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Crater Melanthius on Tethys.
Crater Melanthius on Tethys. Image credit: NASA/JPL/SSI.

Cassini took this photograph of the 245-km (150-mile) crater Melanthius on the surface of Saturn’s moon Tethys. The central mountains at the heart of Melanthius are left over from when the crater first formed millions of years ago. Cassini took the photo on July 23, 2006 when it was 120,000 kilometers (75,000 miles) from Tethys.

Cassini looks into the 245-kilometer (150-mile) wide crater Melanthius in this view of the southern terrain on Tethys. The crater possesses a prominent cluster of peaks in its center which are relics of its formation.

Notable here is a distinct boundary in crater abundance - the cratering density is much higher in the farthest western terrain (left side of the image) than elsewhere.

North on Tethys (1,071 kilometers, or 665 miles across) is up and rotated 45 degrees to the left.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 23, 2006 at a distance of approximately 120,000 kilometers (75,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 29 degrees. Image scale is 715 meters (2,345 feet) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Original Source: NASA/JPL/SSI News Release

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Did the Earth Flip Over in the Past?

Graphic of the Earth’s flip. Image credit: Maloof Laboratory.
Graphic of the Earth’s flip. Image credit: Maloof Laboratory .

August 31st, 2006: Scientists have found evidence that the Earth might have flipped over in the past, completely shifting the orientation of its poles. The theory has been around for years; that a large mountain range or supervolcano might unbalance the spinning Earth. Over the course of millions of years, the Earth would change the orientation of its axis until the object was balanced at the equator again. The scientists found evidence of magnetic grains in layers of rock sediment on the ocean floor that maintain a record of the Earth’s magnetic field over millions of years.

Imagine a shift in the Earth so profound that it could force our entire planet to spin on its side after a few million years, tilting it so far that Alaska would sit at the equator. Princeton scientists have now provided the first compelling evidence that this kind of major shift may have happened in our world’s distant past.

By analyzing the magnetic composition of ancient sediments found in the remote Norwegian archipelago of Svalbard, Princeton University’s Adam Maloof has lent credence to a 140-year-old theory regarding the way the Earth might restore its own balance if an unequal distribution of weight ever developed in its interior or on its surface.

The theory, known as true polar wander, postulates that if an object of sufficient weight - such as a supersized volcano - ever formed far from the equator, the force of the planet’s rotation would gradually pull the heavy object away from the axis the Earth spins around. If the volcanoes, land and other masses that exist within the spinning Earth ever became sufficiently imbalanced, the planet would tilt and rotate itself until this extra weight was relocated to a point along the equator.

"The sediments we have recovered from Norway offer the first good evidence that a true polar wander event happened about 800 million years ago," said Maloof, an assistant professor of geosciences. "If we can find good corroborating evidence from other parts of the world as well, we will have a very good idea that our planet is capable of this sort of dramatic change."

Maloof’s team, which includes researchers from Harvard University, the California Institute of Technology and the Massachusetts Institute of Technology as well as Princeton, will publish their findings in the Geological Society of America Bulletin on Friday, Aug. 25.

True polar wander is different from the more familiar idea of "continental drift," which is the inchwise movement of individual continents relative to one another across the Earth’s surface. Polar wander can tip the entire planet on its side at a rate of perhaps several meters per year, about 10 to 100 times as fast as the continents drift due to plate tectonics. Though the poles themselves would still point in the same direction with respect to the solar system, the process could conceivably shift entire continents from the tropics to the Arctic, or vice versa, within a relatively brief geological time span.

While the idea that the continents are slowly moving in relation to one another is a well-known concept, the less familiar theory of true polar wander has been around since the mid-19th century, several decades before continental drift was ever proposed. But when the continents were proven to be moving under the influence of plate tectonics in the 1960s, it explained so many dynamic processes in the Earth’s surface so well that true polar wander became an obscure subject.

"Planetary scientists still talk about polar wander for other worlds, such as Mars, where a massive buildup of volcanic rock called Tharsis sits at the Martian equator," Maloof said. "But because Earth’s surface is constantly changing as the continents move and ocean crustal plates slide over and under one another, it’s more difficult to find evidence of our planet twisting hundreds of millions of years ago, as Mars likely did while it was still geologically active."

However, the sediments that the team studied in Svalbard from 1999 to 2005 may have provided just such long-sought evidence. It is well known that when rock particles are sinking to the ocean floor to form layers of new sediment, tiny magnetic grains within the particles align themselves with the magnetic lines of the Earth. Once this rock hardens, it becomes a reliable record of the direction the Earth’s magnetic field was pointing at the time of the rock’s formation. So, if a rock has been spun around by a dramatic geological event, its magnetic field will have an apparently anomalous orientation that geophysicists like those on Maloof’s team seek to explain.

"We found just such anomalies in the Svalbard sediments," Maloof said. "We made every effort to find another reason for the anomalies, such as a rapid rotation of the individual crustal plate the islands rest upon, but none of the alternatives makes as much sense as a true polar wander event when taken in the context of geochemical and sea level data from the same rocks."

