December 7, 2012

The Bubble Nebula

Blown by the wind from a massive star, this interstellar apparition has a surprisingly familiar shape. Cataloged as NGC 7635, it is also known simply as The Bubble Nebula. Although it looks delicate, the 10 light-year diameter bubble offers evidence of violent processes at work. Above and right of the Bubble's center is a hot, O star, several hundred thousand times more luminous and around 45 times more massive than the Sun. A fierce stellar wind and intense radiation from that star has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud. The intriguing Bubble Nebula lies a mere 11,000 light-years away toward the boastful constellation Cassiopeia. This view of the cosmic bubble is composed of narrowband and broadband image data, capturing details in the emission region while recording a natural looking field of stars.

Image Credit & Copyright: Yves Van den Broek
Explanation from:

Eclipsed Moon

Cody, Wyoming, USA
June 4, 2012

Image Credit & Copyright: Mack H. Frost

December 6, 2012

An Iridescent Cloud over Colorado

Why would a cloud appear to be different colors? A relatively rare phenomenon known as iridescent clouds can show unusual colors vividly or a whole spectrum of colors simultaneously. These clouds are formed of small water droplets of nearly uniform size. When the Sun is in the right position and mostly hidden by thick clouds, these thinner clouds significantly diffract sunlight in a nearly coherent manner, with different colors being deflected by different amounts. Therefore, different colors will come to the observer from slightly different directions. Many clouds start with uniform regions that could show iridescence but quickly become too thick, too mixed, or too far from the Sun to exhibit striking colors. This iridescent cloud was photographed above Boulder, Colorado in November 2007.

Image Credit & Copyright: August Allen
Explanation from:

December 5, 2012

Earth at Night

This new global view of Earth's city lights is a composite assembled from data acquired by the Suomi National Polar-orbiting Partnership (NPP) satellite. The data was acquired over nine days in April 2012 and 13 days in October 2012. It took 312 orbits to get a clear shot of every parcel of Earth's land surface and islands. This new data was then mapped over existing Blue Marble imagery of Earth to provide a realistic view of the planet.

The image was made possible by the satellite's "day-night band" of the Visible Infrared Imaging Radiometer Suite, which detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe dim signals such as city lights, gas flares, auroras, wildfires and reflected moonlight.

The day-night band observed Hurricane Sandy, illuminated by moonlight, making landfall over New Jersey on the evening of October 29. Night images showed the widespread power outages that left millions in darkness in the wake of the storm. 

Image Credit: NASA's Earth Observatory/NOAA/DOD
Explanation from:

Comet Lovejoy over Paranal

Comet Lovejoy Paranal

Seen here before sunrise from Paranal Observatory in Chile, the sungrazing comet's tails stretch far above the eastern horizon. Spanning over 20 degrees they rise alongside the plane of the our Milky Way Galaxy. A breathtaking spectacle in itself, Lovejoy performs on this celestial stage with southern stars and nebulae, including the Large and Small Magellanic clouds right of the telescope dome, and the glow of zodiacal light along the left edge of the frame. With Paranal's Very Large Telescope units in the foreground, this wide-angle scene was captured on December 23, 2011.

Image Credit & Copyright: Guillaume Blanchard
Explanation from:

December 3, 2012

The Umbra of Earth

The dark, inner shadow of planet Earth is called the umbra. Shaped like a cone extending into space, it has a circular cross section most easily seen during a lunar eclipse. For example in December 2011 the Full Moon slid across the southern half of Earth's umbral shadow, entertaining moonwatchers around much of the planet. In the total phase of the eclipse, the Moon was completely within the umbra for 51 minutes. Recorded from Beijing, China, this composite eclipse image uses successive pictures from totality (center) and partial phases to trace out a large part of the umbra's curved edge. Background stars are visible in the darker eclipse phases. The result shows the relative size of the shadow's cross section at the distance of the Moon, as well as the Moon's path through Earth's umbra.

Image Credit & Copyright: Wang, Letian
Explanation from: