RSSArchive for April, 2010

Hubble wants you for the Zoo

The famous Sombrero Galaxy

The public can join Galaxy Zoo to help scientists categorise thousands of distant galaxies. This one is the famous Sombrero Galaxy.

As the Hubble Space Telescope achieves the major milestone of two decades on orbit, NASA and the Space Telescope Science Institute, or STScI, in Baltimore are celebrating Hubble’s journey of exploration with several online educational activities.

There are also opportunities for people to explore galaxies as armchair scientists and send personal greetings to Hubble for posterity.

NASA’s best-recognised, longest-lived and most prolific space observatory was launched April 24, 1990, aboard the space shuttle Discovery during the STS-31 mission. Hubble discoveries revolutionised nearly all areas of current astronomical research from planetary science to cosmology.

Over the years, Hubble has suffered broken equipment, a bleary-eyed primary mirror, and the cancellation of a planned shuttle servicing mission. But the ingenuity and dedication of Hubble scientists, engineers and NASA astronauts allowed the observatory to rebound and thrive. The telescope’s crisp vision continues to challenge scientists and the public with new discoveries and evocative images.

“Hubble is undoubtedly one of the most recognised and successful scientific projects in history,” said Ed Weiler, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. “Last year’s space shuttle servicing mission left the observatory operating at peak capacity, giving it a new beginning for scientific achievements that impact our society.”

A Hubble image of part of the Eagle Nebula

A Hubble image of part of the Eagle Nebula

Get involved with Hubble

Hubble fans worldwide are being invited to take an interactive journey with Hubble by visiting http://www.nasa.gov/externalflash/Hubble20/. They can also visit http://www.hubblesite.org to share the ways the telescope has affected them. Follow the “Messages to Hubble” link to send an e-mail, post a Facebook message, or send a cell phone text message. Fan messages will be stored in the Hubble data archive along with the telescope’s science data.

For those who use Twitter, you can follow @HubbleTelescope or post tweets using the Twitter hashtag #hst20.

The public also will have an opportunity to become at-home scientists by helping astronomers sort out the thousands of galaxies seen in a Hubble deep field observation.

STScI is partnering with the Galaxy Zoo consortium of scientists to launch an Internet-based astronomy project where amateur astronomers can peruse and sort galaxies from Hubble’s deepest view of the universe into their classic shapes: spiral, elliptical, and irregular.

Dividing the galaxies into categories will allow astronomers to study how they relate to each other and provide clues that might help scientists understand how they formed.

To visit the Galaxy Zoo page, go to http://www.hubble.galaxyzoo.org

A screenshot from Galaxy Zoo

A screenshot from Galaxy Zoo

For educators and students, STScI is creating an educational website called “Celebrating Hubble’s 20th Anniversary.” It offers links to facts and trivia about Hubble, a news story that chronicles the observatory’s life and discoveries, and the IMAX “Hubble 3D” educator’s guide.

An anniversary poster containing Hubble’s “hall-of-fame” images, including the Eagle Nebula and Saturn, also is being offered with downloadable classroom activity information. Visit the website at http://amazing-space.stsci.edu/hubble_20

To date, Hubble has observed more than 30,000 celestial targets and amassed more than a half-million pictures in its archive. The last astronaut servicing mission to Hubble in May 2009 made the telescope 100 times more powerful than when it was launched.

Adapted from information issued by NASA / STScI.

Hubble’s 20th birthday image

Hubble Space Telescope image of part of the Carina Nebula

This turbulent cosmic pinnacle lies within a tempestuous stellar nursery called the Carina Nebula, located 7,500 light-years away in the southern constellation of Carina. The image celebrates the 20th anniversary of Hubble's launch and deployment into an orbit around the Earth.

The best recognised, longest-lived and most prolific space observatory zooms past a milestone of 20 years of operation.

