RSSArchive for October, 2011

Earth from Space – Frozen fields of Antarctica

EO-1 image of ice in Antarctica

Satellite image of fields of ice on the Antarctic coast.

THOUGH IT IS ALL COMPOSED of frozen water, ice is hardly uniform. On October 7, 2011, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this image of a variety of ice types off the coast of East Antarctica.

Brilliant white ice fills the right half of this image. It is fast ice, and derives its name from the fact that it holds fast to the shore. This ice is thick enough to completely hide the underlying seawater, hence its brilliant white colour.

Trapped within the fast ice, and stuck along the edge of it, are icebergs. Icebergs form by calving off ice shelves—thick slabs of ice attached to the coast. Ice shelves can range in thickness from tens to hundreds of metres, and the icebergs that calve off of them can tower over nearby sea ice. One iceberg, drenched with meltwater, has toppled and shattered (image upper right). The water-saturated ice leaves a blue tinge.

The icebergs along the edge of the fast ice are likely grounded on the shallow sea floor, and their presence may help hold the fast ice in place.

Farther out to sea is pack ice that drifts with winds and currents. Much thinner than the fast ice, the translucent pack ice appears in shades of blue-grey.

The pack ice includes some newly formed sea ice. As seawater starts to freeze, it forms tiny crystals known as frazil (image centre). Although the individual crystals are only millimetres across, enough of them assembled together are visible from space.

Constantly moved by ocean currents, frazil often appears in delicate swirls. Frazil crystals can coalesce into thin sheets of ice known as nilas (image top). Sheets of nilas often slide over each other, eventually merging into thicker layers of ice.

NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Text adapted from information issued by Michon Scott based on image interpretation by Ted Scambos, National Snow and Ice Data Centre.

Download the full-size (4MB) image here.

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Video – Satellites sent into orbit

A HUGE ARIANE 5 ROCKET thunders into space in this dramatic video. The launch took place at Europe’s Spaceport in French Guiana, and the mission was to place two telecommunications satellites, Arabsat-5C and SES-2, into their planned transfer orbits.

Liftoff of flight VA204, the 60th Ariane 5 mission, came at 7:38am (Sydney time) on September 22, 2011.

The 50.5-metre-tall Ariane 5 is a heavy-lift rocket, with a mass of 780 tonnes (including fuel) at lift-off.

Adapted from information issued by ESA / CNES / Arianespace / Photo Optique vidéo du CSG.

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Journey to the Sun!

AN AMBITIOUS MISSION to study the Sun is set for launch in 2017. Solar Orbiter will perform a close-up study of our Sun and inner heliosphere—the uncharted innermost regions of our Solar System—to better understand, and even predict, the unruly behaviour of the star on which our lives depend.

At its closest point, the spacecraft will be closer to the Sun than any previous spacecraft, braving the fierce heat and will carry its telescopes to almost one-quarter of Earth’s distance from our nearest star.

The European Space Agency’s Solar Orbiter will be the first satellite to provide close-up views of the Sun’s polar regions, which are very difficult to see from Earth. It will be able to almost match the Sun’s rotation around its axis for several days, and so it will be able for the first time to see solar storms building up over an extended period from the same viewpoint. It will also deliver data of the side of the Sun not visible from Earth.

Following “gravity assist” swing-bys of Venus and the Earth, Solar Orbiter will settle into a 168-day-long orbit around the Sun from which the spacecraft will begin its data collection mission.

Along this orbit, the spacecraft will reach closest approach to the Sun every five months—at around 42 million kilometres.

Adapted from information issued by ESA.

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Rover’s eye view of Mars

WHILE NASA’S MARS EXPLORATION ROVER Opportunity was travelling from Victoria crater to Endeavour crater, between September 2008 and August 2011, the rover team took an end-of-drive image on each Martian day that included a drive.

A new video compiles these 309 images, providing an historic record of the three-year trek that totalled about 21 kilometres across a Martian plain pocked with small craters.

The video shows the rim of Endeavour becoming visible on the horizon partway through the journey and growing larger as Opportunity neared that goal. The drive included detours, as Opportunity went around large expanses of treacherous terrain along the way.

The rover team also produced a sound track for the video, using each drive day’s data from Opportunity’s accelerometers. The low-frequency data has been sped up 1,000 times to yield audible frequencies.