The findings, he said, could possibly explain odd changes in ocean chemistry that occurred about 800 million years ago. Other similar changes in the ocean have cropped up in ancient times, Maloof said, but at these other times scientists know that an ice age was to blame.

"Scientists have found no evidence for an ice age occurring 800 million years ago, and the change in the ocean at this juncture remains one of the great mysteries in the ancient history of our planet," he said. "But if all the continents were suddenly flipped around and their rivers began carrying water and nutrients into the tropics instead of the Arctic, for example, it could produce the mysterious geochemical changes science has been trying to explain."

Because the team obtained all its data from the islands of Svalbard, Maloof said their next priority would be to seek corroborating evidence within sediments of similar age from elsewhere on the planet. This is difficult, Maloof said, because most 800-million-year-old rocks have long since disappeared. Because the Earth’s crustal plates slide under one another over time, they take most of geological history back into the planet’s deep interior. However, Maloof said, a site his team has located in Australia looks promising.

"We cannot be certain of these findings until we find similar patterns in rock chemistry and magnetics on other continents," Maloof said. "Rocks of the same age are preserved in the Australian interior, so we’ll be visiting the site over the next two years to look for additional evidence. If we find some, we’ll be far more confident about this theory’s validity."

Maloof said that true polar wander was most likely to occur when the Earth’s landmasses were fused together to form a single supercontinent, something that has happened at least twice in the distant past. But he said we should not worry about the planet going through a major shift again any time soon.

"If a true polar wander event has occurred in our planet’s history, it’s likely been when the continents formed a single mass on one side of the Earth," he said. "We don’t expect there to be another event in the foreseeable future, though. The Earth’s surface is pretty well balanced today."

Maloof’s research was sponsored in part by the National Science Foundation.

Original Source: Princeton News Release

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Magnetar Crackles with Radio Waves.

Magnetar Crackles with Radio Waves.
Artist illustration of a magnetar. Image credit: NRAO.

August 30th, 2006: Astronomers have discovered a rapidly spinning pulsar with a powerful magnetic field - called a magnetar - that’s demonstrating some brand new tricks. Located about 10,000 light years from Earth, this magnetar is sending out powerful pulses of radio waves at regular intervals; normally magnetars are only seen in the X-ray spectrum. The discoverers think that the magnetic field around the star is twisting, causing huge electric currents to flow - these currents are generating the radio pulses.

Astronomers using radio telescopes from around the world have discovered a spinning neutron star with a superpowerful magnetic field - called a magnetar - doing things no magnetar has been seen to do before. The strange behavior has forced them to scrap previous theories about radio pulsars and promises to give new insights on the physics behind these extreme objects.

The magnetar, approximately 10,000 light-years from Earth in the direction of the constellation Sagittarius, is emitting powerful, regularly-timed pulses of radio waves just like radio pulsars, which are neutron stars with far less intense magnetic fields. Usually, magnetars are visible only in X-rays and sometimes very weakly in optical and infrared light.

"No one has ever found radio pulses coming from a magnetar before. We thought that magnetars didn’t do this," said Fernando Camilo of Columbia University. "This object is going to teach us new things about magnetar physics that we would never have learned otherwise," Camilo added.

Neutron stars are the remnants of massive stars that have exploded as supernovae. Containing more mass than the Sun, they are compressed to a diameter of only about 15 miles, making them as dense as atomic nuclei. Ordinary pulsars are neutron stars that emit "lighthouse beams" of radio waves along the poles of their magnetic fields. As the star spins, the beam of radio waves is flung around, and when it passes the direction of Earth, astronomers can detect it with radio telescopes.

Scientists have found about 1700 pulsars since their first discovery in 1967. While pulsars have strong magnetic fields, about a dozen neutron stars have been dubbed magnetars because their magnetic fields are 100-1,000 times stronger than those of typical pulsars. It is the decay of those incredibly strong fields that powers their strange X-ray emission.

"The magnetic field from a magnetar would make an aircraft carrier spin around and point north quicker than a compass needle moves on Earth," said David Helfand, of Columbia University. A magnetar’s field is 1,000 trillion times stronger than Earth’s, Helfand pointed out.

The new object - named XTE J1810-197 - was first discovered by NASA’s Rossi X-ray Timing Explorer when it emitted a strong burst of X-rays in 2003. While the X-rays were fading in 2004, Jules Halpern of Columbia University and collaborators identified the magnetar as a radio-wave emitter using the National Science Foundation’s (NSF) Very Large Array (VLA) radio telescope in New Mexico. Any radio emission is highly unusual for a magnetar.

Because magnetars had not been seen to regularly emit radio waves, the scientists presumed that the radio emission was caused by a cloud of particles thrown off the neutron star at the time of its X-ray outburst, an idea they soon would realize was wrong.

With knowledge that the magnetar emitted some form of radio waves, Camilo and his colleagues observed it with the Parkes radio telescope in Australia in March and immediately detected astonishingly strong radio pulsations every 5.5 seconds, corresponding to the previously-determined rotation rate of the neutron star.

