Friday, September 28, 2007

Mysterious Energy Burst



CSIRO’s Parkes telescope have detected a huge burst of radio energy.

The radio burst appears to have originated at least one-and-a-half billion light-years [500 Mpc] away but was startlingly strong.

Normally the kind of cosmic activity we’re looking for at this distance would be very faint but this was so bright that it saturated the equipment.

The burst was so bright that at the time it was first recorded it was dismissed as man-made radio interference. It put out a huge amount of power (10exp33 Joules), equivalent to a large (2000MW) power station running for two billion billion years.

The burst may have been produced by an exotic event such as the collision of two neutron stars or be the last gasp of a black hole as it evaporates completely.
The burst lasted just five milliseconds.

Although they’ve found only one burst, the astronomers can estimate how often they occur.
“We’d expect to see a few bursts over the whole sky every day,” said Dr John Reynolds, Officer in Charge at CSIRO’s Parkes Observatory.

A new telescope being built in Western Australia will be ideal for finding more of these rare, transient events.

The discovery of the radio burst is similar to the discovery of gamma-ray bursts in the 1970s, when military satellites revealed flashes of gamma-rays appearing all over the sky. One kind—the so-called long-period bursts—was eventually identified as the explosion (supernova) of a massive star with the associated formation of a black hole.


Thursday, September 27, 2007

Asteroid Mission, Dawn



Dawn spacecraft is on its way to study a pair of asteroids after lifting off Thursday from the Cape Canaveral Air Force Station at 7:34 a.m. EDT

During the next 80 days, spacecraft controllers will test and calibrate the myriad of spacecraft systems and subsystems, ensuring Dawn is ready for the long journey ahead.

Dawn's 4.8-billion-kilometer (3-billion-mile) odyssey includes exploration of asteroid Vesta in 2011 and the dwarf planet Ceres in 2015. These two icons of the asteroid belt have been witness to much of our solar system's history. By using Dawn's instruments to study both asteroids, scientists more accurately can compare and contrast the two. Dawn's science instrument suite will measure elemental and mineral composition, shape, surface topography, and tectonic history, and will also seek water-bearing minerals. In addition, the Dawn spacecraft and how it orbits Vesta and Ceres will be used to measure the celestial bodies' masses and gravity fields.

The spacecraft's engines use a unique, hyper-efficient system called ion propulsion, which uses electricity to ionize xenon to generate thrust. The 30-centimeter-wide (12-inch) ion thrusters provide less power than conventional engines but can maintain thrust for months at a time.

X-rays From Gas Streams Around Young Stars


XMM-Newton has surveyed nearly two hundred stars under formation to reveal, contrary to expectations, how streams of matter fall onto the young stars’ magnetic atmospheres and radiate X-rays.

The results defy astronomer's expectations, as the streams of falling matter interact with the hot corona, cooling it, while the ejected streams of gas heat up in shocks as they are ejected from the star.

The new XMM-Newton results paint a dramatic picture of the role magnetic fields play in star formation. Star formation is a battle between gravity and everything else.

Star formation results in a complicated system in which the young star is surrounded by a disc of gas and dust. This matter then follows one of three different routes. It finds its way onto the star through magnetic funnels, or stays in the disc to form planets, or is thrown clear of the system in a wind or jet created by the overall magnetic field.

With the help of ESA’s X-ray observatory XMM-Newton, Guedel and his 25 international colleagues are now ready to report new details from the front line.

They used XMM-Newton to target stars in the nearby Taurus Molecular Cloud. This vast cloud in space is one of the star - forming regions nearest to Earth and contains over 400 young stars.

Most of these stars are still accumulating matter, a process known as accretion. As falling matter strikes the surface of the star, it typically doubles the temperature of the surface from 5000 Kelvin to 10 000 Kelvin. This produces an excessive amount of ultraviolet radiation emitted by the star and detected by XMM-Newton’s Optical Monitor. Astronomers had thought that the same shock waves that caused the emission of the ultraviolet excess should also produce an excess of X-rays.

Confusingly enough, previous observations seemed to show that young stars that still accrete matter give off less X-ray emission. To investigate this mystery, amongst several others, ESA approved a large programme of observations with XMM-Newton. The space-borne observatory investigated the densest regions of the Taurus Molecular Cloud for a total of more than 7 days.


XMM-Newton’s spectrometers revealed a new and subtle feature suggesting that the falling material cooled the hot X-ray emitting atmosphere of the young stars, suppressing the emission of X-rays.

In certain cases, namely in the more heavily accreting stars, the suppression of the X-rays was such that the team realised that an additional process was at work in these objects. In addition to cooling the outer stellar atmosphere, the gas streams falling onto the star were so dense that they absorbed most of the X-rays that the star’s atmosphere had emitted.

Although such dense streams of gas should also contain dust that would obscure the star at visible wavelengths, the star is seen shining brightly. So what happens to this dust? The team can propose an answer to this as well. The dust is heated so much by the radiation from the star, that it is vaporised before it can fall on the star.

The strong X-ray suppression allowed the team to discover yet another X-ray source associated with the same stars coming from relatively cool gas that does not suffer from absorption. This emission must come from outside the accretion streams. The team interprets the X-rays as evidence that some gas streams ejected by the star form shock waves that heat up very strongly.



Wednesday, September 26, 2007

X-ray Satellites Discover The Biggest Collisions


The orbiting X-ray telescopes XXM-Newton and Chandra have caught a pair of galaxy clusters merging into a giant cluster. The discovery adds to existing evidence that galaxy clusters can collide faster than previously thought.

When individual galaxies collide and spiral into one another, they discard trails of hot gas that stretch across space, providing signposts to the mayhem. Recognising the signs of collisions between whole clusters of galaxies, however, is not as easy.

Undaunted, Renato Dupke and colleagues from the University of Michigan, Ann Arbor, have used ESA’s XMM-Newton and NASA’s Chandra orbiting X-ray observatories, to disentangle the puzzling galaxy cluster, Abell 576.

Previous X-ray observations had hinted that the gas was not moving uniformly across the cluster. Using the superior sensitivity and spectral resolution of XMM-Newton and Chandra’s high spatial resolution, Dupke took readings from two locations in the cluster and saw that there was a distinct difference in the velocity of the gas. One part of the cluster seemed to be moving away from us faster than the other.

The puzzle was that the moving gas itself was cold by astronomical standards. If this gas moved at such high speeds, it should have had a temperature of more than double the measured 50 million degrees Celsius. “The only explanation was to take the Bullet Cluster and turn it in the line of sight, such that one galaxy cluster is directly behind the other” says Dupke.

The Bullet Cluster is a much-studied pair of galaxy clusters, which have collided head on. One has passed through the other, like a bullet travelling through an apple. In the Bullet Cluster, this is happening across our line of sight, so we can clearly see the two clusters.

Dupke realised that Abell 576 is also a collision, but seen head on, so one cluster is now almost directly behind the other. The ‘cold’ clouds of gas are the cores of each cluster, which have survived the initial collision but will eventually fall back together to become one.

The data reveals that the clusters have collided at a speed of over 3300 km/s. This is interesting because there are some computer models of colliding galaxy clusters that suggest that such a high speed is impossible to reach.

Nevertheless, the Bullet Cluster is estimated to have a collision speed similar to the Abell 576 system. There is now a growing body of evidence that these high collision velocities are possible. The job of explaining these high speeds now rests with the cosmologists.

