Saturn Stars in Three Hubble Movies
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Saturn’s
rings are shown at maximum tilt toward Earth, a special
event occurring every 15 years. With the rings fully
tilted, astronomers get the best views of the planet’s
Southern Hemisphere. The 24-second movie is based on
Hubble images taken over a 24-hour span. The images were
taken with Hubble’s Advanced Camera for Surveys.
Click for movie.
Photo
by NASA, ESA, E. Karkoschka (University of Arizona)
and G. Bacon
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(NASA/JPL) Photogenic
Saturn has now become a movie star. Astronomers have woven NASA
Hubble
Space Telescope images of Saturn, its rings, and several of its
moons into three movies. Each movie highlights unique times in
the planet’s 30-year waltz around the Sun. Two of the movies show
the motion of several of Saturn’s moons when the planet’s rings
were tilted nearly edge-on to Earth and to the Sun. These edge-on
alignments of the rings occur roughly once every 15 years. Another
movie presents a clear view of Saturn’s Southern Hemisphere when
the planet’s rings were at maximum tilt toward Earth. Hubble snapped
only about a dozen images during each of these three events, so
astronomers created software to extend the photos into the hundreds
of images needed for a movie. The images were taken with Hubble’s
Wide Field and Planetary Camera 2 in 1995 and the Advanced Camera
for Surveys in 2003.
In March
2003, Saturn’s rings were at maximum tilt toward
Earth, a special event occurring every 15 years. With the rings
fully tilted, astronomers get the best views of the planet’s
Southern Hemisphere. They took advantage of the rings’ unique
alignment by using Hubble to capture some stunning images.
Astronomers then wove those images into a time-lapse
movie of Saturn’s rotation and southern region. The planet
spins more than twice as fast as Earth does, completing a rotation
every 10 hours. As Saturn rotates, so do its rings. But the ring
material is so evenly spread out along each ring that in this
movie one cannot see the rings rotating around Saturn.
After showing Saturn spinning, the movie then
offers a close-up of the planet’s Southern Hemisphere. Astronomers enhanced
the contrast in this close-up sequence to make Saturn’s
features more apparent. The close-up views reveal the planet’s
banded cloud structure, which is similar to Jupiter’s.
Saturn’s clouds, however, are beneath a thick layer of
haze. The haze, however, does not obscure several storms – the
blue and white spots – in the planet’s dynamic atmosphere.
The 24-second movie is based on Hubble images
taken over a 24-hour span. The images were taken with Hubble’s
Advanced Camera for Surveys.
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Taken on November 17, 1995, Hubble’s
Wide Field and Planetary Camera 2 watched for several
hours as the sun
was in the ring plane allowing the shadow of the rings
to appear as only a thin, almost invisble line. Since Saturn’s
moons orbit mostly in the same plane as the rings, their
shadows followed the same line. The 30-second movie is
based on Hubble images taken over a 9½-hour span.
The images were taken Nov. 17, 1995 with Hubble’s
Wide Field and Planetary Camera 2. Click for movie.
Photo
by NASA, ESA, E. Karkoschka (University of Arizona) and
G. Bacon
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The second time-lapse
movie shows the icy moons Mimas, Enceladus, Dione, and Tethys
rounding Saturn when the planet’s
rings were tilted nearly edge-on toward the Sun. This edge-on
alignment
occurs once every 15 years.
The rings’ shadow appears as a thin, almost invisible
line across the planet. Since Saturn’s moons orbit mostly
in the same plane as the rings, their shadows can be seen skirting
the planet’s surface just above the rings.
The moons appear to be moving along an invisible
race track as they speed along their orbital paths. Their speeds
are based
on their respective distances from Saturn. The faster moons are
closest to the planet. Mimas and Enceladus appear first. Mimas
is chasing after Enceladus as the pair race across Saturn. Both
moons cast small shadows on the planet, but only Enceladus casts
a shadow on the rings. The orbit of Mimas is inclined so that
its shadow misses the rings. Dione is the next moon to make its
appearance. Its long shadow also tracks across the ring system.
As the three moons move across Saturn’s disk, the viewer
catches a fleeting view of Tethys as it moves behind the planet
on the right.
The 30-second movie is based on Hubble images
taken over a 9½-hour
span. The images were taken Nov. 17, 1995 with Hubble’s
Wide Field and Planetary Camera 2.
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Taken
on August 6, 1995, Saturn’s rings were very close to
edge-on as they were only visible as a thin line. The
satellites, orbiting almost exactly in the ring plane,
followed this line. They therefore went in front and
behind Saturn around that date. Hubble’s Wide Field and
Planetary Camera 2 captured Titan’s shadow as it moved
across Saturn. Click on image to open movie. Click for
movie.
Photo
by NASA, ESA, E. Karkoschka (University of Arizona)
and G. Bacon |
The third time-lapse
sequence shows the moons Titan and Tethys orbiting Saturn when
the planet’s rings were tilted nearly edge-on toward Earth.
This edge-on alignment happens once every 15 years. The last time
this alignment occurred was in 1995 and 1996.
In the movie,
the moons can easily be seen because the rings are so thin.
Titan and Tethys follow the rings’ thin line
in their orbit around Saturn. But Titan’s shadow is the
first to make an appearance, moving across Saturn’s disk.
Then Titan appears. As Titan makes its trek across the disk,
Tethys appears on the left from behind the planet. It disappears
quickly off the screen as it makes its circular path around Saturn.
These moons seem to move much faster than they actually do because
several hours of viewing time were compressed to make this movie.
The movie also shows the bands of clouds that
make up Saturn’s
atmosphere. This banded structure is similar to Jupiter’s.
A thick haze covers the clouds.
The 15-second movie is based on Hubble images
taken over a 10½-hour
span. The images were taken Aug. 6, 1995 with Hubble’s
Wide Field and Planetary Camera 2.