Dr Jo Dunkley explores the latest research on the ‘missing’ 95% at Science Oxford Live at 7:30pm on Thursday the 25th of August.

One of the outstanding problems in cosmology is to understand the ‘missing’ 95% of the universe. The familiar atoms we are all made of only make up a small fraction of what we think is out there.

We think that about a quarter of the universe is made of Dark Matter, most likely an undiscovered type of particle that we cannot see, but feels the effect of gravity.

The other 70% is what we call Dark Energy, thought to be a form of energy that has the strange effect of making the expansion of the universe accelerate.

Dr. Jo Dunkley is a lecturer at the University of Oxford and is involved in determining properties of the universe including the nature of Dark Matter and Dark Energy.

Finding out what these are, and coming up with ways to investigate their behaviour, is a central part of current research in cosmology. It brings together research in astrophysics and particle physics, and combines theoretical studies with large international experiments.

Dominic McDonald, Head of Public Engagement at Science Oxford Live, said “I first met Jo in 2006 when she was the keynote speaker for a conference to inspire 13-16 year olds. Six years on she is now a leading figure on the Dark Universe and I am delighted to welcome her to Science Oxford Live.”

Asked about the subject of Thursday’s event, Dominic added
“this is a huge unsolved area. We do not know what the vast majority of the universe is actually made up of. Oxford University is leading research into this and it will be fascinating to hear about this challenging area, including the latest developments, from Jo.”

Emma Wightman, Programmes Delivery Manager at Science Oxford Live, said
“Jo is an exceptional Cosmologist and Astrophysicist and a fantastic role model.”

Join Dr. Jo Dunkley at Science Oxford Live on Thursday 25th August to hear about the latest research into the ‘Missing’ universe.

Book your place now

More about Dr. Jo Dunkley

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Press Release

What do you think of when someone mentions the word laser? Music performances? Barcode scanners? Surgery? Communication? Weapons? Well, all of them would be correct and on April 7th, as part of the Frontiers of Science season, Dr Kate Lancaster gave a talk to a Science Oxford Live audience to tell us a bit more about the cutting edge research that happens not far from Oxford and that depends on some of the highest power lasers found around the globe. Dr Lancaster is a physicist and science communicator, with her research focused on laser-driven fusion energy, based at the Science and Technology Facilities Council (STFC) Rutherford Appleton Laboratory.

In a historical whistle-stop tour, Dr Lancaster recalled who was involved in the development of the laser. Although the device, the acronym standing for “light amplification by stimulated emission of radiation”, is governed by equations that were first derived by Einstein, he was too much of a theoretician to have been involved in the practical development which took place some decades later. First of all Townes and Schawlow discovered the MASER, a device in which coherent electromagnetic waves of the microwave frequency are produced using amplification by stimulated emission. By the late 1950s, many scientists were hoping to recreate the same effects with visible light (which is also a form of electromagnetic radiation, but of a shorter wavelength compared to microwaves) and Gould is widely credited with making the realisation that one could achieve this by using two mirrors to produce a narrow, coherent, intense beam of visible light of specific wavelength. Gould was also the first to coin the term LASER (light amplification by stimulated emission of radiation) for the phenomenon but in a twist of fate, he then spent 30 years fighting to be granted the patent for the technology, which was eventually granted to the Bell labs, where his competitors were based. Subsequently, Theodore Maiman was the one who developed the first laser prototype (the ruby laser), and further developments went on from there. Eventually, 10 Nobel prizes related to the development of the laser were awarded in the period between 1964 and 2009 (see table in Short history of laser development, J. Hecht, Optical Engineering, 2009 vol 49, page F99).

So, what are the key aspects of a laser? Dr Lancaster explained that one of the features of lasers is that they produce light which is highly coherent and monochromatic, meaning it is of a specific wavelength. This was demonstrated with a spectrometer (a device which measures the wavelength of the light that it detects) which showed that visible light created a widespread peak in the visible range of 400-650nm. Laser light, on the other hand, created a single sharp peak at a specific wavelength (532nm for a green laser, 630nm for a red laser). Secondly, laser light has very low divergence – if you shone a laser from the Earth to the moon, by the time it got there, the beam would be only a mile wide, which is pretty impressive given the distance. Finally, lasers are highly focusable into a single spot (based on the equation that intensity = power/area, meaning that the smaller the area the laser shines on, the higher the intensity).

Simplistically put, lasers work because photons are released as electrons change between different energy levels within an atom. Spontaneous emission involves an electron moving from a high energy to a low energy level accompanied by the release of a photon and stimulated absorption is the opposite of this process (an electron moves from low to high level whilst gobbling up the energy of a photon). If a photon, which has the energy equivalent to the difference between high and low energy states, comes along to an atom with an electron in a high energy state, it will stimulate the electron to fall into the lower level state, thereby emitting a photon. The emitted photon has the same energy as the original photon, leading to the emission of two waves with the same frequency which constructively interfere and so create a more intense wave. This is called stimulated emission and it is the main principle behind what happens in a laser. In a laser setup, the excitable electrons might be in neodymium atoms used to dope a glass block. This block is enclosed by reflective surfaces, which enable the signal to be amplified, and partial reduction in reflectivity allows this to signal to escape the cavity.

Since the discovery of lasers, there have been a number of new developments in terms of applications, ranging from CDs (1960s), laser cutting and barcode scanners (1970s), clinical applications such as laser surgery and communications using fibre optics (1980s). The improvements in lasers have involved the step-wise solving of a number of problems. Firstly, using Q switching, it was possible to release the laser only when fully saturated (i.e. all electrons are in a high level state), reducing background lasing. Another development was that of chirped pulse amplification (CPA), which uses refraction of the incident beam to temporarily lengthen and disperse the laser light so that its intensity does not damage the optical equipment (meaning that higher intensity can be achieved). These days scientists such as Dr Lancaster at the SFTC Vulcan facility are in the business of using the highest powered lasers to study processes such as fusion, and from her talk we got an impression of the excitement and enthusiasm she has for this field. It seems that at the moment, one of the limitations of fusion energy is the inability to fire the laser often enough – to run a fusion power station, it would be necessary to fire the laser four times every second, whereas it is currently only possible to fire such a powerful device once every half an hour or so. In addition, there is always the containment to think of because the high powered laser has to be located in a vacuum to avoid the laser making plasma of the air that it is surrounded by.

And what does the future hold in store? In biochemistry and structural biology, it may be possible to use small lasers as optical tweezers which would allow the pulling apart of protein and DNA single molecules to unfold them and study their function. Lasers will likely be part of quantum computers which could enable instant calculations to be performed that would render all current encryption algorithms useless, but at the same time create a potential for altogether new encryption methods. On a much larger scale, lasers may be useful in space-based telescope, because they could be effectively artificial star references. In conclusion, Dr Lancaster reckoned that currently the biggest challenge in the field is making a laser that is high powered enough and is able to fire with a high enough repetition rate – so plenty to look at for those currently in the field.

In summary, the talk was by an enthusiastic speaker on a fascinating subject. You can watch Dr Lancaster’s talk on the webcast via the Science Oxford Live website.

Some background:

Kate Lancaster’s website: http://sites.google.com/site/drkatelancaster/
Science & Technology Facilities Council: http://www.stfc.ac.uk/

Electrons, although closely studied by scientists, are often overlooked or held in contempt by the general public. At their peril, I might add. We all use batteries in our walkmans, i-pods, torches, mobile phones; in fact nearly all small mobile electronic devices have batteries. We happily change them when ‘empty’ for new ones and think nothing of handling them. Batteries are, of course, a store house of nearly free electrons, there for our pleasure to use as we please. We think little of taking safety precautions in their use.

But how many of us have been frightened to be caught out in a thunder storm or, even when indoors, hide under the blankets as the mighty crashes of thunder echo through the nightime? These are our same now ‘not-so-friendly’ electrons playing around in the skies enjoying, at last, to be truly free; indulging themselves in discharges of many thousands of amps; enough to strike you down dead, if they pass through your body on their journey to earth.

So what is the true nature of electrons? What are their secrets? Do they have a secret life and hidden identities?

The properties of nearly everything physicists, chemists and even biologists study are controlled by the electrons. Whether it be the colour, the magnetism, the conductivity, the way chemicals interact with one another to form new compounds, the nature of our DNA, or how our brains carry information. The list is endless.

Let us deal first with the type of electrons that provide electricity in our batteries or along the cables in our homes, including the electrons that take part in a bolt of lightning. These are known as FREE electrons. They are not confined in a solid or chemical such as sodium chloride (common salt) or silicon (a semiconductor) but are FREE to travel long distances along wires or to roam around in our i-pods. In this form electrons are small charged particles. They carry a small negative (minus) charge and are therefore attracted to a positive charge and using this property can made to move along a wire from one place to another. Or made to travel across empty space in a vacuum. They move from minus towards plus. The amount of charge or electricity that a single electron carries is miniscule; you need ten million, million, million of them for only one amp of electricity, just about enough electricity to run your TV set. Think how many there will be in a 5000 Amp bolt of lightning; the mind boggles!

