Posted on by Fraser Cain

Images of Wetlands from Space

Image credit: ESA

The Earth’s wetlands are home to some of the most fragile and diverse ecosystems on the planet, and they’re under constant threat from human agriculture, pollution, and settlement. This month the European Space Agency began a program to map 50 wetland areas around the Earth from space to help keep track of their health. ESA’s Envisat is able to tell the difference between dry and waterlogged areas, and will be able to provide annual data about how various wetlands change throughout the seasons.

Dotted across varied regions of our planet are the waterlogged landscapes known as wetlands. Often inaccessible, these muddy areas are actually treasure houses of ecological diversity ? their overall value measured in trillions of Euros.

For much of the last century wetlands have been drained or otherwise degraded, but scientific understanding of their important roles in terms of biology and the water cycle has grown, spurring international efforts to preserve them. On 20 November ESA formally began a project to map wetlands from space, providing data on around 50 sites in 21 countries worldwide.

In 1971 an inter-governmental treaty established the Ramsar Convention on Wetlands, establishing a framework for the stewardship and preservation of wetlands. Today more than 1310 wetlands have been designated as Wetlands of International Importance, a total area of 111 million hectares. The Convention’s 138 national signatories are obliged to report on the state of listed wetlands they are responsible for.

ESA’s new ?1 million Globwetland project is producing satellite-derived and geo-referenced products including inventory maps and digital elevation models of wetlands and the surrounding catchment areas. These products will aid local and national authorities in fulfilling their Ramsar obligations, and should also function as a helpful tool for wetland managers and scientific researchers.

“The Ramsar Convention on Wetlands stresses that targeted assessment and monitoring information is vital for ensuring effective management planning for wetlands, their hydrology and their catchments,” explained Nick Davidson, Ramsar’s Deputy Secretary General. “Yet for wetland managers and decision-makers in many countries access to sound information about wetlands and how they are changing is often a critical gap.

“By working with users at site and catchment scales the Globwetland project should contribute significantly to helping achieve effective management of these critical important ecosystems for biodiversity and human well-being.”

With wetlands often made up of difficult and inaccessible terrain, satellites can help provide information on local topography, the types of wetland vegetation, land cover and use and the dynamics of the local water cycle. In particular radar imagery of the type provided by ESA’s Envisat is able to differentiate between dry and waterlogged surfaces, and so can provide multitemporal data on how given wetlands change seasonally.

Data gathered over four continents
Globwetland products are being provided for a wide range of terrain types to users across four continents: North and South America, Africa, Asia and Europe, including European Russia. In Spain the Globwetland end-user is the government’s Ministry of the Environment.

“We have previously used aerial photography to prepare wetland maps, but this is the first time we will use Earth Observation data,” said Jos? Ram?n Picatoste Ruggeroni, Director General of Nature Conservation and Subdirector General of Biodiversity Conservation. “The areas we are most interested in are land cover and land cover analysis, topography dynamics and subsidence layers, water cycle and quality maps.

“In co-operation with the Spanish regional authorities involved in nature conservation and local wetland managers, we hope to investigate the possibility of achieving a common standard of regularly updated geoinformation to monitor ecological changes in the Spanish Ramsar sites.”

At the other side of the continent, wetlands comprise a third of the territory of the Russian Federation, the majority of it in the form of peatlands. Through much of the 20th century these areas were regarded as wasteland and drained for peat extraction – ending up as unproductive lands that do not contribute either economically or in terms of biodiversity, and also cause ecological problems such as dust storms and uncontrolled carbon dioxide emissions from smouldering peat fires.

In Russia the Globwetland partner is the Ministry of Ecology and Land Use of Moscow region, and has a particular interest in using periodic satellite data to monitor peat fires and estimate how effective a new rewetting project is in preventing further outbreaks.

While in South Africa, Globwetland partner the Department of Environmental Affairs and Tourism (DEAT) seeks to use satellite data to help fulfil its Ramsar obligations for its existing three-site wetlands inventory. The Department also plans to map a separate site, the Prince Edward Islands Special Nature Reserve, for the first time.

South Africa hopes to propose the offshore Reserve for designation as a new Ramsar Wetland of International Importance, but its uncharted nature is currently an obstacle to achieving this. This Southern Ocean site is also being nominated next year as a UNESCO World Heritage Site.

Why are wetlands so valuable?
Studies of wetlands show they store and purify water for domestic use, recharge natural aquifers as they run low, retain nutrients in floodplains, help control flooding and shore erosion and regulate local climate.

Most of all, wetlands support life in spectacular variety and numbers: freshwater wetlands alone are home to four in ten of all the world’s species, and one in eight of global animal species.

