Astronomy Picture of the Day |
APOD: 2023 August 25 - A Season of Saturn
Explanation:
Ringed planet Saturn
will be at its 2023 opposition,
opposite the Sun in Earth's skies, on August 27.
While that puts the sixth planet from the Sun at its
brightest and well-placed
for viewing, its beautiful ring system isn't
visible to the unaided eye.
Still, this sequence of six telescopic images taken a year apart
follows both Saturn and rings as seen from inner planet Earth.
The gas giant's ring plane tilts
from most open in 2018 to approaching edge-on in 2023 (top to bottom).
That's summer to nearly the autumn
equinox for Saturn's northern hemisphere.
In the sharp planetary portraits Saturn's northern
hexagon and a large
storm system are clearly visible in 2018.
In 2023 ice moon Tethys
is transiting, casting its shadow across
southern hemisphere cloud bands while
Saturn's cold blue south pole is emerging
from almost a decade of winter darkness.
APOD: 2022 January 23 - Saturn, Tethys, Rings, and Shadows
Explanation:
Seen from
ice moon Tethys, rings and shadows would display fantastic
views of the Saturnian system.
Haven't dropped in on Tethys lately?
Then
this
gorgeous ringscape from the Cassini spacecraft
will have to do for now.
Caught in sunlight
just below and left of picture center in 2005,
Tethys itself is about 1,000 kilometers in diameter and
orbits not quite five saturn-radii from the center of the gas giant planet.
At that distance (around 300,000 kilometers) it is well outside Saturn's
main
bright rings, but Tethys is still
one of five
major moons that find themselves within the boundaries of
the faint and tenuous outer
E ring.
Discovered in the 1980s, two very small moons
Telesto and
Calypso are locked in stable
along Tethys' orbit.
Telesto precedes and Calypso follows Tethys as the trio
circles Saturn.
APOD: 2018 April 2 - Moons, Rings, Shadows, Clouds: Saturn (Cassini)
Explanation:
While cruising around Saturn,
be on the lookout for picturesque juxtapositions of moons, rings, and shadows.
One quite picturesque arrangement
occurred in 2005 and was captured by
the then Saturn-orbiting Cassini spacecraft.
In the featured image, moons
Tethys and
Mimas
are visible on either side of
Saturn's thin rings, which are seen nearly edge-on.
Across the top of
Saturn are dark
shadows of the wide rings,
exhibiting their impressive complexity.
The
violet-light image brings up the texture of the backdrop:
Saturn's clouds.
Cassini orbited Saturn
from 2004 until September of last year, when the
robotic spacecraft was directed to dive into Saturn to keep it from
contaminating any moons.
APOD: 2017 February 5 - Odysseus Crater on Tethys
Explanation:
Some moons wouldn't survive the collision.
Tethys, one of
Saturn's larger moons
at about 1000 kilometers in diameter, survived the collision,
but today exhibits the resulting expansive impact crater Odysseus.
Sometimes called the Great Basin,
Odysseus
occurs on the leading hemisphere of
Tethys
and shows its great age by the relative amount of smaller craters that occur inside its
towering walls.
The density of Tethys is similar to
water-ice.
The featured image was captured in November by the
robotic Cassini spacecraft
in orbit around Saturn as it swooped past the giant ice ball.
Cassini has now started on its
Grand Finale Tour
which will take it inside Saturn's rings and
culminate in September with a dive into Saturn's thick atmosphere.
APOD: 2016 August 1 - Behind Saturn
Explanation:
What's behind Saturn?
The first answer is the camera itself, perched on the
Cassini spacecraft currently orbiting behind the planet with the
most grand ring system in our Solar System.
The unusual perspective places
Cassini on the far side of Saturn from the Sun so that more than half of Saturn appears dark -- a perspective that no Earth-based observer could achieve.
Behind Saturn, in the context of the
featured infrared image,
is Saturn's moon Tethys, visible as the small speck above the unusual
hexagonal cloud pattern that encompasses Saturn's North Pole.
