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Undulator brings ILC closer to reality

A full-scale undulator module that could produce the intense positron beams needed for next-generation particle colliders has been unveiled by an international team of physicists. Similar modules could be used in future projects such as the International Linear Collider (ILC) and the Compact Linear Collider (CLIC) – both of which aim to collide high-energy positrons with high-energy electrons.

Future collider projects such as the ILC and CLIC will need stable positron sources that are about 60 times more intense than those available today. In addition, these sources must produce positrons that are spin aligned and circularly polarized. Now a team led by Jim Clarke of the UK’s Daresbury Laboratory has developed an undulator that the researchers say fits the bill. The work involved the evaluation of many different designs – both by doing computer simulations and by building small-scale prototypes.

An undulator contains magnets that force an electron beam to follow a specific trajectory, causing the electrons to emit gamma-ray photons. These gamma rays are then used to produce an intense positron beam. “In our design we create a helical magnetic field by using a double helix of superconducting wires, with current flowing in opposite directions in each helix. An electron moves in a helical trajectory through the helical magnetic field. If viewed end-on, the helical trajectory appears as if the electron is describing a circle, hence the emitted radiation is circularly polarized,” says one of the team members, Duncan Scott.

Minimizing leaking heat

Scott explains that one of the main ways of achieving the high efficiency involved locating and minimizing heat leakage in the system. “We designed the system to operate at 80% of the maximum load, but after extensive tests and redesigning some parts we managed to get that down to 70%,” says Scott.

In the ILC, the electron beam that passes through the undulator will then go on to be used in the main electron–positron collisions – so it is crucial that the electron beam is not disrupted by the undulator. While the researchers have not yet tested their device with an actual electron beam, Scott says that a large number of simulations were carried out to ensure that the final beam is stable. “There was a genuine concern that steering this high-quality beam 200 m through a vessel 6 mm in diameter would disrupt the electron beam quality too much,” says Scott. He compares this disruption – which is caused by the electric field of the beam interacting with the vacuum vessel and then feeding back on the beam – to the wake left behind a boat moving through a canal that is then reflected off the canal walls and interacts with the original wake.

A photograph of four undulator prototypes that have been built and tested
Undulator prototypes

“Our work showed that we had to use an extremely smooth copper pipe, with a surface roughness of about 100 nm. In addition, the alignment of each of the 4 m modules [there are 60 in total] has to be accurate to within 300 µm. This is a challenge, but we have a suitably smooth vessel and we believe we can meet the alignment requirements,” explains Scott.

With data from their simulations and studies, the researchers report that the gamma rays generated by their device will be capable of producing about 1010 positrons per electron pulse – the ILC specification – even when the current in the superconducting wires is only 70% of the maximum. This means that the ILC will require about 120 of these undulators lined up in series to generate sufficient gamma rays.

Major hurdle overcome

Scott also points out that producing “a fully working proof-of-principal device that shows we can generate the required number of photons” involved overcoming a major technical hurdle, as was proving to the particle physics community that the device “won’t disrupt the beam quality, short of testing it with the real beam”, both of which the researchers have now accomplished.

In the coming months the team will be looking at passing a real electron beam through the device magnet and measuring the radiation output. The researchers are also currently in discussions with the Argonne National Laboratory in the USA about sending the undulator over to be installed on the electron test beam there. Although it will still be many years before the device is used in the ILC or CLIC, Scott feels that the best thing that physicists designing such machines can do in the meantime is to “clearly demonstrate we know how to build key components such as this undulator”.

Scott also points out that while the undulator would be essential for the ILC and CLIC, similar superconducting undulators are also used in synchrotron light sources and free-electron laser.

The work is described in Physical Review Letters.

Mikhail Lomonosov: the greatest scientist you’ve never heard of

Painting of Mikhail Lomonosov
Founding father: Mikhail Lomonosov was a far-thinking polymath who kick-started Russia’s scientific development. (Courtesy: Peter the Great Museum of Anthropology and Ethnography, Russian Academy of Sciences)

Mikhail Vasilyevich Lomonosov (1711–1765) was one of the most far-sighted, polymathic and colourful scientists who ever lived. Far-sighted, because he pioneered the use of quantitative research methods. Polymathic, because though he died at just 53 he contributed to physics, chemistry, astronomy, metallurgy, mining, poetry, literature, mosaics, glassblowing, meteorology, electricity, grammar and history – and built a chemical laboratory, glass factory and flying machine. Colourful, because of irreverent antics and a hot temper. So why is this Russian genius barely known in the West?