Now let us think about electrons that are confined to a solid material. Remember that our whole universe is made up of ELECTRONS and their opposite number PROTONS that are positively charged and their neutral friends the NEUTRON!

Electrons in a solid are much more rigorously controlled than free electrons. They have to obey very complicated rules that may vary depending on the type of solid they are trapped inside. These rules are very very strict and control such things as how much energy they are allowed to have; how they are allowed, or not allowed, to move around; how they approach and interact with other electrons in the solid; where they are allowed to move to and which places in the solid are forbidden to them. A long list of complicated rules! And another thing; inside a solid no two electrons are allowed to be exactly the same. If two electrons have the same energy then they have to spin in opposite directions like mad dancers to differentiate one from the other. In spite of all the electrons in a solid being different from one another in some way it is important for them to interact with each other in defined ways to hold the solid together, say in the form of a crystal or a DNA molecule. So how can we describe the life of electrons inside a solid?

In the first instance we will think about a single atom of the element silicon. Silicon has fourteen electrons, each with a single negative charge; fourteen protons, each with a positive charge and fourteen friendly neutrons to add a bit of weight but with no charge. The protons and neutrons clump together at the centre of the atom, hugging each other and the electrons dance around them in rings. The first ring has only two electrons, the next ring has eight electrons and the outer ring has four electrons. Now remember all those strict rules I mentioned? This is the first of them, how many electrons are allowed in each ring. The next rule to think about is their energy. Remember electrons in solids must have different energies. The best picture to suggest to you is to think about country or old time dances. Ones with names like the ‘Dashing White Sergeant’, ‘The Veleta’ (an old time dance that is quite gentle and unenergetic), ‘Stripping The Willow’, The Circassian Circle, and Riverdance. Now you may not be familiar with all these dances; they are dances done in sets of four or eight and consist of a number of repeated movements; some slow and formal, other dances fast and energetic.

So think of the first two electrons in the silicon atom innermost circle. Think of these two electrons dancing the Veleta, slow and formal, constantly repeated and never allowed to stop. Now the next ring with eight electrons; let them dance The Stripping The Willow dance. A dance with a set of eight and more energetic than the Veleta and this ring of electrons must continue to dance this dance forever withoutpause. Finally the outermost ring; let them have some excitement and dance the Riverdance without ever thinking of stopping. This is the life of these electrons within this silicon atom.

But what happens when lots of silicon atoms come together to make a silicon crystal? The two innermost rings carry on their set dance but the outermost ring dancing the Riverdance gets a bit more freedom to move around atoms that are their neighbours in the crystal. In some way the dance becomes more chaotic as the atoms race around other atoms as well as part of their dance to hold the crystal together. Hence the dances are very formalised and follow strict rules.

Now the clumps of protons and neutrons hugging each other at the centre of each atom present a regular array of ‘stationary mounds’ in the crystal and may seem not to play much part other than as stationary onlookers and this is true. Most properties of solids are a result of the electrons BUT these stationary clumps do result in some important effects. If a dance with a particular energy is to be danced; the rules may specify a particular route around the crystal. Now if this route has to pass through points where clumps of protons and neutrons are sitting; then this dance CANNOT BE PERFORMED and this represents, and results in, a disallowed energy that cannot be used. This can result in an ENERGY GAP in the spectrum of electron energies. An important physical property, particularly for semiconductors.

These descriptions are a simplification and remember that I said that all electrons had to have different energies or if they have the same energy, then spin in opposite directions. All these strict rules are still true and must be obeyed. In solids like metals there are many, many electrons to cram in and to some extent outer electrons become almost free and can roam around more easily. Hence they conduct electricity to a much greater extent. Metals still have atoms and they also form crystals, the atoms arranging themselves in regular, predestined, arrays as do most solid elements that are not gases or liquids.

A further very important property of electrons in solids is they way that they can interact with light; visible light; infrared light, x-rays. In fact the whole of the ‘Electromagnetic spectrum’. Remember I said that the electron has a specific energy; now if the electron interacts with light it can change its energy. This is a very important property of electrons enabling them to change energy and jump to a different ring in the atom and commence a different dance. How do they do this?

If we think a little; there are many examples of solids interchanging energy with light, called electromagnetic radiation. My first example; think of your television set. Most receive their television programmes through their TV Ariel or satellite dish. How does this work? The electromagnetic wave of radio signal passes over your aerial or is focussed onto the black box at the centre of your satellite dish and the energy that the wave carries cause changes to the electrons in the solid of your dish or aerial. These are seen as small electric currents that are then amplified and converted to show the TV programme. A second example; light is absorbed by living plants. The energy that the light carries causes chemical changes in the plant that give it energy; termed photosynthesis. A final example that brings us close to conventional physics is the solar cell where light shining onto silicon pn junctions converts from light into electricity by energising electrons in the solid silicon.

A single particle of light, called a photon, can interact with an electron in a solid and change the energy of the electron. The electrons will then jump to another ring and commence a different dance designated for its new ring. This process is reversible and an electron in a solid may lose some of its energy and move to a different shell doing a different dance and at the same time emit a single particle of light called a photon. This is the mechanism by which light emitting diodes (LED’s) work.

These processes of interaction of electrons in solids with light are going on around us all the time, all over the universe. Scientists are continually investigating solids and the useful changes that can be brought about to give new materials or other useful effects such as new and novel interactions with laser light and the resulting effects on the electron energy or position in the crystal. A recent area of study has been nanomaterials. This simply means making materials of small dimensions containing only about one hundred atoms. If you pause and think for a moment of the effect of there being only one hundred atoms in a crystal you can realise that it will affect the way the electrons can dance around this small crystal. They are confined to a very small volume and this perturbs and effects their movement. The energy gap that I explained earlier is often affected by becoming a different size, shifting to a higher energy size. The way electricity is conducted through a very thin layer of solid only a few atoms thick will be different from the massive solid. These effects may make conduction easier of harder but will present new and novel properties that may be beneficial to mankind.

Using a combination of instruments on ESO’s Very Large Telescope, astronomers have discovered the most massive stars to date, one weighing at birth more than 300 times the mass of the Sun, or twice as much as the currently accepted limit of 150 solar masses. The existence of these monsters — millions of times more luminous than the Sun, losing weight through very powerful winds — may provide an answer to the question “how massive can stars be?”

A team of astronomers led by Paul Crowther, Professor of Astrophysics at the University of Sheffield, has used ESO’s Very Large Telescope (VLT), as well as archival data from the NASA/ESA Hubble Space Telescope, to study two young clusters of stars, NGC 3603 and RMC 136a in detail. NGC 3603 is a cosmic factory where stars form frantically from the nebula’s extended clouds of gas and dust, located 22 000 light-years away from the Sun. RMC 136a (more often known as R136) is another cluster of young, massive and hot stars, which is located inside the Tarantula Nebula, in one of our neighbouring galaxies, the Large Magellanic Cloud, 165 000 light-years away.

The team found several stars with surface temperatures over 40 000 degrees, more than seven times hotter than our Sun, and a few tens of times larger and several million times brighter. Comparisons with models imply that several of these stars were born with masses in excess of 150 solar masses. The star R136a1, found in the R136 cluster, is the most massive star ever found, with a current mass of about 265 solar masses and with a birthweight of as much as 320 times that of the Sun.

In NGC 3603, the astronomers could also directly measure the masses of two stars that belong to a double star system, as a validation of the models used. The stars A1, B and C in this cluster have estimated masses at birth above or close to 150 solar masses.

Very massive stars produce very powerful outflows. “Unlike humans, these stars are born heavy and lose weight as they age,” says Paul Crowther. “Being a little over a million years old, the most extreme star R136a1 is already ‘middle-aged’ and has undergone an intense weight loss programme, shedding a fifth of its initial mass over that time, or more than fifty solar masses.”

If R136a1 replaced the Sun in our Solar System, it would outshine the Sun by as much as the Sun currently outshines the full Moon. “Its high mass would reduce the length of the Earth’s year to three weeks, and it would bathe the Earth in incredibly intense ultraviolet radiation, rendering life on our planet impossible,” says Raphael Hirschi from Keele University, who belongs to the team.

These super heavyweight stars are extremely rare, forming solely within the densest star clusters. Distinguishing the individual stars — which has now been achieved for the first time — requires the exquisite resolving power of the VLT’s infrared instruments.

The team also estimated the maximum possible mass for the stars within these clusters and the relative number of the most massive ones. “The smallest stars are limited to more than about eighty times more than Jupiter, below which they are ‘failed stars’ or brown dwarfs,” says team member Olivier Schnurr from the Astrophysikalisches Institut Potsdam. “Our new finding supports the previous view that there is also an upper limit to how big stars can get, although it raises the limit by a factor of two, to about 300 solar masses.”