Major cluster-cluster collisions are expected to be rare, with estimates of their frequency ranging from less than one in a thousand clusters to one in a hundred. On collision, their internal gas is thrown out of equilibrium and if unrecognised, causes underestimation of its mass by between 5 and 20 percent.

This is important because the masses of the various galaxy clusters are used to estimate the cosmological parameters that describe how the Universe expands. So, identifying colliding systems is extremely important to our understanding of the Universe.

Tuesday, September 25, 2007

Two More Active Moons Around Saturn



Saturn’s moons Tethys and Dione are flinging great streams of particles into space, according to data from the NASA/ESA/ASI Cassini mission to Saturn. The discovery suggests the possibility of some sort of geological activity, perhaps even volcanic, on these icy worlds.

The particles were traced to the two moons because of the dramatic movement of electrically charged gas in the magnetic environs of Saturn. Known as plasma, the gas is composed of negatively charged electrons and positively charged ions, which are atoms with one or more electrons missing. Because they are charged, the electrons and ions can get trapped inside a magnetic field.

Saturn rotates around itself in just 10 hours and 46 minutes. This sweeps the magnetic field and the trapped plasma through space. Just like a child on a fast-spinning merry-go-round, the trapped gas feels a force trying to throw it outwards, away from the centre of rotation.

Soon after Cassini reached Saturn, in June 2004, it revealed that the planet’s hurried rotation squashes the plasma into a disc and that great fingers of gas are indeed being thrown out into space from the disc’s outer edges. Hotter, more tenuous plasma then rushes in to fill the gaps.

The direction of the ejected electrons points back towards Tethys and Dione. It establishes Tethys and Dione as important sources of plasma in Saturn’s magnetosphere.

Until this result, among Saturn’s inner moons only Enceladus was known to be an active world, with huge geysers spraying gases hundreds of kilometres above the moon’s surface. This new result seems to be a strong indication that there is activity on Tethys and Dione as well.

In the case of Dione and Tethys, more fly-bys are scheduled in the future, which will allow the team and the other instruments a close-up look at the moons. Before that happens, the team has to go back and search for further signs of activity in the data already collected during the Tethys and Dione flybys of 2005.

Saturday, September 22, 2007

Stellar Tiramisu


Looking at the chemical composition of stars that host planets, astronomers have found that while dwarf stars often show iron enrichment on their surface, giant stars do not. The astronomers think that the planetary debris falling onto the outer layer of the star produces a detectable effect in a dwarf star, but this pollution is diluted by the giant star and mixed into its interior.

Just a few years after the discovery of the first exoplanet it became evident that planets are preferentially found around stars that are enriched in iron. Planet-hosting stars are on average almost twice as rich in metals than their counterparts with no planetary system.

The immediate question is whether this richness in metals enhances planet formation, or whether it is caused by the presence of planets. The classic chicken and egg problem. In the first case, the stars would be metal-rich down to their centre. In the second case, debris from the planetary system would have polluted the star and only the external layers would be affected by this pollution.

When observing stars and taking spectra, astronomers indeed only see the outer layers and can't make sure the whole star has the same composition. When planetary debris fall onto a star, the material will stay in the outer parts, polluting it and leaving traces in the spectra taken.

A team of astronomers has decided to tackle this question by looking at a different kind of stars: red giants. These are stars that, as will the Sun in several billion years, have exhausted the hydrogen in their core. As a result, they have puffed up, becoming much larger and cooler.

Looking at the distribution of metals in fourteen planet-hosting giants, the astronomers found that their distribution was rather different from normal planet-hosting stars.

We find that evolved stars are not enriched in metals, even when hosting planets. Thus, the anomalies found in planet-hosting stars seem to disappear when they get older and puff up!

Looking at the various options, the astronomers conclude that the most likely explanation lies in the difference in the structure between red giants and solar-like stars: the size of the convective zone, the region where all the gas is completely mixed. In the Sun, this convective zone comprises only 2% of the star's mass. But in red giants, the convective zone is huge, encompassing 35 times more mass. The polluting material would thus be 35 times more diluted in a red giant than in a solar-like star.

Although the interpretation of the data is not straightforward, the simplest explanation is that solar-like stars appear metal-rich because of the pollution of their atmospheres.

When the star was still surrounded by a proto-planetary disc, material enriched in more heavy elements would fall onto the star, thereby polluting its surface. The metal excess produced by this pollution, while visible in the thin atmospheres of solar-like stars, is completely diluted in the extended, massive atmospheres of the giants.

Friday, September 21, 2007

Killer Electrons In Space


A rare, timely conjunction of ground-based instrumentation and a dozen satellites has helped scientists better understand how electrons in space can turn into ‘killers’.

‘Killer’ electrons are highly energetic, negatively charged particles found in near-Earth space. They can critically, and even permanently, damage satellites in orbit, including telecommunication satellites, and pose a hazard to astronauts.

Several theories have been formulated in the past to explain the origin of killer electrons, and many uncoordinated observations have already been performed. Recently, scientists got a boost in their understanding of this hazardous phenomenon. This was possible thanks to a unique set of data, collected simultaneously, by a global armada of ground and space observatories during the recovery phase of a large geomagnetic storm.

In the aftermath of the storm, the CARISMA (Canadian Array for Realtime Investigations of Magnetic Activity) magnetometer chain observed a type of Ultra Low Frequency (ULF) electromagnetic wave, well-known for creating killer electrons. CARISMA observed the so-called ‘Pc5 waves’ continuously, for many hours, during the recovery phase of a large geomagnetic storm on 25 November 2001. In the meantime, they were also picked up by more than half a dozen scientific satellites located inside Earth’s magnetic environment, or magnetosphere, including NASA’s Polar mission.

Meanwhile, ESA’s four Cluster satellites were located at the boundary of Earth’s magnetosphere, called the magnetopause. They observed undulations, or disturbances of the magnetopause, at the same frequency as that of Pc5 waves observed from inside the magnetosphere.

Taking into account data from all satellites, Earth-based radars and magnetometers, Rae's team were able to reveal the mechanism behind the scenario.

During this event, the velocity of solar wind - a continuous stream of solar particles impacting and shaping Earth’s magnetosphere – was measured at approximately 750 km/s, nearly twice its average speed. The impact of this fast flow of solar particles on Earth’s magnetosphere induced the undulations observed by Cluster.

In turn, these undulations drove compressional waves, which propagated inward from the magnetopause towards Earth. Close to the location of the Polar satellite, these compressional waves coupled with Earth’s magnetic field lines, making the field lines resonate at the frequency of Pc5 waves, which are able to create killer electrons.

Earth’s magnetosphere is a very large, complex and variable system. This makes the understanding of ULF waves, together with the mechanisms for the energy transfer from space to ground, a very difficult matter.

These new results on ULF waves and killer electrons once again highlight the need for simultaneous observations from space and ground. Only with constant monitoring with ground-based instruments data obtained in space can we put into a global context.

Possible Cave On Mars



Mars Odyssey spacecraft has discovered entrances to seven possible caves on the slopes of a Martian volcano. The find is fueling interest in potential underground habitats and sparking searches for caverns elsewhere on the Red Planet.

Very dark, nearly circular features ranging in diameter from about 100 to 250 meters (328 to 820 feet) puzzled researchers who found them in images taken by NASA's Mars Odyssey and Mars Global Surveyor orbiters. Using Mars Odyssey's infrared camera to check the daytime and nighttime temperatures of the circles, scientists concluded that they could be windows into underground spaces.

