On March 2, 2013, NASA’s Solar Dynamics Observatory (SDO) entered its semiannual eclipse season, a period of three weeks when Earth blocks its view of the sun for a period of time each day. On March 11, however, SDO was treated to two transits. Earth blocked SDO’s view of the sun from about 2:15 to 3:45 a.m. EDT. Later in the same day, from around 7:30 to 8:45 a.m. EDT, the moon moved in front of the sun for a partial eclipse.

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This image was taken on March 10, 2013, and received on Earth March 10, 2013 by NASA’s Cassini spacecraft. The camera was pointing toward Rhea at approximately 174,181 miles (280,317 kilometers) away, and the image was taken using the CL1 and CL2 filters. Image credit: NASA/JPL-Caltech/Space Science Institute › Full image and caption

This image was taken on March 09, 2013, and received on Earth March 10, 2013, by NASA’s Cassini spacecraft. The camera was pointing toward Rhea at approximately 1,727 miles (2,779 kilometers) away, and the image was taken using the CL1 and CL2 filters. This image has not been validated or calibrated. Image credit: NASA/JPL-Caltech/Space Science Institute
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This image was taken on March 09, 2013, and received on Earth March 10, 2013, by NASA’s Cassini spacecraft. The camera was pointing toward Rhea at approximately 2,348 miles (3,778 kilometers) away, and the image was taken using the CL1 and CL2 filters. This image has not been validated or calibrated. Image credit: NASA/JPL-Caltech/Space Science Institute
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Following its last close flyby of Saturn’s moon Rhea, NASA’s Cassini spacecraft captured these raw, unprocessed images of the battered icy moon. They show an ancient, cratered surface bearing the scars of collisions with many space rocks. Scientists are still trying to understand some of the curious features they see in these Rhea images, including a curving, narrow fracture or a graben, which is a block of ground lower than its surroundings and bordered by cliffs on either side. This feature looks remarkably recent, cutting most of the craters it crosses, with only a few small craters superimposed.

Cassini flew by Rhea at an altitude of 620 miles (997 kilometers) on March 9, 2013. This flyby was designed primarily for the radio science sub-system to measure Rhea’s gravity field. During closest approach and while the radio science sub-system was measuring the icy satellite’s gravity field, the imaging team rode along and captured 12 images of Rhea’s rough and icy surface. Outbound from Rhea, Cassini’s cameras captured a set of global images from a distance of about 167,000 miles (269,000 kilometers).

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NASA’s Wide-field Infrared Survey Explorer (WISE) has discovered a pair of stars that has taken over the title for the third-closest star system to the sun. The duo is the closest star system discovered since 1916.

Both stars in the new binary system are “brown dwarfs,” which are stars that are too small in mass to ever become hot enough to ignite hydrogen fusion. As a result, they are very cool and dim, resembling a giant planet like Jupiter more than a bright star like the sun.

“The distance to this brown dwarf pair is 6.5 light-years — so close that Earth’s television transmissions from 2006 are now arriving there,” said Kevin Luhman, an associate professor of astronomy and astrophysics at Penn State University, University Park, Pa., and a researcher in Penn State’s Center for Exoplanets and Habitable Worlds.

“It will be an excellent hunting ground for planets because the system is very close to Earth, which makes it a lot easier to see any planets orbiting either of the brown dwarfs.”

The results will be published in the Astrophysical Journal Letters.

The star system is named “WISE J104915.57-531906” because it was discovered in an infrared map of the entire sky obtained by WISE. It is only slightly farther away than the second-closest star, Barnard’s star, which was discovered 6 light-years from the sun in 1916. The closest star system consists of: Alpha Centauri, found to be a neighbor of the sun in 1839 at 4.4 light-years away, and the fainter Proxima Centauri, discovered in 1917 at 4.2 light-years.

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