Lomonosov was the son of a peasant-turned-fisherman from the Archangel province of north-west Russia. His insatiable love of knowledge, and family conflicts, led him in 1730 to borrow a few rubles and depart for Moscow on foot. It was a time when Peter the Great’s reforms were still being bitterly resisted by entrenched clergy and nobility. Indeed, to enter the Slavic Greek Latin Academy he had to pretend to be a son of nobility. When this deception was exposed in 1734, he was nearly expelled.

In 1736 Lomonosov began four years of study in Germany, where he learned the corpuscular theory of light and the need to treat it within a mathematical framework. He began writing poetry, but his revelry and carousing often landed him in trouble. On one trip a recruiter for the Prussian hussars befriended him, got him drunk and convinced him to enlist. The next morning, Lomonosov awoke in uniform in a heavily guarded fortress. It took him days to devise an escape, by climbing two palisades, swimming two moats and eluding cavalry in hot pursuit.

Pioneering polymath

Lomonosov returned to Russia in 1741, joining the Russian Academy of Sciences. Its founding, by Peter the Great in 1724, essentially marked the start of science in Russia – but it was still staffed by often incompetent foreigners (Bernoulli and Euler had left). Rude and mocking to inept colleagues, Lomonosov landed himself under house arrest following one violent episode. He was released after delivering odes to the Empress and a public apology, and became the Academy’s first Russian academician in 1745.

At the Academy, Lomonosov undertook a breathtaking range of experiments. He transformed Russian chemistry from art into science, introducing quantitative methods and laboratory instruction. He built Russia’s first chemical laboratory, where he conducted about 4000 tests and experiments. He used corpuscular theory to explain the elasticity of air, considered heat a form of rotational motion, introduced the idea of absolute zero and a version of conservation of matter and energy. He developed self-recording thermometers and designed a model helicopter to take them to the upper atmosphere. (A full-scale version was never built.) He designed and built a glass factory, and created a huge (6.4 × 4.8 m) mosaic, The Battle of Poltava. He also founded Moscow State University, although Pushkin called Lomonosov himself “our first university”.

But Lomonosov could not escape embroiling himself in fierce attacks and counterattacks with opponents. These fights reflected in academic circles the ongoing conflict that Peter the Great had set in motion between religion and science.

Many episodes in his life were dramatic. He and co-worker Georg Richmann each built “thunder machines” to measure electricity during thunderstorms. During one storm on 26 July 1752, Lomonosov’s frightened family begged him to leave the lab. He brushed them off, but was interrupted by Richmann’s servant, asking him to come quickly. Lomonosov rushed to Richmann’s house, which had its own machine, to find his colleague dead, having been killed by a blast of bolt lightning – of which Lomonosov then offered the first theoretical model.

Lack of recognition

Why Lomonosov is not better known in the West has something to do with a lack of good material about him not in Russian. His biography – Russia’s Lomonosov by the chemist Boris Menshutkin (the English translation appeared in 1952) – is dry and focuses on Lomonosov’s chemical contributions. The most sensitive account in English, written by physicist Pyotr Kapitsa in 1966 (Soviet Physics Uspekhi 8 720), is but nine pages long.

Furthermore, polymaths tend to be underappreciated both because their ambitions exceed their ability to complete projects, and because we cannot believe that people are able to overflow traditional disciplinary boundaries. My favourite illustration of this is by French historian of chemistry Ferdinand Hoefer, who wrote that “among the Russian chemists who have become known as chemists, we mention Mikhail Lomonosov, who mustn’t be confused with the poet of this name”.

Yet another factor is that some claims made for Lomonosov are hyperbolic, smacking of Cold War assertions of Russian superiority. Lomonosov also made mistakes, notably denying the proportionality of weight and mass. Whether Lomonosov was first to observe the atmosphere of Venus is an interesting controversy bound to be revived next year with the 2012 transit of Venus.

