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Not since Galileo invented the telescope,
over 400 years ago, has our view of the universe
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been so transformed.
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In April 1990, astronauts stationed the Hubble
Space Telescope in orbit… above the blurring
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effects of Earth’s atmosphere.
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It returned scenes of unprecedented beauty.
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As well as clear, sharp images of a dynamic,
changing universe.
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Stars…
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Planets…
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Galaxies… each evolving in time, from birth…
to dissipation… and death.
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This portrait of a Universe in Motion… is
Hubble’s enduring legacy.
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The Hubble Space Telescope is now regarded
as one of most revolutionary scientific instruments
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ever built.
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While not the only telescope launched into
orbit, it has surely been the most versatile.
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Spacewalking astronauts returned four times
to upgrade its instruments to newer and more
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powerful technologies.
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As a result, Hubble has been able to probe
the life cycle of stars, from their birth
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in nurseries of dust-laden clouds of gas...
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All the way to their final farewell: as delicate
nebulae, slowly blown into space… or as
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titanic supernova explosions that outshine
their host galaxies.
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Hubble has peered into the breeding grounds
of new solar systems: dusty discs around newborn
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stars that may condense into planets.
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And it has transported us into the billions
of galaxies that spread out across the depths
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of time and space.
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One of the most photogenic galaxies is a grand
spiral called M74, located about 32 million
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light years from Earth.
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Amateur astronomers have long known it as
the “phantom galaxy,” because of its low
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surface brightness.
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Hubble astronomers, on the other hand, saw
spiral arms laced with delicate tendrils of
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dust silhouetted against bright ribbons of
stars.
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These spiral arms are not like spokes on a
wheel.
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They are density waves that move around the
galaxy compressing gas… and stimulating
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the birth of vast waves of new stars.
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Using Hubble, astronomers are uncovering fascinating
details within galaxies they once considered
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featureless and bland.
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NGC 1132 is an immense ball of stars some
320 million light years away.
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Astronomers have concluded that this giant
is the product of a gravitational feeding
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frenzy.
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Hubble showed that its surroundings are dotted
with dense clusters of stars.
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They are what’s left of galaxies that were
swallowed by 1132.
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How galaxies grow and evolve over time is
an enduring mystery that Hubble astronomers
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have sought to unravel.
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The first galaxies are thought to have formed
out of clumps of gas in the early Universe.
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These proto-galaxies came together to form
larger and larger galaxies.
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Such galactic mergers may play out over hundreds
of millions of years.
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Hubble has shown that it is an elegant waltz
of stars and gas… choreographed by gravity
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on a grand cosmic stage.
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As the galaxies pass each other, their gravity
pulls stars and gas into the space between
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them, building vast luminous bridges stretching
tens of thousands of light years.
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As the galaxies fall together again, long
streams of gas and dust, known as tidal tails,
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wrap around their disrupted shapes.
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As the galaxy cores approach each other, the
gas and dust clouds that envelop them can
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be dramatically accelerated.
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This results in shockwaves that ripple through
interstellar clouds….
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Setting off bursts of star formation that
appear as brilliant blue knots.
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Gravity is not the only force that can tear
a galaxy apart.
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Hubble spotted a spiral galaxy plowing through
a cluster of galaxies.
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There, it is has encountered a vast cloud
of superheated gas.
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Drag from this cloud is stripping away gas
from the galaxy, creating tattered threads
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and blue tendrils.
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It’s also pulling away streams of murky
dust, as shown by the dark brown tangled region
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around the galaxy’s center.
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When Hubble observations are combined with
X-ray images, a bright, extended fog can be
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seen enveloping the galaxy and streaming off
into space.
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In the end, this encounter will leave the
galaxy with very little gas, and almost no
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chance of forming any new stars.
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Galaxy collisions are not always destructive.
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Take the case of Centaurus A, 32 million light
years from Earth.
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Shockwaves produced by a collision have sparked
an intense round of star formation, as seen
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in the red patches visible here.
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There is something else about Centaurus A
that stands out.
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Using radio and x-ray telescopes, astronomers
have spotted powerful jets blasting out of
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its center… and broad plumes of matter racing
far beyond the galaxy.
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Where is all that energy coming from?
