http://antwrp.gsfc.nasa.gov/apod/ap061118.html
Sunday, November 19, 2006
Leonids and Leica
http://antwrp.gsfc.nasa.gov/apod/ap061118.html
Monday, October 23, 2006
Star EGGs in the Eagle Nebula
http://antwrp.gsfc.nasa.gov/apod/ap061022.html
Friday, October 06, 2006
Hidden Galaxy IC 342
http://antwrp.gsfc.nasa.gov/apod/ap061005.html
Orbiting a Red Dwarf Star
http://www.nasa.gov/multimedia/imagegallery/image_feature_671.html
Thursday, October 05, 2006
An Unwelcome Place for New Stars
The blue color here represents radiation pouring out from material very close to the black hole. The grayish structure surrounding the black hole, called a torus, is made up of gas and dust. Beyond the torus, only the old red-colored stars that make up the galaxy can be seen. There are no new stars in the galaxy.
http://www.nasa.gov/multimedia/imagegallery/image_feature_670.html
Comet SWAN Brightens
http://antwrp.gsfc.nasa.gov/apod/ap061004.html
Tuesday, October 03, 2006
Light from the Heart Nebula
http://antwrp.gsfc.nasa.gov/apod/ap061003.html
NASA Observes the Antarctic Ozone Hole
When daylight returns to the South Pole after the total darkness of the polar winter, it sets off a series of chemical reactions that destroy ozone in the stratosphere. As spring progresses in the Southern Hemisphere, NASA satellites observe the resulting development of the Antarctic “ozone hole,” an area of exceptionally low concentrations of stratospheric ozone. The hole begins to develop in mid-August each year and peaks in late September or early October. As summer approaches, weather conditions become less favorable for the ozone-destroying reactions, and the ozone layer stabilizes until the next spring.
This image from September 29, 2006, shows the ozone concentration in the stratosphere above the South Pole observed by the Ozone Monitoring Instrument on NASA’s Aura satellite. Greens and yellows show areas with the highest ozone amounts, while blues and purples show where ozone amounts are lowest. A purple veil of extremely low levels of ozone stretches across most of Antarctica, which is roughly centered in the image.
Scientists generally use Dobson Units to describe ozone concentrations. Ozone in the atmosphere isn’t packed into a single layer at a certain altitude above the Earth’s surface; it’s dispersed. The Dobson Unit describes how much ozone there would be in a column of the atmosphere if all the molecules were squeezed into a single layer. One Dobson Unit is the number of molecules of ozone that would be required to create a layer of pure ozone 0.01 millimeters thick at a temperature of 0 degrees Celsius and a pressure of 1 atmosphere (the air pressure at the surface of the Earth).
The average amount of ozone in the atmosphere is roughly 300 Dobson Units, equivalent to a layer 3 millimeters (0.12 inches) thick—the height of 2 pennies stacked together. Any place where the concentration drops below 220 Dobson Units is considered part of the ozone hole. Average ozone concentrations in the ozone hole are around 100 Dobson Units—about the height of a dime. Stratospheric ozone absorbs ultraviolet (UV) light that can be dangerous to living things. A thinner ozone layer increases humans’ and other creatures’ exposure to harmful UV light.
NASA measurements made by aircraft- and ground-based sensors in the 1980s provided much of our initial understanding of the extent of the ozone hole and its link to the chemicals known as chlorofluorocarbons (CFCs), which human activities were releasing into the atmosphere. In 1987, the Montreal Protocol banned the worst of the ozone-destroying chemicals. Today, NASA scientists are using the latest tools—including satellite observations and computer models of atmospheric chemistry and weather—to determine what effect the ban on CFCs and related chemicals has had and how long we will have to wait for a full ozone layer recovery. NASA shares the latest information and satellite images of the ozone hole with the public on its Ozone Watch Website.
NASA image provided by the Ozone Hole Watch Website.
Friday, September 29, 2006
What's Old is New in the Large Magellanic Cloud
This vibrant image from NASA's Spitzer Space Telescope shows the Large Magellanic Cloud, a satellite galaxy to our own Milky Way galaxy. The Large Magellanic Cloud, located 160,000 light-years from Earth, is one of a handful of dwarf galaxies that orbit the Milky Way.
The infrared image offers astronomers a unique chance to study the lifecycle of stars and dust in a single galaxy. Nearly one million objects are revealed for the first time in this Spitzer view, which represents about a 1,000-fold improvement in sensitivity over previous space-based missions. Most of the new objects are dusty stars of various ages populating the Large Magellanic Cloud; the rest are thought to be background galaxies.
The blue color in the picture, seen most prominently in the central bar, represents starlight from older stars. The chaotic, bright regions outside this bar are filled with hot, massive stars buried in thick blankets of dust. The red color around these bright regions is from dust heated by stars, while the red dots scattered throughout the picture are either dusty, old stars or more distant galaxies. The greenish clouds contain cooler interstellar gas and molecular-sized dust grains illuminated by ambient starlight.
Astronomers say this image allows them to quantify the process by which space dust -- the same stuff that makes up planets and even people -- is recycled in a galaxy. The picture shows dust at its three main cosmic hangouts: around the young stars, where it is being consumed (red-tinted, bright clouds); scattered about in the space between stars (greenish clouds); and in expelled shells of material from old stars (randomly-spaced red dots).
http://www.nasa.gov/multimedia/imagegallery/image_feature_666.html
RCW 86: Historical Supernova Remnant
http://antwrp.gsfc.nasa.gov/apod/ap060928.html
Sunday, September 24, 2006
NGC 1499: The California Nebula
http://antwrp.gsfc.nasa.gov/apod/ap060924.html