At about 300 feet from the cargo bay of the space shuttle Challenger, Bruce McCandless II was farther out than anyone had ever been before. Guided by a Manned Maneuvering Unit (MMU), astronaut McCandless, pictured above, was floating free in space. McCandless and fellow NASA astronaut Robert Stewart were the first to experience such an 'untethered space walk' during Space Shuttle mission 41-B in 1984. The MMU works by shooting jets of nitrogen and has since been used to help deploy and retrieve satellites. NASA
The rear windows of the Space Shuttle Endeavour reflect sunlight in this view of part of the cargo bay, 115 nautical miles above the Earth. The Space Radar Laboratory SRL-2 Multipurpose Experiment Support Structure MPESS is seen at bottom frame. Also partially seen are other experiments including other components of the primary payload. NASA
What does the largest moon in the Solar System look like? Ganymede, larger than even Mercury and Pluto, has a surface speckled with bright young craters overlying a mixture of older, darker, more cratered terrain laced with grooves and ridges. Like Earth's Moon, Ganymede keeps the same face towards its central planet, in this case Jupiter. NASA
Taken by a telescope onboard NASA's Swift satellite, this stunning vista represents the highest resolution image ever made of the Andromeda Galaxy - at ultraviolet wavelengths. The mosaic is composed of 330 individual images covering a region 200,000 light-years wide. It shows about 20,000 sources, dominated by hot, young stars and dense star clusters that radiate strongly in energetic ultraviolet light. NASA
Just one minute before midnight EDT, Friday, August 28, 2009, the Space Shuttle Discovery began a long arc into a cloudy sky. Following the launch, a bright and remarkably colorful trail was captured in this time exposure from the Banana River Viewing Site, looking east toward pad 39A at the Kennedy Space Center. NASA
The bright clusters and nebulae of planet Earth's night sky are often named for flowers or insects, and NGC 6302 is no exception. With an estimated surface temperature of about 250,000 degrees C, the central star of the Butterfly Nebula is exceptionally hot though - shining brightly in ultraviolet light but hidden from direct view by a dense torus of dust. This dramatically detailed close-up of the dying star's nebula was recorded by the newly upgraded Hubble Space Telescope. NASA, ESA, and the Hubble SM4 ERO Team
Testing advanced designs for high-speed aircraft in 1948, an engineer makes final calibrations to a model mounted in the 6 x 6 Foot Supersonic Wind Tunnel at the NACA Ames Aeronautical Laboratory, Moffett Field, California. NACA, NASA’s predecessor organization the National Advisory Committee for Aeronautics, was established in March 1913 by Congress to 'supervise and direct the scientific study of the problems of flight, with a view to their practical solutions.' The Ames Aeronautical Laboratory is now NASA’s Ames Research Center. NASA
The first identified compact galaxy group, Stephan's Quintet is featured in this stunning image from the newly upgraded Hubble Space Telescope. About 300 million light-years away, only four galaxies of the group are actually locked in a cosmic dance of repeated close encounters. The odd man out is easy to spot, though. The bluish galaxy at the upper left (NGC 7320) is much closer than the others. A mere 40 million light-years distant, it isn't part of the interacting group. NASA, ESA, and the Hubble SM4 ERO Team
Backdropped by a view of Earth, space shuttle Atlantis (STS-129) is featured in this image photographed by an Expedition 21 crew member on the International Space Station soon after the shuttle and station began their post-undocking relative separation. Undocking of the two spacecraft occurred at 3:53 a.m. (CST) on Nov. 25, 2009. NASA
Russian cosmonaut Maxim Suraev, Expedition 22 flight engineer, poses for a photo with the current growth experiment on the BIO-5 Rasteniya-2 (Plants-2) payload in the Zvezda Service Module of the International Space Station. NASA
At least 60,000 mostly Kurdish refugees have entered Turkey since Thursday after Islamic State militants surrounded a Kurdish stronghold in northern Syria. Some are calling for US airstrikes to stop the group's advance.
ByDominique Soguel, Correspondent
Tens of thousands of Syrians have crossed into Turkey in recent days, fleeing an Islamic State offensive that has opened up another front in Syria's civil war as the US weighs a bombing campaign there.