The critical point

Lomonosov worked in almost complete isolation from other scientists or even those who appreciated science. For instance, he had to beg a sponsor to allow him to spend his leisure time conducting chemistry and physics experiments the way others would spend theirs on billiards. Kapitsa also realized that Lomonosov’s genius is partly obscured because he lived in a time and place where the lack of a scientific environment made it easy – and possibly inevitable – for even a genius to go astray. Great science, like great art, requires an educated and demanding audience. This was not present in Russia at the time and one of Lomonosov’s principal contributions was to begin a coupling between science and culture.

We need to remember Lomonosov. Centuries have passed since scientists have needed to struggle for cultural recognition of the importance of science and its beneficial impact on humanity – but that luxury is now being eroded. We may have to take up Lomonosov’s struggle once again.

LHC trials proton–lead collisions

Physicists at CERN’s Large Hadron Collider (LHC) are analysing the results of their first attempt at colliding protons and lead ions. Further attempts at proton–lead collisions are expected over the next few weeks. If these trials are successful, a full-blown experimental programme could run in 2012.

Since the Geneva lab began experiments with the LHC in 2009, it has mostly been used to send two beams of protons in opposite directions around the 27 km accelerator, with the hope of spotting, among other things, the Higgs boson in the resulting collisions. Two beams of lead ions have also been smashed into each other in order to recreate the hot dense matter, known as a quark–gluon plasma, that was present in the early universe.

But to fully understand the results of such collisions, physicists need to know the properties of the lead ions before they collide. That is, their “cold state” before vast amounts of heat are released by the collisions. One way to do this, according to Urs Wiedemann at CERN, is to collide protons with lead ions.

Parton distribution

The problem at the moment is that our knowledge of the “parton distribution functions” for high-energy lead ions is not good enough to fully understand the results of lead–lead collisions at the LHC. Partons are the quarks and gluons that make up hadrons such as protons and neutrons – and hence the lead nuclei. At low energies hadrons can be thought of as containing just three valence quarks that interact via gluons. However, at the energies found in the LHC, hadrons comprise a large number of additional partons that can significantly affect how collisions occur. This “sea” of partons is described by a distribution function, which cannot be calculated to the desired degree of accuracy – so physicists must rely on experimental measurements.

The advantage of lead–proton collisions is that when a proton smashes into a lead nucleus, it does not heat the nucleus up much. The collision can therefore be analysed to reveal important details about the parton distribution functions of the lead ions in their cold state.

First test ‘successful’

The first test occurred on Monday and lasted 16 hours. CERN accelerator physicist John Jowett described it as “extremely successful”. Jowett and colleagues first injected a few lead bunches in the presence of 304 proton bunches. A few bunches of each were then accelerated to the LHC’s current full energy of 3.5 TeV for protons and 287 TeV for lead – or 1.38 TeV per lead nucleon.

At this top energy both beams are extremely relativistic. This means that with a small adjustment of the orbits, the protons and lead ions take the same time to complete one circuit of the accelerator. Initially, the lead and proton bunches met some 9 km away from the ATLAS experiment, but the team was able to move this meeting point back to the centre of ATLAS. This procedure lines up the bunches so they collide properly in all four experiments.

Jowett stresses that the beams were separated transversely so there have been no collisions yet. He added, “We still need to do some analysis of our data to determine whether the lead beam sizes were being blown up more than they usually are by other effects – that’s important for projecting future performance.”

Further sessions on proton–lead collisions are planned at the LHC over the next four weeks, although most of the beam time in November will be devoted to lead–lead collisions.

N.B. This article was updated on 3 November 2011.

Alpha might vary across the universe

Spectrum of a quasar


A look into the anatomy of a quasar’s spectrum (Credit: Michael Murphy, Swinburne University of Technology/NASA/ESA)

By Tushna Commissariat

A paper published in Physical Review Letters this week talks about how one of the fundamental constants of our universe – the fine-structure constant (α) – may vary across the universe. If you feel like you have heard something about this before, that is because the researchers have been looking into this particular phenomenon for almost a decade now.

They published a pre-print of this work on the arXiv server in August 2010, but the paper was only published in PRL yesterday, the delay perhaps reflecting how profound the finding could be.

