINZER: The center
of our Milky Way, we know that there's a black
hole that's about maybe three million times the
mass of our own Sun. And yet, because black holes
are so incredibly dense, the actual size
of the black hole is still fairly small, but
incredibly, incredibly powerful gravitationally. NARRATOR: As their
name suggests, these black beasts
are essentially black because no
light can escape them. So one can only be observed when
its gravity effects something else in space, such
as a passing star, or when it's gorging
on matter around it. [music playing] So what is the reigning
black hole champion? The current record holder
for the largest black hole appears to be in the incredibly
luminous quasar which has the prosaic sounding
name HS 1946 plus 7658. Why do I say it's the
largest black hole? Because we know it is the most
luminous quasar in the universe that's been found so far. The black hole that's
holding it together, that's producing the energy,
needs to be about 10 billion times the mass of the Sun. That corresponds to a
black hole, which is larger than our entire solar system. In fact, it's just
out there to remind us how bizarre, seemingly, a
simple force like gravity can actually be. NARRATOR: The largest
supermassive black hole wields power in the center
of a galaxy, but there are other big luminous
objects in the universe. In fact, there are some that
seem to exist everywhere we look. When we glance into
the nighttime sky, we see stars, twinkling dots
of light that are actually luminous balls of plasma. Although they may
seem small from Earth, stars come in a
variety of sizes, from red dwarfs, which are
about 1/12 the mass of our Sun, to blue-white super giants
that can get as big as 150 solar masses. Our Milky Way holds 100 billion
stars, including our Sun, which is over 300,000 times
the mass of planet Earth. And this cosmic beacon
is a literal powerhouse in our solar system. [music playing] NATE MCCRADY: This natural
gas power plant produces about 300 megawatts of power,
and that's enough to power a few 100,000 homes. But that's only a tiny fraction
of our Sun's energy output. The Sun's power is
about two billion, billion times the
amount of this planet. So even in spite
of its distance, the Sun is able to
warm our entire planet. NARRATOR: Even so, our Sun
isn't the largest or the most powerful star by a long shot. NATE MCCRADY: The most powerful
stars are about a million times as powerful as the Sun. So if you wanted to compare
that with the Hoover Dam, you would need 30 million,
million Hoover Dams per person on the planet to
generate that much power. There's really no human scale
to imagine this power output. [music playing] NARRATOR: The largest
and most powerful stars that produce this kind of energy
are called red hyper giants. NATE MCCRADY: That's a class
of stars that's even larger and super giant stars. So typically, stars like our Sun
are fusing hydrogen into helium to make their energy, but
hyper giant stars have already exhausted all the
hydrogen in their core and they're fusing hydrogen
into helium in the outskirts around the corner, and
that makes them extremely hot and energetic, and all
that energy causes the star to swell up. And so star ends up with
a very large surface area, surface areas of the size of the
Earth's orbit or even bigger. NARRATOR: Within the hefty
field of red hyper giants, VY Canis Majoris appears to
have the largest diameter. It's 2,000 times
wider than our Sun, and consequently, it would take
the world's fastest race car 2,600 years to circle it once. This stellar champ lives about
5,000 light years from Earth in the constellation
Canis Majoris. If you replace the Sun
with VY Cains Majoris, if you put this hyper giant
star where the Sun is, its radius would extend
out past Saturn's orbit. It'd be about nine times as far
from the Sun as the Earth is. So this is a much broader in
diameter star than our Sun is. [music playing] NARRATOR: Astronomers determine
the radius of such a large star by looking at its temperature. NATE MCCRADY: We use
measurements of the temperature of the star's surface,
which we can get from the color of
the star, and then we will also measure the total
power output or luminosity of the star, and
by combining those, we can determine what the total
surface area is of the star, and from that, we
get its diameter. AMY MAINZER: Now, that
assumes that you can measure its luminosity fairly well,
and that you know something about its temperature
from its color. Most of the time,
they just simply appear as pinpoints of light,
and it's impossible to actually resolve it. Although there are
new instruments now called interferometers which are
capable of resolving even very tiny point sources, like stars. And in some cases, there
have been direct measurements of stellar diameters. [music playing] NARRATOR: VY Canis Majoris will
not be a title holder forever. The red hyper giant
is losing mass at the rate of almost 30
Earth masses or more per year. MICHELLE THALLER:
The largest stars in the universe, like VY
Canis Majoris are actually dying stars, that as
stars begin to die, they burn their nuclear
fuel much less stably. They puff out over time. NATE MCCRADY: VY Canis
