At about 100 meters from the cargo bay of the space shuttle Challenger, Bruce McCandless II was further 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. With a mass over 140 kilograms, an MMU is heavy on Earth, but, like everything, is weightless when drifting in orbit. The MMU was replaced with the SAFER backpack propulsion unit.

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Volcano Tungurahua erupted spectacularly last year. Pictured above, molten rock so hot it glows visibly pours down the sides of the 5,000-meter high Tungurahua, while a cloud of dark ash is seen being ejected toward the left. Wispy white clouds flow around the lava-lit peak, while a star-lit sky shines in the distance. The above image was captured last year as ash fell around the adventurous photographer. Located in Ecuador, Tungurahua has become active roughly every 90 years since for the last 1,300 years. Volcano Tungurahua has started erupting again this year and continues erupting at a lower level even today.

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What does the surface of Saturn's mysterious moon Iapetus look like? To help find out, the robotic Cassini spacecraft now orbiting Saturn was sent soaring last week just 2,000 kilometers from the unique equatorial ridge of the unusual walnut-shaped two-toned moon. The above image from Cassini is from about 4,000 kilometers out and allows objects under 100-meters across to be resolved. Cassini found an ancient and battered landscape of craters, sloping hills, and mountains as high as 10 kilometers and so rival the 8.8-kilometer height of Mt. Everest on Earth. Just above the center of this image is a small bright patch where an impacting rock might have uncovered deep clean water ice. Space scientists will be studying flyby images like this for clues to the origin of Iapetus' unusual shape and coloring with particular emphasis because no more close flybys of the enigmatic world are planned.

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Bright, hot, supergiant star Deneb lies at top center in this gorgeous skyscape. The 20 frame mosaic spans an impressive 12 degrees across the northern end of Cygnus the Swan. Crowded with stars and luminous gas clouds along the plane of our Milky Way Galaxy, Cygnus is also home to the dark, obscuring Northern Coal Sack Nebula, extending from Deneb toward the bottom center of the view. The reddish glow of NGC 7000, the North America Nebula, and IC 5070, the Pelican Nebula, are at the upper left, but many other nebulae and star clusters are identifiable throughout the wide field. Of course, Deneb itself is the alpha star of Cygnus and is also known to northern hemisphere skygazers for its place in two asterisms -- marking the top of the Northern Cross and a vertex of the Summer Triangle.

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X-rays from young stars and infrared light from stars and cosmic dust are combined in this false color image of a star-forming region in Corona Australis, the Southern Crown. The small star grouping is fittingly known as the Coronet Cluster. A mere 420 light-years distant, the Coronet Cluster offers a relatively close-up view of stars and protostars evolving with a wide range of masses. The observations suggest that energetic x-rays come from the hot, extended stellar atmospheres or coronae of the Coronet stars. The tantalizing multi-wavelength view spans about 2 light-years and was produced using data from the orbiting Chandra Observatory (x-ray) and the Spitzer Space Telescope (infrared).

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How do stars form? To help study this complex issue, astronomers took a deep image in infrared light of an active part of our Milky Way Galaxy where star formation is rampant. In IRDC G11.11-0.11, thick clouds of dust and gas are congealing into stars that are so dark that humans living there would see an empty night sky. The image, though, taken last year by the Spitzer Space Telescope in infrared light, shows vast glowing fields of gas and dust, indicating that much of this dust is heated by forming stars. The centers of some clouds, such as the snake-like structure on the upper left, are so thick and cold that they are dark even in infrared light. Many of the red dots are glowing dust shrouds centered on very young newly formed stars. The unusual red sphere below the snake is actually a supernova remnant, the glowing shell of a young star so massive it evolved rapidly and exploded. The region spans about 150 light years and lies about 10,000 light years away toward the constellation of Sagittarius.

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An unusual triangle of light will be particularly bright near the eastern horizon before sunrise during the next two months for observers in Earth's northern hemisphere. Once considered a false dawn, this triangle of light is actually Zodiacal Light, light reflected from interplanetary dust particles. The triangle is clearly visible toward the left of the frame taken from the Paranal Observatory in Chile in July. Zodiacal dust orbits the Sun predominantly in the same plane as the planets: the ecliptic. Zodiacal light is so bright this time of year because the dust band is oriented nearly vertical at sunrise, so that the thick air near the horizon does not block out relatively bright reflecting dust. Zodiacal light is also bright for people in Earth's northern hemisphere in March and April just after sunset.

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A Full Moon rising can be a dramatic celestial sight, and Full Moons can have many names. For example, tonight's Full Moon, the one nearest the autumnal equinox in the northern hemisphere, is popularly called the Harvest Moon. According to lore the name is a fitting one because farmers could work late into the night at the end of the growing season harvesting crops by moonlight. In the same traditions, the Full Moon following the Harvest Moon is the Hunter's Moon. But, recorded on a trip to the American southwest, this contribution to compelling images of moonrise is appropriately titled Saguaro Moon.

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The dark expanse below the equator of the Sun is a coronal hole -- a low density region extending above the surface where the solar magnetic field opens freely into interplanetary space. Shown in false color, the picture was recorded on September 19th in extreme ultraviolet light by the EIT instrument onboard the space-based SOHO observatory. Studied extensively from space since the 1960s in ultraviolet and x-ray light, coronal holes are known to be the source of the high-speed solar wind, atoms and electrons that flow outward along the open magnetic field lines. The solar wind streaming from this coronal hole triggered colorful auroral displays on planet Earth begining late last week, enjoyed by spaceweather watchers at high latitudes.

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Most bright stars in our Milky Way Galaxy reside in a disk. Since our Sun also resides in this disk, these stars appear to us as a diffuse band that circles the sky. The above panorama of a northern band of the Milky Way's disk covers 90 degrees and is a digitally created mosaic of several independent exposures. Scrolling right will display the rest of this spectacular picture. Visible are many bright stars, dark dust lanes, red emission nebulae, blue reflection nebulae, and clusters of stars. In addition to all this matter that we can see, astronomers suspect there exists even more dark matter that we cannot see.

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