Evidence that the holes may be openings to cavernous spaces comes from the temperature differences detected from infrared images taken in the afternoon and in the pre-dawn morning. From day to night, temperatures of the holes change only about one-third as much as the change in temperature of surrounding ground surface.

They are cooler than the surrounding surface in the day and warmer at night. Their thermal behavior is not as steady as large caves on Earth that often maintain a fairly constant temperature, but it is consistent with these being deep holes in the ground.

Whether these are just deep vertical shafts or openings into spacious caverns, they are entries to the subsurface of Mars. Somewhere on Mars, caves might provide a protected niche for past or current life, or shelter for humans in the future.

The holes "Seven Sisters," are at some of the highest altitudes on the planet, on a volcano named Arsia Mons near Mars' tallest mountain.

These are at such extreme altitude, they are poor candidates either for use as human habitation or for having microbial life. Even if life has ever existed on Mars, it may not have migrated to this height.

The observations have prompted researchers using Mars Odyssey and NASA's newer Mars Reconnaissance Orbiter to examine the Seven Sisters. The goal is to find other openings to underground spaces at lower elevations that are more accessible to future missions to Mars.

The key to finding these was looking for temperature anomalies at night -- warm spots. That instrument produced both visible-light and infrared images researchers used for examining the possible caves.


Thursday, September 20, 2007

Hidden Planet Pushes Star's Ring


A young star's strange elliptical ring of dust likely heralds the presence of an undiscovered Neptune-sized planet, says a University of Rochester astronomer in the latest Monthly Notices of the Royal Astronomical Society.

Stars in the early stages of life are surrounded by dust clouds that thin out and dissipate as the star reaches maturity, becoming rings in their final stages. One star, however, has a dust ring that has long puzzled astronomers because it is not centered around the star as usual. Instead, the ring is elliptical, with the parent star off to one side.

Roughly 250 planets have been discovered so far around stars other than our Sun. Most have been revealed by the way the planets influence their parent stars, but Quillen has been working for years on understanding the delicate interaction between stellar dust disks and the planets that shape them. She is now one of the world's experts in predicting planet size and position from the features of a star's dust ring.

Quillen used new images from the Hubble Space Telescope that caught the star, Fomalhaut, and its surrounding ring almost edge-on and in more detail than ever before. Fomalhaut, 25 light-years away, is the brightest star in the autumn sky. Using a device called a coronagraph that blocks out a star's light so dimmer objects near it can be seen, the Hubble revealed that Fomalhaut was indeed off-center within its ring. The images were also clear enough to show that the ring itself had a surprisingly sharp edge.

That sharp edge was the clue Quillen was looking for. Since ascertaining one of the first extra-solar planets using dust-ring analysis in 2002, Quillen has greatly strengthened her planet-ring interaction models. Treating the ring like a hydrodynamic structure, for instance, is necessary for younger stars whose dust is relatively fine and acts more like a fluid—while the physics of dust collision become dominant in older ring systems where the dust has begun clumping into larger bodies.

The sharp inside edge of Fomalhaut, Quillen calculated, demanded that a relatively small, Neptune-size planet was tucked right up against the inner side of the ring, using its gravity to toss dust in the area out of orbit.

When stars form from a giant cloud of gas and dust, the angular momentum of the cloud carries over to all the objects that form from the cloud, including new planets. Those new planets should, initially at least, orbit in nice, circular paths—not elliptical ones. Fomalhaut's ring is offset by 1.4 billion miles, more than 15 times the distance from the Earth to the Sun, suggesting the hidden planet's orbit is also tremendously skewed.

Wednesday, September 19, 2007

Dwarf Star Gulps Giant To Form Supernova


A team of European and American astronomers has announced the discovery of the best evidence yet for the nature of the star systems that explode as type Ia supernovae. The team obtained a unique set of observations with the European Southern Observatory's Very Large Telescope and the Keck I 10-meter telescope in Hawaii.

The researchers were able to detect the signature of the material that surrounded the star before it exploded. The evidence strongly supports the scenario in which the explosion occurred in a double-star system where a white dwarf is fed by a red giant.

The powerful 10 meter Keck Telescope with its recently refurbished high-resolution spectrograph finally gives us the capability to follow these supernovae for months, as we have done here. We are now busy taking advantage of this new window of opportunity. This is really an exciting avenue that Keck opens up to us.

Because type Ia supernovae are extremely luminous and quite similar to one another, these exploding events have been used extensively as cosmological reference beacons to trace the expansion of the universe.

However, despite significant recent progress, the nature of the stars that explode and the physics that governs these powerful explosions have remained poorly understood.

In the most widely accepted models of type Ia supernovae, the pre-explosion white dwarf star interacts with a much larger companion star. Because of the proximity of the two stars and the strong gravitational attraction produced by the very compact white dwarf, the companion star continuously loses mass, "feeding" the white dwarf. When the mass of the white dwarf exceeds a critical value slightly higher than the mass of the sun, it explodes.

The team of astronomers studied in great detail SN 2006X, a type Ia supernova that exploded 70 million light-years away from us, in the stunning spiral galaxy Messier 100.

The observations were made with the Ultraviolet and Visual Echelle Spectrograph mounted at ESO's 8.2 meter Very Large Telescope on four different occasions, over a time span of four months. A fifth late-time epoch spectrum of SN 2006X was secured with the Keck Telescope. The astronomers also made use of radio data obtained with National Radio Astronomy Observatory's Very Large Array as well as with images extracted from the NASA/European Space Agency Hubble Space Telescope archive.

The most remarkable finding is the clear evolution seen in the absorption profile of the sodium lines over the few months following the explosion. This, the astronomers deduce, is linked to the presence of a number of expanding shells surrounding the system. These shells are left over from the star that was force-feeding the white dwarf until its sudden catastrophic and spectacular death.

The material we have uncovered probably lies in a series of shells having a radius of the order of 0.05 light-years, or roughly 3,000 times the distance between Earth and the sun.  The material is moving with a velocity of 50 km/s, implying that the material would have been ejected some 50 years before the explosion.

Is not certain whether SN 2006X is a unique case, or is instead representative of all type Ia supernovae. Additional studies of similar objects will be crucial for determining that.

Such a velocity is typical for the winds of red giant stars. The system that exploded was thus most likely composed of a white dwarf that acted as a giant "vacuum cleaner," drawing gas off of its red giant companion. In this case, however, the cannibal act proved mortal for the white dwarf. This is the first time that any clear and direct evidence for material surrounding the exploding star has been found.

We should know even more within the next year.

Tuesday, September 18, 2007

Best Views of Planet Mars Now Online


Anyone connected by Internet can now see planet Mars better than at any time in history, through the eye of HiRISE, the most powerful camera ever to orbit another planet.

A University of Arizona-based team that runs the High Resolution Imaging Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter has just released more than 1,200 Mars images to the Planetary Data System, the U.S. space agency's mission data archive.

Not only has the team released 1.7 Terabytes of HiRISE data -- the largest single dataset ever delivered to NASA's space mission data library -- but also a user-friendly way for the public to easily see HiRISE images.

Thanks to tools available on HiRISE's any Internet user can quickly pull up and explore the same remarkable images that both thrill and confound scientists.