On April 24, 1990, the space shuttle and crew of STS-31 were launched to deploy the NASA/ESA Hubble Space Telescope into a low-Earth orbit. What followed was one of the most remarkable sagas of the space age.

Hubble’s unprecedented capabilities have made it one of the most powerful science instruments ever conceived by humans, and certainly the one most embraced by the public. Hubble’s discoveries have revolutionised nearly all areas of current astronomical research, from planetary science to cosmology. And, its pictures are unmistakably out of this world.

At times Hubble’s starry odyssey has played out like a space soap opera: with broken equipment, a bleary-eyed primary mirror and even a Space Shuttle rescue/repair mission cancellation.

But the ingenuity and dedication of Hubble scientists, engineers, and NASA and ESA astronauts have allowed the observatory to rebound time and time again. Its crisp vision continues to challenge scientists with exciting new surprises and to enthral the public with ever more evocative colour images.

NASA, ESA and the Space Telescope Science Institute (STScI) are celebrating Hubble’s journey of exploration with a stunning new picture.

The brand new Hubble anniversary image highlights a small portion of one of the largest observable regions of starbirth in the galaxy, the Carina Nebula. (See the large version here.) Towers of cool hydrogen laced with dust rise from the wall of the nebula.

The scene is reminiscent of Hubble’s classic Pillars of Creation photo from 1995, but even more striking in appearance.

The image captures the top of a pillar of gas and dust, three light-years tall, which is being eaten away by the brilliant light from nearby bright stars. The pillar is also being pushed apart from within, as infant stars buried inside it fire off jets of gas that can be seen streaming from towering peaks like arrows sailing through the air.

The Hubble Space Telescope in orbit

The Hubble Space Telescope in orbit

Hubble’s public involvement

Another exciting component of the anniversary will be the launch of the revamped European website for Hubble, spacetelescope.org. ESA will also be sponsoring the Hubble Pop Culture Contest that calls for fans to search for examples of the observatory’s presence in everyday life (http://www.spacetelescope.org/projects/20anniversary/hubblepopculture/).

Hubble fans worldwide are being invited to share the ways in which the telescope has affected them. They can send an e-mail, post a Facebook message (to http://www.facebook.com/hubblespacetelescope) or use the Twitter hashtag #hst20. Or, they can visit the “Messages to Hubble” page on http://hubblesite.org, type in their entry and read selections from other messages that have been received.

Fan messages will be stored in the Hubble data archive along with the telescope’s many terabytes of science data. Future researchers will be able to read these messages and understand how Hubble had such an impact on the world.

To date, Hubble has looked at over 30,000 celestial targets and amassed over half a million pictures in its archive.

The last heroic astronaut-servicing mission to Hubble in May 2009 made the telescope 100 times more powerful than when it was launched. In addition to its irreplaceable scientific importance, Hubble brings cosmic wonders into millions of homes and schools every day.

Adapted from information issued by ESA. Image credit: NASA, ESA, M. Livio and the Hubble 20th Anniversary Team (STScI).

Comet crash caused climate change?

Artist's impression of an asteroid or comet striking the Earth.

Artist's impression of a comet striking the Earth.

Earth was struck by thousands of cometary fragments over the course of an hour 13,000 years ago, leading to a dramatic cooling of the planet, according to astronomer Professor Bill Napier of the Cardiff University Astrobiology Centre.

The cooling, by as much as 8 degrees C, interrupted the warming which was occurring at the end of the last ice age and caused glaciers to readvance.

Evidence has been found that this catastrophic change was associated with some extraordinary extraterrestrial event.

The change is marked by the occurrence of a “black mat” layer a few centimetres thick found in rock layers at many sites throughout the United States containing high levels of soot indicative of continental-scale wildfires.

There are also microscopic hexagonal diamonds (nano-diamonds), which are produced by high-pressure shock events and are found only in meteorites or impact craters.

These findings led to the suggestion that the catastrophic changes of that time were caused by the impact of an asteroid or comet 4 km across on the Laurentide ice sheet, which at that time covered what would become Canada and the northern part of the United States.

The cooling lasted over a thousand years, and its onset coincides with the rapid extinction of 35 genera of North American mammals, as well as the disruption of the Palaeoindian culture.

The chief objection to the idea is that the odds against the Earth being struck by an asteroid this large only 13,000 years ago are a thousand to one against. And the heat generated by the rising fireball would have been limited by the curvature of the horizon and could not explain the continent-wide occurrence of wildfires.

Multiple comet crashes the cause?

Professor Napier has now come up with an model that accounts for the major features of the catastrophe without involving such an improbable event. According to his concept, the Earth ran into a dense trail of material from a large disintegrating comet.

Fragments of comet 73/P Schwassman-Wachmann 3

Comets sometimes break into many pieces, such as 73/P Schwassman-Wachmann 3, seen in this Hubble Space Telescope image from 2005.

He points out that there is compelling evidence that such a comet entered the inner planetary system between 20,000 and 30,000 years ago and has been fragmenting ever since, giving rise to a number of closely related meteor streams and asteroids known as the Taurid Complex.

In the course of the giant comet’s disintegration, the environment of the interplanetary system would have been hazardous and the Earth would probably have run through at least one dense swarm of cometary material.

The new model indicates that such an encounter would last for about an hour during which thousands of impacts would take place over continental areas, each releasing the energy of a megaton-class nuclear bomb, generating the extensive wildfires which took place at that time. The nano-diamonds at the extinction boundary would then be explained as having come in with the comet swarm.

One recent meteorite is known which may have come from this giant comet progenitor—the Tagish Lake meteorite, which fell over Yukon Territory in January 2000. It has the highest abundance of nano-diamonds of any meteorite so far analysed.

Professor Napier sums up his model: “A large comet has been disintegrating in the near-Earth environment for the past 20,000 to 30,000 years, and running into thousands of fragments from this comet is a much more likely event than a single large collision. It gives a convincing match to the major geophysical features at this boundary.”

Adapted from information issued by the RAS. Image credits: NASA / ESA / H. Weaver (JHU/APL) / M. Mutchler / Z. Levay (STScI) / G. Rhemann and M. Jager.

Antarctic glacier retreats

Image of Crane Glacier on the Larsen B Ice Shelf on April 6, 2002

This image of Crane Glacier on the Larsen B Ice Shelf on the Antarctic Peninsula was captured on April 6, 2002. Compare with the image below.

In late Southern Hemisphere summer of 2002, the Larsen B Ice Shelf on the Antarctic Peninsula disintegrated into thousands of pieces.

The collapse appears to have been due to a series of warm summers on the Antarctic Peninsula, which culminated with an exceptionally warm summer in 2002. On the surface of the shelf, rows of melt ponds settled into natural crevasses, driving the cracks all the way through the ice shelf.

This pair of images from NASA’s Landsat 7 satellite shows the dramatic impact the collapse had on many of the glaciers that fed the Larsen B Ice Shelf. The loss of the shelf caused the flow of most of the glaciers around the bay to accelerate significantly. More rapid flow and calving of icebergs caused the margins to retreat inland.

The image above was captured on April 6, 2002, about two months after the dramatic collapse. The bay (image right) is filled with slush and icebergs from the collapsed shelf.

Autumn snows have probably already dusted the surface of the mélange of ice; snowfall and seasonal sea ice kept much of the debris frozen in place the first winter after the collapse. The terminus of the Crane Glacier extends into the bay like a fan.

Throughout the summer of 2003, remaining fragments of the shelf broke away, and the mélange of icebergs and smaller ice pieces from the previous summer’s collapse began to drift away.

Without the stabilizing presence of the ice shelf, the Crane Glacier retreated dramatically. Its fan-shaped terminus became C-shaped as the glacier’s centre crumbled more rapidly than the edges pressed against the mountain walls.