As they continued to observe XTE J1810-197, the scientists got more surprises. Whereas most pulsars become weaker at higher radio frequencies, XTE J1810-197 does not, remaining a strong emitter at frequencies up to 140 GHz, the highest frequency ever detected from a radio pulsar. In addition, unlike normal pulsars, the object’s radio emission fluctuates in strength from day to day, and the shape of the pulsations changes as well. These variations likely indicate that the magnetic fields around the pulsar are changing as well.

What’s causing this behavior? At the moment, the scientists believe that the magnetar’s intense magnetic field is twisting, causing changes in the locations where huge electric currents flow along the magnetic-field lines. These currents likely generate the radio pulsations.

"To solve this mystery, we’ll continue monitoring this crazy object with as many telescopes as we can get our hands on and as often as possible. Hopefully, seeing all these changes with time will give us a deeper understanding of what is really going on in this very extreme environment," said team member Scott Ransom of the National Radio Astronomy Observatory.

Because they expect that XTE J1810-197 will fade at all wavelengths, including the radio, the scientists also have observed it with the NSF’s Robert C. Byrd Green Bank Telescope and Very Long Baseline Array (VLBA), Parkes and the Australia Telescope Compact Array in Australia, the IRAM telescope in Spain, and the Nancay Observatory in France. John Reynolds and John Sakissian of Parkes Observatory, Neil Zimmerman of Columbia University and Juan Penalver and Aris Karastergiou of IRAM also are members of the research team. The scientists reported their initial findings in the August 24 issue of the scientific journal Nature.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Original Source: NRAO News Release

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Astrophoto: Star Trails over Namibia by Josch Hambsch.

Astrophoto:  Star Trails over Namibia. Image by: Josch Hambsch
Astrophoto: Star Trails over Namibia: Image by: Josch Hambsch" alt="Astrophoto: Star Trails over Namibia. by: Josch Hambsch.

August 30th, 2006: Arc lights had been used in lighthouses for several years when Thomas Edison began seeking a way to improve them. Arc lamps use two rods of carbon arranged so that their tips are almost touching. When sufficient electricity is sent to each, the current jumps between them and causes the carbon to become incandescent. Although carbon burns very slowly, over time the rods erode and have to be replaced. The year was 1881 when Edison embarked on a solution and the result of his success spread around the globe to both light and inadvertently curse the darkness.

Edison set out to solve several problems: create a sufficient vacuum to prevent the carbon from oxidizing, find more suitable material to serve as a filament and reduce the scale needed to produce an artifical electrical light source. After securing a German pump that could produce a high vacuum, Edison tested 6,000 different materials until a carbonized cardboard filament remained lit for 170 hours. It was the first practical incandescent light bulb. Of course, Edison’s real achievement lay in his design of a system that enabled many lights powered from a common source to be switched on and off independent of each other. This idea has evolved into the modern power grid. During the more than one hundred and twenty years that have followed, the incandescent light and its halogen, neon and florescent descendants have proliferated into every corner of the world.

For thousands of years prior to this, humankind had lived in darkness after sunset with only the light of burning wood, wax or oil to provide illumination. Our connection to the night sky during this period ran very deep. From all but the largest cities, people venturing outside at night would see a black sky punctuated by the glow of over five thousand visible stars, the planets and the Milky Way arcing overhead. It filled our forebears’ minds with wonder, reminded them that they were surrounded by the Universe and found its way into their most profound beliefs.

Today, electricity is plentiful, night lighting is ubiquitous but the night sky that was visible throughout all of human history is no longer with us. It’s been replaced by a soft glow from our urbanized areas. Now, for over two thirds of the world’s population, views of the Milky Way and all but the brightest stars and planets are hidden behind domes of artificial daylight. These bright blankets continue to expand in all directions limiting our personal connection with the Universe to an ever dwindling number of remote locations.

When night lighting extends beyond its purpose, it’s called light pollution. It comes from poorly designed streetlights. Billboards, decorative lights, and poorly shielded security lights but street lighting is the largest contributor. Some cities and communities are joining with astronomers to work together and address their local situation. For example, Los Angeles now recognizes three problems associated with light pollution: light trespass- when glare shines into neighboring windows or the eyes of an automobile driver; night sky loss - when glare is directed into the sky above - and energy waste, estimated to be hundreds of millions of dollars annually for the United States, alone. Organizations like the International Dark Sky Association of Tucson, Arizona, have also formed to reduce the problem though educational outreach and legislative lobbying.

Belgium astronomer Josch Hambsch, who produced the remarkable picture that accompanies this article, pursues his astrophotography projects and variable star studies from his light polluted backyard observatory. However, his vacation travels occasionally include a visit to a dark site in Namibia and earlier this summer Josch made another trip.

If you take a camera and anchor it to a fixed location, like a tripod, aim it at the sky and open the shutter for several minutes, the stars will form tails due to the spinning of the Earth. This picture was produced using this method. It represents an entire night, looking south from Namibia. 128 separate five-minute images were combined to produce this result. The stars form circles about the south celestial pole but the background glow is not from light pollution. It is produced by the combined light from some of the Milky Way’s four hundred billion stars. This image was exposed with a Canon 20D camera and a 12-24mm f/4 Sigma zoom lens, set to a focal length of 12mm.