Tethys actually orbits Saturn right in the ring plane, which places the 1000-km moon much farther from
Cassini than the planet itself.
Cassini has been
studying Saturn and its moons for 12 years, but, unfortunately, its amazing mission will soon come to an end.
In order to
protect life that may exist on or inside Saturn's moons, the robotic spacecraft will be directed to
crash into Saturn's thick atmosphere next September.
APOD: 2015 April 5 - Saturn, Tethys, Rings, and Shadows
Explanation:
Seen from
ice moon Tethys, rings and shadows would display fantastic
views of the Saturnian system.
Haven't dropped in on Tethys lately?
Then
this
gorgeous ringscape from the Cassini spacecraft
will have to do for now.
Caught in sunlight
just below and left of picture center in 2005,
Tethys itself is about 1,000 kilometers in diameter and
orbits not quite
five saturn-radii from the center
of the gas giant planet.
At that distance (around 300,000 kilometers) it is well outside Saturn's
main
bright rings, but Tethys is still
one of five
major moons that find themselves within the boundaries of
the faint and tenuous outer
E ring.
Discovered in the 1980s, two very small moons
Telesto
and Calypso are locked in stable
locations
along Tethys' orbit.
Telesto precedes and Calypso follows Tethys as the trio
circles Saturn.
APOD: 2012 December 31 - Saturn's Rings from the Dark Side
Explanation:
What do Saturn's rings look like from the dark side?
From Earth, we usually see Saturn's rings from the same side
of the ring plane that the Sun illuminates them -- one might call this the bright side.
Geometrically, in the
above picture taken in August by the
robot Cassini spacecraft now orbiting
Saturn,
the Sun is behind the camera but on the
other side of the ring plane.
Such a vantage point gives a
breathtaking views of the most
splendid ring system in the Solar System.
Strangely, the rings have similarities to a
photographic negative of a front view.
For example, the dark band in the middle is actually the
normally bright B-ring.
The ring brightness as recorded from different angles
indicates ring thickness and particle density of ring particles.
At the top left of the frame is Saturn's moon
Tethys, which although harder to find, contains much more mass than the
entire ring system.
APOD: 2012 December 22 - Saturn at Night
Explanation:
Splendors seldom seen
are revealed in this glorious picture from
Saturn's shadow.
Imaged
by Cassini on October 17, 2012 during its 174th orbit,
the ringed planet's night side is viewed
from a perspective 19 degrees below the ring plane at a distance
of about 800,000 kilometers with the Sun almost directly behind
the planet.
A 60 frame mosaic, images made with infrared, red, and violet filters
were combined to create an enhanced, false-color view.
Strongly backlit, the rings look bright away from the planet
but dark in silhouette against the gas giant.
Above center, they reflect a faint, eerie light on the cloud tops while
Saturn casts its own dark shadow on the rings.
A similar Cassini image from 2006 also
featured planet Earth as a pale blue dot in the distance.
Instead, this scene includes icy moons
Enceladus (closer to the rings) and
Tethys below the rings on the left.
APOD: 2012 November 6 - Methone: Smooth Egg Moon of Saturn
Explanation:
Why is this moon shaped like a smooth egg?
The robotic Cassini spacecraft completed the first flyby ever of Saturn's small moon
Methone
in May and discovered that the moon has no obvious craters.
Craters, usually caused by impacts, have been seen on every
moon,
asteroid, and comet nucleus
ever imaged in detail -- until now.
Even the Earth and
Titan have
craters.
The smoothness and egg-like shape of the
3-kilometer diameter moon might be caused by
Methone's
surface being able to shift --
something that might occur were the moon coated by a deep
pile of sub-visual
rubble.
If so, the most similar objects in our Solar System would include Saturn's moons
Telesto,
Pandora,
Calypso, as well as asteroid
Itokawa,
all of which show sections that are unusually smooth.
Methone
is not entirely featureless, though, as some surface sections
appear darker than others.
Although flybys of Methone are
difficult, interest in the nature and
history of this unusual moon is sure to continue.
