Posts Tagged With: Cassini

Astronomy Picture of the Day – In the Shadow of Saturn’s Rings

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2012 July 3

In the Shadow of Saturn’s Rings 

 Image Credit: NASA/JPL-Caltech/Space Science Institute/J. Major

 Explanation: Humanity’s  robot orbiting Saturn has recorded yet another amazing view. That robot, of course, is the  spacecraft Cassini, while the new amazing view includes a  bright moon,  thin rings,  oddly broken clouds, and  warped shadows. Titan, Saturn’s largest moon, appears above as a featureless tan as it is continually shrouded in thick clouds. The rings of Saturn are seen as a thin line because they are so flat and imaged nearly edge on. Details of Saturn’s rings are therefore best visible in the  dark ring shadows seen across the giant planet’s cloud tops. Since the ring  particles orbit in the same plane as Titan, they appear to skewer the foreground moon. In the upper hemisphere of Saturn, the clouds show many details, including  dips in long bright bands  indicating disturbances in a high altitude jet stream. Recent precise measurements of how much Titan  flexes as it orbits Saturn hint that  vast oceans of water might exist deep underground.

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NASA Image of the Day for November 18th – Saturn’s Northern Storm

S Saturn

Saturn’s Northern Storm

This false-color mosaic from NASA’s Cassini spacecraft shows the tail of Saturn’s huge northern storm. In mid-September 2004, the Cassini spacecraft chronicled a similar, but smaller, storm in the southern hemisphere called the “Dragon Storm.”

The head of this storm is beyond the horizon in this view. Saturn’s atmosphere and its rings are shown here in a false color composite made from 12 images taken in near-infrared light through filters that are sensitive to varying degrees of methane absorption. Red and orange colors in this view indicate clouds that are deep in the atmosphere. Yellow and green colors, most noticeable near the top of the view, indicate intermediate clouds. White and blue indicate high clouds and haze. The rings appear as a thin horizontal line of bright blue because they are outside of the atmosphere and not affected by methane absorption.

The oval in the upper left of this image that appears slightly blue is the same hole in the deep clouds of the planet’s atmosphere that can be seen near the tail in a larger false-color mosaic, PIA14903. The blue color comes from the high haze overlying the hole.

This view looks toward the northern, sunlit side of the rings from just above the ring plane. The shadow of the moon Enceladus is visible on the planet in the lower left of the image.

The images were taken with the Cassini spacecraft wide-angle camera using a combination of spectral filters sensitive to wavelengths of near-infrared light. The images filtered at 890 nanometers are projected as blue. The images filtered at 728 nanometers are projected as green, and images filtered at 752 nanometers are projected as red.

The images were taken on Jan. 12, 2011, over about one hour at a distance of approximately 684,000 miles (1.1 million kilometers) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 52 degrees. The images were re-projected to the same viewing geometry, so that scale in this final mosaic is 76 miles (122 kilometers) per pixel.

Image Credit:NASA/JPL-Caltech/Space Science Institute

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Daily Astronomy Pic for October 12th

Astronomy Picture of the Day

Discover the cosmos!Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2011 October 12

 

Saturn: Shadows of a Seasonal Sundial
Image Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA  

 

Explanation: Saturn’s rings form one of the larger sundials known. This sundial, however, determines only the season of Saturn, not the time of day. In 2009, during Saturn’s last equinox, Saturn’s thin rings threw almost no shadows onto Saturn, since the ring plane pointed directly toward the Sun. As Saturn continued in its orbit around the Sun, however, the ring shadows become increasingly wider and cast further south. These shadows are not easily visible from the Earth because from our vantage point near the Sun, the rings always block the shadows. The above image was taken in August by the robotic Cassini spacecraft currently orbiting Saturn. The rings themselves appear as a vertical bar on the image right. The Sun, far to the upper right, shines through the rings and casts captivatingly complex shadows on south Saturn, on the image left. Cassini has been exploring Saturn, its rings, and its moons since 2004, and is expected to continue until at least the maximum elongation of Saturn’s shadows occurs in 2017.

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NASA Image of the Day for October 10th

Electrical Circuit Between Saturn and Enceladus

This artist’s concept shows a glowing patch of ultraviolet light near Saturn’s north pole that occurs at the “footprint” of the magnetic connection between Saturn and its moon Enceladus. The footprint and magnetic field lines are not visible to the naked eye, but were detected by the ultraviolet imaging spectrograph and the fields and particles instruments on NASA’s Cassini spacecraft. The footprint, newly discovered by Cassini, marks the presence of an electrical circuit that connects Saturn with Enceladus and accelerates electrons and ions along the magnetic field lines. In this image, the footprint is in the white box marked on Saturn, with the magnetic field lines in white and purple.

A larger white square above Enceladus shows a cross-section of the magnetic field line between the moon and the planet. This pattern of energetic protons was detected by Cassini’s magnetospheric imaging instrument (MIMI) on Aug. 11, 2008.

The patch near Saturn’s north pole glows because of the same phenomenon that makes Saturn’s well-known north and south polar auroras glow: energetic electrons diving into the planet’s atmosphere. However, the “footprint” is not connected to the rings of auroras around Saturn’s poles (shown as an orange ring around the north pole in this image).

The Cassini plasma spectrometer complemented the MIMI data, with detection of field-aligned electron beams in the area. A team of scientists analyzed the charged particle data and concluded that the electron beams had sufficient energy flux to generate a detectable level of auroral emission at Saturn. Target locations were provided to Cassini’s ultraviolet imaging spectrograph team. On Aug. 26, 2008, the spectrograph obtained images of an auroral footprint in Saturn’s northern hemisphere.

The newly discovered auroral footprint measured about 1,200 kilometers (750 miles) in the longitude direction and less than 400 kilometers (250 miles) in latitude, covering an area comparable to that of California or Sweden. It was located at about 65 degrees north latitude.

In the brightest image the footprint shone with an ultraviolet light intensity of about 1.6 kilorayleighs, far less than the Saturnian polar auroral rings. This is comparable to the faintest aurora visible at Earth without a telescope in the visible light spectrum. Scientists have not yet found a matching footprint at the southern end of the magnetic field line.

The background star field and false color images of Saturn and Enceladus were obtained by Cassini’s imaging science subsystem.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif. manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The ultraviolet imaging spectrograph team is based at the University of Colorado, Boulder. The magnetospheric imaging team is based at the Johns Hopkins University Applied Physics Laboratory, Laurel, Md. The Cassini plasma spectrometer team is based at the Southwest Research Institute, San Antonio, Texas.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

Image credit: NASA/JPL/JHUAPL/University of Colorado/Central Arizona College/SSI

 
 
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