NATIONAL GEOGRAPHIC'S BEST SPACE PICTURES THIS WEEK XXVIII

Week's Best Space Pictures: Sahara Glows, Hawaii Erupts, and Greenland Melts
By Dan Vergano and Jane J. Lee, National Geographic News, 3 October 2014.

See Saturn's winds spin, Sahara sands gleam, and a galaxy puzzle astronomers in this week's best space pictures.

1. Twinkle, Twinkle

The Sahara twinkles under a stretch of the Milky Way galaxy in an image taken on board the International Space Station by NASA astronaut Reid Wiseman.

Wiseman and his fellow Expedition 41 crew members will perform two spacewalks in the next couple of weeks for maintenance and repair work. (Read about the Milky Way galaxy in National Geographic magazine.)

2. Dwarf Galaxy Poses Puzzle

A nearby dwarf galaxy - seen as a cloudy splash of stars in this Hubble Space Telescope view - seems suspiciously young to astronomers.

Dubbed DDO 68, the youthful-looking galaxy is surprising because it resides only about 39 million light-years away, according to the European Space Agency. That's unusually close since most young galaxies are billions of light-years away.

Observers suspect that DDO 68 is actually much older than it looks and is enjoying a sudden crop of star births. Those new stars have likely been spawned by a chance collision of dust clouds in the galaxy in the past billion years. Finding more ancient stars among the new-borns may tell researchers the true age of DDO 68.

3. Burning Bright

Live fast and die young. That's the story for "hypergiant" stars such as AG Carinae, seen in this September 29 view from the European Space Agency.

Seventy times more massive than the sun, AG Carinae shines 1.5 million times more brightly than our star does, and is only about 20,000 light-years away.

Nevertheless, AG Carinae can't be seen with the naked eye. Much of its light is in the ultraviolet range, and its surroundings are swathed in interstellar dust. A nebula of stardust fired off from AG Carinae's roiling surface at seven million miles per hour (11.26 million kilometres per hour) gives the star its distinctive appearance.

4. Winds Whirl on Saturn

Clouds sweep across Saturn's upper atmosphere as fast as 1,100 miles per hour (1,800 kilometres per hour), in a view revealed by the Cassini spacecraft.

Nothing stops the winds from swirling to fantastically high speeds because Saturn lacks a real surface. Cassini captured this scene from a perch some 1.1 million miles (1.8 million kilometres) above the rings on the sunlit side of the whirligig world.

5. Volcano's Glow Bathes Milky Way

Photograph by Wally Pacholka, TWAN

The Milky Way basks in the cherry red glow of Kilauea Crater, a roiling vent on the world's largest active volcano.

This panorama, taken from Mauna Loa on Hawaii's Big Island, includes glimpses of Mars and Saturn on the far right. (Related: "Hawai'i Volcanoes National Park.")

6. Glaciers Sliding Seaward

Meltwater plumes pour off of southern Greenland's glaciers in an image captured last month by NASA's Aqua satellite.

Measuring how these rivers flow out from under the glaciers - the flow scores bedrock and carries debris into the ocean - can help scientists better understand the rivers' contribution to rising sea levels worldwide.

Photo gallery by Mallory Benedict.

[Source: National Geographic News. Edited. Some links added.]