Pale arcs in a layer of marine clouds trace the paths of ships in the North Pacific as seen by NASA's Terra satellite in a false-color picture taken in September and released Sunday.
Clouds form when water droplets condense around airborne particles, such as dust and sea salt crystals. Over the open ocean, there are fewer natural particles, so the water droplets that do form tend to grow relatively large.
But air pollution from ship exhaust creates smaller cloud droplets, which are more reflective and thus brighter in the enhanced image.
A bright star cluster glitters like a fireworks display over a cloud of interstellar gas and dust in a Hubble Space Telescope picture released July 6.
The young cluster, dubbed NGC 3603, is filled with stars that were born around the same time but have grown up to have different sizes and masses. Because more massive stars die sooner than less massive ones, the cluster acts like a cosmic petri dish, in which astronomers can study the various stages of stars' life cycles.
Silvery swirls show where oil from the Gulf spill had reached the barrier islands off Mississippi as of June 27.
The islands, seen in a recently released NASA satellite image, provide a sense of scale for the nearshore ribbons of oil: Petit Bois Island (top center) is about six miles (ten kilometers) long. It's one of seven barrier islands that, along with some mainland areas of Mississippi and Florida, make up the Gulf Islands National Seashore.
In a death scene worthy of Shakespeare, a dying midsize star puts on a colorful show for the Hubble Space Telescope in a picture released June 28.
In the final stages of life, sunlike stars expand their surface layers and become red giant stars. These layers then get expelled, exposing compact cores called white dwarfs, which light up surrounding gases.
The resulting structures are called planetary nebulae—so named because the wispy nebulae looked like gas giant planets through the telescopes of the 18th century, when the term was coined. (Explore a telescope time line.)
The map shows light from our own Milky Way galaxy as a bright band cutting lengthwise through the image. But Planck also captured a mottled backdrop of ancient light known as the cosmic microwave background, or CMB—the afterglow of the big bang.
Studying the minute differences in temperature within the CMB should help astronomers understand where and how the very first stars and galaxies took shape.
Shown in a computer simulation released July 2, stellar debris surrounds a galaxy like our Milky Way, as it might have appeared five billion years ago, during a period of heavy galactic collisions.
Led by scientists at the U.K.'s Durham University, a team of "galactic archaeologists" says the simulation helps prove that ancient stars in a halo around the Milky Way are the remains of older, smaller galaxies that collided and merged with our galactic home.
Starry Night Over Persia
The plane of the Milky Way arcs over the ninth-century mountain fortress of Alamut in Iran in a long-exposure picture taken in May and released this week. A streaking meteor can be seen at top right.
Built into Iran's Elburz Mountains, the fortress's prison once held the famous Persian astronomer Nasir al-Din al-Tusi, who was later released and eventually spurred construction of the Maragha observatory, at the time one of the largest and most advanced in the world.
Here Be Dragons
In visible light (bottom) a dark swath cuts through the glow of dust and gas in the nebula known as M17, which is lighted by the massive stars being born in the region.
But for the infrared eye of the Spitzer Space Telescope (top), a red-eyed "dragon" emerges from the darkness, seeming to soar against a backdrop of swirling color—dust and gas heated by the furious rate of star formation in the nebula.
Astronomers think stars are forming at a rapid clip inside the dark, dragon-shaped cloud too. But since the cloud has yet to spawn the hottest, most massive stars, the region doesn't yet shine in infrared.