APOD: 2012 September 16 - Saturn: Bright Tethys and Ancient Rings
Explanation:
How old are Saturn's rings?
No one is quite sure.
One possibility is that the rings formed relatively recently in our
Solar System's history, perhaps only about 100 million years ago when
a moon-sized object
broke up near Saturn.
Evidence for a young ring age includes a basic
stability
analysis for rings,
and the fact that the rings are so bright and
relatively unaffected by numerous small dark
meteor impacts.
More recent
evidence, however, raises the possibility that some of
Saturn's rings
may be billions of years old and so almost as
old as Saturn itself.
Inspection of images by the Saturn-orbiting Cassini spacecraft
indicates that some of
Saturn's ring particles temporarily
bunch and collide, effectively recycling
ring particles by bringing
fresh bright ices to the surface.
Seen here,
Saturn's rings were imaged in their true colors by the
robotic
Cassini in late October.
Icy bright Tethys,
a moon of Saturn likely brightened by a sandblasting
rain of ice from sister moon
Enceladus, is visible in front of
the darker rings.
APOD: 2012 April 14 - Six Moons of Saturn
Explanation:
How many moons does Saturn have?
So far 62 have
been discovered, the smallest only a fraction
of a kilometer across.
Six of its largest satellites can be seen here, though, in a sharp
Saturnian family portrait
taken on March 9.
Larger than Earth's Moon and even slightly larger than Mercury,
Titan
has a diameter of 5,150 kilometers and starts the line-up
at the lower left.
Continuing to the right across the frame are
Mimas,
Tethys, [Saturn],
Enceladus,
Dione, and
Rhea at far right.
Saturn's first known natural satellite, Titan was
discovered in 1655 by
Dutch astronomer Christiaan Huygens, while most recently the
satellite provisionally designated
S/2009 S1 was found
by the Cassini Imaging Science Team in 2009.
Tonight,
Saturn reaches opposition
in planet Earth's sky, offering
the best telescopic views of the ringed planet and moons.
APOD: 2010 February 17 - An Unusually Smooth Surface on Saturn's Calypso
Explanation:
Why is this moon of Saturn so smooth?
This past weekend, humanity's Saturn-orbiting
Cassini spacecraft
passed as close to Saturn's small moon
Calypso as it ever has, and imaged the small moon in unprecedented detail.
Pictured above is an early return, raw, unprocessed image of the 20-km long irregularly shaped moon.
Like its sister moon
Telesto and the shepherd moon
Pandora, Calypso has shown itself to be unusually smooth,
much smoother than most of Saturn's larger moons.
A leading hypothesis for Calypso's smoothness is that much of the moon's surface is actually a relatively loose jumble of rubble -- making
Calypso
a rubble-pile moon.
The loose nature of the small
ice pieces
allows them to fill in many small craters and other surface features.
Calypso orbits Saturn always behind Saturn's much larger moon
Tethys, whereas
Telesto's orbit always precedes Tethys.
Calypso's extremely white surface -- not unlike
fresh snow -- may result from the
continuous accumulation of fresh ice particles falling in from
Saturn's E ring.
APOD: 2010 January 27 - Tethys Behind Titan
Explanation:
What's that behind Titan? It's another of Saturn's moons:
Tethys.
The robotic
Cassini spacecraft orbiting Saturn
captured
the heavily cratered Tethys
slipping behind
Saturn's atmosphere-shrouded
Titan late last year.
The largest crater on
Tethys,
Odysseus, is easily visible on the distant moon.
Titan shows not only its thick and opaque orange lower atmosphere,
but also an unusual upper layer of
blue-tinted haze.
Tethys,
at about 2 million kilometers distant, was twice as far from
Cassini as was Titan when the
above image was taken.
In 2004, Cassini released the
Hyugens probe
which landed on Titan and provided humanity's
first
views of the
surface of the Solar System's only known
lake-bearing moon.
APOD: 2009 December 8 - Ice Moon Tethys from Saturn Orbiting Cassini
Explanation:
What processes formed the unusual surface of Saturn's moon Tethys?
