Space Pictures This Week: Star Gems, Galaxy Bubbles, Fogbow

Aurora From Above

Photograph courtesy NASA

Seen in a picture taken Monday from the International Space Station, a brilliant green aurora is capped by a red band of light.

Auroras are produced when charged particles from the sun strike atoms in Earth's atmosphere, and the colors depend on which types of atoms get hit. Oxygen usually generates green lights, but lower energy oxygen collisions or nitrogen atoms can create red glows.

Published September 30, 2011

Facing Shangri-La

Image courtesy Caltech/SSI/NASA

Saturn's moon Titan seems to be trying on the planet's rings in a newly released picture taken by NASA's Cassini orbiter. The view shows a dark region on the moon dubbed Shangri-La, east of the landing site of the Huygens probe.

Cassini delivered Huygens to Titan late in 2004, and the probe landed in January 2005. During its descent and landing, the spacecraft sent back about four hours' worth of data, including pictures of the pebble-strewn landscape hidden below the moon's thick atmosphere.

Published September 30, 2011

Galaxy Blowing Bubbles

Image courtesy ESA/NASA

Pink bubbles of glowing gas punctuate the irregularly shaped dwarf galaxy Holmberg II in a newly released picture from the NASA/ESA Hubble Space Telescope. The bubbles formed when very massive stars died as supernovae, blowing out and heating material with violent shock waves.

The small galaxy is a patchwork of dense star-forming regions and barren areas that can stretch thousands of light-years across. The galaxy's diffuse nature means that delicate structures such as these bubbles don't often get deformed by gravitational interactions.

Published September 30, 2011

Arctic Fogbow

Photograph by Paul Souders, Barcroft/Fame Pictures

While yachting off the coast of Svalbard, Norway, photographer Paul Souders snapped this picture of a fogbow, a rainbow-like phenomenon that appears when sunlight is refracted—or bent—through fog droplets.

Water droplets in rain are large enough to act like prisms, bending sunlight to produce the well-defined bands of color in rainbows. But the much smaller droplets in fog scatter light more, producing almost white bows sometimes tinged with faint color.

Published September 30, 2011

Sizing Up a Super-Earth

Illustration by R. Hurt, Caltech/NASA

An artist's rendering shows the differences between Earth (left) and a so-called super-Earth, the planet 55 Cancri e. Discovered in 2004, this alien world orbits closer to its star then Mercury does to the sun, finishing a year in less than 18 hours.

Previous data had suggested that 55 Cancri e is a dense, rocky world, based on its measured size and mass. But new observations with NASA's Spitzer Space Telescope show that the planet is larger than thought—about twice the size of Earth—with a mass 7.8 times that of our world.

These findings hint that the hot planet has a lower density, with a fifth of its mass coming from lighter materials, including water.

Published September 30, 2011