“The sound represents the vibrations of the rover while moving on the surface of Mars,” said Paolo Bellutta, a rover planner at NASA’s Jet Propulsion Laboratory, who has plotted many of Opportunity’s drives and coordinated production of the video.

“When the sound is louder, the rover was moving on bedrock. When the sound is softer, the rover was moving on sand.”

Opportunity and its rover twin, Spirit, completed their three-month prime missions on Mars in April 2004. Both rovers continued for years of bonus, extended missions. Both have made important discoveries about wet environments on ancient Mars that may have been favourable for supporting microbial life.

Spirit stopped communicating in 2010. Opportunity continues its work at Endeavour. NASA will launch the next-generation Mars rover, car-size Curiosity, next month for arrival at Mars’ Gale crater in August 2012.

Here’s a video that explains the huge trek Opportunity made to reach Endeavour crater.

Adapted from information issued by NASA / JPL / Caltech.

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Milky Way galaxy is a ‘snake pit’

CSIRO's Australia Telescope Compact Array

CSIRO's Australia Telescope Compact Array was used to make a map of galactic gas polarisation.

A PIT OF WRITHING SNAKES. That’s what the first picture of turbulent gas inside our Milky Way galaxy looks like.

Professor Bryan Gaensler of the University of Sydney, Australia, and his team used a CSIRO radio telescope in eastern Australia to make the ground-breaking image, published in the journal Nature today.

The space between the stars in our Galaxy is not empty, but is filled with thin gas that continually swirls and churns.

“This is the first time anyone has been able to make a picture of this interstellar turbulence,” said Professor Gaensler. “People have been trying to do this for 30 years.”

Turbulence makes the Universe magnetic, helps stars form, and spreads the heat from supernova explosions through the Galaxy

“We now plan to study turbulence throughout the Milky Way. Ultimately this will help us understand why some parts of the Galaxy are hotter than others, and why stars form at particular times in particular places,” Professor Gaensler said.

Spectacular image

Gaensler and his team studied a region of our Galaxy about 10,000 light-years away in the constellation Norma.

They used CSIRO’s Australia Telescope Compact Array near Narrabri, NSW, because “it is one of the world’s best telescopes for this kind of work,” as Dr Robert Braun, Chief Scientist at CSIRO Astronomy and Space Science explained.

The radio telescope was tuned to receive radio waves that come from the Milky Way. As these waves travel through the swirling interstellar gas, one of their properties—polarisation—is very slightly altered, and the radio telescope can detect this.

(Polarisationis the direction the waves “vibrate”. Light can be polarised—for instance, some sunglasses filter out light polarised in one direction while letting through other light.)

Gas turbulence map of part of the Milky Way

A map has been made of the gas in our Milky Way galaxy. The 'snakes' are regions of gas where the density and magnetic field are changing rapidly as a result of turbulence.

The researchers measured the polarisation changes over an area of sky and used them to make a spectacular image of overlapping entangled tendrils, resembling writhing snakes.

The “snakes” are regions of gas where the density and magnetic field are changing rapidly as a result of turbulence.

Best match

The “snakes” also show how fast the gas is churning — an important number for describing the turbulence.

Team member Blakesley Burkhart, a PhD student from the University of Wisconsin, made several computer simulations of turbulent gas moving at different speeds.

These simulations resembled the “snakes” picture, with some matching the real picture better than others.

By picking the best match, the team concluded that the speed of the swirling in the turbulent interstellar gas is around 70,000 kph—relatively slow by cosmic standards.

Adapted from information issued by CSIRO. Images courtesy B. Gaensler et al. (data: CSIRO/ATCA) and David Smyth, CSIRO.

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Aussie shares Nobel Prize for physics

Artist's impression of a black hole

In 1998, two research teams announced the discovery that the expansion of the universe was accelerating.

THE ROYAL SWEDISH ACADEMY OF SCIENCES has awarded the Nobel Prize in Physics for 2011 to the leaders of the teams that discovered the accelerating expansion of the universe.

One half of the prize has been awarded to Saul Perlmutter (The Supernova Cosmology Project, Lawrence Berkeley National Laboratory and University of California) and the other half jointly to Brian P. Schmidt (The High-z Supernova Search Team, Australian National University, Australia) and Adam G. Riess (The High-z Supernova Search Team, Johns Hopkins University and Space Telescope Science Institute, Baltimore, USA).

