Posted on by Fraser Cain

ESA Picks an Asteroid to Move

Computer animation of Don Quijote and its asteroid target. Image credit: ESA. Click to enlarge.
Based on the recommendations of asteroid experts, ESA has selected two target asteroids for its Near-Earth Object deflecting mission, Don Quijote.

Don Quijote is an asteroid-deflecting mission currently under study by ESA?s Advanced Concepts Team (ACT). Earlier this year the NEO Mission Advisory Panel (NEOMAP), consisting of well-known experts in the field, delivered to ESA a target selection report for Europe?s future asteroid mitigation missions, identifying the relevant criteria for selecting a target and picking up two objects that meet most of those criteria. The asteroids? temporary designations are 2002 AT4 and 1989 ML.

With this input and the support of ESA?s Concurrent Design Facility (CDF) experts, the Advanced Concepts Team has now completed an extensive assessment of suitable mission architectures, launch strategies, propulsion system options and experiments.

The current scenario envisages two spacecraft in separate interplanetary trajectories. One spacecraft (Hidalgo) will impact an asteroid, the other (Sancho) will arrive earlier at the target asteroid, rendezvous and orbit the asteroid for several months, observing it before and after the impact to detect any changes in its orbit.

Industrial studies are now about to start; it will be down to European experts to propose alternative solutions for the design of the low-cost NEO precursor mission. This will be the first step towards the development of a means to tackle asteroid impacts ? one of the few natural disasters that our technology can prevent.

A near miss?
While the eyes of the world were on the Asian tsunami last Christmas, one group of scientists were watching uneasily for another potential natural disaster ? the threat of an asteroid impact.

On 19 December 2004 MN4, an asteroid of about 400 m, lost since its discovery six months earlier, was observed again and its orbit was computed. It immediately became clear that the chances that it could hit the Earth during a close encounter in 2029 were unusually high. As the days passed the probability did not decrease and the asteroid became notorious for surpassing all previous records in the Torino and Palermo impact risk scales – scales that measure the risk of an asteroid impact just as the Richter scale quantifies the size of an earthquake.

Only after earlier observations of the object were found and a more accurate trajectory was computed did it become clear that it would not impact the Earth ? at least not in 2029. Impacts on later dates, though unlikely, have not been totally ruled out. It is extremely difficult to tell what will happen unless we come up with a better way to track this or other NEOs and if necessary take steps to tackle them.

Most world experts agree that this capability is now within our reach. A mission like ESA?s Don Quijote could provide a means to assess a threatening NEO and take concrete steps to deflect it away from the Earth.

But every good performance needs rehearsing and in order to be ready for such a threat, we should try our hardware on a harmless asteroid first. Don Quijote would be the first mission to make such an attempt. The big question was: which asteroid and what should it be like?

Looking for the perfect target
The NEO population contains a confusing variety of objects, and deciding which physical parameters are most relevant for mitigation considerations is no trivial task. But the NEOMAP experts took on the challenge and in February 2005 provided ESA with their recommendations on the asteroid selection criteria for ESA?s deflection rehearsal.

People might wonder whether performing a deflection test, such as that planned for Don Quijote, represents any risk to our planet. What if things go wrong? Could we create a problem, rather than learn how to avoid one?

Experts world-wide say the answer is no. Even a very dramatic impact of a heavy spacecraft on a small asteroid would only result in a minuscule modification of the object?s orbit. In fact the change would be so small that the Don Quijote mission requires two spacecraft ? one to monitor the impact of the other. The second spacecraft measures the subtle variation of the object?s orbital parameters that would not be noticeable from Earth.

Target objects can also be selected so that all possible concerns are avoided altogether, by looking into the way the distance between the asteroid?s and the Earth?s orbits changes with time. If the target asteroid is not an ?Earth crosser?, as is the case with NEOs in the ?Amor? class (which have orbits with perihelion distance well in excess of 1 AU), testing a deflection manoeuvre represents no risk to the Earth.

Other considerations related to the orbit of the target asteroid are also important, especially the change of orbital velocity that is required by the spacecraft to ?catch up? with the target asteroid ? the so-called ?delta V?. This should be sufficiently small to minimise the required amount of spacecraft propellant and enable the use of cheaper launchers, but high enough to allow the same spacecraft to be used with a number of possible targets.