An assessment of the monetary value of natural ecosystems published in Nature in 1997 arrived at a figure of 27.7 trillion Euros (33 trillion dollars), with wetland ecosystems making up ?12.5 trillion ($14.9 trillion) ? or 45% – of this total.

Much of human civilisation has been based around river valleys and floodplains. However, global freshwater consumption rose sixfold during the 20th century, a rate more than double that of population growth. And world population is set to rise by 70 million people a year for the next two decades.

Couple that trend with the threat of accelerating climate change, and biologically-productive and hydrologically-stabilising wetlands look like necessities we can ill do without.

Original Source: ESA News Release

Posted on by Fraser Cain

The Next Supernova?

Image credit: ESO

The European Southern Observatory has released new images of a relatively nearby star, Eta Carina, which could be in the final stages of its life and could explode as a supernova in the near future (astronomically-speaking) – within the next 10-20,000 years or so. The star is 7,500 light years away, 100 times the mass of the Sun, and the most luminous object in the Milky Way. Since 1841, it has created a beautiful nebula around itself by continuously shedding outside layers while it spins quickly. By watching how Eta Carina changes, astronomers will gain valuable insights into the final stages of a supermassive star’s life.

Ever since 1841, when the until then inconspicuous southern star Eta Carinae underwent a spectacular outburst, astronomers have wondered what exactly is going on in this unstable giant star. However, due to its considerable distance – 7,500 light-years – details of the star itself were beyond observation.

This star is known to be surrounded by the Homunculus Nebula, two mushroom-shaped clouds ejected by the star, each of which is hundreds of times larger than our solar system.

Now, for the first time, infrared interferometry with the VINCI instrument on ESO’s Very Large Telescope Interferometer (VLTI) enabled an international team of astronomers [1] to zoom-in on the inner part of its stellar wind. For Roy van Boekel, leader of the team, these results indicate that “the wind of Eta Carinae turns out to be extremely elongated and the star itself is highly unstable because of its fast rotation.”

A monster in the southern sky
Eta Carinae, the most luminous star known in our Galaxy, is by all standards a real monster: it is 100 times more massive than our Sun and 5 million times as luminous. This star has now entered the final stage of its life and is highly unstable. It undergoes giant outbursts from time to time; one of the most recent happened in 1841 and created the beautiful bipolar nebula known as the Homunculus Nebula (see ESO PR Photo 32a/03). At that time, and despite the comparatively large distance – 7,500 light-years – Eta Carinae briefly became the second brightest star in the night sky, surpassed only by Sirius.

Eta Carinae is so big that, if placed in our solar system, it would extend beyond the orbit of Jupiter. This large size, though, is somewhat arbitrary. Its outer layers are continually being blown into space by radiation pressure – the impact of photons on atoms of gas. Many stars, including our Sun, lose mass because of such “stellar winds”, but in the case of Eta Carinae, the resulting mass loss is enormous (about 500 Earth-masses a year) and it is difficult to define the border between the outer layers of the star and the surrounding stellar wind region.

Now, VINCI and NAOS-CONICA, two infrared-sensitive instuments on ESO’s Very Large Telescope (VLT) at the Paranal Observatory (Chile), have probed the shape of the stellar wind region for the first time. Looking down into the stellar wind as far as possible, the astronomers could infer some of the structure of this enigmatic object.

The astronomer team [1] first used the NAOS-CONICA adaptive optics camera [2], attached to the 8.2-m VLT YEPUN telescope, to image the hazy surroundings of Eta Carinae, with a spatial resolution comparable to the size of the solar system, cf. PR Photo 32a/03.

This image shows that the central region of the Homunculus nebula is dominated by an object that is seen as a point-like light source with many luminous “blobs” in the immediate vicinity.

Towards the limit
In order to obtain an even sharper view, the astronomers then turned to interferometry. This technique combines two or more telescopes to achieve an angular resolution [3] equal to that of a telescope as large as the separation of the individual telescopes (cf. ESO PR 06/01 and ESO PR 23/01).

For the study of the rather bright star Eta Carinae the full power of the 8.2-m VLT telescopes is not required. The astronomers thus used VINCI, the VLT INterferometer Commissioning Instrument [4], together with two 35-cm siderostat test telescopes that served to obtain “First Light” with the VLT Interferometer in March 2001 (see ESO PR 06/01).

The siderostats were placed at selected positions on the VLT Observing Platform at the top of Paranal to provide different configurations and a maximum baseline of 62 meters. During several nights, the two small telescopes were pointed towards Eta Carinae and the two light beams were directed towards a common focus in the VINCI test instrument in the centrally located VLT Interferometric Laboratory. It was then possible to measure the angular size of the star (as seen in the sky) in different directions.

Pushing the spatial resolution of this configuration to the limit, the astronomers succeeded in resolving the shape of the outer layer of Eta Carinae. They were able to provide spatial information on a scale of 0.005 arcsec, that is about 11 AU (1650 million km) at the distance of Eta Carinae, corresponding to the full size of the orbit of Jupiter.