In 1998, cosmology was shaken at its foundations as the two teams presented their findings. Headed by Saul Perlmutter, one of the teams had set to work in 1988. Brian Schmidt headed another team, launched at the end of 1994, where Adam Riess was to play a crucial role.

The research teams raced to map the Universe by locating the most distant supernovae (exploding stars). More sophisticated telescopes on the ground and in space, as well as more powerful computers and new digital imaging sensors, opened the possibility in the 1990s to add more pieces to the cosmological puzzle.

The teams used a particular kind of supernova, called type Ia supernova. It is an explosion of an old compact starthat is as heavy as the Sun but as small as the Earth. A single such supernova can emit as much light as a whole galaxy.

Brian Schmidt, Saul Perlmutter, Adam Riess

Recipients of the 2011 Nobel Prize for Physics— Brian Schmidt, Saul Perlmutter and Adam Riess.

Greatest enigma in physics

All in all, the two research teams found over 50 distant supernovae whose light was weaker than expected—this was a sign that the expansion of the Universe was accelerating.

The potential pitfalls had been numerous, and the scientists found reassurance in the fact that both groups had reached the same astonishing conclusion.

For almost a century, the Universe has been known to be expanding as a consequence of the Big Bang about 14 billion years ago. However, the discovery that this expansion is accelerating is astounding. If the expansion will continue to speed up the Universe will end in ice.

The acceleration is thought to be driven by dark energy, but what that dark energy is remains an enigma—perhaps the greatest in physics today.

What is known is that dark energy constitutes about three quarters of the Universe.

Therefore the findings of the 2011 Nobel Laureates in Physics have helped to unveil a Universe that to a large extent is unknown to science. And everything is possible again.

More information: Check out this great video on dark energy and the expansion of the universe. It features one of the Nobel Prize winners, Saul Perlmutter.

Adapted from information issued by the Royal Swedish Academy of Sciences.

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Earth from Space – Petermann Ice Island

Petermann Ice Island seen from space

The huge Petermann Ice Island broke free from Greenland's Petermann Glacier in August 2010.

AFTER  MORE THAN A YEAR and several thousand kilometres of sailing the seas, Petermann Ice Island is still drifting in the North Atlantic off the shores of Newfoundland, Canada.

Once a hunk of ice fives times the size of Manhattan Island, the ice island has splintered several times since it dropped off the edge of Greenland’s Petermann Glacier.

Yet still it behaves a bit like the massive ice sheet it left 14 months ago.

Astronauts on the International Space Station used a digital camera to capture this view of Petermann Ice Island A, fragment 2, off of the northeast coast of Newfoundland on August 29, 2011.

Spanning roughly 4 kilometres by 3.5 kilometres, the ice island is covered with melt ponds and streams, much as the surface of Greenland looks in mid-summer.

As ice melts on top of the Greenland ice sheet, the melt water forms streams and pools in the depressions on the ice surface. Drawn downslope by gravity—much like streams on a mountainside—water also runs toward the edges of the ice. In some cases, it cracks through it and rushes to the bottom.

Such processes appear to be at work on the ice island as well.

August 2011 was a busy month in the life of the ice island, according to the Canadian Ice Service. On August 7, it became grounded on a shoal or shallow seafloor off of St. Anthony, Newfoundland, where it sat for 11 days.

By August 18, the ice island broke free and began drifting again, only to split into two large pieces about five days later. The Ice Service last reported on it on August 25.

See the full-size image of the Petermann Ice Island here.

Astronaut photograph provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre. Text adapted from information issued by Mike Carlowicz.

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Earth from Space – Roze Glacier

Satellite image of Roze Glacier

Russia's remote Severny Island is home to the huge Roze Glacier.

PART OF THE RUSSIAN FEDERATION, the archipelago of Novaya Zemlya consists of two big islands—Yuzhny in the southwest, and Severny in the northeast—separated by a narrow strait. The archipelago divides the Barents Sea from the Kara Sea.

An ice cap covers much of Severny, and from this ice cap, several outlet glaciers flow seaward. The easternmost glacier on Severny’s southeastern coast is Roze.

On June 5, 2011, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this natural-colour image of Roze Glacier fringed by sea ice.