Navigation and deflection measurements requirements set some heavy constraints on the target selection. The shape, density, and size are all important factors, but are often poorly known. A spacecraft orbiting an asteroid needs to know about the object?s gravitational field in order to navigate. The ?impactor spacecraft? must know the position of the centre of mass to define the point it is aiming for.

Asteroids come in all sort of flavours, but as far as composition is concerned two main types dominate. Our still rudimentary knowledge of the abundance of asteroids of different types in the near-Earth asteroid population indicates that the next hazardous asteroid is more likely to be a ?C-type?, than an ?S-type?. C-types have dark surfaces with a carbonaceous spectral signature, while S-types have brighter surfaces, their spectra matching closely that of silicates. The surface properties of the target asteroid -and in particular the percentage of light that it reflects – are a critical factor in the final phase of the impactor spacecraft navigation. The brighter it looks the easier it is to aim at. However for a rehearsal the target should not be too easy.

ESA has selected asteroids 2002 AT4 and (10302) 1989 ML as mission targets because they represent best compromise among all the (sometimes conflicting) selection criteria. A decision on which of the two will become the final destination of both Sancho and Hidalgo spacecraft will be made in 2007.

Don Quijote ? the knight errant rides again
The phase of internal studies on the Don Quijote mission is now over, and it is time for the space industry to suggest suitable design solutions. ESA has made an open invitation to European space companies to submit proposals on possible designs. The selection of the most promising ones will take place towards the end of the year. In early 2006, two teams should start working on their interpretations of this technology demonstration mission. A year later, once the results are available, ESA will select the final design to be implemented, and then Don Quijote will be ready to take on an asteroid!

Additional Notes
Don Quijote is a NEO deflection test mission based entirely on conventional spacecraft technologies. It would comprise two spacecraft – one of them (Hidalgo) impacting an asteroid at a very high relative speed while a second one (Sancho) would arrive earlier at the same asteroid and remain in its vicinity before and after the impact to measure the variation on the asteroid?s orbital parameters, as well as to study the object.

Asteroid 2004 MN has now been given an official designation, (99942) Apophis. Recent observations using Doppler radar using Arecibo radio telescope in Puerto Rico have reduced the impact probability during future encounters to very small levels, though they have not totally ruled out an Earth impact. In 2029, the asteroid will have the closest approach ever witnessed for an object of this size, swinging by the Earth at a distance of around 32,000 kilometres. Its trajectory will be well within the geosynchronous orbit used by most telecommunications and weather satellites, and the object will be visible to the naked eye. Further radar measurements are expected in 2013.

Original Source: ESA News Release

Posted on by Fraser Cain

Delta Launches New GPS Satellite

Boeing Delta II rocket launching new GPS satellite. Image credit: Boeing. Click to enlarge.
A Boeing [NYSE: BA] Delta II launch vehicle today successfully delivered the first of the modernized Block IIR Global Positioning System (GPS) satellites to space for the U.S. Air Force.

The Delta II rocket carrying the GPS IIR-14 (M) spacecraft lifted off from Space Launch Complex 17A at Cape Canaveral Air Force Station, Fla., yesterday at 11:37 p.m. EDT. Following a nominal 24-minute flight, the rocket deployed the satellite to a transfer orbit.

“We are honored to be the United States Air Force’s choice to launch the GPS satellites and proud to have delivered the first modernized spacecraft to its targeted orbit. Tonight’s success is a direct result of the hard work and dedication of Boeing’s Delta team,” said Dan Collins, vice president, Boeing Expendable Launch Systems.

The Boeing Delta II 7925-9.5 configuration vehicle used for this mission featured a Boeing first stage booster powered by a Pratt & Whitney Rocketdyne RS-27A main engine and nine Alliant Techsystems (ATK) solid rocket boosters. An Aerojet AJ10-118K engine powered the storable propellant restartable second stage. A Thiokol Star-48B solid rocket motor propelled the third stage prior to spacecraft deployment. The rocket also flew with a nine-and-a-half-foot diameter Boeing payload fairing.

A redundant inertial flight control assembly built by L3 Communications Space & Navigation provided guidance and control for the rocket that enabled a precise deployment of the satellite.

The GPS IIR-14 (M) mission also marked the 100th flight of the Delta II using the ATK 40-inch diameter version solid rocket motors.

Boeing provides launches for the GPS program aboard Delta II vehicles and has a planned GPS manifest through at least 2007.