To help find out,
NASA
sent the
robotic Cassini spacecraft right past the enigmatic ice moon in 2005.
Pictured above is one of the highest resolution images of an entire face of Tethys yet created.
The pervasive white color of
Tethys is thought to be created by
fresh ice particles continually falling onto the moon from Saturn's diffuse
E-ring -- particles expelled by Saturn's moon
Enceladus.
Some of the unusual cratering patterns on
Tethys
remain less well understood, however.
Close inspection of the
above image
of Tethys' south pole will reveal a
great rift running diagonally down from the middle:
Ithaca Chasma.
A leading theory for the creation of this
great canyon is anchored in the tremendous moon-wide surface cracking that
likely occurred when
Tethys' internal oceans froze.
If so, Tethys may once have
harbored
internal oceans, possibly similar to the underground oceans some hypothesize to exist under the
surface of Enceladus today.
Might ancient life be frozen down there?
APOD: 2009 November 10 - Saturn After Equinox
Explanation:
The other side of Saturn's ring plane is now directly illuminated by the Sun.
For the previous 15 years, the southern side of
Saturn
and its rings were directly illuminated, but since
Saturn's equinox in August,
the orientation has reversed.
Pictured above last month, the robotic
Cassini spacecraft orbiting Saturn
has captured the giant planet and its
majestic rings soon after equinox.
Imaged from nearly behind, Saturn and its moon
Tethys each show a crescent phase to
Cassini that is not visible from Earth.
As the rings continue to point nearly toward the Sun, only a
thin shadow of Saturn's rings
is visible across the center of the planet.
Close inspection of Saturn's rings, however, shows superposed bright features identified as
spokes that are thought to be groups of very small electrically charged ice particles.
Understanding the nature and
dynamics of spokes is not fully understood and remains a
topic of research.
APOD: 2009 September 1 - Shadows of Saturn at Equinox
Explanation:
Unusual shadows and dark rings appeared around Saturn near its equinox last month.
At that time -- early August --
Saturn's ring plane
pointed directly at the Sun.
Visible above,
Saturn's moon
Tethys casts a shadow visible only on the far right.
Saturn's own shadow
blacks out a large swath of rings on the right.
The night side of Saturn glows with
ringshine -- sunlight reflected by ring particles back onto Saturn.
Images near equinox at Saturn
are giving astronomers a
chance to search for unexpected shadows that may illuminate
previously unknown features of Saturn's complex
ring system.
Cassini,
the robotic spacecraft orbiting
Saturn that took
this image,
is not expected to survive to the next
Saturnian equinox
in 15 years.
APOD: 2009 March 4 - Saturn in View
Explanation:
Very good telescopic
views of Saturn can be expected in the coming days
as the ringed planet
nears opposition on March 8th, its closest
approach to Earth in 2009.
Of course, opposition means opposite the Sun in planet
Earth's sky -
an arrangement that occurs almost yearly for Saturn.
But while Saturn itself grows larger in telescopic images,
Saturn's rings seem to be vanishing as
their tilt to our line-of-sight
decreases.
In fact, the rings will be nearly invisible, edge-on from
our perspective, by September 4.
Recorded on February 28, this sharp image was made with the 1 meter
telescope at
Pic Du Midi, a
mountain top
observatory in the French Pyrenees.
The rings are seen to be tilted nearly edge-on, but
remarkable details are visible in the gas giant's cloud bands.
The icy moon Tethys appears just beyond
the rings at the lower left.
APOD: 2008 June 24 - Ithaca Chasma: The Great Rift on Saturn's Tethys
Explanation:
What created the Great Rift on Saturn's moon Tethys?
No one is sure.
More formally named
Ithaca Chasma,
the long canyon running across the right of the
above image
extends about 2,000 kilometers long and spreads as much as 100 kilometers wide.
The above image
was captured by the Saturn-orbiting robotic
Cassini spacecraft
as it zoomed by the icy moon last month.
