NATIONAL GEOGRAPHIC'S SPACE PICTURES THIS WEEK XXXIX

Space Pictures This Week: Lunar Gravity, Venusian Volcano
By National Geographic News, 6 December 2012.

1. Cassiopeia’s Bubble

A new camera called the One Degree Imager, located at Kitt Peak National Observatory in Arizona, is responsible for this enticingly crisp image of the Bubble Nebula. Released on December 4, this close-up highlights the sphere of gas blown out by the nebula's central star, which is 45 times larger than our own sun.

Located in the constellation Cassiopeia, the Bubble Nebula is ten light-years across. Intense radiation from the massive star causes the otherworldly glow that lights up what looks like a celestial soap bubble.

(Related: "Amazing Hubble Images.")

2. Midnight Light

Delicate green auroras light up the water at Buksnesfjord, Norway, in a picture taken just after midnight on December 4.

(See pictures of auroras sparked by a massive solar flare.)

3. Great Escape

Sheets of plasma - or superheated gas - break off from the surface of the sun in this image taken in extreme ultraviolet light. Before floating free, the plasma rose up and danced along pathways determined by magnetic fields. These unseen forces pushed and pulled the gas into contorted shapes.

(Learn about the sun.)

4. New Look

What looks like a jawbreaker is actually a gravity map of the moon. Red areas indicate places with higher gravity fields while blue areas indicate lower gravity fields.

(Learn about lunar exploration.)

Twin probes circling the moon - part of NASA's GRAIL mission - since 2011 have been recording changes in gravity as they fly over peaks and valleys on the lunar surface. As one probe flies over an area with a greater gravity field, the washing-machine-size instrument speeds up slightly, increasing the distance between it and its sister probe. These minute changes in position have enabled scientists to construct this very detailed view of local changes in the moon's gravity.

(How well do you know your moon myths? Take our quiz.)

5. Grainy Picture

In this artist's conception of fine-grained particles around a brown dwarf - or a failed star - bits of debris are on their way to becoming a rocky planet.

Current thinking on Earth-like, rocky planet formation says that random collisions between tiny debris occur in the disc of material surrounding new-born stars. But the recent discovery of such a disc surrounding a brown dwarf has some astronomers rethinking that hypothesis. If planets can form from the debris around these failed stars, then rocky planets may be much more common than previously thought.

(Related: "Coldest Star Found-No Hotter Than Fresh Coffee.")

6. Night Vision

The Suomi NPP satellite captured this night-time image of the aurora australis over the Antarctic coast south of South Africa. Despite the winter darkness and a waning crescent moon, the auroras produced enough light for sensors on board the new NASA and National Oceanic and Atmospheric Administration satellite to capture the boundary between the ice shelf and what some scientists call the Southern, or Antarctic, Ocean (dark line across the bright centre swirl).

Launched last year, Suomi NPP enables scientists to capture night-time images of the Earth's atmosphere and surface. The new sensor is so sensitive, it can capture the lights from one ship at sea.

(Learn about Antarctica.)

7. Pearl Islands

In NASA's Landsat 5 satellite image, the Mergui Archipelago shows off the vibrant greens of its rain forests and the brilliant blues of the surrounding tropical ocean. Located along the southern border of Myanmar (Burma), next to Thailand, the area is known for valuable pearl oysters (Pinctada maxima) and a highly diverse concentration of plants and animals.

(See photos of Myanmar.)

8. Venusian Volcano

The Venusian atmosphere is made mostly of carbon dioxide, along with periodic spikes in sulphur. Recent research has found that volcanoes on the planet's surface, seen here in an artist's conception, are likely injecting that sulphur into the upper atmosphere. Direct confirmation is difficult, however, since Venus's thick atmosphere precludes a peek at its peaks.

Top image: Maps of the moon showing gravity anomalies measured by NASA's GRAIL mission (source).

[Source: National Geographic News. Edited. Top image added.]