The GPS network supports U.S. military operations conducted from aircraft, ships, land vehicles and by ground personnel. Additional use includes mapping, aerial refueling and rendezvous, geodetic surveys, and search and rescue operations.

GPS provides military and civilian users three-dimensional position location data in longitude, latitude and elevation as well as precise time and velocity. The satellites orbit the earth every 12 hours, emitting continuous navigation signals. The signals are so accurate, time can be figured to within one millionth of a second, velocity within a fraction of a mile-per-second and location to within 100 feet.

The new GPS IIR-14 (M) is the first of the modernized GPS satellites that incorporates various improvements to provide greater accuracy, increased resistance to interference and enhanced performance for users.

A unit of The Boeing Company, Boeing Integrated Defense Systems is one of the world’s largest space and defense businesses. Headquartered in St. Louis, Boeing Integrated Defense Systems is a $30.5 billion business. It provides network-centric system solutions to its global military, government and commercial customers. It is a leading provider of intelligence, surveillance and reconnaissance systems; the world’s largest military aircraft manufacturer; the world’s largest satellite manufacturer and a leading provider of space-based communications; the primary systems integrator for U.S. missile defense; NASA’s largest contractor; and a global leader in sustainment solutions and launch services.

Original Source: Boeing News Release

Posted on by Mark Mortimer

Book Review: The Dancing Universe

To understand physics is to understand the motion of the objects surrounding our everyday lives. Studying wheels that turn on the ground is simple. Studying galaxies that spin is another thing altogether. However, the principles of a galaxy’s motion and that of a wheel are amazingly similar. Sometimes all we need do is build an imaginary scenario in our minds to postulate one truth, once given another.

Gleiser really promotes this idea of mental model building in his book as he chronologically steps through 3000 years of history. Further, by placing the reader beside the historical figure, he gives a feel for the real person. He does this by locating the person geographically, identifying supporters and detractors, and adding descriptions of any relevant tools. For example, Philolaus of Croton, around 450 BC, lived in Southern Italy but was encouraged by an unfriendly mob to move to Greece. Using Pythagorean principles, he postulated a framework of celestial objects that explained day and night on Earth. In so doing he was the first to place the sun at the centre of the universe. Philolaus had no tools at hand, but he did live with a collection of like minded thinkers. In a style like this, Gleiser not only shows the contributions of many people but he also shows how society’s collective knowledge replaced the belief that god(s) were responsible.

The chronological sequence gets a rough start as Gleiser begins by thoroughly assessing primitive philosophy. The first chapter delves into creation myths of long ago when people without much information tried to build a comprehension of their existence. With this, a reader may expect a strong leaning toward philosophy throughout. This is not the case, as aside from particular researchers involved with both physics and philosophy, the remaining contents fixates purely on the progress of physics. As expected, there are: the Greeks and their postulating, the trials between the Roman Catholic church and science, the empowerment of universities, and the transcendence of the individual. Some early researchers referred to may be unknown, but otherwise Gleiser includes all the big names.

This study of the main contributors turns out to be Gleiser’s actual intent. He uses this book as the text in a large physics class for non-science majors. Hence, though he alludes to the value of physics, he focuses on the people and their contributions. He likely has been doing this for some time as all his descriptions are extremely clear, simple and easy to follow. For instance, he uses the traditional means of describing special relativity; this being a person in a train and another at the station. Yet, he clearly describes the experimental basis for never having light at rest and thus needing light to have the same speed independent of the observer. No equations reside in the pages, nor pictures, though a few simple diagrams facilitate understanding. Because of this, Glacier’s non-science majors are likely very thankful.

However, Glacier short changes his students. Though his knowledge of physics and refined presentation skills comes across very well, he doesn’t tempt the students (or other readers) to deepen their understanding. For example, there is no push for them to spend more time wondering why the physical laws exist and are (apparently) universal. I liked the very brief discussion regarding the big bang and the time immediately before and after. Sadly, I didn’t really see any hooks that might draw in a reader. As such, this book is a great review and summary but does very little to encourage the advancement of knowledge, i.e., the making of new researchers.

The very word cosmology engenders visions of apparently unending borders. Going on a mission to explore where none have gone before seems like the only game in town. Marcelo Gleiser in his book The Dancing Universe provides some real background for those non-specialists who want to know more about the borders. And should society’s interest continue to grow, there just might come a time when people can travel to find if a border exists.