Scaled down to terrestial dimensions, this achievement compares to making the distinction between an egg and a billiard ball at a distance of 2,000 kilometers.

A most unusual shape
The VLTI observations brought the astronomers a surprise. They indicate that the wind around Eta Carinae is amazingly elongated: one axis is one-and-a-half times longer than the other! Moreover, the longer axis is found to be aligned with the direction in which the much larger mushroom-shaped clouds (seen on less sharp images) were ejected.

Spanning a scale from 10 to 20-30,000 AU, the star itself and the Homunculus Nebula are thus closely aligned in space.

VINCI was able to detect the boundary where the stellar wind from Eta Carinae becomes so dense that it is no longer transparent. Apparently, this stellar wind is much stronger in the direction of the long axis than of the short axis.

According to mainstream theories, stars lose most mass around their equator. This is because this is where the stellar wind gets “lifting” assistance from the centrifugal force caused by the star’s rotation. However, if this were so in the case of Eta Carinae, the axis of rotation (through the star’s poles) would then be perpendicular to both mushroom-shaped clouds. But it is virtually impossible that the mushroom clouds are positioned like spokes in a wheel, relative to the rotating star. The matter ejected in 1841 would then have been stretched into a ring or torus.

For Roy van Boekel, “the current overall picture only makes sense if the stellar wind of Eta Carinae is elongated in the direction of its poles. This is a surprising reversal of the usual situation, where stars (and planets) are flattened at the poles due to the centrifugal force.
The next supernova?

Such an exotic shape for Eta Carinae-type stars was predicted by theoreticians. The main assumption is that the star itself, which is located deep inside its stellar wind, is flattened at the poles for the usual reason. However, as the polar areas of this central zone are then closer to the centre where nuclear fusion processes take place, they will be hotter. Consequently, the radiation pressure in the polar directions will be higher and the outer layers above the polar regions of the central zone will get more “puffed up” than the outer layers at the equator.

Assuming this model is correct, the rotation of Eta Carinae can be calculated. It turns out that it should spin at over 90 percent of the maximum speed possible (before break-up).

Eta Carinae has experienced large outbursts other than the one in 1841, most recently around 1890. Whether another outburst will happen again in the near future is unknown, but it is certain that this unstable giant star will not settle down.

At the present, it is losing so much mass so rapidly that nothing will be left of it after less than 100,000 years. More likely, though, Eta Carinae will destroy itself long before that in a supernova blast that could possibly become visible in the daytime sky with the naked eye. This may happen “soon” on the astronomical time-scale, perhaps already within the next 10-20,000 years.

Original Source: ESO News Release

Posted on by Fraser Cain

Fundamental Force of Nature Has Changed Over Time?

Image credit: Hubble

Physicists from Northeastern University believe that a fundamental force of nature, the bond between electrons and protons, has been strengthening since the Big Bang. In fact, they believe it might have been 200,000 times weaker ten billion years ago – and this could mirror the discovery that the Universe seems to be accelerating apart. They’ve based their research on the light from quasars ten billion light-years away. This theory is very controversial; however, as another experiment has demonstrated that the strength of the bond hasn’t changed in at least two billion years.

In this topsy-turvy world of changing trends and stormy alliances, two Northeastern University scientists propose an answer to why even the fundamental constants of nature don’t seem constant anymore. The bond between electrons and protons, called the fine structure constant, or alpha, may not be constant and may have been 200,000 times weaker about ten billion years ago. This is a recent astronomy finding that is hotly debated because it departs from the standard model of physics and may point to modifications introduced by string theory — the modern “Theory of Everything” which attempts to unify all forces in nature.

According to Drs. Luis Anchordoqui and Haim Goldberg of the Department of Physics at Northeastern University in Boston, Mass., this apparent tiny change in alpha through the years may mirror the apparent accelerating expansion rate of the Universe, as if electrons and protons clung ever more tightly together as the Universe began to fly apart. The scientists describe this process in a recent issue of Physical Review D: Vol. 68, 083513 (2003).

“The apparent change in the fine structure constant remains controversial, partly because it stands in contrast to standard field theory, the basis of all the successes in atomic and nuclear physics, in which this constant is an unvarying input to all calculations,” said Anchordoqui. “We find, however, that the apparent change agrees with a variety of different types of observations.”

Light signals from exceedingly bright and distant galaxies called quasars seem to indicate that the bond between electrons and protons was weaker in the early universe. Light left these galaxies about 10 billion years ago and thus reflects the state of matter (and the laws of nature) from that epoch. This apparent change in the fine structure constant has been observed in several independent measurements.