By 2003, Crane Glacier had retreated dramatically

By 2003, Crane Glacier had retreated dramatically as fragments of the ice shelf broke away.

The unusually bright blue tinge of the ice debris in the February 20 image (above) is the reflection from the pure ice on the underside of the ice shelf fragments. Many of the icebergs that crumbled from the edge of the shelf were too tall and narrow to float upright, and they toppled over.

The surface of an ice shelf gets covered by snow, but the underside is very pure ice. Pure, thick ice absorbs a small amount of red light. Photo-like satellite images such as these are made by combining the satellite’s observations of red, green, and blue wavelengths of light reflected from the Earth’s surface. When all these visible wavelengths are strongly reflected, the surface looks white; when the reddest light is absorbed, the reflection takes on a bluish tinge.

NASA images by Robert Simmon based on Landsat-7 data. Text adapted from information issued by Rebecca Lindsey.

Desert lake fills with water

Lake Frome, as seen on April 20, 2010

After image: Water fills parts of Lake Frome, as seen on April 20, 2010 by NASA’s Earth Observing-1 (EO-1) satellite.

In central Australia, spanning the borders between several states, lies an expanse of ephemeral lakes. This area receives 149 to 216 millimetres (less than an inch) of rainfall a year on average, and the basins pass most of their time as saltpans.

Occasional rains do, however, fill them with water.

In South Australia, at the southern end of an arc of saltpans, is Lake Frome. When Frome fills, the waters usually come from precipitation in the northern Flinders Ranges, or from water overflowing from another saltpan to the north, Lake Callabonna.

The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured these natural-colour images of Lake Frome on April 10, 2010 (above), and March 7, 2009 (below).

The area covered shows the eastern edge of the saltpan; the land to the east has a slightly higher elevation and consists of a network of typically dry river channels. Inside the saltpan, the land surface is uneven. Areas shaped like sloppy teardrops rise above the surrounding plain.

Lake Frome, as seen on March 7, 2009

Before image: In 2009, Lake Frome was bone dry.

In the 2009 image, the salt lake appears bone-dry, filled with off-white sediment. In the 2010 image, however, water has infiltrated the area. Water on the land surface appears in shades of dull green, and a temporary river runs north-south through the image. Water also fills a network of small temporary lakes in the southeast.

Throughout much of Lake Frome, water makes its presence known not through standing water but through mud and/or welt salts. Water seeping through typically dry sediments had darkened the surface, especially in the west.

Water flowing southward into Lake Frome continued a pattern of drainage that began earlier in 2010. Rains in central Australia filled impermanent rivers from Queensland to South Australia. The water initially filled river channels in the north before travelling southward.

As Lake Frome lies at the southern reaches of saltpans in this region, it was one of the last areas to fill with water.

NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team and the United States Geological Survey. Text adapted from information issued by Michon Scott.

Earth was wet in its youth

Earth seen from space

Extreme greenhouse concentrations weren't needed to keep Earth's oceans from freezing billions of years ago.

Four billion years ago, our then stripling Sun radiated only 70 to 75 percent as much energy as it does today. Other things on Earth being equal, with so little energy reaching the planet’s surface, all water on the planet should been have frozen.

But ancient rocks hold ample evidence that the early Earth was awash in liquid water – a planetary ocean of it. So something must have compensated for the reduced solar output and kept Earth’s water wet.

To explain this apparent paradox, a popular theory holds there must have been higher concentrations of greenhouse gases in the atmosphere, most likely carbon dioxide, which would have helped retain a greater proportion of the solar energy that arrived.

But a team of scientists including researchers from Stanford have analysed the mineral content of 3.8-billion-year-old marine rocks from Greenland and concluded otherwise.

Swirls of cloud over the ocean

Swirls of cloud over the ocean

“There is no geologic evidence in these rocks for really high concentrations of a greenhouse gas like carbon dioxide,” said Dennis Bird, professor of geological and environmental sciences.