Within R136, only four stars weighed more than 150 solar masses at birth, yet they account for nearly half of the wind and radiation power of the entire cluster, comprising approximately 100 000 stars in total. R136a1 alone energises its surroundings by more than a factor of fifty compared to the Orion Nebula cluster, the closest region of massive star formation to Earth.

Understanding how high mass stars form is puzzling enough, due to their very short lives and powerful winds, so that the identification of such extreme cases as R136a1 raises the challenge to theorists still further. “Either they were born so big or smaller stars merged together to produce them,” explains Crowther.

Stars between about 8 and 150 solar masses explode at the end of their short lives as supernovae, leaving behind exotic remnants, either neutron stars or black holes. Having now established the existence of stars weighing between 150 and 300 solar masses, the astronomers’ findings raise the prospect of the existence of exceptionally bright, “pair instability supernovae” that completely blow themselves apart, failing to leave behind any remnant and dispersing up to ten solar masses of iron into their surroundings. A few candidates for such explosions have already been proposed in recent years.

Not only is R136a1 the most massive star ever found, but it also has the highest luminosity too, close to 10 million times greater than the Sun. “Owing to the rarity of these monsters, I think it is unlikely that this new record will be broken any time soon,” concludes Crowther.

Each nation gets a blip and a flashing dot on the map whenever they detonate a nuclear weapon, with a running tally kept on the top and bottom bars of the screen. Hashimoto, who began the project in 2003, says that he created it with the goal of showing”the fear and folly of nuclear weapons.” It starts really slow — if you want to see real action, skip ahead to 1962 or so — but the buildup becomes overwhelming.

Bats’ remarkable ability to ‘see’ in the dark uses the echoes from their own calls to decipher the shape of their dark surroundings. This process, known as echolocation, allows bats to perceive their surroundings in great detail, detecting insect prey or identifying threatening predators, and is a skill that engineers are hoping to replicate.

A team of British researchers has worked with six adult Egyptian fruit bats from Tropical World in Leeds to record and recreate their calls. These calls are pairs of ‘clicks’ from the bats’ tongues that they use to fill their surroundings with acoustic energy; the echoes that return allow the bats to form an image of their environment.

New research published today, Tuesday 11 May, in IOP Publishing’s Bioinspiration & Biomimetics, describes how engineers and biologists from the Universities of Strathclyde and Leeds worked with the bats to record their double-click echolocation call, and its returning echoes, using a miniature wireless microphone sensor mounted on the bat whilst in flight.

During echolocation, some bats are known to use a natural acoustic gain control. This allows them to emit high-intensity calls without deafening themselves, and then to hear the weak echoes returning from surrounding objects. The researchers replicated this system in electronics to allow the sensor to record both the emitted and reflected echolocation signals, providing an insight into the full echolocation process.

The six bats performed up to sixteen flights each along a flight corridor. Each flight was short – lasting only about three seconds – but, with the bats’ clicks only lasting a quarter of a millisecond, a large number of calls were recorded for the scientists to analyse.

Once back into the laboratory, the researchers were able to accurately recreate the echolocation calls using a custom-built ultrasonic loudspeaker. This technique will allow the signals and processes bats use to be applied to human engineering systems such as sonar. Specifically, the researchers are looking to apply these techniques in the positioning of robotic vehicles, used in structural testing applications.

Lead author Simon Whiteley from the Centre for Ultrasonic Engineering at the University of Strathclyde, said, “We aim to understand the echolocation process that bats have evolved over millennia, and employ similar signals and techniques in engineering systems. We are currently looking to apply these methods to positioning of robotic vehicles, which are used for structural testing. This will provide enhanced information on the robots’ locations, and hence the location of any structural flaws they may detect.”

Physicists at McGill University have developed a system for measuring the energy involved in adding electrons to semi-conductor nanocrystals, also known as quantum dots – a technology that may revolutionize computing and other areas of science. Dr. Peter Grütter, McGill’s Associate Dean of Research and Graduate Education, Faculty of Science, explains that his research team has developed a cantilever force sensor that enables individual electrons to be removed and added to a quantum dot and the energy involved in the operation to be measured.

Being able to measure the energy at such infinitesimal levels is an important step in being able to develop an eventual replacement for the silicon chip in computers – the next generation of computing. Computers currently work with processors that contain transistors that are either in an on or off position – conductors and semi-conductors – while quantum computing would allow processors to work with multiple states, vastly increasing their speed while reducing their size even more.

Although the term “quantum leap” is used in everyday language to connote something very large, the word “quantum” itself actually means the smallest amount by which certain physical quantities can change. Knowledge of these energy levels enables scientists to understand and predict the electronic properties of the nanoscale systems they are developing.

“We are determining optical and electronic transport properties,” Grütter said. “This is essential for the development of components that might replace silicon chips in current computers.”

The electronic principles of nanosystems also determine their chemical properties, so the team’s research is relevant to making chemical processes “greener” and more energy efficient. For example, this technology could be applied to lighting systems, by using nanoparticles to improving their energy efficiency. “We expect this method to have many important applications in fundamental as well as applied research,” said Lynda Cockins of McGill’s Department of Physics.

The principle of the cantilever sensor sounds relatively simple. “The cantilever is about 0.5 mm in size (about the thickness of a thumbnail) and is essentially a simple driven, damped harmonic oscillator, mathematically equivalent to a child’s swing being pushed,” Grütter explained. “The signal we measure is the damping of the cantilever, the equivalent to how hard I have to push the kid on the swing so that she maintains a constant height, or what I would call the ‘oscillation amplitude.’ ”

Dr. Yoichi Miyahara, Aashish Clerk and Steven D. Bennett of McGill’s Dept. of Physics, and scientists at the Institute for Microstructural Sciences of the National Research Council of Canada contributed to this research, which was published online late yesterday afternoon in the Proceedings of the National Academy of Sciences. The research received funding from the Natural Sciences and Engineering Research Council of Canada, le Fonds Québécois de le Recherche sur la Nature et les Technologies, the Carl Reinhardt Fellowship, and the Canadian Institute for Advanced Research.

This image shows the electrostatic energy given off when electrons are added to a quantum dot. It was created with an atomic-force microscope. Photo Credit: Dept. of Physics, McGill University.

Shooting lasers at the sky can make the germ of a raincloud, a new study shows. In an experiment that smacks of science fiction, scientists used a high-powered laser to squeeze water from air, both indoors and out.

Although the technique is unlikely to be an instant rainmaker anytime soon, it could plant the seeds for more eco-friendly cloud manipulation.

“This is the first time that a laser was used to condense water from both laboratory experiments and from the atmosphere,” says Jérôme Kasparian of the University of Geneva, a coauthor of the study. The work appeared in the May 2 Nature Photonics.

Atmospheric scientists have been trying to build artificial clouds since the 1940s, with mixed success. The most popular method, shooting particles of silver iodide into the sky, relied on the fact that raindrops need something to condense around.

“It’s just like when you take a shower with hot water — it’s very humid in your bathroom, but it’s not raining,” Kasparian says. Water droplets need a surface to condense on, like a mirror in a bathroom or a speck of dust or pollen in the atmosphere.

Previous experimenters hoped droplets would form around flakes of silver, salt or other materials just like on a bathroom mirror. “The idea is, you provide more condensation nuclei, you get more condensation,” Kasparian says. “It seems obvious, but in practice no one could really prove that it works.”

Kasparian and colleagues took inspiration from a mist-making apparatus that was invented in 1911 to detect cosmic rays, highly energetic subatomic particles that come from deep space. A physicist named Charles Wilson noticed that when cosmic rays strike a sealed container filled with water vapor, they leave a visible trail of water droplets behind them. This works because the cosmic rays knock electrons off the water molecules, leaving behind charged particles that act like specks of dust for water to congeal around.

“Our idea was to mimic what happens in a Wilson chamber,” Kasparian says. “If you get some condensation with cosmic rays, we should get even more condensation with a laser.”

Kasparian and his colleagues tested this idea by shooting a high-powered infrared laser into a cloud chamber. The laser shot extremely short pulses of intense light, which each carrying several terawatts — or a trillion watts — of energy.

The view fogged up immediately. Droplets about 50 micrometers in diameter formed first, and grew to about 80 micrometers in diameter over the next three seconds. “The effect in the cloud chamber was very spectacular and visible by bare eye,” Kasparian says. “We expected an effect, definitely. But that magnitude was pretty much a surprise.”

Next, the researchers took the laser out in the backyard to try it on the sky. They rolled the laser, called “Teramobile” for its terawatt power and its mobility, onto the lawn behind the physics building at the Free University of Berlin on several nights in the fall of 2008. The clouds, if they formed, would be too distant to see with the naked eye, so the team used a second laser to confirm the cloudy view.

