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Researchers using the NASA / ESA
Hubble Space Telescope

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recently took advantage
of a rare opportunity

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to record Saturn when
its rings are edge-on,

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resulting on a unique movie featuring
both of the giant planet's poles.

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Saturn is only in this
position every 15 years or so

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and this favourable orientation
has allowed a sustained study

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of the two beautiful
and dynamic aurorae,

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Saturn's own northern
and southerns lights.

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This is the Hubblecast.

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News and images from the
NASA / ESA Hubble Space Telescope.

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Travelling through time and space
with our host, Dr. J

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EPISODE 33: Saturn's stunning double show
a. k. a. Dr. Joe Liske.

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Hello and welcome to the Hubblecast.

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It takes Saturn nearly
30 years to orbit our Sun.

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And so, chances to view both
of its poles simultaneously

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are few and far between.

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Hubble has been snapping pictures
of Saturn's aurorae since 1990.

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But 2009 brought the rare
opportunity for Hubble to image Saturn

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with its rings edge-on and
with both of its poles visible.

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As Saturn was approaching its equinox, both
poles were equally illuminated by the Sun,

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allowing for spectacular shots
of Saturn's active aurorae.

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An enormous and grand ringed planet,

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Saturn is certainly one of the most
intriguing bodies orbiting the Sun.

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Hubble has now taken a fresh
look at the fluttering aurorae

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that light up both of Saturn's poles.

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These recent observations go
well beyond just a still image

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and have allowed researchers to monitor
the behaviour of both Saturn's poles

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in the same shot over a
sustained period of time.

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The movie they created from the
data collected over several days

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during January and March 2009,

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has aided astronomers studying both
Saturn's northern and southern aurorae.

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Given the rarity of such an event,

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this new footage will likely be
the last and best equinox movie

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that Hubble captures over
a planetary neighbour.

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Despite its remoteness, the Sun
is still Saturn's parent star

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and, as we all now, a parent's
influence is far reaching.

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The Sun constantly emits a stream
of particles, called the solar wind,

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which reaches all of the planets in
the Solar System, including Saturn.

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When this stream of
electrically charged particles

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gets close to a planet with a magnetic
field, like Saturn or the Earth,

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the field traps the particles and bounces
them back and forth between the poles.

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A natural consequence of the shape
of the planet's magnetic field,

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a series of invisible 'traffic
lanes', exist between the two poles

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along which the electrically
charged particles are confined

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as they oscillate between the poles.

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The magnetic field is stronger at the poles
and the particles tend to concentrate there,

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where they interact with atoms in
the upper layers of the atmosphere,

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creating aurorae, the familiar glow that
the inhabitants of the Earth's polar regions

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know as the northern
and southern lights.

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At first glance, the light
show of Saturn's aurorae

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appears to be symmetric with
respect to the two poles.

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However, analysing the
new data in greater detail,

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astronomers have discovered
some subtle differences

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between the northern
and southern aurorae.

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And this reveals important information
about Saturn's magnetic field.

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The northern auroral oval is slightly smaller
and more intense than the southern one,

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implying that Saturn's magnetic field is
not equally distributed across the planet.

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It is slightly uneven and stronger
in the north than the south.

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As a result, the electrically
charged particles in the north

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are accelerated to higher energies

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as they are fired toward the
atmosphere than those in the south.

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This confirms a previous result
obtained by the space probe Cassini,

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in orbit around the
ringed planet since 2004.

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These dramatic light shows
observed by Hubble on Saturn

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are not just a charming feature,
but they actually teach us something

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about the conditions on one of our
most magnificent planetary neighbours.

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This is Dr. J
signing off for the Hubblecast.

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Once again, nature has surprised us
beyond our wildest imagination...

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Hubblecast is produced
by ESA / Hubble

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at the European
Southern Observatory in Germany.

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The Hubble mission is a project
of international cooperation

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between NASA and
the European Space Agency.

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Now that you've caught up with Hubble

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make sure to get the
latest from the ground too.

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The ESOCast highlights the best of
the European Southern Observatory

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and its powerful telescopes that
observe from high in the Chilean Andes

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at the southern hemisphere's best known
sites for astronomical observations.