Wednesday, August 29, 2007

Steamy Star in NGC 1333

Credit: NASA/JPL-Caltech/R. A. Gutermuth (Harvard-Smithsonian CfA)

This image from NASA's Spitzer Space Telescope shows a stellar nursery called NGC 1333. Spitzer discovered that a pre-planetary disk of dust surrounding an embryonic star within this region, called NGC 1333-IRAS 4B, is drenched with water vapor.

NGC 1333 is located about 1,000 light-years away in the Perseus constellation. It is a cloud of gas and dust that is busy manufacturing new stars. Spitzer surveyed four of the very youngest stars in this region and 26 others elsewhere, but found only one, NGC 1333-IRAS 4B, with water vapor. This might be because NGC 1333-IRAS 4B is in just the right orientation for Spitzer to view deep inside the developing star system and detect the water vapor.

Friday, August 24, 2007

Hubble Captures Uranus's Rings on Edge

Credit:NASA, ESA, and M. Showalter (SETI Institute)

This series of images from NASA's Hubble Space Telescope shows how the ring system around the distant planet Uranus appears at ever more oblique (shallower) tilts as viewed from Earth - culminating in the rings being seen edge-on in three observing opportunities in 2007. The best of these events appears in the far right image taken with Hubble's Wide Field Planetary Camera 2 on August 14, 2007.

The edge-on rings appear as two spikes above and below the planet. The rings cannot be seen running fully across the face of the planet because the bright glare of the planet has been blocked out in the Hubble photo (a small amount of residual glare appears as a fan- shaped image artifact). A much shorter color exposure of the planet has been photo- composited to show its size and position relative to the ring plane.

Earthbound astronomers only see the rings' edge every 42 years as the planet follows a leisurely 84-year orbit about the Sun. However, the last time the rings were tilted edge-on to Earth astronomers didn't even know they existed.

With further analysis of the Hubble data, astronomer Mark Showalter of the SETI Institute in Mountain View, Calif., hopes to detect some of the small moons that may shepherd the debris into distinct rings.

Until Voyager 2 flew by Uranus in January 1986, the rings were only known from the way they temporarily blocked the light of stars passing behind the planet. Hubble provided some of the first images of the ring system as viewed from Earth's distance of approximately 2 billion miles. The advent of adaptive optics gave ground-based observers using large telescopes comparatively sharp views.

The rings were discovered in 1977, so this is the first time for a Uranus ring crossing to be observed from Earth. Earth's orbit around the Sun permits three opportunities to view the rings edge-on: Uranus made its first ring crossing as seen from Earth on May 3; it made its second crossing on August 16; and will cross for the third time on February 20, 2008. Though the last ring crossing relative to Earth will be hidden behind the Sun, most of Earth's premier telescopes, including Keck, Hubble, the European Southern Observatory's Very Large Telescope and the Hale Telescope on Mt. Palomar, plan to focus on the planet again in the days following December 7, 2007. On December 7 the rings will be perfectly edge-on to the Sun.

Showalter is a member of a team led by Imke de Pater of the University of California, Berkeley, who reported that the rings of micron-sized dust have changed significantly since the Voyager 2 spacecraft photographed the Uranus system 21 years ago. Observations were also gleaned from near-infrared adaptive optics observations with the Keck II telescope on May 28, 2007, and reported in an article appearing on August 23 in Science Express, the online edition of Science Magazine.

Wednesday, August 15, 2007

Speeding-Bullet Star Leaves Enormous Streak Across Sky

Speeding-Bullet Star Leaves Enormous Streak Across Sky

NASA's Galaxy Evolution Explorer has spotted an amazingly long comet-like tail behind a star streaking through space at supersonic speeds. The star, named Mira after the Latin word for "wonderful," has been a favorite of astronomers for about 400 years. It is a fast-moving, older star called a red giant that sheds massive amounts of surface material.

The space-based Galaxy Evolution Explorer scanned the popular star during its ongoing survey of the entire sky in ultraviolet light. Astronomers then noticed what looked like a comet with a gargantuan tail. In fact, material blowing off Mira is forming a wake 13 light-years long, or about 20,000 times the average distance of Pluto from the sun. Nothing like this has ever been seen before around a star.

Astronomers say Mira's tail offers a unique opportunity to study how stars like our sun die and ultimately seed new solar systems. As Mira hurtles along, its tail sheds carbon, oxygen and other important elements needed for new stars, planets and possibly even life to form. This tail material, visible now for the first time, has been released over the past 30,000 years.

"This is an utterly new phenomenon to us, and we are still in the process of understanding the physics involved," said co-author Mark Seibert of the Observatories of the Carnegie Institution of Washington in Pasadena. "We hope to be able to read Mira's tail like a ticker tape to learn about the star's life."

Billions of years ago, Mira was similar to our sun. Over time, it began to swell into what's called a variable red giant - a pulsating, puffed-up star that periodically grows bright enough to see with the naked eye. Mira will eventually eject all of its remaining gas into space, forming a colorful shell called a planetary nebula. The nebula will fade with time, leaving only the burnt-out core of the original star, which will then be called a white dwarf.

Some Images

1. Johnny Appleseed of the Cosmos
A new ultraviolet mosaic from NASA's Galaxy Evolution Explorer shows a speeding star named Mira (pronounced my-rah) that is leaving an enormous trail of "seeds" for new solar systems.