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Answering that question has become a major
focus of Hubble observations since the day
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it was launched.
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Astronomers had long noticed that the centers
of large galaxies are unusually bright.
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They speculated that there must be some kind
of massive object lurking there.
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Could these objects be dense collections of
stars?
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Or are they a breed of supermassive black
holes, millions or even billions of times
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the mass of our sun?
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Hubble’s search for the answer began in
the center of a giant nearby galaxy, M87.
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Astronomers saw that its color was not quite
the same on both sides.
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One side was shifted towards blue and the
other towards red, a hint that it must be
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rotating very quickly.
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This is because the wavelength of light is
changed by the motion of whatever is emitting
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it.
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This is also known as the Doppler effect.
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Think about how the pitch of a train whistle
drops as it races past.
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Similarly, if something in space is moving
towards you, the wavelength of its light gets
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squashed, making it appear bluer.
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If the object is moving away, its light gets
stretched, making it redder.
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By measuring how much the colors had shifted
from one side of the disk to the other, astronomers
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were able to determine its speed of rotation.
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It turned out that this disk was spinning
at a rate of hundreds of kilometers per second.
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Astronomers concluded that an object must
be lurking in its center that’s at least
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4 billion times the mass of our Sun – a
supermassive black hole.
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This was a key piece of evidence in the discovery
that supermassive black holes occupy the centers
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of most, if not all, large galaxies, including
our own Milky Way.
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Back in the early 20th century, the young
astronomer Edwin Hubble joined a larger quest
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to understand the scales of time and distance
that define our universe.
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To make his measurements, he observed stars
in the nearby Andromeda galaxy, just 2.5 million
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light years away.
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His namesake, the Hubble Space Telescope,
has extended those measurements to the far
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limits of time and space.
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In its legendary Deep Field images, Hubble
stared into seemingly blank regions of sky,
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revealing thousands of faint galaxies from
the early days of the universe.
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These blotchy collections of stars are infant
galaxies.
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Over the 10 billion years their light has
traveled to reach us, some may have evolved
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into galaxies that resemble our own…
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With a supermassive black hole in its center…
spiral arms… exploding stars… solar systems…
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planets… and perhaps even life.
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Hubble has shown that our Milky Way galaxy
is a dynamic cosmic laboratory.
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Some of its most striking and beautiful images
are giant structures known as nebulae.
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This one is nicknamed Horsehead, after its
clear and curiously familiar shape.
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Rising from a sea of gas and dust, this so-called
dark nebula is a cold, dark, dusty cloud set
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against a background of glowing gas.
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Then there’s the famed Eagle Nebula, nicknamed
the Pillars of Creation.
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A group of hot young stars is scouring these
luminous towers with fierce winds of energetic
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particles.
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Dense pockets of gas resist these winds.
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Within them, are cocoons of gas and dust,
where new stars are being born.
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You can see the same process underway in the
Monkeyhead Nebula, about 6400 light-years
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away in the constellation of Orion.
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The Monkeyhead is a stellar nursery with all
the ingredients needed for star formation.
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Its peaceful beauty masks the violent events
within it.
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In places where stars are able to form at
high rates, Hubble astronomers have zeroed
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in on the moment of birth.
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One team has been collecting high-resolution
Hubble images of energetic jets of matter
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being shot from newborn stars.
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Unlike most astronomical phenomena, which
can appear motionless over centuries of time,
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these jets visibly change on human timescales.
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Using Hubble, astronomers can see knots of
gas brightening and dimming.
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This shows that these jets are not being launched
in a steady stream.
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Rather, they are racing out sporadically in
clumps.
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The irregular structure of these jets is likely
caused by material that periodically falls
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onto an infant star.
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This image shows how violent the end stages
of star formation can be.
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In the constellation of Cygnus, a few thousand
light-years away, lies a compact star-forming
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region called S106.
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The beautiful colors of this nebula mask the
violent events taking place within.
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A young star, named S106 IR, is being born
at the heart of the nebula.
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In the final stages of its formation, the
star is ejecting material at high speed, disrupting
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surrounding clouds of gas and dust.
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3D visualizations show the extent to which
the star has carved its surroundings into
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a complex shape, including hollow cavities.