Hypotheses for the
formation of Ithaca Chasma include cracking of
Tethy's outer crust
as the moon cooled long ago, and that somehow the rift is related to the huge
Great Basin
impact crater named
Odysseus,
visible elsewhere on the unusual moon.
Cassini has now been orbiting
Saturn
for about four years and is scheduled to continue to probe and
photograph Saturn for at least two more years.
APOD: 2007 December 18 - Unusual Silica Rich Soil Discovered on Mars
Explanation:
You're rolling across Mars when you unexpectedly uncover some unusually light soil.
You stop. You turn. You return to inspect the soil and find out it is almost purely
silica -- the main ingredient in
quartz and
glass.
Such soil has never been found on
Mars before. What created this soil?
Since you are the robotic
rover Spirit currently rolling across Mars,
you send the images and data back to
Earth for analysis.
Your scientist friends from the blue water planet say that such soil on Earth is usually created by either volcanic steam or a
hot spring.
The second hypothesis in particular indicates, once again, a
wet past for part of Mars,
as possibly hot water saturated with silica deposited the white soil.
Intriguingly, on Earth, living
microbes
typically flourish under either condition.
Pictured above, the uncovered light soil is
visible on the right.
APOD: 2007 December 17 - Saturn's Ancient Rings
Explanation:
How old are Saturn's rings?
No one is quite sure.
One possibility is that the rings formed relatively recently in our
Solar System's history, perhaps only about 100 million years ago when
a moon-sized object
broke up near Saturn.
Evidence for a young ring age includes a basic
stability
analysis for rings,
and the fact that the rings are so bright and
relatively unaffected by numerous small dark
meteor impacts.
New
evidence, however, raises the possibility that some of
Saturn's rings
may be billions of years old and so almost as
old as Saturn itself.
Inspection of images by the Saturn-orbiting Cassini spacecraft
indicates that some of
Saturn's ring particles temporarily
bunch and collide, effectively recycling
ring particles by bringing
fresh bright ices to the surface.
Seen here,
Saturn's rings were imaged in their true colors by the
robotic
Cassini in late October.
Icy bright Tethys,
a moon of Saturn likely brightened by a sandblasting
rain of ice from sister moon
Enceladus, is visible in front of
the darker rings.
APOD: 2007 September 9 - The Great Basin on Saturns Tethys
Explanation:
Some moons wouldn't survive the collision.
Tethys, one of
Saturn's larger moons
at about 1000 kilometers in diameter, survived the collision, but sports today the expansive
impact crater Odysseus.
Sometimes called the Great Basin,
Odysseus
occurs on the leading hemisphere of
Tethys
and shows its great age by the relative amount of smaller craters that occur inside its
towering walls.
Another large crater,
Melanthius,
is visible near the moon's terminator.
The density of Tethys is similar to
water-ice.
The above digitally enhanced image was captured in July by the
robot Cassini spacecraft
in orbit around Saturn as it swooped past the giant ice ball.
APOD: 2006 November 7 - Janus: Potato Shaped Moon of Saturn
Explanation:
Janus is one of the stranger moons of Saturn.
First, Janus
travels in an unusual orbit around Saturn where it periodically trades places with its sister moon
Epimetheus,
which typically orbits about 50 kilometers away.
Janus,
although slightly larger than
Epimetheus, is
potato-shaped and
has a largest diameter of about 190 kilometers.
Next, Janus is covered with large craters but strangely appears to lack small craters.
One possible reason for this is a fine dust that might cover the small moon,
a surface also hypothesized for
Pandora and
Telesto.
Pictured above,
Janus was captured in front of the
cloud tops of
Saturn in late September.
APOD: 2006 February 22 - An Unusually Smooth Surface on Saturns Telesto
Explanation:
Why is Saturn's small moon Telesto so smooth?
Possibly Telesto
is covered with a type of granular icy material similar to that suspected of covering
Pandora, another of Saturn's small moons.
If so, Telesto might be
more like a pile of rubble
than a solid body.
This recently uncovered
Solar System
mystery is currently a topic of research, however.