“It also worked quite well in the free atmosphere,” Kasparian says. “That was quite surprising, and a very good surprise.”

Kasparian thinks lasers could provide a more reliable and environmentally friendly way to build clouds. “If you can seed clouds and get some control or at least modulation on the weather, the implications are huge for agriculture, many other economic sectors, many aspects of human life,” Kasparian says. “There are potentially huge consequences.”

“It is a clever technique,” says John Latham of the National Center for Atmospheric Research in Boulder, Colo. But he’s skeptical that laser-built clouds could actually make it rain on demand. “Rainfall production requires many conditions to be met,” he cautions.

Image Credit: Jean-Pierre Wolf / University of Geneva

Phys­i­cists say they have de­tected the heav­i­est “an­ti-nu­cle­us” to date, a rare spec­i­men of a sort of mirror-image form of or­di­nary mat­ter.

The find­ing may shed light on cos­mic sym­me­tries, and asym­me­tries, that ex­plain why most of the an­ti­mat­ter orig­i­nally pro­duced at the birth of the uni­verse is gone, ac­cord­ing to sci­en­tists.

An an­ti­par­t­i­cle is a var­i­ant of one of the nor­mal build­ing blocks of mat­ter that has equal weight, but is op­po­site in elec­tri­cal charge and cer­tain oth­er re­spects, to its “nor­mal” par­t­i­cle coun­ter­part. As a nu­cle­us is the co­re of an or­di­nary at­om, an an­ti-nu­cle­us is the co­re of an “an­ti-at­om.”

The new­found an­ti-nu­cle­us al­so con­tains the first ex­am­ple of a smaller, equally ex­ot­ic com­po­nent build­ing block that phys­i­cists call an an­ti-strange quark.

The dis­cov­ery “may have un­prec­e­dent­ed con­se­quenc­es for our view of the world,” said the­o­ret­i­cal phys­i­cist Horst Stoe­cker, Vi­ce Pres­ident of the Helm­holtz As­socia­t­ion of Ger­man Na­tional Lab­o­r­a­to­ries. “This an­ti­mat­ter pushes open the door to new di­men­sions in the nu­clear chart — an idea that just a few years ago, would have been viewed as im­pos­si­ble.”

The find­ing, at the U.S. De­part­ment of En­er­gy’s Brook­ha­ven Na­tional Lab­o­r­a­to­ry in New York, may al­so help shed light on the work­ings of com­pact ce­les­tial ob­jects known as neu­tron stars, re­search­ers said.

The nu­cle­us of a nor­mal at­om on Earth con­sists of build­ing blocks called pro­tons and neu­trons, which in turn con­tain smaller com­po­nents known as quarks. These quarks ap­pear in two types, ar­bi­trarily called “up” and “down” va­ri­eties.

The stand­ard Per­i­od­ic Ta­ble of El­e­ments is a grid ar­ranged by num­ber of pro­tons, which de­ter­mine each chem­i­cal el­e­men­t’s prop­er­ties in its bas­ic in­ter­ac­tions with oth­er el­e­ments.

But phys­i­cists al­so use a more com­plex, three-di­men­sion­ chart which adds in­forma­t­ion on the dif­fer­ing num­ber of neu­trons that can oc­cur in sam­ples of each el­e­ment. The 3-D chart al­so in­di­cates a num­ber known as “s­trangeness,” which de­pends on the pres­ence of so-called “s­trange” quarks. Nu­clei con­taining one or more strange quarks are called hy­per­nu­clei.

For or­di­nary mat­ter with­out strange quarks, the strange­ness val­ue is ze­ro and the chart is flat. Hy­per­nu­clei are charted on a sep­a­rate grid, which is shown as if hov­er­ing above the stand­ard ta­ble. The new dis­cov­ery of strange an­ti­mat­ter with an an­ti­strange quark—an “an­ti­hy­per­nu­cle­us”—marks the first en­try be­low the stand­ard grid, sci­en­tists ex­plain.

The bi­zarre par­t­i­cle was de­tected as a re­sult of high-speed col­li­sions of gold nu­clei at the Rel­a­tiv­is­t Heavy Ion Col­lider, the Brook­ha­ven lab­o­r­a­to­ry’s at­om smash­er. The re­sults were pub­lished March 4 on the on­line edi­tion of the re­search jour­nal Sci­ence.

The study of the new an­ti­hyp­er­nu­cle­us al­so yields a val­u­a­ble sam­ple of hy­per­nu­clei, and has im­plica­t­ions for our un­der­stand­ing of the struc­ture of col­lapsed stars, called neu­tron stars, re­search­ers said. “The strange­ness val­ue could be non-ze­ro in the co­re of col­lapsed stars,” said Jin­hui Chen, one of the lead au­thors, of the Shang­hai In­sti­tute of Ap­plied Phys­ics and a post­doc­tor­al re­searcher at Kent State Uni­vers­ity in Ohio. The new mea­sure­ments “will help us dis­tin­guish be­tween mod­els that de­scribe these ex­ot­ic states of mat­ter.”

The find­ings al­so pave the way for ex­plor­ing vi­ola­t­ions of fun­da­men­tal sym­me­tries be­tween mat­ter and an­ti­mat­ter that oc­curred in the early uni­verse, mak­ing pos­si­ble the very ex­ist­ence of our world, phys­i­cists added.

Smashups be­tween at­omic nu­clei at the col­lider are be­lieved to fleet­ingly re­pro­duce con­di­tions that ex­isted a mi­nus­cule frac­tion of a sec­ond af­ter the Big Bang, which sci­en­tists be­lieve gave birth to the uni­verse as we know it some 13.7 bil­lion years ago.

In both events, quarks and an­ti­quarks emerge with equal abun­dance, ac­cord­ing to phys­i­cists. At the lab­o­r­a­to­ry, among the col­li­sion frag­ments that sur­vive to the fi­nal state, mat­ter and an­ti­mat­ter are still meas­ured as close to equally abun­dant. In con­trast, an­ti­mat­ter ap­pears to be largely ab­sent from the pre­s­ent-day uni­verse.

“Under­stand­ing pre­cisely how and why there’s a pre­dom­i­nance of mat­ter over an­ti­mat­ter re­mains a ma­jor un­solved prob­lem of physics,” said Brook­ha­ven phys­i­cist Zhang­bu Xu, anoth­er one of the lead au­thors. “A so­lu­tion will re­quire mea­sure­ments of sub­tle de­via­t­ions from per­fect sym­me­try be­tween mat­ter and an­ti­mat­ter, and there are good prospects for fu­ture an­ti­mat­ter mea­sure­ments at RHIC [Rel­a­tiv­is­t Heavy Ion Col­lider] to ad­dress this key is­sue.”

In a sin­gle col­li­sion of gold nu­clei at the col­lider, many hun­dreds of par­t­i­cles burst out at the point of the crash. Most of these don’t ac­tu­ally come from the pre­vi­ously ex­ist­ing, col­lid­ing ob­jects as such. Rath­er, they are formed from the en­er­gy of the col­li­sion, by the con­ver­sion of en­er­gy in­to mass in ac­cord­ance with Ein­stein’s fa­mous equa­t­ion E = mc2.

The par­t­i­cles leave tell­tale tracks in a de­tec­tor hooked up to the col­lider, called the STAR de­tec­tor. Sci­en­tists an­a­lyzed about a hun­dred mil­lion col­li­sions to spot the new an­ti­nu­clei, which aren’t di­rectly detecta­ble them­selves but are iden­ti­fa­ble through the byprod­ucts in­to which they dis­in­te­grate. Al­to­geth­er, 70 spec­i­mens of the new an­ti­nu­cle­us were de­tected.

STAR de­tec­tor sci­en­tists, who come from 54 in­sti­tu­tions in 13 coun­tries, say they should be able to disco­ver even heav­i­er an­ti­nu­clei soon. The­o­ret­i­cal phys­i­cist Stoe­cker and his team have pre­dicted that strange nu­clei around dou­ble the mass of the newly disco­vered state should be par­tic­u­larly sta­ble.

Re­search­ers are re­port­ing that they have passed a ma­jor hur­dle in the quest to cre­ate a radic­ally new kind of com­put­er, the quan­tum com­put­er.

Quan­tum com­put­ers would ex­ploit the some­times ap­par­ently non­sen­si­cal laws of quan­tum phys­ics, or na­ture at the sub­a­tom­ic scale, to achieve un­prec­e­dent­ed pow­er and speed.

A ma­jor chal­lenge been find­ing a way to ma­ni­pu­late in­di­vid­ual elec­trons, elec­tric­ally charged com­po­nents of atoms. Elec­trons are seen as the most likely can­di­dates to con­sti­tute the new machi­nes’ pro­cess­ing com­po­nents, or “qu­bits.”