Josch also combined the individual images into an animation that shows the stars’ motion during the night and the spectacular arcing of the Milky Way as it sets.

Written by R. Jay GaBany

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Birth of Stars Seen by AKARI.

Birth of Stars Seen by AKARI.
IC 1396. Image credit: AKARI.

August 30th, 2006: The Japanese AKARI spacecraft - formerly known as Astro-F - captured this photograph of the reflection nebula IC 1396. This nebula is a bright star-forming region located about 3,000 light years from Earth in the constellation Cepheus, and it contains several young stars dozens of times more massive than our Sun. AKARI was able to reveal many new stars that were previously invisible because of its ability to see in the far infrared spectrum.

AKARI, the Japan Aerospace Exploration Agency (JAXA) infrared astronomical satellite with ESA participation, is continuing its survey of the sky and its mapping of our cosmos in infrared light. New exciting images recently taken by AKARI depict scenes from the birth and death of stars.

AKARI’s Infrared Camera (IRC) imaged the reflection nebula IC 1396 in the constellation Cepheus (a reflection nebula is a cloud of dust which reflects the light of nearby stars). IC 1396 is a bright star-forming region located about 3000 light years from our Solar System, in a region where very massive stars – several tens of times as massive as our Sun - are presently being born. Massive young stars in the central region of the image have swept out the gas and dust to the periphery of the nebula, creating a hollow shell-like structure.

A new generation of stars is now taking place within the compressed gas in these outer shell structures. With this high-resolution and high-quality image of IC 1396, AKARI has revealed for the first time the detailed distribution of the gas and dust swept out over the entire nebula.

A comparison between a visible image of IC 1396 and AKARI’s view of the same area shows that stars being born in regions that appear dark in visible light (left), do however appear bright if observed in infrared light (right).

The gas that has been swept out creates the bright filament-like structures seen in infrared in the surrounding regions. The dust in the gas is heated by the intense light coming from both the massive star at the centre of the nebula and the newly born stars in the dense gas itself, and emits infrared light.

The bright clump seen on the slightly off-centre right-hand side is known as the 'Elephant Trunk Nebula’, a star forming region too. It appears as a dark nebula in the visible light (left image), but it is very bright in the infrared. It is a clump of dense gas that was not originally blown away because of its very high density.

Many recently born stars that were previously unknown are now expected to be detected thanks to AKARI’s new image, while the detailed analysis of these data will reveal the story of the star formation in this area.

AKARI’s Far-Infrared Surveyor (FIS) instrument imaged the red giant 'U Hydrae’, a star located at about 500 light years from our Sun. AKARI’s observations have revealed very extended clouds of dust surrounding this object.

Stars with masses close to that of our Sun will expand during the later stages of their life becoming so-called 'red-giant’ stars. During the final phase of their life such stars often eject gas from their surface into interstellar space - dust is formed in the ejected gas, and this mixture of gas and dust expands and escapes from the star.

AKARI’s superior quality and high-resolution imaging allowed the clear detection of a shell-like dust cloud surrounding U Hydrae at a distance of about 0.3 light years from the central star, implying that a short and violent ejection of mass took place in the star about 10 000 years ago.

AKARI (formerly known as ASTRO-F) was launched on 21 February 2006 (UT) from the Uchinoura Space Centre, Japan, and started its complete sky survey in April 2006.

Original Source: ESA News Release

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Atlantis Will Ride Out Ernesto.

Atlantis Will Ride Out Ernesto.
Atlantis rolls back to the launch pad. Image credit: NASA.

August 30th, 2006: NASA managers decided on Tuesday that Tropical Storm Ernesto won’t pose a threat to the Space Shuttle Atlantis, so they rolled it back out to the launch pad. There will still be high winds, so Atlantis will be locked down to the launch pad on Tuesday evening. If all goes well, Atlantis could launch as early as next week, returning to the International Space Station to continue its construction. The Kennedy Space Center will remain closed until Thursday, depending on the storm’s track.

NASA managers decided early Tuesday to move the Space Shuttle Atlantis from its launch pad into the Vehicle Assembly Building for protection from approaching Tropical Storm Ernesto, but later in the day, when the weather forecast improved, they reversed the decision and began moving Atlantis back to the pad.

Assessments of updated weather forecasts convinced shuttle managers that Atlantis would be protected from the storm at the pad at NASA’s Kennedy Space Center.

Atlantis is expected to be locked down at the launch pad about 8 p.m. EDT Tuesday. The rotating service structure, which will surround the spacecraft and serve as a protective barrier from the storm, will be put around Atlantis about 30 minutes later.

Depending on the effects of Ernesto on Kennedy, a new launch date for Atlantis’ STS-115 mission to the International Space Station could be set once storm damage is evaluated and work resumes at the launch pad. A launch attempt may be possible next week.

Kennedy is expected to close ahead of the storm late Tuesday and remain closed until at least Thursday. The center’s emergency operations personnel will stay on-site to monitor the storm and make initial damage assessments after it passes.

The STS-115 crew, Commander Brent Jett, Pilot Chris Ferguson, mission specialists Joe Tanner, Dan Burbank, Heide Stefanyshyn-Piper and Canadian astronaut Steve MacLean, returned to NASA’s Johnson Space Center Tuesday morning. Crew members would return to Kennedy after a new launch date is scheduled.