These images must contain hundreds of important discoveries about Mars, We just need time to realize what they are.

The HiRISE camera takes images of 3.5-mile-wide (6 km) swaths as the orbiter flies at about 7,800 mph between 155 and 196 miles (250 to 316 km) above Mars' surface. For at least the next 18 months, HiRISE will collect thousands of color, black-and-white and stereo images of the Martian surface, resolving features as small as 40 inches across, covering about one percent of the planet.

The team based at UA's HiRISE Operations Center began releasing selected images on the Internet when science operations began in November 2006. Team members began reprocessing all the images taken up to March 25, 2007, using improved calibration, or image correction techniques, in April.

HiRISE Web site gives general users, as well as scientists, a tool to quickly home in on any location within a single huge HiRISE image, which often will be a gigabyte image measuring 20,000 pixels by 50,000 pixels. The tool, which was developed by ITT-Visual Information Solutions in Boulder, is called the IAS Viewer. Users can download it for free directly from the HiRISE Website.

The advantage to IAS-Viewer technology is that it transmits only the amount of data needed to render that portion of the image displayed on the computer screen. That is, each time a user zooms in on a image, he or she doesn't download a completely new set of pixels. Instead, the user is downloading only the higher resolution parts of the image data, which are added to the image data already downloaded by the viewer. The IAS Viewer ultimately renders the selected part of the image in high resolution by adding more and more pixels.



Monday, September 17, 2007

Liquid Telescope On The Moon


An international team including researcher Ermanno Borra, from Université Laval's Center for Optics, Photonics, and Laser, has taken another step toward building a liquid telescope on the moon. The researchers have found a combination of materials that allows the creation of a highly reflective liquid mirror capable of functioning even under harsh lunar conditions.

Liquid mirror telescopes differ from conventional telescopes by their primary mirrors--the ones that gather and focus light--which are made from a reflective liquid instead of polished glass. Poured into a spinning container, the liquid spreads out and forms a thin, perfectly smooth, and parabolic shape that can be used as a telescope mirror.

In a 1991 paper published in the Astrophysical Journal, Professor Borra had suggested the building of a liquid telescope on the moon. In that paper demonstrated the practical and economic advantages of liquid mirror telescopes over their conventional counterparts and explained how an observatory free from the Earth's atmospheric disturbance could further our understanding of the early universe.

The project, which seemed almost like science-fiction at the time, gained renewed interest in 2004 when it received financial support from the NASA Institute for Advanced Concepts, an organization which funds projects that can potentially push back the limits of science and space technology.

The project's main challenge consisted in finding a liquid capable of resisting the conditions on the moon's surface and functioning in temperatures required for infrared observations, i.e. below -143 degrees Celsius.

In their Nature article, the researchers explain how they successfully coated an ionic liquid with silver by vaporizing it in a vacuum, something never achieved before in the field of optics. The resulting silver layer is perfectly smooth, highly reflective, remains stable for months, and the ionic liquid on which it lies does not evaporate.

The liquid mirror envisioned for the lunar telescope would be 20 to 100 meters in diameter, making it up to 1,000 times more sensitive than the proposed next generation of space telescopes.

Such a lunar telescope will not be available to researchers in the near future.

Sunday, September 16, 2007

Photonic laser thruster



The photonic laser thruster, created by the Bae Institute in California, overcomes the inefficiency of photon particles producing thrust by bouncing them many times between two mirrors.

Photon particles have been considered inefficient for producing thrust because they have zero mass and no electric charge. The PLT system overcomes the inherent photonic inefficiency by bouncing photons many times between two mirrors.

On Dec. 21, 2006, Bae used a photonic laser and a sophisticated photon beam amplification system to demonstrate that photonic energy could generate amplified thrust between two spacecraft by bouncing photons many thousands of times between them. Repeated experiments since then have confirmed the results.

The patent-pending PLT was built and monitored with off-the-shelf laboratory components at the Southern California laboratory of the Bae Institute, which was founded in 2002 by Bae to develop innovative space and medical technologies for commercial and government applications. Bae has pursued advanced propulsion concepts such as antimatter and fusion propulsion for more than 20 years at SRI International, Brookhaven National Lab and the AFRL.

With an amplification factor of 3000, the photon thrust generated from the egg-sized laser head in the PLT prototype is equivalent to the thrust that can currently only be generated by orders-of-magnitudes larger and heavier industrial or weapons-grade lasers.

Although PLT can be used for a wide range of space applications, including accelerating spacecraft to near light speed, Bae has more immediate goals. He plans to include PLT in a photon tether formation flight (PTFF), another of his patent-pending ideas for controlling spacecraft flying in formation with nanometer precision. By integrating PLT and space tethers, PTFF will enable the creation of large telescopes and synthetic apertures in space for high-resolution earth or space monitoring. Bae said PTFF promises precision 100,000 times greater than existing formation flying spacecraft missions, notably the Proba-3 currently planned by the European Space Agency.

As a result of the successful PLT demonstration, thrust power requirements for a wide range of NASA spacecraft formation flight configurations, such as SPECS and MAXIM, are well within today's space power budgets. No other propellants are needed with PLT, resulting in mass energy savings, extended spacecraft missions, and contaminant-free operation for highly precise sensors, Bae said.

Although built on a shoestring budget, the maximum photon thrust was demonstrated to be 35 uN, which is already close to, or sufficient power for many envisioned space missions. The Bae Institute is now seeking funding to scale up and construct space flight-ready PLT systems.

In addition to conventional formation flying, fractionated space architectures can benefit tremendously from the versatility and flexibility of a tightly controlled PLT system.

Saturday, September 15, 2007

To Mars and Beyond




Astra Rocket Company is working on a propulsion system that could shorten trips in space and improve fuel efficiency.

This coming January, Astra Rocket Company will test the VX-200, a full-scale ground prototype of the variable specific impulse magnetoplasma rocket (VASIMIR), first conceived in 1979 by the company's president and CEO, astronaut and plasma physicist Franklin Chang Diaz. The rocket is an attempt to improve on current space-propulsion technologies, and it would use hot plasma, heated by radio waves and controlled by a magnetic field, for propulsion. Chang Diaz believes that the system would allow rockets to travel through space at higher speeds, with greater fuel efficiency.

If the prototype demonstrates sufficient efficiency, thrust, and specific impulse on the ground, the next step will be the VF-200, a flight version of the rocket. Ad Astra plans to fly the VF-200 to the International Space Station, where it would help maintain the space station's orbit. If all this goes according to plan, Chang Diaz hopes to eventually build VASIMIRs that could travel to Mars and beyond.


Friday, September 14, 2007

Mini-MagOrion technology




Andrews Space created a new concept for the propulsion of spacebound vehicles based on the Orion concept from the late 1950s. The new concept builds on the original Orion concept by reducing the size and implementing magnetic implosion technology.

The newest concept -- dubbed Mini-MagOrion, or MMO -- takes the old Project Orion concept of using small nuclear explosions, one after another, to propell a spacecraft faster than any propulsion system in use today. The MMO concept also builds on the original MagOrion concept which failed due to certain technological limitations -- superconductor limitations -- and political issues -- sending a vehicle to the sky which had the ability to launch multiple nuclear explosives at high rates of repetition.