Prince­ton phys­i­cist Ja­son Pet­ta said he and some col­leagues have dem­on­strat­ed a meth­od that al­ters the prop­er­ties of a lone elec­tron with­out dis­turb­ing the tril­lions of elec­trons in its im­me­di­ate sur­round­ings. The feat is con­sid­ered es­sen­tial to the de­vel­op­ment of quan­tum com­put­ers.

Petta has fash­ioned a new meth­od of trap­ping one or two elec­trons in mi­cro­scop­ic cor­rals cre­ated by ap­ply­ing to mi­nus­cule elec­trodes volt­ages, or elec­tric fields that move elec­trons. Writ­ing in the Feb. 5 edi­tion of the re­search jour­nal Sci­ence, Pet­ta and col­leagues de­scribe how elec­trons trapped in these cor­rals form “spin qu­bits,” quan­tum ver­sions of clas­sic com­put­er in­forma­t­ion un­its known as bits.

Pre­vi­ous ex­pe­ri­ments used a tech­nique in which elec­trons were ex­posed to mi­cro­wave radia­t­ion. How­ev­er, be­cause it af­fect­ed all the elec­trons un­iformly, the tech­nique could not be used to ma­ni­pu­late sin­gle elec­trons in spin qu­bits. It al­so was slow. Pet­ta’s meth­od not only achieves con­trol of sin­gle elec­trons, but it does so ex­tremely rap­id­ly, he said—in a bil­lionth of a sec­ond.

Sub­a­tom­ic par­t­i­cles are found to fol­low the laws of quan­tum phys­ics—in which, for ex­am­ple, they can be in two places at once—as long as these par­t­i­cles stay alone or in very small groups. When they come into con­tact with a great­er mass, the quan­tum ef­fects norm­ally ap­pear to van­ish.

“If you can take a small enough ob­ject like a sin­gle elec­tron and iso­late it well enough from ex­ter­nal per­turba­t­ions, then it will be­have quan­tum me­chan­ic­ally for a long pe­ri­od of time,” said Pet­ta. “All we want is for the elec­tron to just sit there and do what we tell it to do. But the out­side world is sort of pok­ing at it, and that pro­cess of the out­side world pok­ing at it causes it to lose its quan­tum me­chan­ical na­ture.”

When the elec­trons in Pet­ta’s ex­pe­ri­ment are in what he calls their quan­tum state, they are “co­her­en­t,” fol­lowing rules that are radic­ally dif­fer­ent from the world seen by the na­ked eye. Liv­ing for frac­tions of a sec­ond in the realm of quan­tum phys­ics be­fore they are rat­tled by ex­ter­nal forc­es, the elec­trons obey a un­ique set of phys­i­cal laws that gov­ern the be­hav­ior of ultra-small ob­jects. Quan­tum com­put­ers would be de­signed to take ad­van­tage of these char­ac­ter­is­tics.

In ad­di­tion to elec­trical charge, elec­trons pos­sess some­thing akin to rota­t­ion. In the quan­tum world, ob­jects can turn in ways that are at odds with com­mon ex­perience. The Aus­tri­an the­o­ret­i­cal phys­i­cist Wolf­gang Pau­li, who won the No­bel Prize in Phys­ics in 1945, pro­posed that an elec­tron in a quan­tum state can as­sume one of two states, “spin-up” or “spin-down.” It can be im­ag­ined as be­hav­ing like a ti­ny ba­r mag­net with spin-up cor­re­spond­ing to the north pole point­ing up and spin-down cor­re­spond­ing to the north pole point­ing down.

An elec­tron in a quan­tum state can sim­ul­ta­ne­ous­ly be par­tially in the spin-up state and par­tially in the spin-down state or any­where in be­tween, a quan­tum me­chan­ical prop­er­ty called “su­per­po­si­tion of states.” A qu­bit based on the spin of an elec­tron could have nearly lim­it­less po­ten­tial be­cause it can be nei­ther strictly on nor strictly off.

New de­signs could take ad­van­tage of a rich set of pos­si­bil­i­ties of­fered by har­ness­ing this prop­er­ty to en­hance com­put­ing pow­er. In the past dec­ade, the­o­rists and math­e­mati­cians have de­signed for­mu­las that ex­ploit this mys­te­ri­ous su­per­po­si­tion to per­form in­tri­cate cal­cula­t­ions at speeds un­matched by supercom­put­ers to­day.

Pet­ta’s work is aimed at ex­ploiting elec­tron spin.

“In the quest to build a quan­tum com­put­er with elec­tron spin qu­bits, nu­clear spins are typ­ic­ally a nui­sance,” said Gui­do Burk­ard, a the­o­ret­i­cal phys­i­cist at the Uni­vers­ity of Kon­stanz in Germany. “Petta and cowork­ers dem­on­strate a new meth­od that uti­lizes the nu­clear spins for per­forming fast quan­tum opera­t­ions. For sol­id-state quan­tum com­put­ing, their re­sult is a big step for­ward.”

Pet­ta’s spin qubits, which he en­vi­sions as the co­re of fu­ture quan­tum log­ic el­e­ments, are cooled to ultra-cold tem­per­a­tures and trapped in two ti­ny cor­rals known as quan­tum wells on the sur­face of a chip made of high-pur­ity gal­li­um ar­se­nide. The depth of each well is con­trolled by var­y­ing the volt­age on ti­ny elec­trodes or gates. Like a jug­gler toss­ing two balls be­tween his hands, Petta can move the elec­trons from one well to the oth­er by se­lec­tively switch­ing the gate volt­ages.

Be­fore this ex­pe­ri­ment, it was­n’t clear how ex­pe­ri­menters could ma­ni­pu­late the spin of one elec­tron with­out dis­turb­ing the spin of anoth­er in a closely packed space, ac­cord­ing to phys­i­cist Phuan Ong, di­rec­tor of the Prince­ton Cen­ter for Com­plex Ma­te­ri­als.

Pet­ta’s re­search al­so is part of the fledg­ling field of “spin­tron­ics” in which sci­en­tists are stu­dy­ing how to use an elec­tron’s spin to cre­ate new types of elec­tronic de­vices. Most elec­trical de­vices to­day op­er­ate on the ba­sis of anoth­er key prop­er­ty of the elec­tron, its charge.

There are many more chal­lenges to face, Pet­ta said. “Our ap­proach is really to look at the build­ing blocks of the sys­tem, to think deeply about what the lim­ita­t­ions are and what we can do to over­come them,” he added. “But we are still at the lev­el of just ma­ni­pu­lat­ing one or two quan­tum bits, and you really need hun­dreds to do some­thing use­ful.” As ex­cit­ed as he is about pre­s­ent prog­ress, long-term ap­plica­t­ions are still years away, he added; “it’s a one-day-at-a-time ap­proach.”

Astronomers using ESO’s Very Large Telescope have detected, in another galaxy, a stellar-mass black hole much farther away than any other previously known. With a mass above fifteen times that of the Sun, this is also the second most massive stellar-mass black hole ever found. It is entwined with a star that will soon become a black hole itself.

The stellar-mass black holes found in the Milky Way weigh up to ten times the mass of the Sun and are certainly not be taken lightly, but, outside our own galaxy, they may just be minor-league players, since astronomers have found another black hole with a mass over fifteen times the mass of the Sun. This is one of only three such objects found so far.

The newly announced black hole lies in a spiral galaxy called NGC 300, six million light-years from Earth. “This is the most distant stellar-mass black hole ever weighed, and it’s the first one we’ve seen outside our own galactic neighbourhood, the Local Group,” says Paul Crowther, Professor of Astrophysics at the University of Sheffield and lead author of the paper reporting the study. The black hole’s curious partner is a Wolf–Rayet star, which also has a mass of about twenty times as much as the Sun. Wolf–Rayet stars are near the end of their lives and expel most of their outer layers into their surroundings before exploding as supernovae, with their cores imploding to form black holes.

In 2007, an X-ray instrument aboard NASA’s Swift observatory scrutinised the surroundings of the brightest X-ray source in NGC 300 discovered earlier with the European Space Agency’s XMM-Newton X-ray observatory. “We recorded periodic, extremely intense X-ray emission, a clue that a black hole might be lurking in the area,” explains team member Stefania Carpano from ESA.

Thanks to new observations performed with the FORS2 instrument mounted on ESO’s Very Large Telescope, astronomers have confirmed their earlier hunch. The new data show that the black hole and the Wolf–Rayet star dance around each other in a diabolic waltz, with a period of about 32 hours. The astronomers also found that the black hole is stripping matter away from the star as they orbit each other.

“This is indeed a very ‘intimate’ couple,” notes collaborator Robin Barnard. “How such a tightly bound system has been formed is still a mystery.”

