December 29, 2012

Volcano and Aurora in Iceland


Sometimes both heaven and Earth erupt. In Iceland in 1991, the volcano Hekla erupted at the same time that auroras were visible overhead. Hekla, one of the most famous volcanoes in the world, has erupted at least 20 times over the past millennium, sometimes causing great destruction. The last eruption occurred only twelve years ago but caused only minor damage. The green auroral band occurred fortuitously about 100 kilometers above the erupting lava.

Image Credit & Copyright: Sigurdur H. Stefnisson
Explanation from: http://apod.nasa.gov/apod/ap120708.html

Otherworldly Planet Rise


What would a sunrise look like on another world? So far, humanity has only recorded sunrises on Mars and Earth, but it is fun to wonder what they would look like on planets known and yet unknown. Planets far from their parent star would record the rise of an unusually bright point of light rather than a round orb. Although this might appear to be what is on this picture, the careful combination of long exposures and creative lighting is actually based on Venus-rise from planet Earth, captured through Mesa Arch in Canyonlands National Park, Utah, USA. Picturesque buttes and mesas dot the background landscape. The orange sky is created by air scattering and dust, but is likely reminiscent of dusty skyscapes on Mars.

Image Credit & Copyright: Robert Arn
Explanation from: http://apod.nasa.gov/apod/ap110411.html

December 28, 2012

Milky Way above Easter Island

Milky Way Galaxy - Easter Island

Why were the statues on Easter Island built? No one is sure. What is sure is that over 800 large stone statues exist there. The Easter Island statues, stand, on the average, over twice as tall as a person and have over 200 times as much mass. Few specifics are known about the history or meaning of the unusual statues, but many believe that they were created about 500 years ago in the images of local leaders of a lost civilization. In this picture, some of the stone giants were illuminated in 2009 under the central band of our Milky Way Galaxy.

Image Credit & Copyright: Manel Soria
Explanation from: http://apod.nasa.gov/apod/ap120618.html

A Quadruple Lunar Halo over Spain


Sometimes falling ice crystals make the atmosphere into a giant lens causing arcs and halos to appear around the Sun or Moon. Near Madrid, Spain, where a winter sky displayed not only a bright Moon but as many as four rare lunar halos. The brightest object, near the top of the above image, is the Moon. Light from the Moon refracts through tumbling hexagonal ice crystals into a 22 degree halo seen surrounding the Moon. Elongating the 22 degree arc horizontally is a circumscribed halo caused by column ice crystals. More rare, some moonlight refracts through more distant tumbling ice crystals to form a (third) rainbow-like arc 46 degrees from the Moon and appearing here just above a picturesque winter landscape. Furthermore, part of a whole 46 degree circular halo is also visible, so that an extremely rare - especially for the Moon - quadruple halo was actually imaged. The snow-capped trees in the foreground line the road Puerto de Navacerrada in the Sierra de Guadarrama mountain range near Madrid. Far in the background is a famous winter skyscape that includes Sirius, the belt of Orion, and Betelgeuse all visible between the inner and outer arcs. Halos and arcs typically last for minutes to hours, so if you do see one there should be time to invite family, friends or neighbors to share your unusual lensed vista of the sky.

Image Credit & Copyright: Dani Caxete
Explanation from: http://apod.nasa.gov/apod/ap121203.html

December 27, 2012

Ash and Lightning above an Icelandic Volcano


Why did the picturesque 2010 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 2010 March 20, with a second eruption starting under the center of a small glacier on 2010 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. In this picture during the second eruption, lightning bolts illuminate ash pouring out of the Eyjafjallajökull volcano.

Image Credit & Copyright: Sigurður Stefnisson
Explanation from: http://apod.nasa.gov/apod/ap120730.html

December 26, 2012

Sarychev Peak Eruption seen from the International Space Station

Sarychev Peak Eruption

A fortuitous orbit of the International Space Station allowed the astronauts this striking view of Sarychev Volcano (Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Sarychev Peak is one of the most active volcanoes in the Kuril Island chain, and it is located on the northwestern end of Matua Island. Prior to June 12, the last explosive eruption occurred in 1989, with eruptions in 1986, 1976, 1954, and 1946 also producing lava flows. Ash from the multi-day eruption has been detected 2,407 kilometers east-southeast and 926 kilometers west-northwest of the volcano, and commercial airline flights are being diverted away from the region to minimize the danger of engine failures from ash intake.

This detailed astronaut photograph is exciting to volcanologists because it captures several phenomena that occur during the earliest stages of an explosive volcanic eruption. The main column is one of a series of plumes that rose above Matua Island on June 12. The plume appears to be a combination of brown ash and white steam. The vigorously rising plume gives the steam a bubble-like appearance.

In contrast, the smooth white cloud on top may be water condensation that resulted from rapid rising and cooling of the air mass above the ash column. This cloud, which meteorologists call a pileus cloud, is probably a transient feature: the eruption plume is starting to punch through. The structure also indicates that little to no shearing wind was present at the time to disrupt the plume. (Satellite images acquired 2-3 days after the start of activity illustrate the effect of shearing winds on the spread of the ash plumes across the Pacific Ocean.)