2. A Real Shooting Star
This artist's animation illustrates a star flying through our galaxy at supersonic speeds, leaving a 13-light-year-long trail of glowing material in its wake.

3. Evolution of Mira's Enormous Tail
This chart illustrates the length (top) and age (bottom) of a long comet-like tail of material trailing behind a speeding star called Mira (pronounced My-rah).

4. Anatomy of a Shooting Star
A close-up view of a star racing through space faster than a speeding bullet can be seen in this image from NASA's Galaxy Evolution Explorer.

5. Supersonic Bullet
A bullet traveling through air at about 1.5 times the speed of sound can be seen in this image.

6. Mira's Tail There All Along
As this composite demonstrates, Mira's tail is only visible in ultraviolet light (top), and does not show up in visible light (bottom).

Tuesday, August 07, 2007

Quadruple Galaxy Merger - CL0958+4702

Credit: NASA/JPL-Caltech/K. Rines (Harvard-Smithsonian CfA)

Whopper Galaxy Collision

One of the biggest galaxy collisions ever observed is taking place at the center of this image. The four white blobs in the middle are large galaxies that have begun to tangle and ultimately merge into a single gargantuan galaxy. The whitish cloud around the colliding galaxies contains billions of stars tossed out during the messy encounter. Other galaxies and stars appear in yellow, orange and red hues. Blue shows hot gas that permeates this distant region of tightly packed galaxies.

NASA's Spitzer Space Telescope spotted the four-way collision, or merger, in a giant cluster of galaxies, called CL0958+4702, located nearly five billion light-years away. The dots in the picture are a combination of galaxies in the cluster; background galaxies located behind the cluster; and foreground stars in our own Milky Way galaxy.

Infrared data from Spitzer are colored red in this picture, while visible-light data from a telescope known as WIYN are green. Areas where green and red overlap appear orange or yellow. Since most galaxies in the cluster contain old stars that are visible to Spitzer and WIYN, those galaxies appear orange. Blue represents X-ray light captured by NASA's Chandra X-ray Observatory. The colliding galaxies appear white because they are in areas where all the colors overlap.

The WIYN telescope, located near Tucson, Ariz., is owned and operated by the WIYN Consortium, which consists of the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatory.

Thursday, August 02, 2007

Uncovering the Veil Nebula

NASA's Hubble Space Telescope photographed three magnificent sections of the Veil Nebula — the shattered remains of a supernova that exploded thousands of years ago. This series of images provides beautifully detailed views of the delicate, wispy structure resulting from this cosmic explosion. The Veil Nebula is one of the most spectacular supernova remnants in the sky. The entire shell spans about 3 degrees on the sky, corresponding to about 6 full moons.

The Veil Nebula is a prototypical middle-aged supernova remnant, and is an ideal laboratory for studying the physics of supernova remnants because of its unobscured location in our Galaxy, its relative closeness, and its large size. Also known as the Cygnus Loop, the Veil Nebula is located in the constellation of Cygnus, the Swan. It is about 1,500 light-years away from Earth.

Stars in our Galaxy, and in other galaxies, are born and then die. How long a star lives depends on how massive it is. The more massive the star, the shorter its life. When a star significantly more massive than our Sun runs out of fuel, it collapses and blows itself apart in a catastrophic supernova explosion. A supernova releases so much light that it can outshine a whole galaxy of stars put together. The exploding star sweeps out a huge bubble in its surroundings, fringed with actual stellar debris along with material swept up by the blast wave. This glowing, brightly colored shell of gas forms a nebula that astronomers call a "supernova remnant."

Such a remnant can remain visible long after the initial explosion fades away. Scientists estimate that the Veil supernova explosion occurred some 5,000 to 10,000 years ago.

The small regions captured in these Hubble images provide stunning close-ups of the Veil. Fascinating smoke-like wisps of gas are all that remain visible of what was once a star in our Milky Way Galaxy. The intertwined rope-like filaments of gas in the Veil Nebula result from the enormous amounts of energy released as the fast-moving debris from the explosion plows into its surroundings and creates shock fronts. These shocks, driven by debris moving at 600,000 kilometers per hour, heat the gas to millions of degrees. It is the subsequent cooling of this material that produces the brilliant glowing colors.

The Hubble images of the Veil Nebula are striking examples of how processes that take place hundreds of light-years away can sometimes resemble effects we see around us in our daily life. Although caused by different forces, the structures show similarities to the patterns formed by the interplay of light and shadow on the bottom of a swimming pool, rising smoke, or a ragged cirrus cloud.

Although only about one star per century in our Galaxy will end its life in this spectacular way, these explosions are responsible for making all chemical elements heavier than iron, as well as being the main producers of oxygen in the universe. Elements such as copper, mercury, gold, and lead are forged in these violent events. The expanding shells of supernova remnants mix with other clouds in the Milky Way and become the raw material for new generations of stars and planets. The chemical elements that constitute Earth, and indeed those of which we ourselves are made, were formed deep inside ancient stars and distributed by supernova explosions in nebulae like the one we see here.

The images were taken with Hubble's Wide Field Planetary Camera 2 (WFPC2) in November 1994 and August 1997. The color is produced by creating a composite of three different images. The colors indicate emission from different kinds of atoms excited by the shock: blue shows oxygen, green shows sulfur, and red shows hydrogen.

Credit: NASA, ESA, and theHubble Heritage(STScI/AURA)-ESA/Hubble Collaboration