During STS-115, Atlantis’ astronauts will deliver and install the 17.5-ton, bus-sized P3/P4 integrated truss segment on the station. The girder-like truss includes a set of giant solar arrays, batteries and associated electronics. The P3/P4 truss segment will provide one-fourth of the total power-generation capability for the completed station.

For information about the STS-115 crew and mission, visit: http://www.nasa.gov/shuttle

Original Source: NASA News Release

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Rings Lit by Saturn’s Shine.

Rings Lit by Saturn’s Shine.
Saturn’s rings. Image credit: NASA/JPL/SSI.

August 30th, 2006: This is a view looking down onto the unlit side of Saturn’s rings, lit only by the reflected light from the planet. There are also two small moons in the image: Atlas and Pandora. Cassini took this photo on July 25, 2006 when it was approximately 1 million kilometers (600,000 miles) from Saturn.

This view looks down onto the unlit side of Saturn’s ringplane. It nicely shows a near-arm/far-arm brightness asymmetry in the B ring: The near arm of the B ring (in the lower half of the image) is notably darker from this viewing geometry than is the far arm (above).

Imaging scientists believe this to be a manifestation of the reflection of light from the disk of Saturn falling predominantly on the far arm of the rings. (At the time this image was taken, Cassini was more or less on the dark side of the planet.) As the B ring is the thickest part of Saturn’s rings, it scatters less sunlight from below, and reflects more Saturn shine from above, than either the A or C rings, making the effect look more dramatic in the B ring.

Two small moons appear in this scene as well: Atlas (32 kilometers, or 20 miles across) is visible above and left of center and outside the A ring; Pandora (84 kilometers, or 52 miles across) can be seen near upper right beyond the F ring. Between the two moons lie multiple clumps of material in the F ring.

The image was taken in visible light with the Cassini spacecraft wide-angle camera on July 25, 2006 at a distance of approximately 1 million kilometers (600,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 128 degrees. Image scale is 58 kilometers (36 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Original Source: NASA/JPL/SSI News Release

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Hubble’s View of Supernova Remnant Cassiopeia A.

Hubble’s View of Supernova Remnant Cassiopeia A.
Cassiopeia A. Image credit: Hubble.

August 29th, 2006: NASA’s Hubble Space Telescope took this photograph of supernova remnant Cassiopeia A, one of the youngest remnants we know of in the Milky Way. The image was made up of 18 separate photos taken by Hubble using its Advanced Camera for Surveys, and it reveals the faint swirls of expanding debris. Astronomers believe the star that used to live at the centre exploded as a supernova about 340 years ago (as well as the 10,000 years it took for the light to reach us).

A new image taken with NASA’s Hubble Space Telescope provides a detailed look at the tattered remains of a supernova explosion known as Cassiopeia A (Cas A). It is the youngest known remnant from a supernova explosion in the Milky Way. The new Hubble image shows the complex and intricate structure of the star’s shattered fragments.

The image is a composite made from 18 separate images taken in December 2004 using Hubble’s Advanced Camera for Surveys (ACS), and it shows the Cas A remnant as a broken ring of bright filamentary and clumpy stellar ejecta. These huge swirls of debris glow with the heat generated by the passage of a shockwave from the supernova blast. The various colors of the gaseous shards indicate differences in chemical composition. Bright green filaments are rich in oxygen, red and purple are sulfur, and blue are composed mostly of hydrogen and nitrogen.

A supernova such as the one that resulted in Cas A is the explosive demise of a massive star that collapses under the weight of its own gravity. The collapsed star then blows its outer layers into space in an explosion that can briefly outshine its entire parent galaxy. Cas A is relatively young, estimated to be only about 340 years old. Hubble has observed it on several occasions to look for changes in the rapidly expanding filaments.

In the latest observing campaign, two sets of images were taken, separated by nine months. Even in that short time, Hubble’s razor-sharp images can observe the expansion of the remnant. Comparison of the two image sets shows that a faint stream of debris seen along the upper left side of the remnant is moving with high speed - up to 31 million miles per hour (fast enough to travel from Earth to the Moon in 30 seconds!).

Cas A is located ten thousand light-years away from Earth in the constellation of Cassiopeia. Supernova explosions are the main source of elements more complex than oxygen, which are forged in the extreme conditions produced in these events. The analysis of such a nearby, relatively young and fresh example is extremely helpful in understanding the evolution of the universe.

Original Source: Hubble News Release

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High Altitude Clouds on Mars.

High Altitude Clouds on Mars.
High altitude clouds on Mars. Image credit: ESA.

August 28th, 2006: ESA scientists have discovered some extremely high altitude clouds on Mars - between 80 and 100 km (50 to 62 miles) high. These newly found clouds were uncovered by ESA’s Mars Express spacecraft, while it was watching distant stars as they passed behind Mars. The light from the stars was distorted as it passed through the Martian atmosphere, allowing scientists to measure the intervening cloud layers. The atmosphere at that altitude is so cold that scientists think the clouds must be made of carbon dioxide.