Only one other system of this type has previously been seen, but other systems comprising a black hole and a companion star are not unknown to astronomers. Based on these systems, the astronomers see a connection between black hole mass and galactic chemistry. “We have noticed that the most massive black holes tend to be found in smaller galaxies that contain less ‘heavy’ chemical elements,” says Crowther. “Bigger galaxies that are richer in heavy elements, such as the Milky Way, only succeed in producing black holes with smaller masses.” Astronomers believe that a higher concentration of heavy chemical elements influences how a massive star evolves, increasing how much matter it sheds, resulting in a smaller black hole when the remnant finally collapses.

In less than a million years, it will be the Wolf–Rayet star’s turn to go supernova and become a black hole. “If the system survives this second explosion, the two black holes will merge, emitting copious amounts of energy in the form of gravitational waves as they combine,” concludes Crowther. However, it will take some few billion years until the actual merger, far longer than human timescales. “Our study does however show that such systems might exist, and those that have already evolved into a binary black hole might be detected by probes of gravitational waves, such as LIGO or Virgo.”

Image credit: ESO/L. Calçada

Astronomers studying two exploding stars, or supernovae, have found evidence the blasts received an extra boost from newborn black holes. The supernovae were found to emit jets of particles traveling at more than half the speed of light.

Previously, the only catastrophic events known to produce such high-speed jets were gamma-ray bursts, the universe’s most luminous explosions. Supernovae and the most common type of gamma-ray bursts occur when massive stars run out of nuclear fuel and collapse. A neutron star or black hole forms at the star’s core, triggering a massive explosion that destroys the rest of the star.

“The explosion dynamics in typical supernovae limit the speed of the expanding matter to about three percent the speed of light,”
explained Chryssa Kouveliotou, an astrophysicst at NASA’s Marshall Space Flight Center in Huntsville, Ala., co-author of one of the new studies. “Yet, in these new objects, we’re tracking gas moving some 20 times faster than this.”

The new results, published in this week’s edition of the journal Nature, used observations from several space and ground-based observatories, including NASA’s SWIFT satellite.

The astronomers discovered the ultrafast debris by studying two supernovae at radio wavelengths using numerous facilities, including the National Science Foundation’s Very Large Array in Socorro, N.M., and the Robert C. Byrd Green Bank Telescope in West Virginia. One team used the real-time operating mode of the European Very Long Baseline Interferometry Network, an international collaboration of radio telescopes, to rapidly analyze data.

“In every respect, these objects look like gamma-ray bursts — except that they produced no gamma rays,” said Alicia Soderberg at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

Soderberg led a team that studied SN 2009bb, a supernova discovered in March 2009. It exploded in the spiral galaxy NGC 3278, located about 130 million light-years away.

The other object is SN 2007gr, which was first detected in August 2007 in the spiral galaxy NGC 1058, some 35 million light-years away. The study team, which included Kouveliotou and Alexander van der Horst, a NASA Postdoctoral Program Fellow in Huntsville, was led by Zsolt Paragi at the Netherlands-based Joint Institute for Very Long Baseline Interferometry in Europe.

The researchers searched for gamma-ray signals associated with the supernovae using archived records in the Gamma-Ray Burst Coordination Network located at NASA’s Goddard Space Flight Center in Greenbelt, Md. The project distributes and archives observations of gamma-ray bursts by NASA’s Swift spacecraft, the Fermi Gamma-ray Space Telescope and many others. However, no bursts coincided with the supernovae.

Unlike typical core-collapse supernovae, the stars that produce gamma-ray bursts possess what astronomers call a “central engine” — likely a nascent black hole — that drives particle jets clocked at more than 99 percent the speed of light.

By contrast, the fastest outflows detected from SN 2009bb reached 85 percent the speed of light and SN 2007gr reached more than 60 percent of light speed.

“These observations are the first to show some supernovae are powered by a central engine,” Soderberg said. “These new radio techniques now give us a way to find explosions that resemble gamma-ray bursts without relying on detections from gamma-ray satellites.”

Perhaps as few as one out of every 10,000 supernovae produce gamma rays that we detect as a gamma-ray burst. In some cases, the star’s jets may not be angled in a way to produce a detectable burst. In others, the energy of the jets may not be enough to allow them to overcome the overlying bulk of the star.

“We’ve now found evidence for the unsung crowd of supernovae — those with relatively dim and mildly relativistic jets that only can be detected nearby,” Kouveliotou said. “These likely represent most of the population.”

For more information, images and animation about this discovery, visit: http://www.nasa.gov/swift

A far-off so­lar sys­tem seems to be form­ing from a strange dust whose make­up is un­like that of our and oth­er so­lar sys­tems, as­tro­no­mers say.

The researchers at the Univers­ity of Cal­i­for­nia Los An­ge­les found ev­i­dence for the forma­t­ion of young, rocky plan­ets from dust cir­cling a star some 500 light-years away. A light-year is the dis­tance light trav­els in a year.

“Un­til now, warm dust found around oth­er stars has been very si­m­i­lar in com­po­si­tion to as­ter­oi­dal or com­et­ary ma­te­ri­al in our So­lar Sys­tem,” said the uni­vers­ity’s Carl Melis, who led the re­search while a grad­u­ate stu­dent.

But this case is diff­er­ent, he said.

“Typic­ally, dust de­bris around oth­er stars, or our own Sun, is of the ol­i­vine, py­rox­ene, or sil­ica va­ri­e­ty, min­er­als com­monly found on Earth,” he noted. But this ma­te­ri­al “is not one of these dust types. We have yet to iden­ti­fy what spe­cies it is.”

Melis re­ported the find­ings last Wednes­day at the annual Amer­i­can As­tro­nom­i­cal So­ci­e­ty meet­ing in Wash­ing­ton, D.C.

The star, known as HD 131488, ap­pears to be sur­rounded by warm dust in a re­gion called the ter­res­tri­al plan­et zone, where tem­per­a­tures are si­m­i­lar to those on Earth, Melis said. He added that the dust seems to harbor rocky, emb­ry­onic planets that have re­cently coll­ided.

“What makes HD 131488 truly un­ique is the un­iden­ti­fied dust spe­cies re­leased from the col­lid­ing bod­ies as well as the pres­ence of cold dust far away from the star,” said as­tron­o­mer Ben­ja­min Zuck­er­man of the univers­ity, a co-author of the re­search. “These two char­ac­ter­is­tics make HD 131488 un­like any oth­er star with ev­i­dence for mas­sive quanti­ties of dust in its ter­res­tri­al plan­et zone.”

The re­search­ers an­a­lyzed the warm in­ner dust through in­fra­red im­ag­ing and spec­tros­co­py us­ing an in­stru­ment called T-ReCS on the Gem­i­ni South tel­e­scope in Chil­e. Spec­tros­co­py is the anal­y­sis of the com­po­si­tion of ob­jects us­ing the spec­trum of light they give off.

Melis and his team ar­gue that the most plau­si­ble ex­plana­t­ion for the un­usu­al abun­dance of warm dust is a re­cent col­li­sion of two rocky plan­e­tary mass bod­ies.

While the mys­te­ri­ous warm dust lies at a dis­tance from HD 131488 that is com­pa­ra­ble to the Earth-Sun separa­t­ion, the team al­so found cool­er dust about 45 times fur­ther out. This out­er dusty re­gion is anal­o­gous to the Kuiper Belt in our own So­lar Sys­tem where many mi­nor plan­ets or­bit the Sun just be­yond the or­bit of Nep­tune.

“The hot dust al­most cer­tainly came from a re­cent cat­a­stroph­ic col­li­sion be­tween two large rocky bod­ies in HD 131488’s in­ner plan­e­tary sys­tem,” Melis said. But the cool­er dust “is probably left over from plan­et forma­t­ion that took place far­ther away from HD 131488.”

HD 131488 lies in the di­rec­tion of the con­stella­t­ion Cen­tau­rus and is three times heav­i­er and 33 times more lu­mi­nous than our own Sun. The star is part of a ma­jor, south­ern-hem­i­sphere star form­ing re­gion known as the Upper-Cen­tau­rus-Lupus as­socia­t­ion whose mem­bers are be­lieved to be about 10 mil­lion years old. By con­trast, the Sun and Earth are about 4.6 bil­lion years old.

Radio astronomers have uncovered 17 millisecond pulsars in our galaxy by studying unknown high-energy sources detected by NASA’s Fermi Gamma-ray Space Telescope. The astronomers made the discovery in less than three months. Such a jump in the pace of locating these hard-to-find objects holds the promise of using them as a kind of “galactic GPS” to detect gravitational waves passing near Earth.

A pulsar is the rapidly spinning and highly magnetized core left behind when a massive star explodes. Because only rotation powers their intense gamma-ray, radio and particle emissions, pulsars gradually slow as they age. But the oldest pulsars spin hundreds of times per second — faster than a kitchen blender. These millisecond pulsars have been spun up and rejuvenated by accreting matter from a companion star.

“Radio astronomers discovered the first millisecond pulsar 28 years ago,” said Paul Ray at the Naval Research Laboratory in Washington.
“Locating them with all-sky radio surveys requires immense time and effort, and we’ve only found a total of about 60 in the disk of our galaxy since then. Fermi points us to specific targets. It’s like having a treasure map.”