The constant α is a combination of another three constants – the speed of light “c”, the charge of an electron “e” and Plank’s constant “h” – and is given by α = e2/hc.

John Webb and colleagues first looked at the light coming from very distant quasars in 1999, using the Keck Observatory in Hawaii and more recently the Very Large Telescope in Chile, to see if α really was a fundamental constant or if it varied with time or space. They use distant quasars simply as light sources that span across billions of light years. The spectrum of the quasar light carries an imprint of atoms in gas clouds that the light traverses through on its way to Earth. These spectral “fingerprint” absorption lines (known as “metal absorption lines”) are then compared with the same fingerprints found in laboratories here on Earth to infer any changes to α.

What the researchers found, after looking at the light from almost 300 quasars (as of 2010) was that α was decreasing in one direction as seen from the Earth and increasing in the exactly opposite direction. This asymmetry in the two hemispheres has been dubbed the “Australian dipole” by the researchers and has a statistical significance of about 4 σ. While some scientists were sceptical of the finding in 2010, others called it “the news of the year in physics”. If the discovery is confirmed, it would have profound implications on our understanding of the universe and on many of our current cosmological theories.

If you would like to refresh your memory about the paper or find out what it’s all about, take a look at the news story written by Hamish Johnston last year here, or take a look at the feature article written for Physics World by lead author of the paper, John Webb, here.

Sticky tank climbs the walls

By Hamish Johnston

A major breakthrough in gecko physics occurred in 2002 when Kellar Autumn and colleagues at Lewis and Clark College in Oregon showed that the lizards use Van der Waals forces to stick to (and scurry up) smooth vertical walls.

Since then, researchers have worked hard to mimic the structures found on gecko feet. Indeed, Stanford University’s Sangbae Kim has already built a “Stickybot” robotic lizard that is capable of climbing walls. Stickybot solved an important problem facing a gecko-inspired climber – how to make a foot that sticks when you want it to, yet releases when the climber takes a step upwards. Kim’s solution is “directional adhesion”, whereby the stickiness of a foot depends on the directions of the forces applied to it.

Another approach to the stick/release problem involves using continuous treads of an adhesive material that resemble those you would find on an army tank or bulldozer. The main problem with such “tank” climbers is that a tail is needed to ensure that there is an inward force at the front of the tread so that it grabs onto the wall.

stickytank.jpg

Now, Jeff Krahn and colleagues at Simon Fraser University in Canada have invented a tank robot that doesn’t need a tail – something that greatly simplifies the robot’s design. You can see the robot in action in the video above.

Another feature of the robot, according to the researchers, is that it is the first tank robot to use treads with microstructures that mimic gecko feet (right). Previous climbing tanks had used flat, unstructured materials.

Krahn’s robot, however, has treads covered in tiny mushroom-like structures that protrude slightly from the surface. The caps of the mushrooms are about 10 µm in diameter, with the stalks being about half that size. According to Krahn, this overhang allows the treads to grab on to rough surfaces.

The robot is described in a paper published in Smart Materials and Structures.

Dancing in the quantum world

Pressure limits tumour growth

Physicists in France have found that the simple application of mechanical pressure can slow down the growth of a tumour and limit its size. The researchers, who carried out their work using mice cells, say the results could lead to better diagnostic tools for cancer and perhaps eventually to new kinds of drugs to treat the disease.

It is well known that tumours form and develop into cancers when the DNA inside living cells mutates, but how that development is influenced by the environment around a tumour remains a subject of debate. The new research, by Jean-François Joanny of the Curie Institute in Paris and colleagues, investigates how a tumour’s growth is limited by the pressure it experiences as it pushes against the surrounding healthy tissue.

It is difficult to separate out the roles of genetics, biochemistry and mechanics in a tumour within a living organism. To get around this problem Joanny’s team does its work on the laboratory bench using a tumour-like ball of mouse cells with a diameter of a few tenths of a millimetre. The researchers place the simulated tumour into a bag several millimetres long and made from a semi-permeable polymer. This is then put into a solution containing nutrients that allow the cells to grow. Left alone in this state the tumour would have continued to grow for two to three weeks, until it reached a steady-state in which cell death exactly balances cell division.