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At the outer edges of these cavities, the
gas has been compressed into shock fronts.
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The material spewing off the star not only
gives the cloud its hourglass shape, it is
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heating it up to temperatures of 10,000 degrees
Celsius.
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The star’s radiation excites the gas, making
it glow like a fluorescent light bulb.
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A star is born when pressure and heat in its
core causes hydrogen gas to undergo nuclear
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fusion.
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The heat generated by this process pushes
outward… countering the inward pull of gravity.
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From the violence of their birth, most stars
spend their lives shining in relative peace,
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gradually using up the hydrogen fuel that
makes up their cores.
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Smaller, cooler stars are incredibly efficient.
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A red dwarf, with 10% the mass of our sun,
can burn for ten trillion years… almost
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a thousand times the current age of the universe.
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By comparison, larger, hotter stars like our
sun burn more quickly.
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At about 5 billion years old, our own sun
has gone through half its expected lifespan.
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By observing stars similar to the Sun, scientists
now have a good idea of what will happen to
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our Solar System in the distant future.
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The sun will grow steadily hotter… causing
it to swell into a so-called red giant.
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When the Sun does this, it will destroy the
inner planets of the Solar System.
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Next, the outer layers will puff out, forming
a dense cloud of gas and dust that will obscure
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the visible light from the star.
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In this stage, it forms a proto-planetary
nebula.
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Only dim infrared emissions from the dust
cloud and reflected starlight let astronomers
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see anything at all.
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Hubble images of this stage show a wide variety
of shapes, hinting at the complex dynamics
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at work inside.
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The spiral structure of this nebula is particularly
unusual, and is likely due to a second orbiting
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star that is producing swirling patterns in
the gas and dust.
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Over a period of a few thousand years, radiation
from the hot remains of the star excites the
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gas in the nebula, causing it to glow.
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The once faint nebula now becomes a bright
and mysterious cloud called a planetary nebula.
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This type of nebula populates our galaxy…
with luminous shapes that draw the gaze of
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many a sky watcher.
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Eventually, planetary nebulae fade to nothing
as their gas and dust diffuse into space.
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All that remains is the tiny white dwarf — a
form that our Sun will take billions of years
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from now.
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Planetary nebulae are more than just beautiful
shapes that grace our galactic skies.
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They show important stages in the life cycle
of stars… and how they interact with and
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even shape their surroundings.
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Hubble has given astronomers the sharpest
views yet of these ghostly, dynamic structures.
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Take the Ring Nebula, just over 2,000 light
years away from Earth.
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From Earth’s perspective, it looks like
a simple elliptical body with a fuzzy boundary.
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But Hubble observations show that the nebula
is shaped more like a distorted doughnut.
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The doughnut hole may look empty, but it is
full of lower density gas that stretches toward
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and away from us, creating a shape a little
like a rugby ball that’s been slotted into
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the doughnut’s hole.
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The space surrounding the nebula is turbulent
and full of knotty structures that formed
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long ago.
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If we were able to rotate the Ring Nebula
by 90 degrees and view it side on, it would
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look more like the nebula M76, also known
as the “Little Dumbbell.”
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In the act of dying, sun-like stars cast most
of their mass out into the galactic winds.
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In time, the atoms in our own sun may well
be swept up into new suns, new solar systems.
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In the cycles of star birth and star death,
the galaxy is dominated by a rare and extremely
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violent breed.
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Stars ten times the mass of our sun, and even
larger, burn hot and fast.
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Intense temperatures and pressure ignite nuclear
fusion reactions in their cores.
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Hydrogen gas turns to helium, oxygen, carbon,
calcium, silicon… all the way to iron.
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The outward pressure from heat radiating from
the star’s core is no longer enough to hold
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it up under the crushing weight of these elements.
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Gravity wins the battle… and the star’s
core collapses inward.
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That produces a shock wave that races out
through the star’s volume and obliterates
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it.
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Of the 200 million odd stars in our galaxy,
one goes supernova about every century or
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so.
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The last one to be seen in the Milky Way was
observed by the astronomer Johannes Kepler
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in 1604, just five years before the invention
of the telescope.
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The most famous supernova in recent years
appeared in 1987 in the Large Magellanic Cloud,
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a dwarf galaxy just above the plane of the
Milky Way.