The unexpected finding originated last October when the
robot Cassini spacecraft,
currently orbiting
Saturn,
swooped past the 24-kilometer moon and captured the
first ever image of Telesto's surface.
Telesto orbits Saturn always just ahead of the much
larger moon Tethys.
Pictured above,
Telesto's unusually smooth surface was found to show some
large craters and
boulders, but not the high density of craters found on nearby
Tethys or most other Saturnian moons.
APOD: 2006 February 8 - The Great Basin on Tethys
Explanation:
Some moons wouldn't survive the collision.
Tethys, one of
Saturn's larger moons
at about 1000 kilometers in diameter, survived the collision, but sports today the expansive
impact crater Odysseus.
Sometimes called the Great Basin,
Odysseus
occurs on the leading hemisphere of
Tethys
and shows its great age by the relative amount of smaller craters that occur inside its
towering walls.
The density of Tethys is similar to
water-ice.
The above digitally enhanced image was captured late last year by the
robot Cassini spacecraft
in orbit around Saturn as it swooped past the giant ice ball.
APOD: 2005 October 12 - Cratered Cliffs of Ice on Saturns Tethys
Explanation:
The surface of
Saturn's
moon Tethys is riddled with icy cliffs and craters.
The most detailed images ever taken of
Tethys
were captured late last month as the robot
Cassini spacecraft
swooped past the frozen ice moon.
The above image was taken from about 32,000 kilometers distant and
shows a jagged landscape of long cliffs covered with craters.
At the bottom of many craters appears some sort of unknown light-colored substance,
in contrast to the unknown dark substance that appears at the bottom of Saturn's moon
Hyperion.
Tethys is one of the
larger moons of Saturn, spanning about 1,000 kilometers across.
The density of Tethys indicates a composition
almost entirely of
water ice.
Tethys
is thought to have been predominantly liquid sometime in its distant past,
creating some of its long ice-cliffs
as it cracked during
freezing.
APOD: 2005 July 22 - Tethys, Rings, and Shadows
Explanation:
Seen from
ice moon Tethys,
rings and shadows would play across
fantastic
views of the Saturnian system.
Haven't dropped in on Tethys lately?
Then
this
gorgeous ringscape from the Cassini spacecraft
will have to do for now.
Caught in sunlight
just below and left of picture center,
Tethys itself is about 1,000 kilometers in diameter and
orbits not quite
five saturn-radii from the center
of the gas giant planet.
At that distance (around 300,000 kilometers) it is well outside Saturn's
main
bright rings, but Tethys is still
one of five
major moons that find themselves within the boundaries of
the faint and tenuous outer
E
ring.
Discovered in the 1980s, two very small moons
Telesto
and Calypso are locked in stable
locations
along Tethys' orbit.
Telesto precedes and Calypso follows Tethys as the trio
circles Saturn.
APOD: 2004 November 29 - Saturn's Moon Tethys from Cassini
Explanation:
Tethys is one of the larger and closer moons of Saturn.
The Cassini spacecraft now orbiting
Saturn
passed near the
frozen moon
at the end of October,
capturing the most detailed images since the
Voyager spacecrafts
in the early 1980s.
Tethys
is composed almost completely of water ice and shows a large impact crater that nearly circles the moon. Because this crater did not disrupt the moon,
Tethys
is hypothesized to be at least partly liquid in its past.
Two smaller moons,
Telesto and
Calypso, orbit Saturn just ahead of and behind Tethys.
Giovanni Cassini discovered Tethys in 1684.
The Cassini spacecraft is scheduled for a close fly-by of
Tethys in September 2005.
APOD: 2003 February 22 - Infrared Saturn
Explanation:
This delightfully detailed
false-color
image of Saturn was taken in January 1998 by the
orbiting Hubble Space Telescope.
The picture is a combination of three images from Hubble's
NICMOS instrument and shows the lovely ringed planet in reflected
infrared
sunlight.
Different colors indicated varying heights and compositions of cloud
layers generally thought to consist of ammonia ice crystals.