On Earth, however, studies of a natural nuclear fission reactor which operated in Gabon two billion years ago reveal no change in the fine structure constant, down to an accuracy of one part in ten million. Thus, if the fine structure constant has changed, it did not do so evenly through the years. Anchordoqui and Goldberg attempt to reconcile this discrepancy.

They propose that the apparent change in the fine structure constant is coupled to “quintessence.” This is a theory of dark energy in which a mysterious universal repulsive force, once weaker long ago, now dominates over the force of gravity and is causing the universe to fly apart at a never-expanding rate. Anchordoqui and Goldberg worked with one particular model of quintessence proposed by Drs. Andreas Albrecht and Constantinos Skordis of the University of California, Davis, in 2000. They found that their own theory of the fine structure constant, when viewed in the context of this quintessence model, provides agreement between the quasar data and the Gabon data.

That is, the fine structure constant was measurably weaker ten billion years ago, but as quintessence assumed dominance about eight billion years ago, the force between electrons and protons became stronger and “more constant.”

The strength of the electron-proton bond from any matter created anytime within the last several billion years is essentially indistinguishable.

The reason for this lies in the peculiar behavior of the Albrecht-Skordis model, in which the quintessence field has all but ceased its variation during the present era. The model is also consistent with landmark data collected by the NASA Wilkinson Microwave Anisotropy Probe, which has determined fundamental properties of the universe, such as its age and shape, an announcement made in February 2003. Anchordoqui and Goldberg said analyzing the light from even more distant quasars will reveal a steady decrease in electron-proton binding strength.

Also, they said their theory could be tested soon with just a ten-fold improvement in sensitivity in measuring the acceleration of different objects in free fall. This is because a variation in the fine structure constant would imply a variation of this type of acceleration as the chemical makeup varied, a violation in the equivalence principle introduced by Albert Einstein in his general theory of relativity. Two proposed space-based mission will have this sensitivity: the MICROSCOPE mission from France’s Centre National d’Etudes Spatiales, expected to fly in 2005; and a NASA-ESA mission called STEP, Satellite Test of the Equivalence Principle. “We may be able to test this model of a ‘changing’ fine structure constant within a couple of years with instruments on satellites,” said Goldberg. “Or, we could continue observing alpha in lab experiments for another several billion years to see changes on the order of the quasar values. I’m counting on the satellites.” For more information, refer to Anchordoqui and Goldberg’s journal article, “Time Variations of the Fine Structure Constant Driven by Quintessence,” available at http://arXiv.org/abs/hep-ph/0306084.

Original Source: Northeastern University

Posted on by Fraser Cain

Pluto Mission Will Study Jupiter Too

Image credit: SWRI

Although the main goal of the NASA’s New Horizons mission will be to send a spacecraft to Pluto, the mission designers figure they can examine Jupiter on the way out as well – and get a valuable gravity boost that would shave years off the mission. If all goes as planned, New Horizons would launch in 2006, and pass Jupiter in early 2007 (probably three times closer than Cassini did in 2000); it will reach the Pluto-Charon system in 2015. After Pluto, New Horizons would then be re-targeted to fly past a Kuiper Belt Object.

The main goal of NASA’s New Horizons mission may be to explore Pluto-Charon and the Kuiper belt beginning in 2015, but first the mission plans to fly by the solar system’s largest planet, Jupiter, during February-March 2007. The Jupiter flyby would be used by New Horizons to provide a gravitational assist that shaves years off the trip time to Pluto-Charon and the Kuiper belt.

During the flyby, plans call for New Horizons to use its instrument payload, consisting of cameras, spectrometers, radiometers, and space plasma and dust sensors, to make a variety of scientific observations. Toward that end, the New Horizons team has formally kicked off its planning of the Jupiter flyby science observations. Southwest Research Institute? (SwRI?) and the Johns Hopkins University Applied Physics Laboratory (APL) lead the mission. Major partners include Ball Aerospace, Lockheed-Martin, Boeing, NASA Goddard Space Flight Center and the California Institute of Technology Jet Propulsion Laboratory.

“Every spacecraft must check out its instruments and pointing capabilities in flight prior to reaching its target,” says mission project scientist Dr. Hal Weaver of the Johns Hopkins University Applied Physics Laboratory. “By virtue of the gravity assist maneuver at Jupiter, New Horizons has a unique opportunity to do its check out on a very worthy and exciting scientific target.”

“New Horizons presents NASA’s next opportunity to study the complex and fascinating Jupiter system,” says Dr. Alan Stern, principal investigator of the New Horizons mission and director of the SwRI Space Studies Department. “To accomplish its gravity-assist maneuver on the way to Pluto-Charon, our spacecraft will venture at least three times closer to Jupiter than the Cassini spacecraft did in late 2000 when it used Jupiter for a gravity assist on the way to Saturn.

