October 20, 2012

Tungurahua Erupts

Tungurahua Volcano Eruption

Volcano Tungurahua sometimes erupts spectacularly. On this picture, molten rock so hot it glows visibly pours down the sides of the 5,000-meter high Tungurahua, while a cloud of dark ash is seen being ejected toward the left. Wispy white clouds flow around the lava-lit peak, while a star-lit sky shines in the distance. This image was captured in 2006 as ash fell around the adventurous photographer. Located in Ecuador, Tungurahua has become active roughly every 90 years for the last 1,300 years.

Image Credit & Copyright: Patrick Taschler
Explanation from: http://apod.nasa.gov/apod/ap120402.html

October 19, 2012

Saguaro Moon


A Full Moon rising can be a dramatic celestial sight, and Full Moons can have many names. For example, this Full Moon, the one nearest the autumnal equinox in the northern hemisphere, is popularly called the Harvest Moon. According to lore the name is a fitting one because farmers could work late into the night at the end of the growing season harvesting crops by moonlight. In the same traditions, the Full Moon following the Harvest Moon is the Hunter's Moon. But, recorded on a trip to the American southwest, this contribution to compelling images of moonrise is appropriately titled Saguaro Moon.

Image Credit & Copyright: Stefan Seip
Explanation from: http://apod.nasa.gov/apod/ap070926.html

October 16, 2012

A Pileus Iridescent Cloud over Ethiopia


Yes, but how many dark clouds have a multicolored lining? Pictured, behind this darker cloud, is a pileus iridescent cloud, a group of water droplets that have a uniformly similar size and so together diffract different colors of sunlight by different amounts. This image was taken just after the picturesque sight was noticed by chance by a photographer in Ethiopia. A more detailed picture of the same cloud shows not only many colors, but unusual dark and wavy bands whose origins are thought related to wave disturbances in the cloud.

Image Credit & Copyright: Esther Havens
Explanation from: http://apod.nasa.gov/apod/ap110824.html

October 15, 2012

A Sonic Boom

sonic boom plane

Is this what a sonic boom looks like? When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane. When this shock wave passes, a listener hears all at once the sound emitted over a longer period: a sonic boom. As a plane accelerates to just break the sound barrier, however, an unusual cloud might form. The origin of this cloud is still debated. A leading theory is that a drop in air pressure at the plane described by the Prandtl-Glauert Singularity occurs so that moist air condenses there to form water droplets. This, an F/A-18 Hornet was photographed just as it broke the sound barrier. Large meteors and the space shuttle frequently produce audible sonic booms before they are slowed below sound speed by the Earth's atmosphere.

Image Credit: Ensign John Gay, USS Constellation, US Navy
Explanation from: http://apod.nasa.gov/apod/ap070819.html

October 14, 2012

Ash and Lightning above Eyjafjallajökull Volcano


Why did the volcanic eruption in Iceland create so much ash? Although the large ash plume was not unparalleled in its abundance, its location was particularly noticeable because it drifted across such well populated areas. The Eyjafjallajökull volcano in southern Iceland began erupting on March 20, 2010, with a second eruption starting under the center of a small glacier on April 14. Neither eruption was unusually powerful. The second eruption, however, melted a large amount of glacial ice which then cooled and fragmented lava into gritty glass particles that were carried up with the rising volcanic plume. On this picture, lightning bolts illuminate ash pouring out of the Eyjafjallajökull volcano.

Image Credit & Copyright: Marco Fulle
Explanation from: http://apod.nasa.gov/apod/ap100419.html