The eye-catching rings cast a shadow
on
Saturn's upper hemisphere.
The bright stripe seen within the left portion of the shadow
is infrared sunlight streaming through the large
gap
in the rings known
as the Cassini Division.
Two of
Saturn's many moons have also put in an appearance,
Tethys just
beyond the planet's disk at the upper right, and Dione at the lower left.
Presently, Saturn shines brightly in evening skies as a
pale yellow "star" near the constellation
Orion.
APOD: 2002 May 19 - Saturn's Moon Tethys
Explanation:
Tethys is one of the larger and closer moons of Saturn.
It was visited by both
Voyager spacecraft -
Voyager 1 in November 1980 and by
Voyager 2 in August 1981.
Tethys
is now known to be composed almost completely of water ice.
Tethys shows a large
impact crater
that nearly circles the planet.
That the impact that caused this crater did not
disrupt the moon is taken as evidence that
Tethys was not completely frozen in its past.
Two smaller moons,
Telesto and
Calypso, orbit
Saturn just ahead of and behind Tethys.
Giovanni Cassini discovered Tethys in 1684.
In 1997, NASA
launched a
spacecraft named Cassini to Saturn that will arrive in 2004.
APOD: July 24, 1999 - Infrared Saturn
Explanation:
This delightfully detailed
false color image of Saturn
was earmarked to
celebrate the 8th anniversary of the orbiting Hubble Space Telescope.
The picture is a combination of three images taken in January 1998
and shows the lovely ringed planet in reflected
infrared light.
Different colors indicated varying heights and compositions of cloud
layers generally thought to consist of ammonia ice crystals.
The eye-catching rings cast a shadow
on Saturn's upper hemisphere,
while the bright stripe seen within the left portion of the shadow
is infrared
sunlight streaming through the large
gap in the rings known
as the Cassini Division.
Two of
Saturn's many moons have also put in an appearance,
Tethys just
beyond the planet's disk at the upper right, and Dione at the lower left.
APOD: October 18, 1998 - Saturns Rings Seen Sideways
Explanation:
Saturn's rings
are actually very thin.
This picture
from the
Hubble Space Telescope
was taken on August 6, 1995 when the rings lined up sideways as seen from
Earth.
Saturn's largest moon
Titan is seen on the left, and Titan's
shadow can be seen on
Saturn's cloud tops!
Titan itself looks a brownish color because of its thick atmosphere. Four
other moons of Saturn can be seen just above the ring plane, which are,
from left to right:
Mimas,
Tethys,
Janus, and Enceladus. If you look
carefully, you will note that the dark band across the planet is actually
the shadow of the rings, and is slightly displaced from the real
rings - which are best seen away from the planet.
Saturn's
rings are not solid - they are composed of ice chunks which range
in size from a grain of sand to a house.
APOD: April 24, 1998 - Infrared Saturn
Explanation:
This delightfully detailed
false color image of Saturn
has been earmarked to
celebrate the 8th anniversary of the orbiting Hubble Space Telescope.
The picture is a combination of three images taken in January of this year
with the Hubble's new NICMOS instrument and shows the lovely ringed planet in reflected
infrared light.
Different colors indicated varying heights and compositions of cloud
layers generally thought to consist of ammonia ice crystals.
The eye-catching rings cast a shadow
on Saturn's upper hemisphere,
while the bright stripe seen within the left portion of the shadow
is infrared
sunlight streaming through the large
gap in the rings known
as the
Cassini Division.
Two of
Saturn's many moons have also put in an appearance,
Tethys just
beyond the planet's disk at the upper right, and Dione at the lower left.
APOD: May 31, 1997 - Saturn with Moons Tethys and Dione
Explanation:
Saturn and two of its larger moons -
Tethys and
Dione - were photographed by the
Voyager 1
spacecraft which flew by the planet in November of 1980.
This picture gives an indication of
Saturn's extensive ring system, which
can be seen casting a shadow on the planet, as does Tethys.
