On August 1, almost the entire Earth-facing side of the sun erupted in a tumult of activity. This image from the Solar Dynamics Observatory shows the C3-class solar flare (white area on upper left), a solar tsunami (wave-like structure, upper right), multiple filaments of magnetism lifting off the stellar surface, large-scale shaking of the solar corona, radio bursts, a coronal mass ejection and more. NASA/SDO/AIA
Looking westward, one of the STS-109 crew members photographed the newly serviced and upgraded Hubble Space Telescope near the earth's limb to the upper right of the center of this 70mm image from 2002. The Space Shuttle Columbia was located over the Atlantic Ocean southwest of the Cape Verde Islands when this image was acquired. NASA
With its drag chute opened, orbiter Columbia is silhouetted against the brilliant xenon lights at the KSC Shuttle Landing Facility in March 2002. Columbia landed with its crew of seven after a successful 11-day mission servicing the Hubble Space Telescope. This was Columbia's last successful landing; the shuttle was tragically destroyed a year later during re-entry. NASA
The glowing, swirling material at Saturn's poles is its auroral 'curtains,' rising more than a thousand miles above the cloud tops. Saturn's auroral displays are caused by an energetic wind from the Sun that sweeps over the planet, much like Earth's aurora, which is occasionally seen in the nighttime sky. The process that triggers these auroras is similar to the phenomenon that causes fluorescent lamps to glow. NASA/ESA/J. Clarke/Boston Univ./G. Bacon/STScI
An engineer operates a rig used for studying film-cooling of combustors in 1952. In this method of cooling, a film of relatively cool air is maintained between the hot gases and the combustor wall to serve as an insulator for the wall. He sees the equipment indirectly, through a periscopic arrangement of mirrors and a window of bullet-proof glass. NASA/Glenn Research Center
NEEMO 13 crewmembers pose for a group photo at their undersea habitat during a training session for the 13th NASA Extreme Environment Mission Operations (NEEMO) mission. From the left are Constellation program aerospace engineer/aquanaut Christopher Gerty, astronaut/aquanauts Richard R. Arnold II, Nicholas J. M. Patrick (commander) and Japan Aerospace Exploration Agency's (JAXA) Satoshi Furukawa. Habitat technicians Jim Buckley and Dewey Smith can be seen through the port in the background. The crew is spending 10 days on an undersea mission aboard the National Oceanic and Atmospheric Administration's Aquarius Underwater Laboratory, which is operated by the University of North Carolina. NASA
This artist's concept depicts the pulsar planet system discovered by Aleksander Wolszczan in 1992. Wolszczan used the Arecibo radio telescope in Puerto Rico to find three planets - the first of any kind ever found outside our solar system - circling a pulsar called PSR B1257+12. Pulsars are rapidly rotating neutron stars, which are the collapsed cores of exploded massive stars. They spin and pulse with radiation, much like a lighthouse beacon. Here, the pulsar's twisted magnetic fields are highlighted by the blue glow. NASA/JPL-Caltech
This image from NASA's Spitzer Space Telescope shows the Eagle nebula in different hues of infrared light. Each view tells a different tale. The left picture shows lots of stars and dusty structures with clarity. Dusty molecules found on Earth called polycyclic aromatic hydrocarbons produce most of the red; gas is green and stars are blue. NASA/JPL-Caltech/ Institut d'Astrophysique Spatiale
NASA's Human Robotic Systems Project, part of the agency's Exploration Technology Development Program, focused on human and robotic mobility systems for the moon, but also looked at communication and command and control systems that will connect the explorers with Earth and each other. The Moses Lake dunes provided a wide variety of soil consistencies and terrain that allowed the team to put prototype scout robots, rovers, cargo carriers, cranes and spacesuits through tests in a harsh and changing environment. NASA/Sean Smith
This composite image shows Z Camelopardalis, or Z Cam, a double-star system featuring a collapsed, dead star, called a white dwarf, and a companion star, as well as a ghostly shell around the system. The massive shell provides evidence of lingering material ejected during and swept up by a powerful classical nova explosion that occurred probably a few thousand years ago. The image combines data gathered from the far-ultraviolet and near-ultraviolet detectors on NASA's Galaxy Evolution Explorer on Jan. 25, 2004. NASA/JPL-Caltech
Obama phoned Russia's Vladimir Putin Thursday to discuss a US proposal for resolving the Ukraine crisis. Earlier, the US moved to begin a regimen of sanctions against Russia. Will those be enough to prevent Russia's annexation of Crimea?
[Updated 9:30 p.m. ET] President Obama appealed to Russian President Vladimir Putin late Thursday, during a personal phone call, to agree to direct talks with Ukraine aimed at resolving, through diplomacy rather than military confrontation, Russia's concerns about the future direction of the Ukrainian government and of the rights of ethnic Russians living in Ukraine.