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It was so bright it was visible to the naked
eye.
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Launched three years later, Hubble has been
tracking the evolving spectacle for over a
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quarter of a century.
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Astronomers have marveled at the complexity
of the explosion, including the patterns etched
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by its expanding shock wave.
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Even though a supernova is only bright for
a short period of time, the dusty clouds it
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leaves behind can last for millennia.
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Their effect on the surrounding interstellar
gas lasts even longer.
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Although no supernova in our galaxy has ever
been observed with a telescope, plenty of
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supernova remnants have been.
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Hubble’s sharp images of their complex structures
help explain the sequence of events… as
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well as the profound impact these explosions
have on the galaxy.
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Take the Crab supernova, one of the most interesting,
and most studied, objects in all of astronomy.
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Japanese and Chinese astronomers witnessed
the explosion in the year 1054.
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The
filaments shown in these images are the tattered
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remains of the star, consisting mostly of
hydrogen.
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The collapsed core of the star embedded in
the center is barely visible in this Hubble
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image.
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Yet you can see its effects.
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The bluish glow comes from electrons whirling
at nearly the speed of light around magnetic
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field lines that extend from the star’s
collapsed core.
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Astronomers have been poring over the nebula
itself, still growing at a rate of a thousand
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kilometers a second.
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What they’ve found is that the filaments
of matter that roared out of the blast contain
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large volumes of dust, an array of mostly
carbon or silicate compounds that absorb visible
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light.
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These solid particles are crucial for the
formation of solar systems.
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Within the Crab nebula, there is enough dust
to make 30-40,000 Earths.
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Galaxies all around the universe bear witness
to the dusty legacy of countless supernovae.
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The bright central region of the famous pinwheel
galaxy, for example, is surrounded by dark,
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dusty lanes.
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In spiral galaxies, hot winds from exploding
stars have helped push these clouds toward
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the periphery as well as above and below their
flat discs.
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You can see evidence of this in our view of
the Milky Way galaxy.
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Dark dust lanes and ominous clouds dominate
our view into the disc, while tendrils of
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dust reach far above it.
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Some dust clouds are destined to light up
with new stars, as you can see in one of the
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Milky Way’s small companion galaxies: The
Large Magellanic Cloud.
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Its most dramatic feature is the Tarantula
Nebula, a bright region of glowing gas and
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energetic star formation.
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The Tarantula, shown in a these Hubble images,
glows brightly because hydrogen gas within
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it is being excited by ultraviolet radiation
from newborn stars.
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In a wider view, the luminous Tarantula Nebula
stands out from its host galaxy.
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It is the brightest known star-forming region
in the local Universe and one of the most
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attractive spots in the night sky.
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Thanks to Hubble, there is a place within
our own galaxy where you can see not only
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stars, but solar systems, being born.
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In the constellation of Orion the Hunter,
just under the three stars that make up its
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belt, is the majestic Orion Nebula.
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It draws our attention for its beauty and
mystery.
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Ancient civilizations saw meaning as well,
including the Maya in what is now southern
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Mexico and northern Central America.
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In their story of creation, three of the brightest
stars in the Orion constellation represented
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a hearth.
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The nebula was the fire that warms it.
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At 1,500 light years distance, it’s one
of the best-known examples of a star-forming
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nebula – a swirling cloud of gas and dust
where stars begin their journey of life.
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Within it, Hubble astronomers discovered isolated
pockets of gas called proplyds.
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These are protoplanetary discs that form around
newborn stars in spinning mixtures of gas
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and dust.
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00:31:36,140 --> 00:31:41,820
These discs are now thought to be planetary
systems in the making.
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The brightest star in the Trapezium star cluster
affects the nearby discs by heating up the
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gas within them, causing them to shine brightly.
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00:31:52,760 --> 00:31:59,590
The excited material produces many glowing
cusps that face the bright star.
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Other interesting features enhance the look
of these captivating objects, including jets
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00:32:04,330 --> 00:32:08,620
and dramatic shock waves.
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00:32:08,620 --> 00:32:16,740
They are formed when the stellar wind from
the nearby massive star meets gas in the nebula.
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00:32:16,740 --> 00:32:20,640
The interaction produces shapes like boomerangs
or arrows.