The glacier pushes slowly seaward between two rocky ridges. Uneven snow cover on the rock surfaces creates a patchwork of brown and white. Some snow also rests on the adjacent sea ice, which appears in shades of white and gray. In the east, a large patch of gray ice immediately offshore may owe its colour to a layer of melt water or simply a lack of snow cover.

On the glacier itself, isolated pools of melt water form ovals and slivers of blue-gray. Dwarfing the melt ponds, two long parallel stripes extend southward toward the coast. The stripes look like debris along the sides of a relatively fast-flowing ice stream, which may have picked up rocks and dirt from an upslope rock outcrop.

Glaciers gain ice through snow accumulation, and lose it through melting and calving icebergs. A report released in 2006 by the Laboratoire d’Etudes en Géophysique et Océanographie Spatiales stated that Roze Glacier, in addition to other glaciers along Severny’s southeastern coast, underwent overall ice loss between 1990 and 2000.

Several hundred years ago, the Little Ice Age prompted many glaciers to advance. Glaciers do not respond to changing climate immediately, but may advance or retreat years, decades, even centuries afterwards.

A study published in 2009 reported that the glaciers on Novaya Zemlya likely reached their maximum extent related to the Little Ice Age near the end of the nineteenth century, and have since retreated at varying rates.

See the full-size image of Roze Glacier here.

NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Text adapted from information issued by Michon Scott based on image interpretation by Walt Meier, National Snow and Ice Data Centre.

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Fried Egg nebula home to hypergiant

ASTRONOMERS HAVE TAKEN AN IMAGE of a colossal star that belongs to one of the most rare classes of stars in the Universe…the yellow hypergiants.

The new picture is the best ever taken of a star in this class and shows for the first time a huge dusty double shell surrounding the star.

The star and its shells resemble an egg white around a yolky centre, leading the astronomers to nickname the object the Fried Egg Nebula.

The monster star, known to astronomers as IRAS 17163-3907, has a diameter about a thousand times bigger than our Sun.

And at a distance of about 13,000 light-years from Earth, it is the closest yellow hypergiant found to date and new observations show it shines some 500,000 times more brightly than the Sun.

Unexpected discovery

Yellow hypergiants are in an extremely active phase of their evolution, undergoing a series of explosive events. This particular star has ejected four times the mass of the Sun in just a few hundred years.

The material flung out during these bursts has formed the extensive double shell of the nebula, which is made of dust rich in silicates and mixed with gas.

Fried Egg Nebula

This picture of the nebula around a rare yellow hypergiant star called IRAS 17163-3907 is the best ever taken of a star in this class and shows for the first time a huge dusty double shell surrounding the star. The star and its shells resemble an egg white around a yolky centre, leading astronomers to nickname the object the Fried Egg Nebula.

“This object was known to glow brightly in the infrared but, surprisingly, nobody had identified it as a yellow hypergiant before,” said Eric Lagadec (European Southern Observatory, ESO), who led the team that produced the new images using ESO’s Very Large Telescope (VLT).

The next supernova?

If the Fried Egg Nebula were placed in the centre of the Solar System the Earth would lie deep within the star itself and the planet Jupiter would be orbiting just above its surface.

The much larger surrounding nebula would engulf all the planets and dwarf planets and even some of the comets that orbit far beyond the orbit of Neptune.

The outer shell has a radius of 10,000 times the distance from the Earth to the Sun.

The star is likely to soon die an explosive death—it will be one of the next supernova explosions in our galaxy.

Supernovae provide much-needed chemicals to the surrounding interstellar environment and the resulting shock waves can kick start the formation of new stars.

Adapted from information issued by ESO / E. Lagadec.

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Herschel telescope reveals invisible cosmos

HERSHEL, A CUTTING-EDGE SPACE OBSERVATORY, carries the largest, most powerful infrared telescope ever launched.

A pioneering mission of the European Space Agency, it is studying the origin and evolution of stars and galaxies to help understand how the Universe came to be the way it is today.

For this purpose Herschel is looking, at far-infrared and submillimetre wavelengths, at objects that are among the coldest in space.

Launched in May 2009 it has already given great results to the scientific community by revealing invisible parts of the universe.

More information:

ESA Herschel mission

Adapted from information issued by ESA.

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