Extending above the visible surface of the Sun , the faint, tenuous solar corona can't be easily seen from Earth, but it is measured to be hundreds of times hotter than the photosphere itself. What makes the solar corona so hot? Astronomers have long sought the source of the corona's heat in magnetic fields which loft monstrous loops of solar plasma above the photosphere. NASA
Here is what the Earth looks like during a solar eclipse. The shadow of the Moon can be seen darkening part of Earth. This shadow moves across the Earth at over 1,200 miles per hour. Only observers near the center of the dark circle see a total solar eclipse - others see a partial eclipse where only part of the Sun appears blocked by the Moon. Centre National d'Etudes Spatiales/NASA
Voyager 1 looked back at Saturn on Nov. 16, 1980, four days after the spacecraft flew past the planet, to observe the appearance of Saturn and its rings from this unique perspective. A few of the spokelike ring features discovered by Voyager appear in the rings as bright patches in this image, taken at a distance of 3.3 million miles from the planet. NASA/Jet Propulsion Laboratory
This floating ring is the size of a galaxy. In fact, it is part of the photogenic Sombrero Galaxy, one of the largest galaxies in the nearby Virgo Cluster of Galaxies. The dark band of dust that obscures the mid-section of the Sombrero Galaxy in optical light actually glows brightly in infrared light. R. Kennicutt/Steward Obs./SSC/JPL/Caltech/NASA
Erupting from the flames and smoke beneath it, NASA's Deep Impact spacecraft lifts off at 1:47 p.m. EST on January 12, 2005 from Launch Pad 17-B, Cape Canaveral Air Force Station, Fla. NASA
An art installation, titled 'Solar Equation' by artist Rafael Lozano-Hemmer of Mexico is seen at Federation Square in Melbourne on June 22. The installation is part of 'The Light in Winter' festival, which runs to July 4th. Mick Tsikas/Reuters
The bright sun greets the International Space Station in this Nov. 22, 2009 image, taken from the Russian section of the orbital outpost and photographed by the STS-129 crew. NASA
Voyager 1 acquired this image of Io on March 4, 1979 at 5:30 p.m. PST about 11 hours before its closest approach to the Jupiter moon. The distance to Io was about 304,000 miles. An enormous volcanic explosion can be seen silhouetted against dark space over Io's bright limb. NASA
In February, evening skies were blessed with a glorious Moon and three bright planets; Venus, Jupiter, and Saturn. Larry Koehn/NASA
These shape-shifting galaxies have taken on the form of a giant mask. The icy blue eyes are actually the cores of two merging galaxies, called NGC 2207 and IC 2163, and the mask is their spiral arms. The false-colored image consists of infrared data from NASA's Spitzer Space Telescope (red) and visible data from NASA's Hubble Space Telescope (blue/green). NASA
Egypt's President Abdel-Fattah el-Sissi called it a 'terrorist attack' on soldiers defending the country's borders that will 'not go unanswered.'
BySarah El Deeb, Associated Press
Al Youm Al Saabi Newspaper/Reuters
Gunmen armed with rocket-propelled grenades attacked a border guard post Saturday in Egypt's western desert in a brazen assault that killed 21 troops deployed in the province along the border with neighboring Libya.