Review by Mark Mortimer

Read more reviews online, or purchase a copy from Amazon.com.

Posted on by Fraser Cain

Satellite Picture of Hurricane Rita

Hurricane Rita, taken on September 22. Image credit: ESA. Click to enlarge.
As Hurricane Rita entered the Gulf of Mexico, ESA’s Envisat satellite’s radar was able to pierce through swirling clouds to directly show how the storm churns the sea surface. This image has then been used to derive Rita’s wind field speeds.

Envisat acquired this Advanced Synthetic Aperture Radar (ASAR) image at 0344 UTC on 22 September (2345 on 21 September in US Eastern Daylight Saving Time), when Hurricane Rita was passing west of Florida and Cuba. The image was acquired in Wide Swath Mode with resolution of 150 metres. Envisat’s optical Medium Resolution Imaging Spectrometer (MERIS) is also being used to observe the storm during daylight, returning details of its cloud structure and pressure.

Notably large waves are seen around the eye of Hurricane Rita in the radar image. ASAR measures the backscatter, which is a measure of the roughness of the ocean surface. On a basic level, bright areas of the radar image mean higher backscatter due to surface roughness. This roughness is strongly influenced by the local wind field so that the radar backscatter can be used in turn to measure the wind.

So the Center for Southeastern Tropical Advanced Remote Sensing at the University of Miami used this ASAR image to calculate the speed of Hurricane Rita’s surface wind fields ? showing maximum wind speeds in excess of 200 kilometres per hour.

“The most detailed information about hurricane dynamics and characteristics are obtained from dedicated flights by hurricane hunter aircraft,” explains Hans Graber of CSTARS. “However these flight missions cannot always take place. Satellite remote sensing provides a critical alternative approach.

“It is critical for weather forecasters to obtain reliable characterization of the eye wall dimension and the radii of gale- tropical storm- and hurricane-force winds in order to provide skilful forecasts and warning. Satellite based observations will facilitate better understanding of hurricane evolution and intensification.

“Radar images penetrate through clouds and can easily detect the eye replacement cycle of hurricanes which are precursors to further intensification.”

Rita was a maximum Category Five on the Saffir-Simpson Hurricane Scale when the ASAR image was acquired. As it continues west through the Gulf of Mexico it has weakened to a still-dangerous Category Four. Rita is expected to make landfall on the Gulf coast during the morning of 24 September.

ERS-2 joins in Rita observations
The same day Envisat acquired its ASAR image of Rita, its sister spacecraft ERS-2 also made complementary observations of the hurricane’s underlying wind fields using its radar scatterometer.

This instrument works by firing a trio of high-frequency radar beams down to the ocean, then analysing the pattern of backscatter reflected up again. Wind-driven ripples on the ocean surface modify the radar backscatter, and as the energy in these ripples increases with wind velocity, so backscatter increases as well. Scatterometer results enable measurements of not only wind speed but also direction across the water surface.

What makes ERS-2’s scatterometer especially valuable is that its C-band radar frequency is almost unaffected by heavy rain, so it can return useful wind data even from the heart of the fiercest storms ? and is the sole scatterometer of this type currently in orbit.

The ERS-2 Scatterometer results for Hurricane Rita seen here have been processed by the Royal Netherlands Meteorological Institute (KNMI). They are also routinely assimilated by the European Centre for Medium-Range Weather Forecasting (ECMWF) into their advanced numerical models used for meteorological predictions.

“Scatterometer data from the ERS-2 platform provide high-quality wind information in the vicinity of tropical cyclones,” states Hans Hersbach of ECMWF. “For a Hurricane like Rita, the combination of such observations with [in-situ] dropsonde data enables the analysis system at ECMWF to produce an improved forecast.”

Another Envisat instrument called the Radar Altimeter-2 uses radar pulses to measure sea surface height (SSH) down to an accuracy of a few centimetres.

Near-real time radar altimetry is a powerful tool for monitoring a hurricane’s progress and predicting its potential impact. This is because anomalies in SSH can be used to identify warmer ocean features such as warm core rings, eddies and currents.

The US National Oceanic and Atmospheric Administration (NOAA) is utilising Envisat RA-2 results along with those from other space-borne altimeters to chart such regions of ‘tropical cyclone heat potential’ (TCHP) and improve the accuracy of Hurricane Rita forecasting.