“Astronomically speaking, we will fly just outside of the edge of Jupiter’s large, planet-sized Galilean moon, Callisto.” From its closer range, New Horizons will perform a number of Jupiter system studies not possible from Cassini’s greater flyby distance.

Science planning is going forward to ready the mission for its planned 2006 launch, at the same time that required environmental and safety reviews are also being done. Through the summer of 2004, the New Horizons science team will prioritize its Jupiter science activities from objectives provided by team members as well as interested scientists from around the world. To accomplish this objective, Stern has appointed mission co-investigator and imaging team lead Dr. Jeff Moore of the NASA Ames Research Center to lead the New Horizons Jupiter Encounter Sequencing Team (JEST).

“New Horizons will be the next mission to Jupiter, and it is carrying a sophisticated instrument complement,” says Moore. “We intend to cull and then schedule the most critical needs for scientific observations of Jupiter, its satellites, its magnetosphere and its rings.

“Following that,” Moore continued, “the mission team will design and implement a five-month-long sequence of observations of the Jupiter system to be made from late 2006 through early 2007 as the spacecraft approaches and then recedes from Jupiter.”

“Exploring the Jupiter system is a coveted scientific bonus for New Horizons,” adds Weaver. “It also provides us with a valuable opportunity to check out the instrument payload and many of the flyby procedures we will later use at Pluto-Charon.”

New Horizons is proceeding toward a January 2006 launch, with a planned arrival at Pluto and its moon, Charon, in the summer of 2015. The 465-kilogram (1,025-pound) spacecraft will characterize the global geology and geomorphology of Pluto and Charon, map the surface compositions and temperatures of these worlds, and study Pluto’s atmospheric composition and structure. It will then visit one or more of the icy, primordial bodies in the Kuiper belt where it will make similar investigations.

In July 2002, the National Research Council’s Decadal Survey for Planetary Science ranked the reconnaissance of Pluto-Charon and the Kuiper belt as its highest priority for a new start mission in planetary science, citing the fundamental scientific importance of these bodies to advancing understanding of our solar system.

Original Source: SWRI News Release

Posted on by Fraser Cain

Shuttle Improvements Set to Cost $280 Million

NASA has estimated that implementing the improvements to the space shuttle fleet suggested by the Columbia Accident Investigation Board will set the agency back $280 million USD. One problem that NASA still hasn’t found the solution for is how to give astronauts the ability to repair holes in the wing, like the one that brought down Columbia. The agency is soliciting suggestions from outside as well; since November 12, they’ve received 286 suggestions – mostly from the public.

Posted on by Fraser Cain

NASA Tests a New Ion Engine

Image credit: NASA

NASA has tested a new high-power ion engine which could give future spacecraft significantly more thrust to accomplish exploration of the solar system. The High Power Electric Propulsion (HiPEP) ion engine should eventually be 10 times as powerful as NASA’s Deep Space 1 ion engine which was tested a few years ago. An engine like this will probably power the JIMO probe allowing it to go into and out of orbit around several of Jupiter’s moons and map them in great detail.

NASA’s Project Prometheus recently reached an important milestone with the first successful test of an engine that could lead to revolutionary propulsion capabilities for space exploration missions throughout the solar system and beyond.

The test involved a High Power Electric Propulsion (HiPEP) ion engine. The event marked the first in a series of performance tests to demonstrate new high-velocity and high-power thrust needed for use in nuclear electric propulsion (NEP) applications.

“The initial test went extremely well,” said Dr. John Foster, the primary investigator of the HiPEP ion engine at NASA’s Glenn Research Center (GRC), Cleveland. “The test involved the largest microwave ion thruster ever built. The use of microwaves for ionization would enable very long-life thrusters for probing the universe,” he said.

The test was conducted in a vacuum chamber at GRC. The HiPEP ion engine was operated at power levels up to 12 kilowatts and over an equivalent range of exhaust velocities from 60,000 to 80,000 meters per second. The thruster is being designed to provide seven-to-ten-year lifetimes at high fuel efficiencies of more than 6,000-seconds specific impulse; a measure of how much thrust is generated per pound of fuel. This is a contrast to Space Shuttle main engines, which have a specific impulse of 460 seconds.

The HiPEP thruster operates by ionizing xenon gas with microwaves. At the rear of the engine is a pair of rectangular metal grids that are charged with 6,000 volts of electric potential. The force of this electric field exerts a strong electrostatic pull on the xenon ions, accelerating them and producing the thrust that propels the spacecraft. The rectangular shape, a departure from the cylindrical ion thrusters used before, was designed to allow for an increase in engine power and performance by means of stretching the engine. The use of microwaves should provide much longer life and ion-production capability compared to current state-of-the-art technologies.