Majoris is probably only a few million years old. Stars that are as massive as
it is don't live very long. They use their fuel up
at prodigious rates, then they swell up into
this hyper giant state and only live there for a few
hundred thousand years, a very short timescale, and
then rapidly explodes. NARRATOR: VY Canis Majoris
might have the largest diameter, but when it comes to
possessing the most mass, there's another star
that tips the scale. In the wide world
of stars, there are many contenders
vying for the title as the largest in the universe. But when it comes to stars, big
can mean two different things. NATE MCCRADY: When you talk
about the biggest stars, you could mean
one of two things. You could either mean the star
that has the largest diameter, or you might mean
what it's mass is. The mass is a measure of
how much stuff you have. It's sort of like
your weight when you step on the scale, how much
matter your body is made of. NARRATOR: According
to some astronomers, the most massive star is
located in our Milky Way galaxy. It's part of a binary star
system known as A1, which is actually two stars that
orbit each other once every four days. NATE MCCRADY: We find
there that one of the stars appears to have a mass of about
115 times the mass of the Sun, and the other star is also
enormous, about 84 times the mass of the Sun. So both stars in this binary
are among the most massive stars that we have ever measured. There may be more massive stars
than the combination in A1 in this star cluster, but that's
the most massive that we've been able to measure directly. NARRATOR: These massive stars
will live full, but short lives. NEIL DEGRASSE TYSON: Massive
stars are hugely luminous. Sometimes, they can
outshine millions of stars in their neighborhood. But at a cost. The cost is they will run out
of fuel faster than everybody else. And when they die,
they die spectacularly. They explode their guts and
scatter it across the galaxy. So the cost of living a high
mass life, a high luminous life, the cost of
living in the fast lane is that you explode at
the end of your life. LAURA DANLY: A bright star may
burn out faster and die sooner, but at the same time, those hot
stars are cooking up elements that are essential for life. So without really massive
stars, we wouldn't be here, because you wouldn't
get the iron in my blood and the calcium in my bones. All of those things are formed
only in the most massive stars. [music playing] NARRATOR: We humans
need essential elements from massive stars, but we
also need a planet with a firm surface to stand on. Planets come in two size
groups, large gas giants, like Jupiter, and small
rocky extraterrestrials, such as Earth. In our own solar system,
Jupiter is the largest planet, while Earth trails
in fifth place. Yet, even though Jupiter reigns
supreme in our galactic zip code, it's not the biggest
planet in the universe. The largest planet with a well
known radius is called TrES-4. It's named after the
Trans-Atlantic Exoplanet Survey that discovered it in the
constellation Hercules in 2006. AMY MAINZER: TrES-4 is
unusually large for its mass. We can actually directly
measure its radius, and this particular planet
has an unusually large radius. It's about 70%
bigger than Jupiter, yet it has only about
80% of Jupiter's mass. That's about the same density
as cork, or even whipped cream. If you look at Earth, it's
a rocky planet, very dense. And then even the gas
giant planets like Jupiter are compressed gas and
water and other chemicals, very tightly compressed. This thing, TrES-4 is
like a marshmallow. [music playing] NARRATOR: Although TrES-4
is light for its size, it's about 18 times
larger than Earth. Scientists aren't exactly
sure how TrES-4 got so large. One theory is that the planet's
extremely close distance to its parent star is
cooking up a lot of chemicals in its atmosphere, which
is trapping heat, much like greenhouse gases. AMY MAINZER: This particular
planet is only about 5% of the Earth's Sun distance
from its parent star, so it's very, very close. In fact, so close it orbits
its star every 3 and 1/2 days. So you can imagine how hot and
how just blasted with sunlight this thing must be. Because the planet can't
cool off, it can't shrink. Because when it's very hot,
when gases are very hot, they expand. So this might be contributing
to keeping the radius of this planet so very large. [music playing] NARRATOR: TrES-4 may
be a puffed up planet, but when it comes
to sustaining life, bigger planets don't
offer prime real estate. LAURA DANLY: These giant
planets really are just gas. There's no solid
structure to them at all. There's nowhere
to stand on them. So it's not a very likely
place to find life, because life would have to
continually be blown around in the atmosphere, and that's
a hard thing to evolve from. AMY MAINZER: This planet would
not be a very habitable place because it's so close
to its parent star. It's getting blasted with
radiation from its sun. So it would be a very hot
and unpleasant place to be, at least for humans. [music playing] NARRATOR: TrES-4 currently
has the largest known radius, however, a planet could be
bumped out of first place in the near future. AMY MAINZER: Scientists are
finding new planets basically every day almost at this point. So it's quite possible that we