Millisecond pulsars are nature’s most precise clocks, with long-term, sub-microsecond stability that rivals human-made atomic clocks.
Precise monitoring of timing changes in an all-sky array of millisecond pulsars may allow the first direct detection of gravitational waves — a long-sought consequence of Einstein’s relativity theory.

“The Global Positioning System uses time-delay measurements among satellite clocks to determine where you are on Earth,” explained Scott Ransom of the National Radio Astronomy Observatory in Charlottesville, Va. “Similarly, by monitoring timing changes in a constellation of suitable millisecond pulsars spread all over the sky, we may be able to detect the cumulative background of passing gravitational waves.”

The sources Fermi detected are not associated with any known gamma-ray emitting objects and did not show evidence of pulsing behavior.
However, scientists considered it likely that many of the unidentified sources would turn out to be pulsars.

For a more detailed look at radio wavelengths, Ray organized the Fermi Pulsar Search Consortium and recruited a handful of radio astronomers with expertise in using five of the world’s largest radio telescopes
– the National Radio Astronomy Observatory, Robert C. Byrd Green Bank Telescope in W.Va., the Parkes Observatory in Australia, the Nancay Radio Telescope in France, the Effelsberg Radio Telescope in Germany and the Arecibo Telescope in Puerto Rico.

After studying approximately 100 targets, and with a computationally intensive data analysis still under way, the discoveries have started to pour in.

“Other surveys took a decade to find as many of these pulsars as we have,” said Ransom, who led one of the discovery groups. “Having Fermi tell us where to look is a huge advantage.”

Four of the new objects are “black widow” pulsars, so called because radiation from the recycled pulsar is destroying the companion star that helped spin it up.

“Some of these stars are whittled down to masses equivalent to tens of Jupiters,” said Ray. “We’ve doubled the known number of these systems in the galaxy’s disk, and that will help us better understand how they evolve.”

NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

When our Sun begins to die, it will become a red giant as it runs out of hydrogen fuel at its core. Astronomers have a pretty good idea of what will transpire: the sun will swell to a size so large that it will swallow every planet out to Mars in our solar system. Don’t worry, though, this won’t happen for another 5 billion years. But now, astronomers have been able to watch in detail the death of a sun-like star about 550 light-years from Earth to get a better grasp on what the end might be for our Sun. The star, Chi Cygni, has swollen in size, and is now writhing in its death throes. The star has begun to pulse dramatically in and out, beating like a giant heart. New close-up photos of the surface of this distant star show its throbbing motions in unprecedented detail.

“This work opens a window onto the fate of our Sun five billion years from now, when it will near the end of its life,” said Sylvestre Lacour of the Observatoire de Paris, who led a team of astronomers studying Chi Cygni.

The scientists compared the star to a car running out of gas. The “engine” begins to sputter and pulse. On Chi Cygni, the sputterings show up as a brightening and dimming, caused by the star’s contraction and expansion.

For the first time, astronomers have photographed these dramatic changes in detail.

“We have essentially created an animation of a pulsating star using real images,” stated Lacour. “Our observations show that the pulsation is not only radial, but comes with inhomogeneities, like the giant hotspot that appeared at minimum radius.”

Click here to watch the animation.

Stars at this life stage are known as Mira variables. As it pulses, the star is puffing off its outer layers, which in a few hundred thousand years will create a beautifully gleaming planetary nebula.

Chi Cygni pulses once every 408 days. At its smallest diameter of 300 million miles, it becomes mottled with brilliant spots as massive plumes of hot plasma roil its surface, like the granules seen on our Sun’s surface, but much larger. As it expands, Chi Cygni cools and dims, growing to a diameter of 480 million miles – large enough to engulf and cook our solar system’s asteroid belt.

Imaging variable stars is an extremely difficult task. First, Mira variables hide within a compact and dense shell of dust and molecules. To study the stellar surface within the shell, astronomers need to observe the stars in infrared light, which allows them to see through the shell of molecules and dust, like X-rays enable physicians to see bones within the human body.

Secondly, these stars are very far away, and thus appear very small. Even though they are huge compared to the Sun, the distance makes them appear no larger than a small house on the moon as seen from Earth. Traditional telescopes lack the proper resolution. Consequently, the team turned to a technique called interferometry, which involves combining the light coming from several telescopes to yield resolution equivalent to a telescope as large as the distance between them.

They used the Smithsonian Astrophysical Observatory’s Infrared Optical Telescope Array, or IOTA, which was located at Whipple Observatory on Mount Hopkins, Arizona.

“IOTA offered unique capabilities,” said co-author Marc Lacasse of the Harvard-Smithsonian Center for Astrophysics (CfA). “It allowed us to see details in the images which are about 15 times smaller than can be resolved in images from the Hubble Space Telescope.”

The team also acknowledged the usefulness of the many observations contributed annually by amateur astronomers worldwide, which were provided by the American Association of Variable Star Observers (AAVSO).

In the forthcoming decade, the prospect of ultra-sharp imaging enabled by interferometry excites astronomers. Objects that, until now, appeared point-like are progressively revealing their true nature. Stellar surfaces, black hole accretion disks, and planet forming regions surrounding newborn stars all used to be understood primarily through models. Interferometry promises to reveal their true identities and, with them, some surprises.

The new observations of Chi Cygni are reported in the December 10 issue of The Astrophysical Journal.

Image: Artists concept of Chi Cygni
Credit: ESO/L. Calçada

Within a decade scientists could be able to detect the merger of tens of pairs of black holes every year, according to a team of astronomers at the University of Bonn’s Argelander-Institut fuer Astronomie, who publish their findings in a paper in Monthly Notices of the Royal Astronomical Society. By modelling the behaviour of stars in clusters, the Bonn team find that they are ideal environments for black holes to coalesce. These merger events produce ripples in time and space (gravitational waves) that could be detected by instruments from as early as 2015.

Clusters of stars are found throughout our own and other galaxies and most stars are thought to have formed in them. The smallest looser ‘open clusters’ have only a few stellar members, whilst the largest tightly bound ‘globular clusters’ have as many as several million stars. The highest mass stars in clusters use up their hydrogen fuel relatively quickly (in just a few million years). The cores of these stars collapse, leading to a violent supernova explosion where the outer layers of the star are expelled into space. The explosion leaves behind a stellar remnant with gravitational field so strong that not even light can escape – a black hole.

When stars are as close together as they are in clusters, then although still rare events, the likelihood of collisions and mergers between stars of all types, including black holes, is much higher. The black holes sink to the centre of the cluster, where a core that is completely made of up of black holes forms. In the core, the black holes experience a range of interactions, sometimes forming binary pairs and sometimes being ejected from the cluster completely.

Now Dr Sambaran Banerjee, Alexander von Humboldt postdoctoral fellow, has worked with his University of Bonn colleagues Dr Holger Baumgardt and Professor Pavel Kroupa to develop the first self-consistent simulation of the movement of black holes in star clusters.

The scientists assembled their own star clusters on a high-performance supercomputer, and then calculated how they would evolve by tracing the motion of each and every star and black hole within them.

According to a key prediction of Einstein’s General Theory of Relativity, black hole binaries stir the space-time around them, generating waves that propagate away like ripples on the surface of a lake. These waves of curvature in space-time are known as gravitational waves and will temporarily distort any object they pass through. But to date no-one has succeeded in detecting them.

In the cores of stars clusters, black hole binaries are sufficiently tightly bound to be significant sources of gravitational waves. If the black holes in a binary system merge, then an even stronger pulse of gravitational waves radiates away from the system.

Based on the new results, the next generation of gravitational wave observatories like the Advanced Laser Interferometer Gravitational-wave Observatory (Advanced LIGO) could detect tens of these events each year, out to a distance of almost 5000 million light years (for comparison the well known Andromeda Galaxy is just 2.5 million light years away).

Advanced LIGO will be up and running by 2015 and if the Bonn team are right, from then on we can look forward to a new era of gravitational wave astronomy.

Sambaran comments, “Physicists have looked for gravitational waves for more than half a century. But up to now they have proved elusive. If we are right then not only will gravitational waves be found so that General Relativity passes a key test but astronomers will soon have a completely new way to study the Universe. It seems fitting that almost exactly 100 years after Einstein published his theory, scientists should be able to use this exotic phenomenon to watch some of the most exotic events in the cosmos.”

Image: An artist’s representation of the burst of gravitational waves resulting from the collision of a colliding pair of black holes. Credit: LIGO Scientific Collaboration (LSC) / NASA.

Using a few ultracold ions, intense lasers and some electrodes, researchers have built the first programmable quantum computer. The new system, described in a paper to be published in Nature Physics, flexed its versatility by performing 160 randomly chosen processing routines.

