Astronomers
have created three stunning movies of Saturn
and its rings, using special techniques to extend still images taken by the Hubble Space Telescope
into moving pictures that show the ringed planet
in novel splendor.
Each movie
highlights a different moment in the planet's 30-year orbit around the Sun.
Two of the
movies (15 seconds long and 30 seconds long) show the motion of several of
Saturn's moons when the planet's rings were tilted nearly edge-on towards the Earth and Sun. Such alignments happen
about once every 15 years. The third movie, at 24-seconds long, shows a clear
view of Saturn's southern hemisphere when the planet's rings were most tilted
toward Earth.
Ray Villard
of the Space Telescope Science Institute (STScI),
which oversees the Hubble space telescope's research mission, said the movies
show Saturn at very unique orientations relative to Earth.
"When
Saturn's ring plane was edge-on to earth, the ring becomes a wafer-thin slice
and that's a beautiful opportunity to see the moons very clearly," he
said.
Another set
of images used for the videos and from a similar orientation also impressed
folks at STScI immediately, Villard said.
"What's spectacular about that, which we noticed when the pictures first
were taken, is that you can actually see the shadow from the moon skirting
across the ring plane," he told Space.com. "That would only
happen at a unique time, just like a setting sun."
Software was
used to morph a dozen images, during each of these orbital slices of time, into
the hundreds of images needed for the movies.
The images
were taken by the Hubble's Wide Field Planetary Camera 2 in 1995 and the Advanced Camera
for Surveys in 2003.
Movie
details
The
shortest edge-on ring movie shows the moons Titan
and Tethys
orbiting Saturn. The moons follow the rings' thin line in their orbit around
Saturn. Titan's shadow is the first to appear, moving across Saturn's disk.
Titan follows, with Tethys appearing on the left from behind the planet. The
moons seem to move much faster than they actually do because several hours of
viewing time (images were taken over a 10.5-hour span) were compressed to make
the movie, which also shows bands of clouds that make up Saturn's atmosphere.
The longer
edge-on ring movie shows the icy moons Mimas, Enceladus, Dione and Tethys
rounding Saturn. Enceladus appears first with Mimas right behind. Both moons cast small shadows on the
planet, and Enceladus casts a shadow on the rings. Mimas' orbit is too inclined to hit the rings. Dione then appears with a long shadow that tracks
across the ring system. Tethys appears only briefly as it moves behind the
planet on the right. The images for this movie were taken over a 9.5-hour span.
The maximum
ring-tilt movie first shows Saturn spinning. Although the rings rotate with the
planet, they appear to be stationary because the ring material is spread out so
evenly. Saturn rotates on its axis every 10 hours, more than twice as fast as
Earth.
Next, the
movie offers a close-up of Saturn's southern hemisphere. Astronomers enhanced
the contrast in this sequence to make Saturn's banded cloud structure more
obvious. The images for this movie were taken over a 24-hour span.
NASA's Voyager
and Cassini missions also have generated movies of Saturn. Cassini has been at
Saturn since July 2004, studying the planet, its moons and its ring system.
"Cassini
has shown us those moons are so diverse that it's like finding a little solar system
unto itself," Villard said.
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