Planetary scientists have discovered the highest clouds above any planetary surface. They found them above Mars using the SPICAM instrument on board ESA’s Mars Express spacecraft. The results are a new piece in the puzzle of how the Martian atmosphere works.

Until now, scientists had been aware only of the clouds that hug the Martian surface and lower reaches of the atmosphere. Thanks to data from the SPICAM Ultraviolet and Infrared Atmospheric Spectrometer onboard Mars Express, a fleeting layer of clouds have been discovered at an altitude between 80 and 100 kilometres. The clouds are most likely composed of carbon dioxide.

SPICAM made the discovery by observing distant stars just before they disappeared behind Mars. By looking at the effects on the starlight as it travelled through the Martian atmosphere, SPICAM built up a picture of the molecules at different altitudes. Each sweep through the atmosphere is called a profile.

The first hints of the new cloud layer came when certain profiles showed that the star dimmed noticeably when it was behind the 90–100 kilometre high atmospheric layer. Although this happened in only one percent of the profiles, by the time the team had collected 600 profiles, they were confident that the effect was real.

"If you wanted to see these clouds from the surface of Mars, you would probably have to wait until after sunset" says Franck Montmessin, a SPICAM scientist with Service d’Aeronomie du CNRS, Verrières-le-Buisson, France, and lead author of the results. This is because the clouds are very faint and can only be seen reflecting sunlight against the darkness of the night sky. In that respect, they look similar to the mesospheric clouds, also known as noctilucent clouds, on Earth. These occur at 80 kilometres altitude above our planet, where the density of the atmosphere is similar to that of Mars’ at 35 kilometres. The newly discovered Martian clouds therefore occur in a much more rarefied atmospheric location.

At 90–100 kilometres above the Martian surface, the temperature is just –193º Celsius. This means that the clouds are unlikely to be made of water. "We observe the clouds in super-cold conditions where the main atmospheric component CO2 (carbon dioxide), cools below its condensation point. From that we infer that they are made of carbon dioxide," says Montmessin.

But how do these clouds form? SPICAM has revealed the answer by finding a previously unknown population of minuscule dust grains above 60 kilometres in the Martian atmosphere. The grains are just one hundred nanometres across (a nanometre is one thousand-millionth of a metre).

They are likely to be the 'nucleation centres’ around which crystals of carbon dioxide form to make clouds. They are either microscopic chippings from the rocks on the surface on Mars that have been blown to extreme altitudes by the winds, or they are the debris from meteors that have burnt up in the Martian atmosphere.

The new high-altitude cloud layer has implications for landing on Mars as it suggests the upper layers of Mars’ atmosphere can be denser than previously thought. This will be an important piece of information for future missions, when using friction in the outer atmosphere to slow down spacecraft (in a technique called 'aerobraking’), either for landing or going into orbit around the planet.

Original Source: ESA News Release

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Storm Delays Shuttle Launch.

Storm Delays Shuttle Launch.
Tropical Storm Ernesto. Image credit: NASA.

August 28th, 2006: NASA has pushed back the launch of the Space Shuttle Atlantis because of Tropical Storm Ernesto, currently threatening the East Coast of the United States. The agency has made the decision to roll the shuttle back to its hanger, to protect it from potential damage from the storm. If the rollback does occur, the shuttle won’t be able to fly before its September launch window ends, so it’ll have to be pushed back to October.

Tuesday’s scheduled launch of Space Shuttle Atlantis on its STS-115 mission to the International Space Station is being postponed because of Tropical Storm Ernesto. A new launch date has not been set.

Although no final decision has been made, shuttle managers meeting at NASA’s Kennedy Space Center instructed launch teams Monday to continue preliminary preparations to roll Atlantis off its launch pad and back inside the protection of the Vehicle Assembly Building. Managers will follow developments in Tropical Storm Ernesto’s track. A decision on whether to roll back is expected by midday Tuesday.

Ernesto is forecast to pass near Kennedy on Wednesday afternoon.

The STS-115 crew will remain in Florida until a roll back decision is made. Commander Brent Jett, Pilot Chris Ferguson, and mission specialists Joe Tanner, Dan Burbank, Heide Stefanyshyn-Piper and Canadian astronaut Steve MacLean will study flight plans and spend time with their families.

During STS-115, Atlantis’ astronauts will deliver and install the 17.5-ton, bus-sized P3/P4 integrated truss segment on the station. The girder-like truss includes a set of giant solar arrays, batteries and associated electronics. The P3/P4 truss segment will provide one-fourth of the total power-generation capability for the completed station.

For information about the STS-115 crew and its mission to the International Space Station, visit: http://www.nasa.gov/shuttle

Original Source: NASA News Release

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Universe: What’s Up this Week: August 28 - September 3, 2006.

What’s Up this Week: August 28 - September 3, 2006.
Saturn by Wes Higgins.

August 27th, 2006: Saturn returns to the morning sky and Selene is back to rule the night. Follow along this week as explore the lunar surface and find all that is bright and beautiful under the stars.