Earlier versions of quantum computers have been largely restricted to a narrow window of specific tasks. To be more generally useful, a quantum computer should be programmable, in the same way that a classical computer must be able to run many different programs on a single piece of machinery.

The new study is “a powerful demonstration of the technological advances towards producing a real-world quantum computer,” says quantum physicist Winfried Hensinger of the University of Sussex in Brighton, England.

Researchers led by David Hanneke of the National Institute of Standards and Technology in Boulder, Colo., based their quantum computer on two beryllium ions chilled to just above absolute zero. These ions, trapped by an electromagnetic field on a gold-plated alumina chip, formed the quantum bits, or qubits, analogous to the bits in regular computers represented by 0s and 1s. Short laser bursts manipulated the beryllium ions to perform the processing operations, while nearby magnesium ions kept the beryllium ions cool and still.

Hanneke and colleagues programmed the computer to do operations on a single beryllium ion and on both of the beryllium ions together. In the quantum world, a single qubit can represent a mixture of 0 and 1 simultaneously, a state called a superposition. A laser pulse operation could change the composition of the mixture within the qubit, tipping the scales to make the qubit more likely to become a 1 when measured.

Both of the qubits together could be entangled, a situation where the two qubits are intimately linked, and what happens to one seems to affect the fate of the other. Different combinations of one- and two-qubit operations made up various programs. “We put all these pieces together and asked, what can we do with the circuit?” Hanneke says.

Hanneke and colleagues chose 160 programs for the quantum computer to run. “We picked them, quite literally, at random,” Hanneke says. “We really wanted to sample all possible operations.”

The researchers ran each program 900 times. On average, the quantum computer operated accurately 79 percent of the time, the team reported in their paper, which was published online November 15. “Getting this kind of control over a quantum system is really interesting from a physics perspective,” Hanneke says.

Earlier research has estimated that to be useful, a quantum computer must operate accurately 99.99 percent of the time. Hanneke says that with stronger lasers and other refinements, the system’s fidelity may be improved.

Experimental physicist Boris Blinov says that one of the most exciting things about the new study is that the quantum computer may be scaled up. “What’s most impressive and important is that they did it in the way that can be applied to a larger-scale system,” says Blinov, of the University of Washington in Seattle. “The very same techniques they’ve used for two qubits can be applied to much larger systems.”

This is truly a fascinating experiment, you can find some amazing images of the detector here, and read on to find out more:

UK particle physicists working on the T2K (Tokai-to-Kamioka) neutrino experiment in Japan celebrated today (24th Nov) as the experiment detected its first neutrinos – fundamental particles which are amongst the least understood in the Universe.

T2K – an international experiment led by Japan and part funded by the UK’s Science and Technology Facilities Council (STFC) – will probe the strange properties of the enigmatic neutrino to unprecedented precision, by firing the most intense neutrino beam ever designed from the east coast of Japan, all the way under the country, to a detector near Japan’s west coast.

Neutrino oscillations are one of the frontiers of current particle physics and the T2K project will move us one step closer to understanding the role of the neutrino in the early Universe and may even shed light on the mystery of why there is more matter than anti-matter in the universe.

Professor Dave Wark of Imperial College London and the STFC Rutherford Appleton Laboratory, the International Co-Spokesperson of T2K, said “It was extremely satisfying to see the first events in the detector. It has been the result of a lot of hard work by a large number of people, and I think we will have a sake or two to celebrate and then send a bottle along to CERN as I hear they are going to need quite a few bottles pretty soon as well.”

Neutrinos interact only weakly with matter, and thus pass effortlessly through the Earth (and mostly through the detectors!). Neutrinos exist in three types, called electron, muon, and tau; linked by particle interactions to their more familiar charged cousins like the electron.

Measurements over the last few decades have shown that neutrinos possess the strange property of neutrino oscillations, whereby one type of neutrino will turn into another as they propagate through space. Neutrino oscillations, which require neutrinos to have mass and therefore were not allowed in our previous theoretical understanding of particle physics, probe new physical laws and are thus of great interest in the study of the fundamental constituents of matter.

Among the international team of around 400 physicists from 12 countries, UK scientists have made a significant contribution to the experiment. With 9 UK institutions involved, the UK has produced vital hardware for both the accelerator and detectors. The UK is also playing a leading role in the analysis software for the experiment and will be fully involved in the most exciting bit – using the data to explore the properties of neutrinos. This is expected to begin in January 2010, when the experiment is scheduled to begin production running.

“Within a year T2K should have sensitivity to neutrino properties beyond any existing experiment, and the search for the unknown will begin,” said Professor Wark.

Professor Keith Mason, CEO of the Science and Technology Facility Council (STFC), said, “We’re very excited to be a part of the T2K project. Neutrinos are incredibly difficult to detect but with the skilful engineering that has gone into this experiment we will soon be able to learn much more about these elusive particles, further understand their role in the formation on the Universe and improve our model of particle physics.”

Image Credit: Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo

Scientists at Cornell University report they can now use a light beam carrying a single milliwatt of power to move objects and even change the optical properties of silicon from opaque to transparent at the nanometric scale. Such an advancement could prove very useful for the future of micro-electromechanical (MEMS) and micro-optomechanical (MOMS) systems.

As with any other electromagnetic wave, light can be characterized as the union of an electric and a magnetic field oscillating in perpendicular directions that form small but periodic peaks and valleys in potential energy. These oscillations aren’t enough to influence massive objects; on a small enough scale, though, particles that are hit by the wave tend to slide towards the “valleys” and distribute evenly on a surface. This is the principle exploited by optical and, more recently, sound tweezers to pattern tiny droplets in a predefined way.

However, it is thing is to move a nanoscale object, but another to hit it with a beam strong enough to change its geometry and optical properties, which requires much higher energy levels. To address the issue, the Cornell researchers created two “ring resonators,” circular waveguides whose circumference are a multiple of the wavelength of the light used, and exploited the relationship between beams of light traveling through the rings to make exerting high forces with small energy levels possible.

The two waveguides are three microns wide, one micron apart, and just 190 nanometers thick. When light at an appropriate frequency enters the rings, the waveguides either strongly attract or repel each other depending on whether the beams traveling through them are in phase (meaning a peak in one beam corresponds to a peak in the other) or out of phase.

The repulsion phenomenon might be useful in MEMS, micro-electromechanical systems with moving parts, where a yet unresolved problem is posed by the tendency of silicon components to stick too close together. The repulsion force generated by the resonators could, in other words, separate these components and keep them at the desired, optimal distance increasing the system’s efficiency. MOMS, or micro-optomechanical systems, could also benefit from the team’s research to create tunable filters for a specific optical wavelength.

The research is due to appear in a forthcoming edition of the journal Nature. The work is supported by the National Science Foundation and the Cornell Center for Nanoscale Systems.

What would happen if humans could deliberately create a black hole? Well, for starters we might just unlock the ultimate energy source to create the ultimate spacecraft engine — a potential “black hole-drive” – to propel ships to the stars.

It turns out black holes are not black at all; they give off “Hawking radiation” that causes them to lose energy (and therefore mass) over time. For large black holes, the amount of radiation produced is miniscule, but very small black holes rapidly turn their mass into a huge amount of energy.

This fact prompted Lois Crane and Shawn Westmoreland of Kansas State University to calculate what it would take to create a small black hole and harness the energy to propel a starship. They found that there is a “sweet spot” for black holes that are small enough to be artificially created and to produce enormous amounts of energy, but are large enough that they don’t immediately evaporate in a burst of particles. Their ideal black hole would have a mass of about a million metric tons and would be about one one-thousandth the size of a proton.

To create such a black hole, Crane and Westmoreland envision a massive spherical gamma-ray laser in space, powered by thousands of square kilometers of solar panels. After charging for a few years, this laser would release the pent-up energy equivalent to a million metric tons of mass in a converging spherical shell of photons. As the shell collapses in on itself, the energy becomes so dense that its own gravity focuses it down to a single point and a black hole is born.

The black hole would immediately begin to disgorge all the energy that was compressed to form it. To harness that energy and propel a starship, the black hole would be placed at the center of a parabolic electron-gas mirror that would reflect all the energy radiated from the black hole out the back of the ship, propelling the ship forward. Particle beams attached to the ship behind the black hole would be used to simultaneously feed the black hole and propel it along with the ship.

Such a black hole drive could easily accelerate to near the speed of light, opening up the cosmos to human travelers, but that’s just the beginning. The micro-black hole could also be used as a power generator capable of transforming any matter directly into energy. This energy could be used to create new black holes and new power generators. Obviously, creating and harnessing black holes is not an easy undertaking, but Crane and Westmoreland point out that the black hole drive has a significant advantage over more speculative technologies like warp drives and wormholes: it is physically possible. And, they believe, worth pursuing “because it allows a completely different and vastly wider destiny for the human race. We should not underestimate the ingenuity of the engineers of the future.”