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00:32:20,640 --> 00:32:27,679
In one case, the shock wave makes the proplyd
look like a space jellyfish.
282
00:32:27,679 --> 00:32:34,660
The powerful radiation that allows us to see
these shapes also threatens their existence.
283
00:32:34,660 --> 00:32:40,150
Once heated up, the discs are more likely
to dissipate and dissolve, destroying their
284
00:32:40,150 --> 00:32:43,730
potential to spawn planets.
285
00:32:43,730 --> 00:32:47,710
Some of the bright proplyds are doomed to
be torn apart.
286
00:32:47,710 --> 00:32:56,280
The dimmer ones are the most likely to survive.
287
00:32:56,280 --> 00:33:01,940
Among those that do produce solar systems,
Hubble has been documenting a wide diversity
288
00:33:01,940 --> 00:33:03,360
of planets.
289
00:33:03,360 --> 00:33:16,360
One of them, known as HD189733b, is a huge
gas giant similar to Jupiter.
290
00:33:16,360 --> 00:33:22,420
It lies extremely close to its star, as shown
in this animation.
291
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Proximity to the star makes its climate exceptionally
hot, with temperatures exceeding 1000oC.
292
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A team of scientists used Hubble to observe
it as it passed in front of its parent star.
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While backlit in this way, a planet’s atmosphere
imprints its signature on the starlight, allowing
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00:33:47,280 --> 00:33:56,309
astronomers to decode what is happening on
scales far too small to image directly.
295
00:33:56,309 --> 00:34:02,950
They expected to confirm that the upper layers
of the planet’s atmosphere are boiling off
296
00:34:02,950 --> 00:34:06,280
under the intense starlight.
297
00:34:06,280 --> 00:34:12,329
Hubble’s first observations showed no trace
of this.
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00:34:12,329 --> 00:34:18,500
Just before it could take a second look, the
Swift satellite detected a huge flare coming
299
00:34:18,500 --> 00:34:22,760
from the surface of the star, with powerful
atmosphere-frying X-rays.
300
00:34:22,760 --> 00:34:35,790
When the planet slid into view a few hours
later, the changes were startling.
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00:34:35,790 --> 00:34:43,260
Where astronomers had seen a slumbering planet
before, now they saw an atmosphere furiously
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00:34:43,260 --> 00:34:46,480
boiling away.
303
00:34:46,480 --> 00:34:52,699
In a dramatic plume of gas, the planet was
losing at least 1000 tons of gas from its
304
00:34:52,699 --> 00:34:55,579
atmosphere every second.
305
00:34:55,580 --> 00:35:04,920
There’s no life on a planet that orbits
so close to its parent star.
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00:35:04,920 --> 00:35:10,500
Such planets, however, are allowing Hubble
astronomers to hone their search for Earth-like
307
00:35:10,500 --> 00:35:14,480
planets further out.
308
00:35:14,480 --> 00:35:19,750
When the planet moves between the star and
Earth, Hubble has been able to capture a small
309
00:35:19,750 --> 00:35:27,000
fraction of starlight passing through the
planet’s atmosphere.
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00:35:27,000 --> 00:35:32,859
Astronomers are looking for a hydrogen-carbon
compound called Methane.
311
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On Earth, it’s produced by a combination
of natural and manmade sources, including
312
00:35:38,730 --> 00:35:44,560
fossil fuel production.
313
00:35:44,560 --> 00:35:50,480
On this “hot jupiter,” methane is probably
produced by a complex chemical process in
314
00:35:50,480 --> 00:35:53,560
its atmosphere.
315
00:35:53,560 --> 00:36:00,600
Astronomers plan to use data to identify prebiotic
molecules in the atmospheres of planets in
316
00:36:00,600 --> 00:36:05,140
the “habitable zones” around other stars,
where more moderate temperatures would allow
317
00:36:05,140 --> 00:36:07,640
liquid water to flow.
318
00:36:07,640 --> 00:36:13,890
The new measurements are an important step
toward the ultimate goal of identifying the
319
00:36:13,890 --> 00:36:20,770
conditions, such as temperature, pressure,
winds, clouds, and chemistry on planets where
320
00:36:20,770 --> 00:36:24,610
life could exist.