Monday, August 28 - On this day in 1789, William Herschel discovered Saturn’s moon - Enceladus. The ringed planet is barely skimming the horizon to the east just before sunrise with brilliant Venus. Be sure to check IOTA as well, for the Moon and Spica will perform an occultation tonight.

Although we have traveled this road before, let’s go further south than last night’s lunar study and have another look at Furnerius. Shallower and less impressive than Petavius, Furnerius will fade to obscurity as the Moon waxes. This flooded old crater has no central peak, but a much younger crater has punched a hole in its lava-filled floor. Look for the long "crack" extending from Furnerius’ north shore to crater rim. Perhaps it was caused by the impact? Sharp-eyed observers with good conditions and high power will also spot a multitude of small craters within and along Furnerius’ walls. For binocular viewers, try spotting crater Stevinus to the north and Fraunhofer to the south.

Tonight the Moon sets just as the sky gets dark and presents a fine opportunity to continue our ascent along the Milky Way. Let’s start with a quick look at M11 almost precisely between 3.5 magnitude Lambda Aquilae and 4.1 magnitude Alpha Scutum. At low power it’s possible to get the "Big Picture" of this fine example of a dense Milky Way cluster in northern hemisphere skies. Range through all your eyepieces to bring out more and more stars as the background sky darkens and resolution improves.

After you find the one eyepiece that gives M11 the best view, shift over to Alpha Scutum and check east-northeast for neighboring 7.8 magnitude open cluster NGC 6664. Compare the view to Scutum’s other Messier open cluster - similar sized M26. As one of the faintest Messier clusters, it’s surprising his scope was able to reveal it at all! To locate M26 shift a little less than 3 degrees south-southeast of Alpha. Those with larger scopes should look for a strange void in the middle of the cluster.

Tuesday, August 29 - Need some astronomical inspiration? Then just have a look at the Moon and Jupiter caught together tonight in the starry sky.

On the lunar surface, head to the eastern shore of Mare Nectaris to catch an easily noticed broken black line. This is the western flank of the Pyrenees Mountains which stretch close to 350 kilometers north to south. The black line you see is a good example of a lunar scarp, a feature more like a cliff than a true mountain range. This scarp ends to the north in crater Guttenberg. Just south of Guttenberg, you will find high contrast Santbech.

The Moon is now becoming the "highlight" of the night sky. Try using "higher power" to diminish some of its glare. While southwestern Sagittarius is also high, why not observe some of its other globular clusters?

Center the scope on Epsilon and sweep less than 3 degrees north-northeast to find small 7.7 magnitude globular M69. M69 gives an appearance similar to that of other compact clusters - such as M28 and M80. Small and moderately bright, it appears coarsely textured through smaller instruments and requires larger scopes to bring out its brightest 14th magnitude members. This cluster sits near a blue 7th magnitude star which complicates seeing M69 through binoculars and finderscopes.

Now head a little more than a degree southeast, then north of a pair of 6th magnitude stars to locate NGC 6652 - a very small 9th magnitude globular. Go less than 2 degrees northeast to find brighter (8.1 magnitude), larger M70. Notice how more of M70’s light is concentrated in its core than M69. Continuing a little more than 3 degrees in the direction of Zeta we encounter M54. Through a modest scope, this 7.7 magnitude globular is small, very blue, and intensely concentrated at the core. Larger amateur instruments will only bring out a few 15th magnitude members out of this globular’s faintly glowing form.

Charles Messier discovered M69 and M70 on August 31, 1780 from Paris while trying to confirm a discovery made by Lacaille using a half-inch spyglass in South Africa. These two globulars lie within 2,000 light-years of each other and less than 30,000 light-years from Earth. Due to unusual richness in metal content - for astronomers, "metals" are any elements other than hydrogen and helium - M69 may be a relatively young cluster. At some 90,000 light-years, M54 is the most distant Messier globular cluster - and may not be a globular at all - but the core of a dwarf galaxy beyond the bounds of the Milky Way! In fact M54 is intrinsically larger (300 light-years in diameter) and brighter (magnitude 10.1) than any other globular within the Milky Way itself.

Wednesday, August 30 - On the lunar surface tonight, we’ll return to identify Metius, Fabricus and Janssen to the south. Southwest of this trio you will see a sharply defined small crater known as Vlacq. Power up to resolve its small central mountain peak. Angling off to the west and extending westward is multiple crater Hommel. Look especially for Hommel A and Hommel C which fit nicely and precisely within the borders of the older crater. Note how many individual craters make up its borders. Just north of Hommel is Pitiscus and to its south is Nearch.

Tonight with the Moon in Libra and low to the southwest, deepsky studies will still continue to only be mildly hampered. The main study for tonight will definitely improve once the Moon sets - so while we’re waiting, let’s drop by open cluster M29 less than 2 degrees south-southeast of Gamma Cygni. At lower power, or through small scopes, its handful of brightest members makes this 6.6 magnitude open cluster look more like an asterism than a real group. Lacking any sense of a core, higher power and larger scopes will bring out another dozen or so stars. Those with binoculars will enjoy seeing a few of M29’s brightest stars against a vague nebulosity.