This new class of NEP thrusters will offer substantial performance advantages over the ion engine flown on Deep Space 1 in 1999. Overall improvements include up to a factor of 10 or more in power; a factor of two to three in fuel efficiency; a factor of four to five in grid voltage; a factor of five to eight in thruster lifetime; and a 30 percent improvement in overall thruster efficiency. GRC engineers will continue testing and development of this particular thruster model, culminating in performance tests at full power levels of 25 kilowatts.

“This test represents a huge leap in demonstrating the potential for advanced ion technologies, which could propel flagship space exploration missions throughout the solar system and beyond,” said Alan Newhouse, Director, Project Prometheus. “We commend the work of Glenn and the other NASA Centers supporting this ambitious program.”

HiPEP is one of several candidate propulsion technologies under study by Project Prometheus for possible use on the first proposed flight mission, the Jupiter Icy Moons Orbiter (JIMO). Powered by a small nuclear reactor, electric thrusters would propel the JIMO spacecraft as it conducts close-range observations of Jupiter’s three icy moons, Ganymede, Callisto and Europa. The three moons could contain water, and where there is water, there is the possibility of life.

Development of the HiPEP ion engine is being carried out by a team of engineers from GRC; Aerojet, Redmond, Wash.; Boeing Electron Dynamic Devices, Torrance, Calif.; Ohio Aerospace Institute, Cleveland; University of Michigan, Ann Arbor, Mich.; Colorado State University, Fort Collins, Colo.; and the University of Wisconsin, Madison, Wis.

A print quality photograph of the HiPEP ion engine is at:
http://www.grc.nasa.gov/WWW/PAO/pressrel/2003/03-079addm.html

For information about NASA on the Internet, visit:
http://www.nasa.gov

For more information about NASA’s Glenn Research Center, visit:
http://www.grc.nasa.gov

For more information about Project Prometheus on the Internet, visit:
http://spacescience.nasa.gov/missions/prometheus.htm

Information about JIMO is available on the Internet at:
http://spacescience.nasa.gov/missions/JIMO.pdf

Original Source: NASA News Release

Posted on by Fraser Cain

Antarctica Sees a Total Solar Eclipse

Scientists and tourists saw the first total solar eclipse from the continent of Antarctica in over a century on Sunday. Because of its remote location, some people chose to fly in two airplanes that followed the path of the eclipse, while others waited on an icebreaker. Some people also saw the eclipse from a few of the scientific outposts on the continent that were under the path of totality. The point of the greatest eclipse only lasted for one minute, 55 seconds. The next total eclipse will be in April 2005, and only be visible from the middle of the Pacific Ocean.

Posted on by Fraser Cain

Seeing a Star’s Final Moments

Image credit: Hubble

Although stars can burn for billions of years, their final stages can take a relatively short period of time. In many cases, it only takes a few hundred thousand years for dying stars to slough off their outer layers to create the familiar planetary nebula. Since they happen so quickly, they’re relatively rare to find, but astronomers think they’ve got a candidate with a relatively nearby star called V Hydra. The star is in its final stages, and jets of material have just begun emanating from it.

It takes only a few hundred to a thousand years for a dying Sun-like star, many billions of years old, to transform into a dazzling, glowing cloud called a planetary nebula. This relative blink in a long lifetime means that a Sun-like star’s final moments – the crucial phase when its planetary nebula takes shape – have, until now, gone undetected.

In research reported in the Nov. 20 issue of Nature, astronomers led by Dr. Raghvendra Sahai of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., have caught one such dying star in the act. This nearby star, called V Hydrae, has been captured by the Space Telescope Imaging Spectrograph onboard NASA’s Hubble Space Telescope in the last stages of its demise, just as material has begun to shoot away from it in a high-speed jet outflow.

While previous studies have indicated the role of jet outflows in shaping planetary nebulae, the new findings represent the first time these jets have been directly detected.

“The discovery of a newly launched jet outflow is likely to have a significant impact on our understanding of this short-lived stage of stellar evolution and will open a window onto the ultimate fate of our Sun,” said Sahai.

Other institutions contributing to this paper include: University of California, Los Angeles; Princeton University, Princeton, New Jersey; Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts; and Valdosta State University, Valdosta, Georgia.

Low-mass stars like the Sun typically survive around ten billion years before their hydrogen fuel begins to run out and they start to die. Over the next ten to hundred thousand years, the stars slowly eject nearly half of their mass in expanding, spherical winds. Then – in a poorly understood phase lasting just 100 to 1,000 years – the stars evolve into a stunning array of geometrically shaped glowing clouds called planetary nebulae.

Just how these extraordinary “star-clouds” are shaped has remained unclear, though Sahai, in several previous papers, put forth a new hypothesis. Based on results from a recent Hubble Space Telescope imaging survey of young planetary nebulae, he proposed that two-sided, or bipolar, high-speed jet-like outflows are the primary means of shaping these objects. The latest study will allow Sahai and his colleagues to test this hypothesis with direct data for the first time.

