NATIONAL GEOGRAPHIC'S BEST SPACE PICTURES THIS WEEK XL

Week's Best Space Pictures: Saturn's Rings Go Dark, X-Rays Burst, and a Skyline Burns
By Jane J. Lee, National Geographic News, 23 December 2014.

Cassini views Saturn's rings in a different light, x-rays flare from the sun, and a city's skyline stands out against a fiery sunset in this week's best space pictures.

1. Solar Marble

High-energy x-rays burst from the sun in this image taken by NASA's Solar Dynamics Observatory and the Nuclear Spectroscopic Telescope Array.

The x-rays are courtesy of gas heated to over 3 million degrees Fahrenheit (1.6 million degrees Celsius). The sun's magnetic field guides the path of the resulting energy streams into loops and swirls. (Learn more about the image in "NuSTAR Stares at a New Star.")

2. Iridescent Bedrock

Weathering of Elorza Crater on Mars exposes the planet's bedrock, and what a shiny exposure it is. The deposits are most likely a form of opaline silica. On Earth, this material is used in a number of ways, including in ceramics, as a component in filters, and even to make kitty litter.

3. A New View

This infrared image of the Flame Nebula (centre) and its surroundings showcases a familiar sight in a new light. The Horsehead Nebula, usually spied using visible light, appears in this case as a wispy, orange-brown arc rising from the green cloud on the right.

The Flame Nebula sits about 1,200 light-years away from Earth within the constellation Orion. The smaller glowing blob between the Flame and the Horsehead is a third nebula, NGC 2023.

4. In the Dark

Saturn's famed rings are usually quite dimly lit, as evidenced by this image taken by the Cassini spacecraft. The rings scatter light back to its source - in this case, the sun - and away from the camera.

Thus, when researchers avoid overexposing images of Saturn, the planet's main rings appear shrouded in darkness. But in this case, a dim image is a good thing, because the way in which the rings scatter light can tell astronomers a lot about the particles they contain. (See pictures of huge "snowballs" mucking about in Saturn's rings.)

5. Diamonds in the Sky

Several hot young things shine brightly in the cluster known as Messier 47. The stars' light blue colour indicates a higher temperature compared with the reddish-brown stars in the foreground, which are cooler.

Messier 47 is about 1,600 light-years away and relatively young - at 78 million years old - compared with its sister cluster Messier 46, which is around 300 million years old. (See "New Image of Blue Diamond Cluster Is a Cosmic Showpiece.")

6. Fiery Skyline

The setting sun fires the sky behind St. Michael's Cathedral (double towers on right) in Veszprém, Hungary. The photographer caught the brilliant colours on film on the winter solstice.

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