At the heart of the Mini-MagOrion concept is the idea of compressing initially subcritical fission assemblies by use of an imploding Z-pinch. This enables the lower yield values, external triggering of the fission reaction, and reduces the severity of the environment in which the engine has to operate. The MMO program included the analysis of solid, high Z material compression, paired with the experimental verification / calibration of the analysis.

The MMO concept utilizes a Z-pinch, which uses electrical current to generate a magnetic field to keep that plasma under control. This helps maintain a safe environment for the engine to operate without eradicating the engine, vehicle, and anything close to it.

It is said that the force created by MMO-based engines can push spacebound vehicles to about 10% the speed of light. If this technology can be materialized, the time it takes to complete manned and unmanned space missions will be significantly shortened.

Thursday, September 13, 2007

Mystery Of The Peruvian Meteorite



The cause of illness from meteorite impact was discovered to be decidedly not out-of-this-world.

A significant cosmic event occurred when a massive meteor struck on September 15th outside the farming village of Carancas, near Lake Titicaca.  The meteor created an imposing eight meter (26-foot) deep, 20 meter (65 foot) wide crater. Almost immediately the object was ruled to be a meteor and not something of terrestial origin.

The massive crater emitted strange fumes, which made over 30 villagers violently ill, with headaches and nausea. Reports on the exact number of victims ranged from 30 to about 200. Speculations on possible "out-of-this-world" causes were rampant.

Police blocked off the crater, and the villagers were transported to hospitals.

The director of the health ministry in the Puno region, Jorge Lopez, said none of the patients was in serious condition but that they would have to undergo blood and neurological tests as a precaution in three to six months.

Now, a team of Peruvian researchers have determined the true cause -- ground water tainted with arsenic.

The villagers' reactions were the result of inhaling arsenic fumes, according to, a researcher for Peru's Mining, Metallurgy, and Geology Institute, who visited the crash site.

Peru's soil is rich in arsenic deposits and when the meteor hit, columns of steam were created by the heat from the meteor. This steam bore particles of arsenic, causing the various afflictions.

Villagers described the event as a terrifying experience as they observed the massive flaming ball of rock hurtled at high speed from the skies and the impact scattered debris over a wide radius.  Debris landed on the roof of the closest house, 390 feet from the crater, but no fires were reported to be caused by the debris.

The medical mystery of the meteor and its solution goes to show that there are practical explanations for many "out-of-this-world" phenomena.  The event also was a significant cosmological event, as it marks one of the largest meteor impacts in recent years. For now, the people of Carancas, probably just want to never see another meteorite again.

Wednesday, September 12, 2007

Warm South Pole? On Neptune!



An international team of astronomers using ESO's Very Large Telescope has discovered that the south pole of Neptune is much hotter than the rest of the planet. This is consistent with the fact that it is late southern summer and this region has been in sunlight for about 40 years.

The scientists are publishing the first temperature maps of the lowest portion of Neptune's atmosphere, showing that this warm south pole is providing an avenue for methane to escape out of the deep atmosphere.

The temperatures are so high that methane gas, which should be frozen out in the upper part of Neptune's atmosphere (the stratosphere), can leak out through this region. This solves a long-standing problem of identifying the source of Neptune's high stratospheric methane abundances.

The temperature at the south pole is higher than anywhere else on the planet by about 10 degrees Celsius. The average temperature on Neptune is about minus 200 degrees Celsius.

Is located about 30 times farther away from the Sun than Earth is. Only about 1/900th as much sunlight reaches Neptune as our planet. Yet, the small amount of sunlight it receives significantly affects the planet's atmosphere.

The astronomers found that these temperature variations are consistent with seasonal changes. A Neptunian year lasts about 165 Earth years. It has been summer in the south pole of Neptune for about 40 years now, and they predict that as winter turns to summer in the north pole, an abundance of methane will leak out of a warm north pole in about 80 years.

Neptune's south pole is currently tilted toward the Sun, just like the Earth's south pole is tilted toward the Sun during summer in the Southern Hemisphere. But on Neptune the antarctic summer lasts 40 years instead of a few months, and a lot of solar energy input during that time can make big temperature differences between the regions in continual sunlight and those with day-night variations.

Neptune has the strongest winds of any planet in the Solar System; sometimes, the wind blows there at more than 2000 kilometres per hour. It is certainly not the place you would like to go on a holidays.

The new observations also reveal mysterious high-latitude 'hot spots' in the stratosphere that have no immediate analogue in other planetary atmospheres. The astronomers think that these hot spots are generated by upwelling gas from much deeper in the atmosphere.

Methane is not the primary constituent of Neptune's atmosphere, which, as a giant planet, is mostly composed of the light gases, hydrogen and helium. But it is the methane in Neptune's upper atmosphere that absorbs the red light from the Sun and reflects the blue light back into space, making Neptune appear blue.


Tuesday, September 11, 2007

Mars Water And Climate From NASA Orbiter




Mars Reconnaissance Orbiter is examining several features on Mars that address the role of water at different times in Martian history.

Features examined with the orbiter's advanced instruments include material deposited in two gullies within the past eight years, polar ice layers formed in the recent geologic past, and signs of water released by large impacts when Mars was older.

Last year, discovery of the fresh gully deposits from before-and-after images taken since 1999 by another orbiter, Mars Global Surveyor, raised hopes that modern flows of liquid water had been detected on Mars. Observations by the newer orbiter, which reached Mars last year, suggest these deposits might instead have resulted from landslides of loose, dry materials.

The key question raised by these two deposits is whether water is coming to the surface of Mars today, evidence suggests the new deposits did not necessarily involve water.
One of the fresh deposits is a stripe of relatively bright material several hundred yards long that was not present in 1999 but appeared by 2004.

maging Spectrometer for Mars reveals the deposit is not frost, ice or a mineral left behind by evaporation of salty water. Also, the researchers inspected the slopes above this and five other locations that have bright and apparently young deposits. The slopes are steep enough for sand or loose, dry dust to flow down the gullies. Bright material seen uphill could be the source.

Other gullies, however, offer strong evidence of liquid water flowing on Mars within the last few million years, although perhaps at a different phase of repeating climate cycles. Mars, like Earth, has periodic changes in climate due to the cycles related to the planets' tilts and orbits. Some eras during the cycles are warmer than others. These gullies are on slopes too shallow for dry flows, and images from Mars Reconnaissance Orbiter's high-resolution camera show clear indicators of liquid flows, such as braided channels and terraces within the gullies.

Another new finding from that camera may help undermine arguments that very ancient Mars had a wet climate on a sustained basis. Landscapes with branched channels and fan-like deposits typical of liquid flows were found around several impact craters. Images show close association between some of those flow features and ponded deposits interpreted as material melted by the impact of a meteoroid into ice-rich crust.

This new evidence supports a hypothesis that ancient water flows on the surface were episodic, linked to impact events and subsurface heating, and not necessarily the result of precipitation in a sustained warmer climate. Crater-digging impacts were larger and more numerous during the early Martian era when large drainage networks and other signs of surface water were carved on many parts of the planet.

The radar detected layering patterns near the south pole that suggest climatic periods of accumulating deposits have alternated with periods of erosion.

MIT used effects of Mars' gravity on the orbiter to check whether layered deposits at the south pole are high-density material, such as rock, or lower-density such as ice. Their observations add to other evidence that the layers are mostly water, others used the high-resolution camera to trace a series of distinctive layers near the north pole.