“Now, in the case of V Hydrae, we can observe the evolution of the jet outflow in real-time,” said Sahai, who together with his colleagues will study the star with the Hubble Space Telescope for three more years.

The new findings also suggest what may be driving the jet outflows. Past models of dying stars predict that accretion discs – swirling rings of matter encircling stars – may trigger jet outflows. The V Hydrae data support the presence of an accretion disc surrounding, not V Hydrae itself, but a companion object around the star. This companion is likely to be another star or even a giant planet too dim to be detected. The authors have also found evidence for an outlying large dense disc in V Hydrae, which could enable the formation of the accretion disc around the companion.

Further support in favor of a companion-driven jet outflow comes from the scientists’ observation that the jet fires in bursts: because the companion orbits the star in a periodic fashion, the accretion disc around it is expected to produce regular spurts of material rather than a steady stream.

The Space Telescope Imaging Spectrograph is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. The California Institute of Technology, Pasadena manages JPL for NASA.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Cheap Method for Finding Extrasolar Planets

Image credit: ESA

Astronomers from the University of Texas at Austin believe they’ve figured out an inexpensive way to search for extrasolar planets. After stars like our own Sun use up their fuel they eventually turn into red giant stars, and then shrink again to become white dwarfs. Although the process will likely destroy the inner planets, the outer planets will probably still remain in orbit around the star. These white dwarfs are known to pulsate at a specific rate, so the gravity of a planet moving around the star should affect this pulse rate by a minute amount that should be detectable by inexpensive Earth-based telescopes.

University of Texas at Austin astronomers have invented an inexpensive method to determine if other solar systems like our own exist.

Among the more than 100 stars now known to have planets, astronomers have found few systems similar to ours. It?s unknown if this is because of technological limitations or if our system is truly a rare configuration. The McDonald Observatory astronomers? novel search method uses a Depression-era telescope mated with today?s technology.

Astronomers Don Winget and Edward Nather, graduate students Fergal Mullally and Anjum Mukadem, and colleagues are looking for the “leftovers” of solar systems like ours. Their method searches for the pieces of such a solar system after its star has died, by exploiting a trait of ancient, burnt-out Suns called “white dwarfs.”

University of Texas astronomers Bill Cochran and Ted von Hippel are also involved, along with S.O. Kepler of Brazil?s Universidade Federal de Rio Grande dol Sul and Antonio Kanaan of Brazil?s Universidade Federal de Santa Catarina.

Astronomers know that as Sun-like stars use up their nuclear fuel, their outer layers will expand, and the star will become a “red giant” star. When this happens to the Sun, in about five billion years, they expect it will swallow Mercury and Venus, perhaps not quite reaching Earth. Then the Sun will blow off its outer layers and will exist for a few thousand years as a beautiful, wispy planetary nebula. The Sun?s leftover core will then be a white dwarf, a dense, dimming cinder about the size of Earth. And, most important, it likely will still be orbited by the outer planets of our solar system.

Once a Sun-like system reaches this state, Winget?s team may be able to find it. Their method is based on more than three decades of research on the variability (that is, changes in brightness) of white dwarfs. In the early 1980s, University of Texas astronomers discovered that some white dwarfs vary, or “pulsate,” in regular bursts. More recently, Winget and colleagues discovered that about one-third of these pulsating white dwarfs (PWDs) are more reliable timekeepers than atomic clocks and most millisecond pulsars.

These pulsations are the key to detecting planets. Planets orbiting a stable PWD star will affect observations of its timekeeping, appearing to cause periodic variations in the patterns of pulses coming from the star. That?s because the planet orbiting the PWD drags the star around as it moves. The change in distance between the star and Earth will change the amount of time taken for the light from the pulsations to reach Earth. Because the pulses are very stable, astronomers can calculate the difference between the observed and expected arrival time of the pulses and deduce the presence and properties of the planet. (This method is similar to that used in the discoveries of the so-called “pulsar planets.” The difference is, the pulsar companions are not thought to have formed with their stars, but only after those stars had exploded in supernovae.)

“This search will be sensitive to white dwarfs which were initially between one and four times as massive as the Sun, and should be able to detect planets within two to 20 AU from their parent star. This means we?ll be probing inside the habitable zone for some stars,” Winget said. (An AU, or astronomical unit, is the distance between Earth and the Sun.) “Basically, detecting Jupiter at Jupiter?s distance with this technique is easy. It?s duck soup,” he said.

Easy, but not quick. Outer planets, orbiting their stars at large distances, can take more than a decade to complete one orbit. Therefore, it can take many years of observations to definitively detect a planet orbiting a white dwarf.

