NATIONAL GEOGRAPHIC'S BEST SPACE PICTURES THIS WEEK XXI

Week's Best Space Pictures: Meteors Shower, Sweden Burns, and Rosetta Orbits
By Jane J. Lee, National Geographic News, 15 August 2014.

The Perseids compete with a supermoon, a Swedish forest goes up in smoke, and the Rosetta spacecraft orbits a comet.

1. Early Morning Shower

A multiple exposure highlights the Perseid meteor shower in the early morning hours of August 12.

The image, taken in the mountains north of Madrid, shows the dust and debris from the Swift-Tuttle comet streaming through Earth's atmosphere. Our planet passes through this debris field every summer, making the Perseids one of the most reliable night sky events of the year. (See "Google Doodle Honours 2014 Perseid Meteor Shower.")

2. Wonky Galaxies

NASA's Hubble Space Telescope highlights three galaxies shining against the matte black of space. The image, released August 14, shows two galaxies on the left that are irregularly shaped with diffuse halos. The shape of the galaxy on the right - a side-on view of a spiral - is  more typical. (See "Fossil Galaxy Provides a Window Into the Early Universe.")

3. Swedish Fire

NASA's satellite Landsat 8 captured Sweden's biggest wildfire in 40 years in an image released August 9.

Wildfires aren't common in Sweden, but near-record heat and dry weather during July and August primed the country's forests to burn. Similar conditions have set the stage for an active fire season on the U.S. West Coast this year. (See "Your Shot Pictures: Wildfires From the Front Lines.")

4. Birth of a Supernova

Supernovae produce many of the elements that make up planets and stars and help astronomers calculate the rate of expansion of the universe. The supernova imaged above is called Type Ia, which researchers think involve the detonation of a white dwarf star.

The question, though, is how those white dwarfs ignite to produce a Type Ia explosion. New observations from the Chandra X-ray Observatory suggest that these supernovae are a result of a fusion between two white dwarfs.

5. Rosetta's Comet

The European Space Agency's Rosetta pulled into orbit around the 67P/Churyumov-Gerasimenko comet on August 6 and has started beaming back data. It took ten years for the spacecraft to reach its destination.

The image pictured above, released August 14, shows the upper body (top) of the comet, the neck (middle), and the body (bottom). Rosetta's mission is to study this comet up close and eventually to land on the celestial object.

Rosetta will then drill into the comet to determine its composition and track how the comet changes as it passes our sun. (See "Spacecraft Arrives at Stunning Comet.")

6. Northern Erosion

NASA's Mars Reconnaissance Orbiter captured this image of a 348-mile (560-kilometre) valley - named Chasma Boreale - which cuts across Mars's north pole.

The picture, released August 13, shows layers of sediment and slumping depressions where unknown elements eroded away part of the red planet's surface.

[Source: National Geographic News. Edited.]