Friday, September 7, 2007

Networks Create 'Instant World Telescope'



For the first time, a CSIRO radio telescope has been linked to others in China and Europe in real-time, demonstrating the power of high-speed global networks and effectively creating a telescope almost as big as the Earth.

A CSIRO telescope near Coonabarabran NSW was recently used simultaneously with one near Shanghai, China, and five in Europe to observe a distant galaxy called 3C273.

Data from the telescopes was streamed around the world at a rate of 256 Mb per second to a research centre in Europe, where it was processed with a special-purpose digital processor.

The results were then transmitted to Xi’an, China, where they were watched live by experts in advanced networking at the APAN (Asia-Pacific Advanced Network) Meeting.

The more widely separated the telescopes, the more finely detailed the observations can be. The diameter of the Earth is 12 750 km and the two most widely separated telescopes in our experiment were 12 304 km apart, in a straight line.


Thursday, September 6, 2007

Space-time Distorts Near Neutron Stars



Neutron stars contain the most dense observable matter in the universe. They cram more than a sun’s worth of material into a city-sized sphere, meaning a few cups of neutron-star stuff would outweigh Mount Everest. Astronomers use these collapsed stars as natural laboratories to study how tightly matter can be crammed under the most extreme pressures that nature can offer.

There could be exotic kinds of particles or states of matter, such as quark matter, in the centers of neutron stars, but it’s impossible to create them in the lab. The only way to find out is to understand neutron stars.

To address this mystery, scientists must accurately and precisely measure the diameters and masses of neutron stars. In two concurrent studies, one with the European Space Agency’s XMM-Newton X-ray Observatory and the other with the Japanese/NASA Suzaku X-ray observatory, astronomers have taken a big step forward.

Using XMM-Newton, Bhattacharyya and his NASA Goddard colleague Tod Strohmayer observed a binary system known as Serpens X-1, which contains a neutron star and a stellar companion. They studied a spectral line from hot iron atoms that are whirling around in a disk just beyond the neutron star’s surface at 40 percent the speed of light.

Previous X-ray observatories detected iron lines around neutron stars, but they lacked the sensitivity to measure the shapes of the lines in detail. Thanks to XMM-Newton’s large mirrors, Bhattacharyya and Strohmayer found that the iron line is broadened asymmetrically by the gas’s extreme velocity, which smears and distorts the line because of the Doppler effect and beaming effects predicted by Einstein’s special theory of relativity. The warping of space-time by the neutron star’s powerful gravity, an effect of Einstein’s general theory of relativity, shifts the neutron star’s iron line to longer wavelengths.

We've seen these asymmetric lines from many black holes, but this is the first confirmation that neutron stars can produce them as well. It shows that the way neutron stars accrete matter is not very different from that of black holes.

"We’re seeing the gas whipping around just outside the neutron star’s surface," says Cackett. "And since the inner part of the disk obviously can’t orbit any closer than the neutron star’s surface, these measurements give us a maximum size of the neutron star’s diameter. The neutron stars can be no larger than 18 to 20.5 miles across, results that agree with other types of measurements."

"Now that we’ve seen this relativistic iron line around three neutron stars, we have established a new technique," adds Miller. "It’s very difficult to measure the mass and diameter of a neutron star, so we need several techniques to work together to achieve that goal."

Knowing a neutron star’s size and mass allows physicists to describe the "stiffness," or "equation of state," of matter packed inside these incredibly dense objects. Besides using these iron lines to test Einstein’s general theory of relativity, astronomers can probe conditions in the inner part of a neutron star’s accretion disk.

Wednesday, September 5, 2007

Gaping Hole In The Universe



University of Minnesota astronomers have found an enormous hole in the Universe, nearly a billion light-years across, empty of both normal matter such as stars, galaxies and gas, as well as the mysterious, unseen "dark matter." While earlier studies have shown holes, or voids, in the large-scale structure of the Universe, this new discovery dwarfs them all.

Not only has no one ever found a void this big, but we never even expected to find one this size.

Astronomers have known for years that, on large scales, the Universe has voids largely empty of matter. However, most of these voids are much smaller than the one found by Rudnick and his colleagues. In addition, the number of discovered voids decreases as the size increases.

"What we've found is not normal, based on either observational studies or on computer simulations of the large-scale evolution of the Universe," Williams said. 

Astronomers wondered if the cold spot was intrinsic to the CMB(cosmic microwave background), and thus indicated some structure in the very early Universe, or whether it could be caused by something more nearby through which the CMB had to pass on its way to Earth. Finding the dearth of galaxies in that region by studying NVSS data resolved that question.

"Although our surprising results need independent confirmation, the slightly lower temperature of the CMB in this region appears to be caused by a huge hole devoid of nearly all matter roughly 6-10 billion light-years from Earth," Rudnick said.

How does a lack of matter cause a lower temperature in the Big Bang's remnant radiation as seen from Earth"

In a simple expansion of the universe, without dark energy, photons approaching a large mass -- such as a supercluster of galaxies -- pick up energy from its gravity. As they pull away, the gravity saps their energy, and they wind up with the same energy as when they started.

But photons passing through matter-rich space when dark energy became dominant don't fall back to their original energy level. Dark energy counteracts the influence of gravity and so the large masses don't sap as much energy from the photons as they pull away. Thus, these photons arrive at Earth with a slightly higher energy, or temperature, than they would in a dark energy-free Universe.

Conversely, photons passing through a large void experience a loss of energy. The acceleration of the Universe's expansion, and thus dark energy, were discovered less than a decade ago. The physical properties of dark energy are unknown, though it is by far the most abundant form of energy in the Universe today. Learning its nature is one of the most fundamental current problems in astrophysics.

Tuesday, September 4, 2007

Elusive Waves In Sun's Corona




Scientists for the first time have observed elusive oscillations in the Sun's corona, known as Alfvén waves, that transport energy outward from the surface of the Sun. The discovery is expected to give researchers more insight into the fundamental behavior of solar magnetic fields, eventually leading to a fuller understanding of how the Sun affects Earth and the solar system.

Alfvén waves can provide us with a window into processes that are fundamental to the workings of the Sun and its impacts on Earth.

Alfvén waves are fast-moving perturbations that emanate outward from the Sun along magnetic field lines, transporting energy. Although they have been detected in the heliosphere outside the Sun, they have never before been viewed within the corona, which is the outer layer of the Sun's atmosphere. Alfvén waves are difficult to detect partly because, unlike other waves, they do not lead to large-intensity fluctuations in the corona. In addition, their velocity shifts are small and not easily spotted.

The waves are visible all the time and they occur all over the corona, which was initially surprising.

Insights into the Sun

By tracking the speed and direction of the waves, researchers will be able to infer basic properties of the solar atmosphere, such as the density and direction of magnetic fields. The waves may provide answers to questions that have puzzled physicists for generations, such as why the Sun's corona is hundreds of times hotter than its surface.

The research also can help scientists better predict solar storms that spew thousands of tons of magnetized matter into space, sometimes causing geomagnetic storms on Earth that disrupt sensitive telecommunications and power systems. By learning more about solar disruptions, scientists may be able to better protect astronauts from potentially dangerous levels of radiation in space.

Insights into the Sun

By tracking the speed and direction of the waves, researchers will be able to infer basic properties of the solar atmosphere, such as the density and direction of magnetic fields. The waves may provide answers to questions that have puzzled physicists for generations, such as why the Sun's corona is hundreds of times hotter than its surface.