Observing hurricanes
A hurricane is basically a large, powerful storm centred around a zone of extreme low pressure. Strong low-level surface winds and bands of intense precipitation combine strong updrafts and outflows of moist air at higher altitudes, with energy released as rainy thunderstorms.

Envisat carries both optical and radar instruments, enabling researchers to observe high-atmosphere cloud structure and pressure in the visible and infrared spectrum, while at the same time using radar backscatter to measure the roughness of the sea surface and so derive the wind fields just above it.

Those winds converging on the low-pressure eye of the storm are what ultimately determine the spiralling cloud patterns that are characteristic of a hurricane.

Additional Envisat instruments can be used to take the temperature of the warm ocean waters that power storms during the annual Atlantic hurricane season, along with sea height anomalies related to warm upper ocean features.

Original Source: ESA News Release

Here are some hurricanes pictures.

Posted on by Fraser Cain

Many Galaxies Found in the Early Universe

13 distant galaxies found in a sample of sky. Image credit: ESO. Click to enlarge.
It is one of the major goals of observational cosmology to trace the way galaxies formed and evolved and to compare it to predictions from theoretical models. It is therefore essential to know as precisely as possible how many galaxies were present in the Universe at different epochs.

This is easier to say than to do. Indeed, if counting galaxies from deep astronomical images is relatively straightforward, measuring their distance – hence, the epoch in the history of the universe where we see it [1] – is much more difficult. This requires taking a spectrum of the galaxy and measuring its redshift [2].

However, for the faintest galaxies – that are most likely the farthest and hence the oldest – this requires a lot of observing time on the largest of the telescopes. Until now, astronomers had thus to first carefully select the candidate high-redshift galaxies, in order to minimise the time spent on measuring the distance. But it seems that astronomers were too careful in doing so, and hence had a wrong picture of the population of galaxies.

It would be better to “simply” observe in a given patch of the sky all galaxies brighter than a given limit. But looking at one object at a time would make such a study impossible.

To take up the challenge, a team of French and Italian astronomers [3] used the largest possible telescope with a highly specialised, very sensitive instrument that is able to observe a very large number of (faint) objects in the remote universe simultaneously.

The astronomers made use of the VIsible Multi-Object Spectrograph (VIMOS) on Melipal, one of the 8.2-m telescopes of ESO’s Very Large Telescope Array. VIMOS can observe the spectra of about 1,000 galaxies in one exposure, from which redshifts, hence distances, can be measured. The possibility to observe two galaxies at once would be equivalent to using two VLT Unit Telescopes simultaneously. VIMOS thus effectively multiplies the efficiency of the VLT hundreds of times.

This makes it possible to complete in a few hours observations that would have taken months only a few years ago. With capabilities up to ten times more productive than competing instruments, VIMOS offers the possibility for the first time to conduct an unbiased census of the distant Universe.

Using the high efficiency of the VIMOS instrument, the team of astronomers embarked in the VIMOS VLT Deep Survey (VVDS) whose aim is to measure in some selected patch of the sky the redshift of all galaxies brighter than magnitude 24 in the red, that is, galaxies that are up to 16 million fainter than what the unaided eye can see.

In a total sample of about 8,000 galaxies selected only on the basis of their observed brightness in red light, almost 1,000 bright and vigorously star forming galaxies were discovered at an epoch 1,500 to 4,500 million years after the Big Bang (redshift between 1.4 and 5).

“To our surprise”, says Olivier Le F?vre, from the Laboratoire d’Astrophysique de Marseille (France) and co-leader of the VVDS project, “this is two to six times higher than had been found by previous works. These galaxies had been missed because previous surveys had selected objects in a much more restrictive manner than we did. And they did so to accommodate the much lower efficiency of the previous generation of instruments.”

While observations and models have consistently indicated that the Universe had not yet formed many stars in the first billion years of cosmic time, the discovery made by the scientists calls for a significant change in this picture.

Combining the spectra of all the galaxies in a given redshift range (i.e. belonging to the same epoch), the astronomers could estimate the amount of star formed in these galaxies. They find that the galaxies in the young Universe transform into stars between 10 and 100 times the mass of our Sun in a year.

“This discovery implies that galaxies formed many more stars early in the life of the Universe than had previously been thought”, explains Gianpaolo Vettolani, the other co-leader of the VVDS project, working at INAF-IRA in Bologna (Italy). “These observations will demand a profound reassessment of our theories of the formation and evolution of galaxies in a changing Universe.”