will find another one that's even bigger than this
particular planet anytime. NARRATOR: In
addition to planets, scientists are also discovering
new asteroids all the time. These are rocky bodies
that didn't become planets. And the largest one may exist
in our galactic neighborhood. [music playing] In our own solar system,
billions upon billions of leftover rocks that didn't
become planets take refuge in the asteroid belt. Some are
as small as grains of dust, and others are the
size of nations. Ceres was the first
asteroid ever discovered, and it remains the largest
known asteroid to date. Named after the Roman goddess
of plants and harvest, Ceres is about 600
miles in diameter, so it's almost as large as
the state of California. BOB BRITT: Ceres is so big that
it contains 25% of all the mass in the asteroid belt. Ceres
is so big that if you took all the other asteroids
in the asteroid belt and include them all
together, they'd only be about two or three
times bigger than Ceres. [music playing] NARRATOR: Ceres'
size sets it apart from the rest of the rocks
of the asteroid belt. It would take the Apollo
Lunar Rover 10 days to drive around the asteroid
at 8 miles per hour. But in addition to its size,
its other distinct feature is its round shape. NEIL DEGRASSE TYSON: You have
bullies Idaho potatoes orbiting in the asteroid belt of the
solar system, most of which are craggy chunks of rock. Ceres is large enough, massive
enough that its gravity has overcome the strength of
the rocks that contain it. And any time that happens,
the shape becomes a sphere. [music playing] NARRATOR: Because
of its round shape, Ceres now holds a dual title. AMY MAINZER: The current
definition of a dwarf planet is something that, in
fact, is massive enough and has enough self-gravity to
form itself into around shape. And in fact, since
Ceres is round, we also call it, in addition
to being an asteroid, a dwarf planet. We know only a little bit
about the composition of Ceres right now. We know that it's made
primarily of rock, but it may also have water
ice, and in fact, it could have clay inside it as well. The Dawn Mission is actually
going to go to Ceres and enter into orbit around it,
and they'll bring a whole suite of instruments to bear on it,
so we should learn a lot more about the composition of
this unusually large asteroid in our own solar system. NARRATOR: Ceres may be
the largest asteroid in our solar system, but it's
a big universe out there. AMY MAINZER: It's quite possible
that as we go on to exploring other solar systems
outside of our own, that we may, in fact, someday
find an asteroid larger than Ceres. NARRATOR: Our solar
system contains some oversized objects. The largest planet, Jupiter,
has the biggest moon, name Ganymede. Planet Mars actually
contains the largest volcano, called Olympus Mons. AMY MAINZER: It's
17 miles tall, which makes it about three times
taller than the biggest volcano we have on Earth. It's so tall that if you stood
at the base of Olympus Mons, you wouldn't be able to see
the top due to the curvature of Mars itself. So in our own solar system,
the biggest things definitely have had a powerful shaping
effect on the universe. [music playing] NARRATOR: One might guess that
the Sun would take top honors as the largest thing
in our cosmic suburb. It's 1,000 times more
massive than Jupiter. But is there something bigger? The largest object associated
with our solar system is the Oort cloud. And this is a very diffused
cloud of comets that literally extends about halfway out to the
nearest star, Alpha Centauri. Alpha Centauri is about
4 light years away. NARRATOR: Astronomers estimate
it would take the space shuttle hundreds of thousands of years
to travel around the outer edge of the Oort cloud. The Oort Cloud is
so dark and so distant that we really can't
directly observe it. But what we do
know is that comets come in from every
direction of the sky, so there must be a spherical
cloud of comets far away from us. [music playing] NARRATOR: The origins of the
Oort cloud remain puzzling. One theory is that it was formed
early in our solar system. As comets fell in
towards the forming Sun, they were ejected
into long orbits. Over time, their orbits threw
them out into a giant cloud. AMY MAINZER: It's very
far away, and it's filled with icy remnants
that have just been left in, basically, the same state
that they were from right around the time when our solar
system formed about 4 and 1/2 billion years ago. So they are, you could
say, the archeological remnants of the formation
of our solar system. NARRATOR: The
universe is comprised of things both big and small. But it's the large
structures in space that challenge our understanding
of how the universe works. Although astronomers have
found many substantial objects, the quest to find even
larger ones continues. AMY MAINZER:
Astronomers are hoping to find new large planets,
new huge super clusters, and learn more about the
things that we've already seen. As technology improves, with
better telescopes, better detectors, newer surveys, we
will be able to see farther into space, and
therefore, hopefully, discover even bigger things
than we already know about. [music playing]