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00:36:24,610 --> 00:36:29,550
Astronomers have detected a wide range of
planets around other stars by looking for
322
00:36:29,550 --> 00:36:36,340
clues, like the wobbling motion of a star
as a planet orbits it, or a star getting dimmer
323
00:36:36,340 --> 00:36:42,290
as a planet passes in front of it.
324
00:36:42,290 --> 00:36:52,640
Hubble was able to capture, for the first
time, a direct image of a planet.
325
00:36:52,640 --> 00:36:59,330
Visible from the southern hemisphere, Fomalhaut
is relatively close, at around 25 light-years
326
00:36:59,330 --> 00:37:01,900
away.
327
00:37:01,900 --> 00:37:07,690
It is 15 times brighter than the sun, and
much hotter.
328
00:37:07,690 --> 00:37:13,350
This star is blazing through its hydrogen
fuel supply at such a furious rate that it
329
00:37:13,350 --> 00:37:21,320
will burn out in only a billion years, 10%
of the lifespan of our star.
330
00:37:21,320 --> 00:37:28,550
Its most interesting feature may be a large
disk of dust and gas that surrounds it.
331
00:37:28,550 --> 00:37:35,320
This strange ring is not exactly centered
on the star.
332
00:37:35,320 --> 00:37:40,620
Astronomers suspect that the gravity of another
body — perhaps a planet — is pulling it
333
00:37:40,620 --> 00:37:44,280
out of shape.
334
00:37:44,280 --> 00:37:47,619
The suspected planet is a dim speck.
335
00:37:47,619 --> 00:37:53,710
To see it, astronomers used an instrument
called a coronagraph to block the star’s
336
00:37:53,710 --> 00:37:54,710
light.
337
00:37:54,710 --> 00:37:58,700
Then they gathered a host of clues to find
out what it’s like.
338
00:37:58,700 --> 00:38:05,180
For one, the shape of the disk hints that
the planet is at most three times the mass
339
00:38:05,180 --> 00:38:06,660
of Jupiter.
340
00:38:06,660 --> 00:38:12,900
For another, the planet is much brighter than
expected for an object of its size.
341
00:38:12,900 --> 00:38:20,840
That means it could have an enormous ring
system that reflects starlight in all directions.
342
00:38:20,840 --> 00:38:31,510
One day the material in these rings may even
coalesce to form moons.
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00:38:31,510 --> 00:38:37,590
Hubble is part of a larger quest to discover
and understand solar systems, including our
344
00:38:37,590 --> 00:38:42,870
own.
345
00:38:42,870 --> 00:38:48,630
Among the highlights, astronomers have used
Hubble to track the changing climate of cloudy
346
00:38:48,630 --> 00:38:52,170
Venus.
347
00:38:52,170 --> 00:39:03,800
Dust storms that sweep across the planet Mars.
348
00:39:03,800 --> 00:39:12,530
The aftermath of comet Shoemaker-Levy’s
collision with Jupiter.
349
00:39:12,530 --> 00:39:21,410
Saturn’s stunning rings, and moons.
350
00:39:21,410 --> 00:39:25,570
Uranus’ rings.
351
00:39:25,570 --> 00:39:36,770
And Neptune’s intense, turbulent atmosphere.
352
00:39:36,770 --> 00:39:43,609
In our solar system, few Hubble images compare
to its views of Saturn…
353
00:39:43,609 --> 00:39:50,800
And the fluttering aurorae that light up its
poles.
354
00:39:50,800 --> 00:39:55,740
Scientists created a movie from data collected
over several days during January and March
355
00:39:55,740 --> 00:40:06,210
2009, when the rings appeared edge-on, and
both poles were visible to us.
356
00:40:06,210 --> 00:40:12,320
The Sun emits a wind of particles that reaches
all parts of the Solar System.
357
00:40:12,320 --> 00:40:18,100
When this electrically charged stream gets
close to a planet with a magnetic field, like
358
00:40:18,100 --> 00:40:22,930
Saturn or the Earth, the field traps these
particles.
359
00:40:22,930 --> 00:40:28,620
The magnetic field is stronger at the poles,
so the particles tend to concentrate there,
360
00:40:28,620 --> 00:40:33,430
where they interact with atoms in the upper
layers of the atmosphere.
