Saturn Stars in Three Hubble Movies

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

(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.

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

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.

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.