Saturn's rings are composed of many chunks of ice ranging in size
from a pebble to a car. The rings have several large gaps, the largest of
which is clearly visible in the picture and is named the
Cassini
Division, after its
discoverer.
Saturn
appears brighter than most stars in the sky,
and its rings can be discerned with a small telescope.
A new spacecraft -
Cassini - will visit
Saturn
and is currently scheduled for launch later in 1997.
APOD: May 24, 1997 - Saturn's Rings Seen Sideways
Explanation:
Saturn's rings
are actually very thin.
This picture
from the
Hubble Space Telescope
was taken on August 6, 1995 when the rings lined up sideways as seen from
Earth.
Saturn's largest moon
Titan is seen on the left, and Titan's
shadow can be seen on
Saturn's cloud tops!
Titan itself looks a brownish color because of its thick atmosphere. Four
other moon's of Saturn can be seen just above the ring plane, which are,
from left to right:
Mimas,
Tethys,
Janus, and Enceladus. If you look
carefully, you will note that the dark band across the planet is actually
the shadow of the rings, and is slightly displaced from the real
rings - which are best seen away from the planet.
Saturn's
rings are not solid - they are composed of ice chunks which range
in size from a grain of sand to a house.
APOD: April 29, 1996 - Saturn's Rings Seen Sideways
Explanation:
Saturn's rings
are actually very thin.
This picture
from the
Hubble Space Telescope
was taken on August 6, 1995 when the rings lined up sideways as seen from
Earth.
Saturn's largest moon
Titan is seen on the left, and Titan's
shadow can be seen on
Saturn's cloud tops!
Titan itself looks a brownish color because of its thick atmosphere. Four
other moon's of Saturn can be seen just above the ring plane, which are,
from left to right:
Mimas,
Tethys,
Janus, and Enceladus. If you look
carefully, you will note that the dark band across the planet is actually
the shadow of the rings, and is slightly displaced from the real
rings - which are best seen away from the planet.
Saturn's
rings are not solid - they are composed of ice chunks which range
in size from a grain of sand to a house.
APOD: March 18, 1996 - Saturn with Moons Tethys and Dione
Explanation:
Saturn and two of its larger moons -
Tethys and
Dione - were photographed by the
Voyager 1
spacecraft which flew by the planet in November of 1980.
This picture gives an indication of
Saturn's extensive ring system, which
can be seen casting a shadow on the planet, as does Tethys.
Saturn's rings are composed of many chunks of ice ranging in size
from a pebble to a car. The rings have several large gaps, the largest of
which is clearly visible in the picture and is named the
Cassini
Division, after its
discoverer.
Saturn
appears brighter than most stars in the sky,
and its rings can be discerned with a small telescope.
A new spacecraft -
Cassini - will visit
Saturn
and is currently scheduled for launch in 1997.
APOD: November 25, 1995 - Saturn's Cleanest Moon: Enceladus
Explanation:
Enceladus orbits
Saturn between the smaller
Mimas and the larger
Tethys.
Enceladus is composed mostly of water ice and has the cleanest and purest
ice surface in the
Solar System. It's surface therefore appears
nearly white. The surface also has many unusual groves and relatively few
craters, like
Jupiter's moon
Ganymede. This indicates that the surface is young
and/or newly reformed. To explain this, some astronomers speculate that
Enceladus is susceptible to some sort of
volcanic activity. Enceladus was
originally discovered in 1789 by
William Herschel.
APOD: November 24, 1995 - Saturn's Moon Tethys
Explanation:
Tethys is one of the larger and closer moons of
Saturn. It was visited
by both Voyager spacecraft - Voyager 1 in November 1980 and by Voyager 2 in
August 1981.
Tethys is now known to be composed almost completely of water
ice. Tethys shows a large impact crater that nearly circles the planet.
That the impact that caused this crater did not disrupt the moon is taken
as evidence that Tethys was not completely frozen in its past.
Tethys has two moons named
Telesto and
Calypso that orbit just ahead
of it and behind it. Tethys was originally discovered in 1684 by
Giovanni Cassini.