361
00:40:33,430 --> 00:40:39,430
That’s what creates the familiar nighttime
glow we know as the northern and southern
362
00:40:39,430 --> 00:40:43,849
lights.
363
00:40:43,849 --> 00:40:53,450
Saturn’s auroras are not only charming features,
but they might teach us something about our
364
00:40:53,450 --> 00:41:07,140
own planet and its magnetic field.
365
00:41:07,140 --> 00:41:13,180
Beyond Saturn’s dancing lights… or the
sudden explosion of a star… the universe
366
00:41:13,180 --> 00:41:19,340
appears unmoving against the ponderous march
of cosmic time.
367
00:41:19,340 --> 00:41:24,770
Among its greatest achievements, the Hubble
Space Telescope has been able to track the
368
00:41:24,770 --> 00:41:29,600
large-scale motions of the universe.
369
00:41:29,600 --> 00:41:32,150
Take an event close to home.
370
00:41:32,150 --> 00:41:38,580
Astronomers have long known that the Andromeda
Galaxy, currently 2.5 million light-years
371
00:41:38,580 --> 00:41:42,000
away, is moving toward our Milky Way.
372
00:41:42,000 --> 00:41:49,380
A team of astronomers used the Hubble Space
Telescope to find out how fast the two galaxies
373
00:41:49,380 --> 00:41:55,320
are moving, and whether there will be head
on collision.
374
00:41:55,320 --> 00:42:02,730
They tracked the motion of stars in Andromeda…
then projected their movement into the future.
375
00:42:02,730 --> 00:42:09,190
Based on these findings, they showed the course
of events over the next eight billion years,
376
00:42:09,190 --> 00:42:11,130
as the galaxies move closer...
377
00:42:11,130 --> 00:42:22,340
…then collide… and gradually merge into
a new larger galaxy.
378
00:42:22,340 --> 00:42:37,520
If you could wait a few billion years, our
night sky would change dramatically.
379
00:42:37,520 --> 00:42:45,210
As Andromeda approaches, it will loom large
in the sky.
380
00:42:45,210 --> 00:42:53,400
Later, when the galaxies begin to merge, they
will twist and distort under the pull of their
381
00:42:53,400 --> 00:42:55,280
mutual gravity.
382
00:42:55,280 --> 00:43:03,690
In time, the new combined galaxy will become
an immense ball of stars… what’s known
383
00:43:03,690 --> 00:43:08,530
as an elliptical galaxy.
384
00:43:08,530 --> 00:43:14,540
Even though these two galaxies each have hundreds
of billions of stars in them, the stars are
385
00:43:14,540 --> 00:43:17,300
all relatively far apart.
386
00:43:17,300 --> 00:43:22,130
The chance of any two colliding is extremely
small.
387
00:43:22,130 --> 00:43:30,200
Our Sun, born in the Milky Way almost 5 billion
years ago, will follow a new path as it orbits
388
00:43:30,200 --> 00:43:35,470
a whole new galaxy.
389
00:43:35,470 --> 00:43:40,960
In the universe according to Hubble, galaxies
all around across the cosmos are circling
390
00:43:40,960 --> 00:43:51,900
each other… merging… and moving into ever-larger
and denser groupings.
391
00:43:51,900 --> 00:43:57,530
Using Hubble to survey patterns of galaxies,
scientists have been able to map a mysterious
392
00:43:57,530 --> 00:44:05,190
substance that envelops galaxies and clusters
of galaxies.
393
00:44:05,190 --> 00:44:11,349
This so-called “dark matter” adds to the
gravity of these structures and has been driving
394
00:44:11,349 --> 00:44:16,210
their collapse over time.
395
00:44:16,210 --> 00:44:21,790
Because of the arrangement of galaxies, Astronomers
have long known that dark matter stretches
396
00:44:21,790 --> 00:44:27,400
out across the cosmos in a vast web-like structure.
397
00:44:27,400 --> 00:44:31,440
Actually observing this web has been difficult.
398
00:44:31,440 --> 00:44:39,400
Now, a team of scientists has used Hubble
to make detailed observations of a dark matter
399
00:44:39,400 --> 00:44:46,260
filament, measuring its length, shape and
density.