Instead, the team proposes that the vast global ocean of early Earth absorbed a greater percentage of the incoming solar energy than today’s oceans, enough to ward off a frozen planet.

Earth was a water world

Because the first landmasses that formed on Earth were small – mere islands in the planetary sea – a far greater proportion of the surface was covered with water than today.

The crux of the theory is that because oceans are darker than continents, particularly before plants and soils covered landmasses, seas absorb more sunlight.

“It’s the same phenomenon you will experience if you drive to Wal-Mart on a hot day and step out of your car onto the asphalt,” Bird said. “It’s really hot walking across the blacktop until you get onto the white concrete sidewalk.”

Another key component of the theory is in the clouds. “Not all clouds are the same,” Bird said.

Clouds reflect sunlight back into space to a degree, cooling Earth, but how effective they are depends on the number of tiny particles available to serve as nuclei around which the water droplets can condense. An abundance of nuclei means more droplets of a smaller size, which makes for a denser cloud and a greater reflectivity, or albedo, on the part of the cloud.

The edge of Earth's atmosphere

The edge of Earth's atmosphere

Most nuclei today are generated by plants or algae and promote the formation of numerous small droplets. But plants and algae didn’t flourish until much later in Earth’s history, so their contribution of potential nuclei to the early atmosphere circa 4 billion years ago would have been minimal. The few nuclei that might have been available would likely have come from erosion of rock on the small, rare landmasses of the day and would have caused larger droplets that were essentially transparent to the solar energy that came in to Earth, according to Bird.

“We put together some models that demonstrate, with the slow continental growth and with a limited amount of clouds, you could keep water above freezing throughout geologic history,” Bird said.

Adapted from information issued by Stanford University.

Sun begins a new cycle

Loops in the Sun's magnetic field

Loops in the Sun's magnetic field are often associated with sunspots.

Scientists from Geoscience Australia will be watching changes to Earth’s magnetic field over the coming few years with evidence that the Sun has begun its latest cycle of sunspot activity.

The most recent so called sunspot maximum occurred in 2000 and was followed by a period of decreasing sunspot numbers which was slightly longer than usual. However, scientists are now seeing evidence that the new solar cycle has begun and the number of sunspots may be starting to rise again. If the normal pattern continues they should peak around 2013.

One of the significant effects of sunspots and associated solar flares is the impact on Earth’s magnetic field. The rapid field changes caused by sunspots affect satellite and high-frequency radio communications, telephones and powerlines. They also degrade the accuracy of GPS positions and disrupt magnetic surveying operations.

Another consequence of increased solar activity is auroral displays which are caused by charged particles from the Sun entering Earth’s magnetic field and colliding with gas particles in the atmosphere. Auroras occur more commonly in polar regions, but the phenomenon can sometimes also be seen nearer the equator during periods of intense magnetic activity.

Working in conjunction with the Australian Space Weather Agency, IPS Radio and Space Services, Geoscience Australia will record any increased activity in Earth’s magnetic field at its geomagnetic monitoring stations at Kakadu and Alice Springs in the Northern Territory, Learmonth and Gnangara in Western Australia, Charters Towers in Queensland, near Canberra in the ACT and in Antarctica at Casey, Mawson and Macquarie Island.

Adapted from information issued by Geoscience Australia. Image courtesy TRACE / NASA.

Island of coal

Satellite image of the Panian Coalfield on Semirara Island

The northern part of Semirara Island in the Philippine is dominated by the Panian Coalfield.

This detailed astronaut photograph provides a rare cloud-free view of the northern end of Semirara Island, which is located approximately 280 kilometres to the south of Manila in the Philippines.

The northern part of the island is dominated by the Panian Coalfield, the largest of three coalfields on the island. Most of the coal is used for energy generation in the Philippines, with some exported to India and China.

The Panian coalfield is being mined using open-pit methods. The rock and soil above the coal layers (or seams) is known as overburden. Overburden is removed from the pit and heaped into piles, several of which ring the northern half of the pit.