“You need to look for a long time for a full orbit,” Winget said. “A half-orbit or a third of an orbit will tell us something?s going on there. But for a planet at Jupiter?s distance, a half-orbit is still six years.” Winget added that for this method, “detecting Jupiter at Uranus? distance is easier, but takes even longer.”

For the PWD planet search, Nather conceived a specialized new instrument for McDonald Observatory?s 2.1-meter Otto Struve Telescope. He and Mukadam designed and built the instrument, called Argos, to measure the amount of light coming from target stars. Specifically, Argos is a “CCD photometer” ? a photon counter that uses a charge-coupled device to record images. Located at the prime focus of the Struve Telescope, Argos has no optics other than the telescope?s 2.1-meter primary mirror. Copies of Argos are now being built at other observatories around the world.

Mullally continues the search for planets around white dwarfs with Argos on the Struve Telescope. He has 22 target stars, most of which were identified through the Sloan Digital Sky Survey. When the team finds promising planet candidates with Argos, they will follow up using the 9.2-meter Hobby-Eberly Telescope (HET) at McDonald Observatory.

“If we find large planets orbiting at large distances, that?s a good clue that there might be smaller planets closer in. In that case, what you do is pound away on that target with the largest telescope you have access to,” Winget said. The HET will enable more precise timing of the PWD?s pulses, and thus be able to pinpoint smaller planets.

This search will be able to study types of stars unable to be studied with the doppler spectroscopy method ? the most successful planet search method to date ? Winget said. Because of idiosyncrasies in the make-up of Sun-like stars, the doppler spectroscopy method is not very sensitive in looking for planets around stars twice as massive as the Sun. Roughly half of the stars in Winget?s study will be white dwarfs that were originally these types of stars. For this reason, the PWD study at McDonald can be instrumental in scouting and assessing targets and observing strategies for NASA space missions planned in the next two decades, specifically the Space Interferometry Mission, Terrestrial Planet Finder and Kepler spacecraft.

This research is funded by a NASA Origins grant, as well as an Advanced Research Project grant from the State of Texas. Through funding from the Texas Higher Education Agency, two secondary schoolteachers (Donna Slaughter of Stony Point High School in Round Rock, Texas, and Chris Cotter of Lanier High School in Austin) have been directly involved in this research. Plans are now underway to extend this involvement to other teachers, and the students in their classrooms by bringing the science, scientists and the Observatory directly into the classroom using the Internet. Cotter and his colleagues at Lanier High School are involved with Mullally in testing this concept.

Original Source: McDonald Observatory News Release

Posted on by Fraser Cain

Next Station Crew Announced

Image credit: NASA

NASA has announced the next crew to inhabit the International Space Station: NASA astronaut William S. McArthur Jr and Russian cosmonaut Valery I. Tokarev. Designated Expedition 9, the two men will be launched to the station some time in April 2004 on board a Soyuz rocket from the Baikonur cosmodrome in Kazakhstan. European Space Agency astronaut Andre Kuipers will also join them for the trip and stay on the station for a week before returning with the crew of Expedition 8. McArthur has flown on three shuttle flights, and Tokarev has been on one shuttle flight.

Veteran NASA astronaut William S. McArthur Jr., a retired U.S. Army colonel, and Russian Air Force Colonel Valery I. Tokarev are the next crew for the International Space Station.

McArthur and Tokarev trained as backups for the current Station crew. They will launch to the Station aboard a Russian Soyuz spacecraft in April 2004. Their six-month mission is designated Expedition 9. McArthur will serve as Station Commander and NASA Space Station Science Officer. Tokarev is the Soyuz Commander and Station Flight Engineer. During their stay aboard the orbiting research laboratory, the crew will conduct scientific studies in Earth sciences, life sciences, fundamental biology and microgravity.

European Space Agency (ESA) Astronaut Andre Kuipers joins McArthur and Tokarev on their Soyuz flight. He will spend eight days aboard the Station conducting experiments under a commercial agreement between ESA and the Russian Aviation and Space Agency. Kuipers returns to Earth with Expedition 8 Commander Mike Foale and Soyuz Commander Alexander Kaleri. Kuipers’ backup for the flight is ESA Astronaut Gerhard Thiele.

McArthur flew on three Shuttle missions: STS-58 in 1993; STS-74 in 1995; and STS-92, a Station assembly flight, in 2000. Tokarev first flew in 1999 aboard STS-96. The backup crew for Expedition 9 is veteran NASA astronaut Leroy Chiao, Ph.D., and Russian cosmonaut Salizhan S. Sharipov. Chiao was a Mission Specialist aboard STS-65 in 1994; STS-72 in 1996; and STS-92 in 2000. Sharipov was a Mission Specialist on STS-89 in 1998.

Original Source: NASA News Release