400
00:44:46,260 --> 00:44:51,780
Theories say galaxy clusters form where filaments
of the cosmic web meet.
401
00:44:51,780 --> 00:44:58,370
So the team focused Hubble on one such cluster
with a stream of galaxies moving into it along
402
00:44:58,370 --> 00:45:03,849
several filaments.
403
00:45:03,849 --> 00:45:09,380
The astronomers used data from several ground
telescopes to measure distances to the galaxies
404
00:45:09,380 --> 00:45:18,940
within the filament mapped by Hubble, and
to trace their motions.
405
00:45:18,940 --> 00:45:25,460
In so doing, they made the first ever three-dimensional
reconstruction of a filament.
406
00:45:25,460 --> 00:45:31,340
It extends across at least 60 million light-years
of space.
407
00:45:31,340 --> 00:45:39,730
From our perspective, we see it gently curving
towards us, then continuing almost along our
408
00:45:39,730 --> 00:45:48,770
line of sight, before it plunges into the
back of the galaxy cluster.
409
00:45:48,770 --> 00:45:54,890
Observing and reconstructing the cosmic web
can tell us how the universe has evolved to
410
00:45:54,890 --> 00:45:56,140
date.
411
00:45:56,140 --> 00:46:03,680
Scientists wanted to know how it’s evolving
on an even grander scale.
412
00:46:03,680 --> 00:46:09,619
If dark matter dominates the cosmos, will
its gravity be enough to cause the universe
413
00:46:09,619 --> 00:46:17,710
itself to crash together in a heap at some
point in the distant future?
414
00:46:17,710 --> 00:46:25,830
To find out, they searched for a type of exploding
star that’s visible across the cosmos.
415
00:46:25,830 --> 00:46:32,200
It is the product of a small burned out star
called a white dwarf that orbits a larger
416
00:46:32,200 --> 00:46:33,160
star.
417
00:46:33,160 --> 00:46:40,130
The smaller star pulls matter from its neighbor,
thereby gradually increasing its mass.
418
00:46:40,130 --> 00:46:48,140
Finally, when it reaches a critical mass,
it undergoes a thermonuclear explosion.
419
00:46:48,140 --> 00:46:57,890
These so-called Type 1A explosions are thought
to all have the same intrinsic brightness.
420
00:46:57,890 --> 00:47:03,970
How bright they appear to us is a measure
of how far away they are.
421
00:47:03,970 --> 00:47:09,410
What the scientists found is that the most
distant of the explosions were much fainter
422
00:47:09,410 --> 00:47:13,990
than they expected.
423
00:47:13,990 --> 00:47:19,280
They deduced from this data that the space
between Earth and those distant explosions
424
00:47:19,280 --> 00:47:30,480
had been expanding faster and faster.
425
00:47:30,480 --> 00:47:36,280
Scientists theorized that another unknown
force, dark energy, is actually pushing the
426
00:47:36,280 --> 00:47:42,460
universe apart at an accelerating rate.
427
00:47:42,460 --> 00:47:46,220
This means that the universe will not collapse
in a heap.
428
00:47:46,220 --> 00:47:50,720
Rather, it will keep on expanding forever….
429
00:47:50,720 --> 00:48:00,770
Until all matter and energy eventually dissipate
to nothingness.
430
00:48:00,770 --> 00:48:08,521
In our time, the light of the universe continues
to rain down on Earth in torrents, a measure
431
00:48:08,521 --> 00:48:17,660
of the energy emitted in a constant process
of creation and destruction.
432
00:48:17,660 --> 00:48:24,250
Hubble has led a broad effort to capture this
light in telescopes stationed both on mountaintops
433
00:48:24,250 --> 00:48:27,850
and in space.
434
00:48:27,850 --> 00:48:34,100
Through their lenses, we have seen a universe
that is evolving on all time scales, from
435
00:48:34,100 --> 00:48:41,770
the very short to the very long.
436
00:48:41,770 --> 00:48:49,530
In its own brief time in space, Hubble has
revolutionized the science of astronomy…
437
00:48:49,530 --> 00:48:49,530
while inspiring untold legions of stargazers.
43452
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