Several of the dark coal seams are visible along the sunlit southern wall of the pit (these may be more visible in the larger image version). Plumes of sediment from the overburden piles enter the Sulu Sea along the northern and eastern coastline of the island.

The Semirara coalfields formed 12-23 million years ago along what was then a coastal plain—similar to the current geologic environment of the southeastern Gulf Coast of the United States. Organic materials were deposited in sequences of sandstone and mudstone, which were then covered by limestone as the environment became progressively more marine.

Over geologic time, increased pressure from the overlying rocks changed the layers of organic material into coal.

Image provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre. Text adapted from information issued by William L. Stefanov, NASA-JSC.

Honey, I shrunk the receiver

An artist's impression of the ASKAP radio telescope array

An artist's impression of the ASKAP radio telescope array in Western Australia. ASKAP is currently under construction, and is due to commence operations in early 2013.

A complete radio receiver on a chip measuring just 5mm x 5mm could eventually be used in mobile phones and other communications technologies.

CSIRO and Australian company Sapphicon Semiconductor Pty Ltd have signed an agreement to jointly develop the chip.

The development of a low-cost, ultra-high-bandwidth ‘system-on-chip’ device could also replace traditional receivers currently used in radio astronomy applications, many of which are about the size of a small fridge.

The chip’s first test will be in CSIRO’s Australian SKA Pathfinder (ASKAP)—an array of 36 radio dishes that acts as a single telescope now under construction in Western Australia.

Image of silicon-on-sapphire chips

New silicon-on-sapphire chips are being developed by CSIRO and Sapphicon Semiconductor.

It will be tested in an innovative radio camera (or “phased array feed”) developed by CSIRO, which sits at the focal centre of each ASKAP dish to receive incoming cosmic radio waves.

“This chip will minimise the size and weight of the phased array feed, reduce cost and power, and facilitate maintenance,” said CSIRO Project Director for ASKAP, Dr David DeBoer.

“In our radio camera, it could revolutionise radio astronomy.”

International researchers developing the Square Kilometre Array radio telescope are interested in the R&D proposed by CSIRO and Sapphicon. No other group is developing a fully integrated single-chip receiver.

“This sort of technology, which looks to deliver mass-produced components on low-loss substrates consuming little power, is ideal for the SKA, which potentially needs millions of highly sensitive electronic sensors,” said Professor Richard Schilizzi, Director of the SKA Program Development Office in the UK, which co-ordinates international planning for the SKA.

“CSIRO is to be congratulated on this important step.”

Adapted from information issued by CSIRO / Sapphicon Semiconductor Pty Ltd.

World’s highest volcano

Satellite image of Llullaillaco Volcano.

South America’s Llullaillaco Volcano is the world's highest historically active volcano.

The summit of South America’s Llullaillaco Volcano has an elevation of 6,739 metres (22,110 feet) above sea level, making it the highest historically active volcano in the world.

The current stratovolcano—a cone-shaped volcano built from successive layers of thick lava flows and eruption products like ash and rock fragments—is built on top of an older stratovolcano.

The last explosive eruption of the volcano, based on historical records, occurred in 1877.

This detailed astronaut photograph of Llullaillaco illustrates an interesting volcanic feature known as a coulée (image top right). Coulées are formed from highly viscous, thick lavas that flow onto a steep surface.

As they flow slowly downwards, the top of the flow cools and forms a series of parallel ridges orientated at 90 degrees to the direction of flow (somewhat similar in appearance to the pleats of an accordion).

The sides of the flow can also cool faster than the centre, leading to the formation of wall-like structures known as flow levees (image centre).

Llullaillaco is also a well-known archaeological site—the mummified remains of three Inca children, ritually sacrificed 500 years ago, were discovered on the summit in 1999.

Image provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre. Text adapted from information issued by William L. Stefanov.