Sunday, November 19, 2006

Leonids and Leica

This lovely view from northern Spain at Cape Creus on the easternmost point of the Iberian peninsula, looks out across the Mediteranean and up into the stream of the 2002 Leonid meteor shower. The picture is a composite of thirty separate one minute exposures taken through a fisheye lens. Over 70 leonid meteors are visible, some seen nearly head on. Bright Jupiter is positioned just to the right of the shower's radiant in Leo. Perched on the moonlit rocks at the bottom right, Leica, the photographers' dog, seems to be watching the on going celestial display and adds a surreal visual element to the scene. The 2006 Leonid meteor shower will be much less intense than in 2002, but will be near its predicted peak this weekend. Sky watchers will have their best view under dark skies in early morning hours with Leo rising above the eastern horizon.

http://antwrp.gsfc.nasa.gov/apod/ap061118.html

Monday, October 23, 2006

Star EGGs in the Eagle Nebula

Where do stars form? One place, star forming regions known as "EGGs", are uncovered at the end of this giant pillar of gas and dust in the Eagle Nebula (M16). EGGs, short for evaporating gaseous globules, are dense regions of mostly molecular hydrogen gas that fragment and gravitationally collapse to form stars. Light from the hottest and brightest of these new stars heats the end of the pillar and causes further evaporation of gas - revealing yet more EGGs and more young stars. This picture was taken by the Wide Field and Planetary Camera on board the Hubble Space Telescope.

http://antwrp.gsfc.nasa.gov/apod/ap061022.html

Friday, October 06, 2006

Hidden Galaxy IC 342


Similar in size to other large, bright spiral galaxies IC 342 is a mere 7 million light-years distant in the long-necked, northern constellation Camelopardalis. A sprawling island universe, IC 342 would otherwise be a prominent galaxy in our night sky, but it is almost hidden from view behind the veil of stars, gas and dust clouds in the plane of our Milky Way galaxy. Even though IC 342's light is dimmed by intervening cosmic clouds, this remarkably sharp telescopic image traces the galaxy's own obscuring dust, blue star clusters, and glowing pink star forming regions along spiral arms that wind far from the galaxy's core. IC 342 may have undergone a recent burst of star formation activity and is close enough to have gravitationally influenced the evolution of the local group of galaxies and the Milky Way.

http://antwrp.gsfc.nasa.gov/apod/ap061005.html

Orbiting a Red Dwarf Star

This artist's concept of a gas giant planet orbiting a red dwarf K star shows a planet has not been directly imaged, but its presence was detected in 2003 microlensing observations of a field star in our galaxy. Gravitational microlensing happens when a foreground star amplifies the light of a background star that momentarily aligns with it. Follow-up observations by Hubble Space Telescope in 2005 separated the light of the slightly offset foreground star from the background star. This allowed the host star to be identified as a red dwarf star located 19,000 light-years away. The Hubble observations allow for the planet's mass to be estimated at 2.6 Jupiter masses. The characteristics of the lensing event show that the planet is in a Jupiter-sized orbit around its parent red star. The rings and moon around the gas giant are hypothetical, but plausible, given the nature of the family of gas giant planets in our solar system.

http://www.nasa.gov/multimedia/imagegallery/image_feature_671.html

Thursday, October 05, 2006

An Unwelcome Place for New Stars

This artist's concept depicts a supermassive black hole at the center of a galaxy. NASA's Galaxy Evolution Explorer found evidence that black holes -- once they grow to a critical size -- stifle the formation of new stars in elliptical galaxies. Black holes are thought to do this by heating up and blasting away the gas that fuels star formation.

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

A newly discovered comet has brightened enough to be visible this week with binoculars. The picturesque comet is already becoming a favored target for northern sky imagers. Pictured above just last week, Comet SWAN showed a bright blue-green coma and an impressive tail. Comet C/2006 M4 (SWAN) was discovered in June in public images from the Solar Wind Anisotropies (SWAN) instrument of NASA and ESA's Sun-orbiting SOHO spacecraft. Comet SWAN, near magnitude six, will be visible with binoculars in the northeastern sky not far from the Big Dipper over the next few days before dawn. The comet is expected to reach its peak brightness this week. Passing its closest to the Sun two days ago, Comet SWAN and will be at its closest to the Earth toward the end of this month. Comet SWAN's unusual orbit appears to be hyperbolic, meaning that it will likely go off into interstellar space, never to return.

http://antwrp.gsfc.nasa.gov/apod/ap061004.html

Tuesday, October 03, 2006

Light from the Heart Nebula


What powers the Heart Nebula? The large emission nebula dubbed IC 1805 looks, in whole, like a human heart. The nebula glows brightly in red light emitted by its most prominent element: hydrogen. The red glow and the larger shape are all created by a small group of stars near the nebula's center. A close up spanning about 30 light years contains many of these stars is shown above . This open cluster of stars contains a few bright stars nearly 50 times the mass of our Sun, many dim stars only a fraction of the mass of our Sun, and an absent microquasar that was expelled millions of years ago. The Heart Nebula is located about 7,500 light years away toward the constellation of Cassiopeia.

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

In 185 AD, Chinese astronomers recorded the appearance of a new star in the Nanmen asterism - a part of the sky identified with Alpha and Beta Centauri on modern star charts. The new star was visible for months and is thought to be the earliest recorded supernova. Data from two orbiting X-ray telescopes of the 21st century, XMM-Newton and Chandra, now offer evidence that supernova remnant RCW 86 is indeed the debris from that stellar explosion. Their composite, false-color view of RCW 86 shows the expanding shell of material glowing in x-rays with high, medium, and low energies shown in blue, green, and red hues. Shock velocities measured in the x-ray emitting shell and an estimated radius of about 50 light-years can be used to find the apparent age of the remnant. The results indicate that light from the initial explosion could well have first reached planet Earth in 185 AD. Near the plane of our Milky Way Galaxy, RCW 86 is about 8,200 light-years away.

http://antwrp.gsfc.nasa.gov/apod/ap060928.html

Sunday, September 24, 2006

NGC 1499: The California Nebula

What's California doing in space? Drifting through the Orion Arm of the spiral Milky Way Galaxy, this cosmic cloud by chance echoes the outline of California on the west coast of the United States. Our own Sun also lies within the Milky Way's Orion Arm, only about 1,500 light-years from the California Nebula. Also known as NGC 1499, the classic emission nebula is around 100 light-years long. It glows with the red light characteristic of hydrogen atoms recombining with long lost electrons, stripped away (ionized) by energetic starlight. In this case, the star most likely providing the energetic starlight is the bright, hot, bluish Xi Persei, just right of the nebula and above picture center. Fittingly, this composite picture was made with images from a telescope in California - the 48-inch (1.2-meter) Samuel Oschin Telescope - taken as a part of the second National Geographic Palomar Observatory Sky Survey.

http://antwrp.gsfc.nasa.gov/apod/ap060924.html