October 27, 2012

Aurora over White Dome Geyser

Aurora White Dome Geyser

Sometimes both heaven and Earth erupt. Colorful aurorae erupted unexpectedly earlier October 2012, with green aurora appearing near the horizon and brilliant bands of red aurora blooming high overhead. A bright Moon lit the foreground of this picturesque scene, while familiar stars could be seen far in the distance. With planning, the careful astrophotographer shot this image mosaic in the field of White Dome Geyser in Yellowstone National Park in the western USA. Sure enough, just after midnight, White Dome erupted -- spraying a stream of water and vapor many meters into the air. Geyser water is heated to steam by scalding magma several kilometers below, and rises through rock cracks to the surface. About half of all known geysers occur in Yellowstone National Park. Although the geomagnetic storm that created these aurorae has since subsided, eruptions of White Dome Geyser continue about every 30 minutes.

Image Credit & Copyright: Robert Howell
Explanation from: http://apod.nasa.gov/apod/ap121017.html

Tornado and Rainbow over Kansas

Tornado and Rainbow

The scene might have been considered serene if it weren't for the tornado. During 2004 in Kansas, storm chaser Eric Nguyen photographed this budding twister in a different light - the light of a rainbow. On this picture, a white tornado cloud descends from a dark storm cloud. The Sun, peeking through a clear patch of sky to the left, illuminates some buildings in the foreground. Sunlight reflects off raindrops to form a rainbow. By coincidence, the tornado appears to end right over the rainbow. Streaks in the image are hail being swept about by the high swirling winds. Over 1,000 tornadoes, the most violent type of storm known, occur on Earth every year, many in tornado alley.

Image Credit & Copyright: Eric Nguyen
Explanation from: http://apod.nasa.gov/apod/ap110814.html

October 24, 2012

Fire in the Sky and on the Ground


Astronauts on the International Space Station (ISS) used a digital camera to capture several hundred photographs of the aurora australis, or “southern lights,” while passing over the Indian Ocean on September 17, 2011. If you click on the movie linked above, you can see the flowing ribbons and rays below as the ISS passed from south of Madagascar to just north of Australia between 17:22 and 17:45 Universal Time. Solar panels and other sections of the ISS fill some of the upper right side of the photograph.

Auroras are a spectacular sign that our planet is electrically and magnetically connected to the Sun. These light shows are provoked by energy from the Sun and fueled by electrically charged particles trapped in Earth’s magnetic field, or magnetosphere. In this case, the space around Earth was stirred up by an explosion of hot, ionized gas from the Sun—a coronal mass ejection—that left the Sun on September 14, 2011.

The pressure and magnetic energy of the solar plasma stretches and twists the magnetic field of Earth like rubber bands, particularly in the tail on the night side. This energizes the particles trapped in our magnetic field; that energy is released suddenly as the field lines snap the particles down the field lines toward the north and south magnetic poles.

Fast-moving electrons collide with Earth’s upper atmosphere, transferring their energy to oxygen and nitrogen molecules and making them chemically “excited.” As the gases return to their normal state, they emit photons, small bursts of energy in the form of light. The color of light reflects the type of molecules releasing it; oxygen molecules and atoms tend to glow green, white or red, while nitrogen tends to be blue or purple. This ghostly light originates at altitudes of 100 to 400 kilometers (60 to 250 miles).

Image Credit: NASA
Explanation from: http://earthobservatory.nasa.gov/IOTD/view.php?id=52287

October 22, 2012

Comet between Fireworks and Lightning


Sometimes the sky itself is the best show in town. In January 2007, people from Perth, Australia gathered on a local beach to watch a sky light up with delights near and far. Nearby, fireworks exploded as part of Australia Day celebrations. On the far right, lightning from a thunderstorm flashed in the distance. Near the image center, though, seen through clouds, was the most unusual sight of all: Comet McNaught. The photogenic comet was so bright that it even remained visible though the din of Earthly flashes. Comet McNaught has now returned to the outer Solar System and is now only visible with a large telescope. This image is actually a three photograph panorama digitally processed to reduce red reflections from the exploding firework.

Image Credit & Copyright: Antti Kemppainen
Explanation from: http://apod.nasa.gov/apod/ap110529.html