The research also can help scientists better predict solar storms that spew thousands of tons of magnetized matter into space, sometimes causing geomagnetic storms on Earth that disrupt sensitive telecommunications and power systems. By learning more about solar disruptions, scientists may be able to better protect astronauts from potentially dangerous levels of radiation in space.

What Makes Mars Magnetic?



Scientists think that the secret lies beneath the crust, in the slippery asthenosphere. In order for the mantle to convect and the plates to slide they require a lubricated layer. On Mars this lubrication has long since dried up, but on Earth the plates can still glide around with ease.

If you could pick up a rock from the surface of Mars, then the chances are it would be magnetic. And yet, Mars doesn’t have a magnetic field coming from its core. These rocks are clinging to the signal of an ancient magnetic field, dating back billions of years, to the times when Mars had a magnetic field like Earth’s.

So how have these rocks hung onto their magnetic directions and what do they tell us about Mars? Strangely, the answer to these questions might be sitting here on Earth.

Most continental rocks on Earth align their magnetic moments with the current magnetic field – they are said to have ‘induced’ magnetism. “I consider induced rocks to have ‘Alzheimers’. These are the rocks that forgot where they were born and how to get home,” explains Suzanne McEnroe.

However, not all of Earth’s continental rocks have an induced magnetization. Some rocks stubbornly refuse to swing with the latest magnetic field, and instead keep hold of the direction they were born with. These rocks are said to have a remanent magnetization.

McEnroe and her colleagues have been studying some of Earth’s strongest and oldest remanent magnetic rocks, to find out why they have such good memories. Understanding these rocks may give us clues as to what kind of rocks lie on Mars.

These rocks are around 1 billion years old and have a strong magnetic remanence, more than 30 times larger than typically found in basaltic rocks.

The mining company had assumed that the rocks in this strongly magnetic area were holding an induced magnetic field and that there would be magnetite buried down below. However, they were puzzled when a different mineral – hematite, came out of the drill core. Had they missed their target, or were their assumptions wrong?

By studying the samples under a powerful microscope and modelling their magnetic properties, McEnroe was able to show that the hematite was responsible for the strong magnetic field and that it was holding a remanent field from around 1 billion years ago. “We could see that the hematite contained small intergrowths that carried the magnetism”.

And it turns out that the microstructure of the rock is the key to whether it can hold a remanent magnetization or not. Together with Richard Harrison, a mineral physicist at Cambridge University, UK, and Peter Robinson at NGU, McEnroe has been studying strong remanent magnetic rocks from a variety of places including Scandinavia and the USA.

A study on nearly billion-year-old rocks in Norway showed a remanent magnetic anomaly comparable in scale to those observed on Mars. The remanent magnetic anomaly dominates the local magnetic field to such a degree that more than half the Earth's field is cancelled. It is nearly impossible to use a compass in the area, which cannot point correctly north because of the strong remanent magnetization in the rocks.

What they have found is that rocks containing nanometre scale intergrowths of ilmenite and hematite are better able to cling onto their original magnetization than those without such fine-scale features. “Placing a nanoparticle of ilmenite into the hematite host creates a strong and stable magnetic signal that can survive large changes in temperature and magnetic field over billions of years,” explains Harrison.

So can this tell us anything about the rocks on Mars? “These rocks are good analogues for the magnetic rocks we see on Mars because of their strong magnetism and the length of time they have retained this memory,” says McEnroe. Certainly this nano-scale microstructure is a plausible candidate for the magnetic rocks on Mars.

However, the rocks on Earth can’t answer all our questions.

Monday, September 3, 2007

Star Caught Smoking




Astronomers from France and Brazil have detected a huge cloud of dust around a star. This observation is further evidence for the theory that such stellar puffs are the cause of the repeated extreme dimming of the star.

R Coronae Borealis stars are supergiants exhibiting erratic variability. Named after the first star that showed such behaviour, they are more than 50 times larger than our Sun. R Coronae Borealis stars can see their apparent brightness unpredictably decline to a thousandth of their nominal value within a few weeks, with the return to normal light levels being much slower. It has been accepted for decades that such fading could be due to obscuration of the stellar surface by newly formed dusty clouds.

This 'Dust Puff Theory' suggests that mass is lost from the R Coronae Borealis (R CrB) star and then moves away until the temperature is low enough for carbon dust to form. If the newly formed dust cloud is located along our line-of-sight, it eclipses the star. As the dust is blown away by the star's strong light, the 'curtain' vanishes and the star reappears.

RY Sagittarii is the brightest member in the southern hemisphere of this family of weird stars. Located about 6,000 light-years away towards the constellation of Sagittarius (The Archer), its peculiar nature was discovered in 1895 by famous Dutch astronomer Jacobus Cornelius Kapteyn.

In 2004, near-infrared adaptive optics observations made with NACO on ESO's Very Large Telescope allowed astronomers Patrick de Laverny and Djamel Mékarnia to clearly detect the presence of clouds around RY Sagittarii. This was the first direct confirmation of the standard scenario explaining the light variations of R CrB stars by the presence of heterogeneities in their envelope surrounding the star.

However, the precise place where such dust clouds would form was still unclear. The brightest cloud detected was several hundred stellar radii from the centre, but it had certainly formed much closer. But how much closer?

To probe the vicinity of the star, the astronomers then turned to ESO's Very Large Telescope Interferometer. Combining two different pairs of the 8.2-m Unit Telescopes, the astronomers explored the inner 110 astronomical units around the star. Given the remoteness of RY Sagittarii, this corresponds to looking at details on a one-euro coin that is about 75 km away!

The astronomers found that a huge envelope, about 120 times as big as RY Sagittarii itself, surrounds the supergiant star. But more importantly, the astronomers also found evidence for a dusty cloud lying only about 30 astronomical units away from the star, or 100 times the radius of the star.

"This is the closest dusty cloud ever detected around a R CrB-type variable since our first direct detection in 2004," says Patrick de Laverny, leader of the team. "However, it is still detected too far away from the star to distinguish between the different scenarios proposed within the Dust Puff Theory for the possible locations in which the dusty clouds form."

If the cloud moves at the speed of 300 km/s, as one can conservatively assume, it was probably ejected more than 6 months before its discovery from deeper inside the envelope. The astronomers are now planning to monitor RY Sagittarii more carefully to shed more light on the evolution of the dusty clouds surrounding it.

Two hundred years after the discovery of the variable nature of R CrB, many aspects of the R CrB phenomenon remain mysterious.


Sunday, September 2, 2007

Speeding Star



A new ultraviolet mosaic from NASA's Galaxy Evolution Explorer shows a speeding star that is leaving an enormous trail of "seeds" for new solar systems. The star, named Mira is shedding material that will be recycled into new stars, planets and possibly even life as it hurls through our galaxy.

Mira appears as a small white dot in the bulb-shaped structure at right, and is moving from left to right in this view. The shed material can be seen in light blue. The dots in the picture are stars and distant galaxies.

The Galaxy Evolution Explorer discovered Mira's strange comet-like tail during part of its routine survey of the entire sky at ultraviolet wavelengths. When astronomers first saw the picture, they were shocked because Mira has been studied for over 400 years yet nothing like this has ever been documented before.

Mira's comet-like tail stretches a startling 13 light-years across the sky. For comparison, the nearest star to our sun, Proxima Centauri, is only about 4 light-years away. Mira's tail also tells a tale of its history – the material making it up has been slowly blown off over time, with the oldest material at the end of the tail having been released about 30,000 years ago.