By contrast, a cloud of denser, gray ash—probably a pyroclastic flow—appears to be hugging the ground, descending from the volcano summit. The rising eruption plume casts a shadow to the northwest of the island (image top). Brown ash at a lower altitude of the atmosphere spreads out above the ground at image lower left. Low-level stratus clouds approach Matua Island from the east, wrapping around the lower slopes of the volcano. Only about 1.5 kilometers of the coastline of Matua Island (image lower center) are visible beneath the clouds and ash.

Image Credit: NASA
Explanation from: http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=38985

December 25, 2012

Aurora and Geminid Meteor over Kirkjufell


Kirkjufell, Iceland
December 15, 2012

Image Credit & Copyright: David Clapp

Geminids over Kitt Peak

Geminids over Kitt Peak

Two large telescope domes stand in the foreground of this night sky view from Kitt Peak National Observatory, near Tucson, Arizona, USA. The dramatic scene was recorded in 2010 near the peak of December's Geminid Meteor Shower. With dome slit open, the building closest to the camera houses the 2.3 Meter (90 inch) Bok Telescope operated by Steward Observatory, University of Arizona. Behind the Bok is the Mayall 4 Meter telescope dome. Of course, no telescopes were needed to enjoy the meteors streaking through the sky! The composite image consists of 13 exposures each 15 seconds long, taken with a wide angle lens over a period of about 2 hours during Kitt Peak's warm, clear, night. An annual celestial event, this meteor shower is the result of planet Earth plowing through dust from mysterious, asteroid-like object 3200 Phaethon.

Image Credit & Copyright: David A. Harvey
Explanation from: http://apod.nasa.gov/apod/ap101216.html

On the road to Carina


This rugged road through the dark Atacama Desert seems to lead skyward toward the bright stars and glowing nebulae of the southern Milky Way. If you follow the road you will get to Cerro Armazones peak in Chile, future construction site for the 40-meter class European Extremely Large Telescope. The scene is dominated by the reddish glow of the Carina Nebula, one of our galaxy's largest star forming regions. In fact, the remarkable skyscape is not a composite of varying exposures or a photomontage. Far from sources of light pollution, the landscape illuminated by starlight and the Milky Way above were recorded by a modified digital camera and fast lens. The sensitive system captured both planet Earth and deep sky in a relatively short exposure.

Image Credit & Copyright: Babak Tafreshi
Explanation from: http://apod.nasa.gov/apod/ap120218.html

December 24, 2012

Earthrise - 24 December 1968


The rising Earth is about five degrees above the lunar horizon in this telephoto view taken from the Apollo 8 spacecraft near 110 degrees east longitude. The horizon, about 570 kilometers (350 statute miles) from the spacecraft, is near the eastern limb of the moon as viewed from Earth. Width of the view at the horizon is about 150 kilometers (95 statute miles). On Earth 240,000 statute miles away the sunset terminator crosses Africa. The crew took the photo around 10:40 a.m. Houston time on the morning of December 24, and that would make it 15:40 GMT on the same day. The South Pole is in the white area near the left end of the terminator. North and South America are under the clouds.

Image Credit: NASA
Explanation from: http://spaceflight.nasa.gov/gallery/images/apollo/apollo8/html/as08-14-2383.html

Gas Pillars in the Eagle Nebula (M16): Pillars of Creation in a Star-Forming Region


Undersea corral? Enchanted castles? Space serpents? These eerie, dark pillar-like structures are actually columns of cool interstellar hydrogen gas and dust that are also incubators for new stars. The pillars protrude from the interior wall of a dark molecular cloud like stalagmites from the floor of a cavern. They are part of the "Eagle Nebula" (also called M16 — the 16th object in Charles Messier's 18th century catalog of "fuzzy" objects that aren't comets), a nearby star-forming region 6,500 light-years away in the constellation Serpens.

The pillars are in some ways akin to buttes in the desert, where basalt and other dense rock have protected a region from erosion, while the surrounding landscape has been worn away over millennia. In this celestial case, it is especially dense clouds of molecular hydrogen gas (two atoms of hydrogen in each molecule) and dust that have survived longer than their surroundings in the face of a flood of ultraviolet light from hot, massive newborn stars (off the top edge of the picture). This process is called "photoevaporation. "This ultraviolet light is also responsible for illuminating the convoluted surfaces of the columns and the ghostly streamers of gas boiling away from their surfaces, producing the dramatic visual effects that highlight the three-dimensional nature of the clouds. The tallest pillar (left) is about about 4 light-years long from base to tip.

As the pillars themselves are slowly eroded away by the ultraviolet light, small globules of even denser gas buried within the pillars are uncovered. These globules have been dubbed "EGGs." EGGs is an acronym for "Evaporating Gaseous Globules," but it is also a word that describes what these objects are. Forming inside at least some of the EGGs are embryonic stars — stars that abruptly stop growing when the EGGs are uncovered and they are separated from the larger reservoir of gas from which they were drawing mass. Eventually, the stars themselves emerge from the EGGs as the EGGs themselves succumb to photoevaporation.

The picture was taken on April 1, 1995 with the Hubble Space Telescope Wide Field and Planetary Camera 2. The color image is constructed from three separate images taken in the light of emission from different types of atoms. Red shows emission from singly-ionized sulfur atoms. Green shows emission from hydrogen. Blue shows light emitted by doubly- ionized oxygen atoms.

Image Credit: NASA, ESA, STScI, J. Hester and P. Scowen
Explanation from: http://hubblesite.org/newscenter/archive/releases/1995/44/image/a/