It now remains for astronomers to explain how one can create such a large population of galaxies, producing more stars than previously assumed, at a time when the Universe was about 10-20% of its current age.

Original Source: ESO News Release

Posted on by Fraser Cain

Chandra View of Tycho’s Remnant

Tycho’s Supernova as viewed by the Chandra X-Ray Observatory. Image credit: NASA. Click to enlarge.
In 1572, the Danish astronomer Tycho Brahe observed and studied the explosion of a star that became known as Tycho’s supernova. More than four centuries later, Chandra’s image of the supernova remnant shows an expanding bubble of multimillion degree debris (green and red) inside a more rapidly moving shell of extremely high energy electrons (filamentary blue).

The supersonic expansion (about six million miles per hour) of the stellar debris has created two X-ray emitting shock waves – one moving outward into the interstellar gas, and another moving back into the debris. These shock waves produce sudden, large changes in pressure and temperature, like an extreme version of sonic booms produced by the supersonic motion of airplanes.

According to the standard theory, the outward-moving shock wave should be about 2 light years ahead of the stellar debris. What Chandra found instead is that the stellar debris has kept pace with the outer shock and is only about half a light year behind.

The most likely explanation for this behavior is that a large fraction of the energy of the outward-moving shock wave is going into the acceleration of atomic nuclei to speeds approaching the speed of light. The Chandra observations provide the strongest evidence yet that nuclei are indeed accelerated and that the energy contained in the high-speed nuclei in Tycho’s remnant is about 100 times that observed in high-speed electrons.

This finding is important for understanding the origin of cosmic rays, the high-energy nuclei which pervade the Galaxy and constantly bombard the Earth. Since their discovery in the early years of the 20th century, many sources of cosmic rays have been proposed, including flares on the sun and similar events on other stars, pulsars, black hole accretion disks, and the prime suspect – supernova shock waves. Chandra’s observations of Tycho’s supernova remnant strengthen the case for this explanation.

Original Source: Chandra News Release

Posted on by Fraser Cain

Finding the First Stars

Computer illustration of what the Universe’s first stars looked like. Image credit: CfA. Click to enlarge.
What did the very first stars look like? How did they live and die? Astronomers have ideas, but no proof. The first stars are so distant and formed so long ago that they are invisible to our best telescopes.

Until they explode. Hypernovas (more powerful cousins of supernovas) and their associated gamma-ray bursts offer astronomers the possibility of detecting light from the first generations of stars.

NASA’s Swift satellite already has seen a gamma-ray burst (GRB) with a redshift of 6.29, meaning that the progenitor star exploded about 13 billion years ago, when the universe was less than a billion years old. Theorists Volker Bromm (University of Texas at Austin) and Avi Loeb (Harvard-Smithsonian Center for Astrophysics) predict that one-tenth of the blasts Swift will spot during its operational lifetime will come from stars at a redshift of 5 or greater, that lived and died during the first billion years of the universe.

“Most of those GRBs will come from second generation or later stars,” said Loeb. “But if we get lucky, Swift may even detect a burst from one of the very first stars that formed — a star made of only hydrogen and helium.”

Calculations suggest that such stars, which are called Population III for historical reasons, would have been behemoths weighing 50-500 times as much as the Sun. A Population III star would have gulped its nuclear fuel faster than an SUV, dying quickly and explosively.

“Our best guess right now is that the recent GRB was not from a Pop III star. However, its redshift is high enough to make it very interesting,” said Bromm.

One key question examined by Bromm and Loeb is whether a Pop III star could have generated a GRB — a blast powerful enough to be seen from a distance of more than 13 billion light-years.

The answer they derived is a qualified yes. Pop III stars were massive enough to explode violently, leaving behind a black hole in most cases. However, a Pop III star likely would have to be part of a tight binary system to generate a GRB.

A close binary companion could strip the outer layers of a dying Pop III star, leaving less material to block the star’s explosive death throes. Jets of material generated from the newborn black hole therefore could punch their way out more easily, creating a burst of gamma-ray energy detectable across the universe.

About half of all nearby stars are members of binary or multiple star systems. The frequency of binaries, particularly close binaries, among Pop III stars remains unknown.

