An infrared mosaic image from NASA's Wide-field Infrared Survey Explorer shows the Heart and Soul nebulae located some 6,000 light-years from Earth. the Heart and Soul nebulae form a vast star-forming complex that makes up part of the Perseus spiral arm of our Milky Way galaxy. The nebula to the left is the Heart, designated IC 1805 and named after its resemblance to a human heart. To the right is the Soul nebula, also known as the Embryo nebula, IC 1848 or W5. Also visible near the bottom of this image are two galaxies, Maffei 1 and Maffei 2. NASA/JPL-Caltech/AP
Lightning over the Kennedy Space Center's Launch Pad 39A competes with the xenon lights on the pad illuminating space shuttle Discovery waiting for a scheduled liftoff on the STS-128 mission in August 2009. Courtesy of Justin Deniere/EPA/NASA
In this long-exposure photo released by Japan's Wakayama University Institute for Education on Space, two streaks of the Hayabusa probe, the first spacecraft to complete a round-trip journey to an asteroid, and its capsule streak across the sky near Glendambo in southern Australia as they reenter the Earth's atmosphere late Sunday. Wakayama University Institute for Education on Space/AP
This rendering by artist Akihiro Ikeshita shows the Japanese space probe Hayabusa as it approaches the Earth carrying what scientists hope is a sample of an asteroid. AP Photo/Japan Aerospace Exploration Agency
Comet McNaught streaks across the night sky over Jauerling, Austria on June 9. The green shimmering comet can be seen with the naked eye under ideal conditions and might become as bright as Ursa Major within June. The comet, discovered last year by Australian comet hunter Robert McNaught, entered our solar system for the first time and will be back in the depths of space in early July. Michael Jaeger/Newscom
Astronaut John Grunsfeld performs work on the Hubble Space Telescope in May 2009. NASA
Spacewalking Astronaut Michael Good peers through a window toward Atlantis's crew cabin interior in May 2009. NASA
Images from the MESSENGER spacecraft that flew by Mercury in October 2008 show previously unseen views of Mercury's craters. NASA
This artist's concept illustrates the two types of spiral galaxies that populate our universe: those with plump middles, or central bulges (upper left), and those lacking the bulge (foreground). New observations from NASA's Spitzer Space Telescope provide strong evidence that the slender, bulgeless galaxies can, like their chubbier counterparts, harbor supermassive black holes at their cores. NASA
NASA mission managers monitor the launch of the space shuttle Atlantis from Firing Room Four of the NASA Kennedy Space Center, on Nov. 16, 2009. NASA/Bill Ingalls
While Ukraine is not a NATO member, alliance members in Eastern and Central Europe fear they could be Russia's next targets, prompting the 28-nation bloc to seek a robust response.
ByJulie Pace, AP White House Correspondent
Confronted by a Kremlin-backed military offensive in Ukraine, President Barack Obama and Western allies will approve plans this week to position at least 4,000 troops and military equipment in Eastern Europe, bolstering NATO's security commitments to nervous member states near the Russian border.