Mira is a highly evolved, "red giant" star near the end of its life. Technically, it is called an asymptotic giant branch star. It is red in color and bloated; for example, if a red giant were to replace our sun, it would engulf everything out to the orbit of Mars. Our sun will mature into a red giant in about 5 billion years.

Like other red giants, Mira will lose a large fraction of its mass in the form of gas and dust. In fact, Mira ejects the equivalent of the Earth's mass every 10 years. It has released enough material over the past 30,000 years to seed at least 3,000 Earth-sized planets or 9 Jupiter-sized ones.

While most stars travel along together around the disk of our Milky Way, Mira is charging through it. Because Mira is not moving with the "pack," it is moving much faster relative to the ambient gas in our section of the Milky Way. It is zipping along at 130 kilometers per second, or 291,000 miles per hour, relative to this gas.

Mira's breakneck speed together with its outflow of material are responsible for its unique glowing tail. Images from the Galaxy Evolution Explorer show a large build-up of gas, or bow shock, in front of the star, similar to water piling up in front of a speeding boat. Scientists now know that hot gas in this bow shock mixes with the cooler, hydrogen gas being shed from Mira, causing it to heat up as it swirls back into a turbulent wake. As the hydrogen gas loses energy, it fluoresces with ultraviolet light, which the Galaxy Evolution Explorer can detect.

Mira, also known as Mira A, is not alone in its travels through space. It has a distant companion star called Mira B that is thought to be the burnt-out, dead core of a star, called a white dwarf. Mira A and B circle around each other slowly, making one orbit about every 500 years. Astronomers believe that Mira B has no effect on Mira's tail.

Mira is also what's called a pulsating variable star. It dims and brightens by a factor of 1,500 every 332 days, and will become bright enough to see with the naked eye in mid-November 2007. Because it was the first variable star with a regular period ever discovered, other stars of this type are often referred to as "Miras."

Mira is located 350 light-years from Earth in the constellation Cetus, otherwise known as the whale. Coincidentally, Mira and its "whale of a tail" can be found in the tail of the whale constellation.

Inorganic Dust With Lifelike Qualities



Life on earth is organic. It is composed of organic molecules, which are simply the compounds of carbon, excluding carbonates and carbon dioxide.

Under the right conditions, particles of inorganic dust can become organised into helical structures. These structures can then interact with each other in ways that are usually associated with organic compounds and life itself.

Plasma is essentially the fourth state of matter beyond solid, liquid and gas, in which electrons are torn from atoms leaving behind a miasma of charged particles.

Until now, physicists assumed that there could be little organisation in such a cloud of particles. However, Tsytovich and his colleagues demonstrated, using a computer model of molecular dynamics, that particles in a plasma can undergo self-organization as electronic charges become separated and the plasma becomes polarized. This effect results in microscopic strands of solid particles that twist into corkscrew shapes, or helical structures. These helical strands are themselves electronically charged and are attracted to each other.

Quite bizarrely, not only do these helical strands interact in a counterintuitive way in which like can attract like, but they also undergo changes that are normally associated with biological molecules, such as DNA and proteins, say the researchers. They can, for instance, divide, or bifurcate, to form two copies of the original structure. These new structures can also interact to induce changes in their neighbours and they can even evolve into yet more structures as less stable ones break down, leaving behind only the fittest structures in the plasma.

So, could helical clusters formed from interstellar dust be somehow alive? "These complex, self-organized plasma structures exhibit all the necessary properties to qualify them as candidates for inorganic living matter," says Tsytovich, "they are autonomous, they reproduce and they evolve."

He adds that the plasma conditions needed to form these helical structures are common in outer space. However, plasmas can also form under more down to earth conditions such as the point of a lightning strike. The researchers hint that perhaps an inorganic form of life emerged on the primordial earth, which then acted as the template for the more familiar organic molecules we know today.


Saturday, September 1, 2007

New Type Of Active Galaxy Discovered



By now, you’d think that astronomers would have found all the different classes of AGN — extraordinarily energetic cores of galaxies powered by accreting supermassive black holes. AGN such as quasars, blazars, and Seyfert galaxies are among the most luminous objects in our Universe, often pouring out the energy of billions of stars from a region no larger than our solar system.

But by using Swift and Suzaku, the team has discovered that a relatively common class of AGN has escaped detection. These objects are so heavily shrouded in gas and dust that virtually no light gets out.

Evidence for this new type of AGN began surfacing over the past two years. Using Swift’s Burst Alert Telescope (BAT), a team led by Tueller has found several hundred relatively nearby AGNs that were previously missed because their visible and ultraviolet light was smothered by gas and dust. The BAT was able to detect high-energy X-rays from these heavily blanketed AGNs because, unlike visible light, high-energy X-rays can punch through thick gas and dust.

AGNs are surrounded by a donut-shaped ring of material, which partially obscures our view of the black hole. Our viewing angle with respect to the donut determines what type of object we see. But a team member, thinks these newly discovered AGN are completely surrounded by a shell of obscuring material. We can see visible light from other types of AGN because there is scattered light. But in these two galaxies, all the light coming from the nucleus is totally blocked.

Another possibility is that these AGN have little gas in their vicinity. In other AGN, the gas scatters light at other wavelengths, which makes the AGN visible even if they are shrouded in obscuring material.

By missing this new class, previous AGN surveys were heavily biased, and thus gave an incomplete picture of how supermassive black holes and their host galaxies have evolved over cosmic history. But still future surveys may be wrong.



A Flash Of Light and A Star Explosion Follows



A brief flash of light had been observed two years before this rare cataclysm occurred. This precursor signal, which had never been seen before, raises hopes that astronomers will be able to "predict" explosions and observe stars as they enter the very last moments of their existence.

On 9 October 2006, two years after a Japanese amateur astronomer observed a flash of light in the constellation Lynx in UGC4904, the appearance of an object ten times brighter in the same spot attracted the attention of a European consortium, which mobilized a bank of telescopes.

The supernova, named SN2006jc, reached the maximum luminosity that is characteristic of the most powerful star explosions, more than a billion times brighter than the Sun. Astronomers divide these explosions into two broad categories – supernovae types I and II.

The type I category refers to the disintegration of a small, compact star, known as a white dwarf, which has been made unstable by the accumulation of matter coming from a companion.

The type II category, on the other hand, refers to the explosion of a massive star. In the first case, very little hydrogen and helium is seen in the explosion, whereas in the second type of explosion, these two elements are predominant. SN2006jc does not fit into either category and so has been catalogued in a special sub-category, Ic.

This rarity can be explained by the great mass of the star concerned. It is probably a star of 60 to 100 solar masses which has lost a great quantity of mass previously. Here it is only the central part, a core of carbon and oxygen of 15 to 25 solar masses that explodes. Thus, most of the elements in the explosion come from the core of the star, while the helium observed is only found around the edge and comes from the star's envelope, which was ejected earlier.

Supernova SN2006jc is the only known example of a star explosion for which a flash of light was observed two years earlier. For this reason, it opens up new horizons for predicting massive star explosions. Eta Carinae could be one example of a star similar to SN2006jc close to our galaxy. It also experienced an outburst of luminosity making it the second brightest star in the sky in 1843. A future outburst could be the sign of an imminent explosion.