“Astronomers will address this question of the Pop III binary frequency using a dual approach, both observational and theoretical,” said Bromm. “By searching for high-redshift GRBs, we can constrain that number empirically. We also will try to improve simulations and make them detailed enough to model those details of star formation.”

If binary star systems are common among Pop III stars, then high-redshift GRBs could offer astronomers an ideal opportunity to study the first generation of stars.

“If Pop III binaries are common, Swift will be the first observatory to probe Population III star formation at high redshifts,” said Loeb.

This research has been submitted for publication to The Astrophysical Journal and is available online at http://arxiv.org/abs/astro-ph/0509303.

Original Source: CfA News Release

Posted on by Fraser Cain

Mars Express Mission Extended

Artist illustration of Mars Express. Image credit: ESA. Click to enlarge.
ESA?s Mars Express mission has been extended by one Martian year, or about 23 months, from the beginning of December 2005.

The decision, taken on 19 September by ESA?s Science Programme Committee, allows the spacecraft orbiting the Red Planet to continue building on the legacy of its own scientific success.

Co-ordinated from the beginning with the Mars science and exploration activities of other agencies, Mars Express has revealed an increasingly complex picture of Mars.

Since the start of science operations in early 2004, new aspects of Mars are emerging day by day, thanks to Mars Express data. These include its present-day climate system, and its geological ?activity? and diversity. Mars Express has also started mapping water in its various states.

In building up a global data set for composition and characteristics of the surface and atmosphere, Mars Express has revealed that volcanic and glacial processes are much more recent than expected.

It has confirmed the presence of glacial processes in the equatorial regions, and mapped water and carbon dioxide ice, either mixed or distinct, in the polar regions. Through mineralogical analysis, it found out that large bodies of water, such as lakes or seas, might not have existed for a long period of time on the Martian surface.

Mars Express has also detected methane in the Martian atmosphere. This, together with the possible detection of formaldehyde, suggests either current volcanic activity on Mars, or, more excitingly, that there are current active ?biological? processes.

This hypothesis may be reinforced by the fact that Mars Express saw that the distribution of water vapour and methane, both ingredients for life, substantially overlap in some regions of the planet.

Furthermore, the mission detected aurorae for the first time on the Red Planet. It has made global mapping of the density and pressure of the atmosphere between 10 and 100 kilometres altitude, and studied atmospheric escape processes in the upper layers of the atmosphere. This is contributing to our understanding of the weather and climate evolution of the planet.

There is still much to be discovered by the extraordinary set of instruments on board Mars Express. First, the 23-month extension will enable the Mars Express radar, MARSIS, to restart Martian night-time measurements in December this year.

MARSIS will continue its subsurface studies mainly in the search for liquid and frozen water. By combining subsurface, surface and atmospheric data, Mars Express will provide an unprecedented global picture of Mars and, in particular, its water.

So far, the High Resolution Stereo Camera has imaged only 19% of the Martian surface at high resolution. In the extended phase, it will be able to continue the 3D high-resolution colour imaging. After the Viking missions, Mars Express is building today?s legacy of Mars imagery for present and future generations of scientists.

Thanks to the extension, Mars Express will also be able to study for a second year the way the atmosphere varies during different seasons, and to observe again variable phenomena such as frost, fog or ice.

Finally, Mars Express will be able to revisit those areas where major discoveries, such as new volcanic structures, sedimentary layering, methane sources, nightglow and auroras, have been made, thus allowing to confirm and understand all aspects related to these discoveries.

Original Source: ESA News Release

Posted on by Fraser Cain

Sweeping View of the Rings

Sweeping view of Saturn’s rings. Image credit: NASA/JPL/SSI. Click to enlarge.
A grandiose gesture of gravity, Saturn’s icy rings fan out across many thousands of kilometers of space. The moon Pan (26 kilometers, or 16 miles across) dutifully follows its path, like the billions and billions of particles comprising the rings. The little moon is seen at the center of this view, within the Encke gap.

The famous Cassini Division spans upper left corner of the scene. The Cassini Division is approximately 4,800-kilometers-wide (2,980 miles) and is visible in small telescopes from Earth.

The narrow, knotted F ring is thinly visible just beyond the main rings.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 20, 2005, at a distance of approximately 2.1 million kilometers (1.3 million miles) from Saturn. The image scale on Pan is 13 kilometers (8 miles) per pixel.

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

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

Original Source: NASA/JPL/SSI News Release