Now let’s see what the "I" can "C"... Less than 2 degrees southwest of M29 (just south of 5th magnitude P Cygni) lies another open cluster of similar brightness and size to M29 - IC 4996. How do these two compare? The less conspicuous IC 4996 lies in a richer Milky Way field and consists of fewer and more compact bright stars. Smaller scopes see this one as a patch of nebulosity.

Now for M55. Found in the far reaches of eastern Sagittarius, and west-southwest of Zeta, M55 is one of the coarsest globulars known. At magnitude 7.0, M55 can be seen as a large pale ghost of luminosity in binoculars or finderscopes. This is one very open globular cluster! A multitude of fine, easily resolved stars spread oblately over the mid-power field. Long exposure photos show this to be a true globular glowing with the combined light of almost 100,000 suns.

Thursday, August 31 - Watch as the Moon and Antares slow dance together tonight. Be sure to check IOTA for an occultation...

Tonight’s prominent lunar features are also Astronomical League challenges. Look southwest of previous study Theophilus for the huge form of Maurolycus. Its cratered floor may be either partially lit or fully disclosed depending on your observing time. Note especially Maurolycus’ multiple central mountains. North of Maurolycus you will see the well-eroded remains of Gemma Frisius. Its broken walls will show well under current illumination. Finally look carefully for crater Goodacre which has destroyed Gemma Frisius’ northern wall.

Tonight we begin entering the stream of the Andromedid meteor shower, which peaks off and on for the next couple of months. For those in the northern hemisphere, look for the lazy "W" of Cassiopeia to the northeast. This is the radiant - or relative point of origin - of the stream. At times, this shower has been known to be spectacular, but let’s stick with an accepted fall rate of around 20 per hour. These are the offspring of Beila’s Comet, one that split apart leaving radically different streams. The Andromedids have a reputation for red fireballs with spectacular trains, so watch for them in the weeks ahead.

If you decide to take the scope out tonight, now would be an excellent opportunity to revisit your southern summer sky favorites!

Friday, September 1 - In 1859, solar physicist Richard Carrington observed the first flare ever recorded. Naturally enough, an intense aurora followed the next day. 120 years later in 1979, Pioneer 11 made history as the first probe to fly by Saturn.

Tonight the waxing Moon will be above the Scorpion’s tail. Its most notable features will be the vast area of craters dominating the south-central portion near and along the terminator. Now emerging is Ptolemaeus - just north-northeast of Albategnius. This large round crater is a mountain walled plain filled with lava flow. With the exception of interior crater Ptolemaeus A, binoculars will see it as very smooth. Telescopes however can reveal faint mottling in the surface of the crater’s interior, along with a single elongated craterlet to the northeast. Despite its apparent uniformity, close inspection has revealed as many as 195 interior craterlets within Ptolemaeus! Look for a variety of interior ridges and shallow depressions.

With the moon low to the southwest, we have a chance to go northeast to Cepheus for a new study - NGC 7160. At magnitude 6.1, this small open cluster is easily identified in scopes and may be seen as a faint starfield in binoculars. You’ll find it about a finger-width north of Nu Cephei.

Saturday, September 2 - On the lunar surface tonight, we’ll start by following the southward descent of large crater rings Ptolemaeus, Alphonsus, and Arzachel to a smaller, bright one southwest named Thebit. We’re going to have a look at Hell...

Just west of Thebit and its prominent A crater to the northwest, you see the Straight Wall - Rupes Recta - appearing as a thin, white line. Continue south until you see large, eroded crater Deslandres. On its western shore, is a bright ring that marks the boundary of Hell. While this might seem like an unusual name for a crater, it was named for an astronomer - and clergyman!

Once you’ve been to Hell, let’s go to the heavens for NGC 7235. Locate the star crowded area of Epsilon Cephei which will also include this 7.7 magnitude open cluster in the same low power field. Give it a try. Look for a small, rectangular assortment of 10th magnitude and fainter stars west-northwest of Epsilon.

Sunday, September 3 - Today in 1976, the Viking 2 lander successfully touched down on Mars. By today’s technological standards, the type of equipment aboard Viking 2 would be considered antiquated, so why don’t we visit a couple of "antique" lunar features tonight?

Due south of mighty Copernicus on the eastern edge of Mare Cognitum, you will see a ruined pair of flattened craters. They are Bonpland and Parry - with Frau Mauro just above them. The smallest and brightest of these ancient twins is the eastern Parry. Have a look at its south wall where a huge section is entirely lost. It was near this location that Ranger 7 ended its successful flight in 1964. Just south of Parry is another example of a well-worn Class V crater. See if you can distinguish the ruins of Guericke. Not much is left save for a slight U-shape to its battered walls. These are some of the oldest visible features on the Moon!

If you’d like to head for something very young, have a look at 6.8 magnitude open cluster NGC 6811 in Cygnus. This mid-sized, unusually dense open cluster is found less than finger-width north-northwest of Delta - the westernmost star of the Northern Cross. Like most open clusters, the age of NGC 6811 is measured in millions, rather than billions, of years. Visible in binoculars on most nights, telescopes should show a half dozen or so broadly-spaced resolvable stars overlaying a fainter field. Be sure to return again on a moonless night, and have another look a disparate double Delta!

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