Clamping down with sugar

To find out what effect pressure has on this growth, the team adds long sugar molecules to the solution. These molecules are too large to pass through the tiny pores in the bag and so remain outside the bag, creating an imbalance in their concentration that forces solution out of the bag in order to try and restore equilibrium. The greater concentration of solute outside the bag then exerts mechanical pressure onto the bag, and this pressure is felt by the tumour inside. This is repeated using identically prepared tumours, each one in its own bag and immersed in a solution with a different concentration of sugar, therefore exposing each tumour to a different pressure.

The team found that the higher the pressure the slower the tumour growth and the smaller the tumour’s ultimate size. For example, exerting a pressure of 500 pascals (just 0.5% of atmospheric pressure), halved both the growth rate of the tumour and its steady-state volume.

To establish exactly how pressure slows growth, Joanny and co-workers froze the tumours, cut them into very thin slices and covered the slices with two kinds of antibody. This reveals the distribution of dying and dividing cells in each tumour – the two kinds of cell fluorescing at a different wavelength. They discovered, contrary to expectations, that applying pressure to a tumour does not appreciably change the rate of cell death. Instead, pressure only appears to affect cell division, reducing it throughout the tumour, but especially in the core.

No room for division

Comparing these results with a computer simulation, the researchers concluded that this slower growth results directly from the mechanical pressure, rather than any biochemical processes affected by the change in pressure. The simulation represents pairs of cells as mutually repelling particles, each of which divides into a new pair when their separation exceeds a certain value. With cell death represented by a constant rate of particle removal, increasing the pressure on the outside of the simulated tumour yields a reduction in growth that matches that observed in the experiments.

Having found that placing a tumour under pressure reduces the final size of that tumour, team member Fabien Montel points out that the most invasive, and therefore most dangerous, tumours ought to be those that are able to withstand higher pressures. He says he and his colleagues would like to be able to prove this correlation by placing tiny biosensors onto tumours inside patients and establishing that the most dangerous ones are indeed those subject to higher pressures (he adds that these sensors could ultimately be used as a diagnostic tool to gauge how dangerous individual tumours are). But he says this would be extremely difficult to do with current technology and so a more achievable next step would be to take pieces from tumours that have been removed from patients and expose them to the laboratory stress test, so demonstrating, albeit within idealized conditions, that the pressure–invasiveness correlation is real.

“We are not saying that mechanics is the only way of looking at tumour growth because we know there is a lot of biochemistry involved,” says Montel. “But maybe we don’t have to know all the details of what is going on inside the cell in order to understand its growth.”

The research is described in Phys. Rev. Lett. 107 188102.

Between the lines

Expand your knowledge

With Saul Perlmutter, Adam Riess and Brian Schmidt sharing this year’s Nobel Prize for Physics for discovering that the expansion of the universe is accelerating, you may well want to speed up the rate of increase of your own knowledge about the cosmos. If so, you could do worse than to check out The Manga Guide to the Universe by science journalist Kenji Ishikawa and physicist Kiyoshi Kawabata from the Tokyo University of Science. Translated from the original Japanese, the book contains a neat mix of comic strips (“manga” being the Japanese word for “comics”) and bona fide scientific discussion. Actually, the “proper bits” will be much more worthwhile for physicists than the cartoons, although the latter are still fun even if not that illuminating. One segment on our galaxy includes corny lines such as “The Milky Way, huh? Sounds yummy,” while it takes 10 pages to draw out some fairly weak parallels between football and the Big Bang (players congregate at certain spots on the pitch just as galaxies cluster together). Still, with many popular-science books being criticized for racing through complex ideas far too fast, the gentle pace will ensure that readers are not lost – although their rate of expansion of new knowledge is likely to be fairly small.

  • 2011 No Starch Press £15.99/$19.95pb 256pp

Super-sizing the universe

Talking of things getting bigger, back in 1999 Martin Rees published a book called Just Six Numbers, in which the Cambridge University cosmologist tried to explain how the shape and size of our universe depend on just six key fundamental constants. Shortly afterwards astrophysicist Michael Rowan-Robinson from Imperial College London came out with a similar book called The Nine Numbers of the Cosmos. Now James Stein from California State University has written Cosmic Numbers, in which he argues that 13 numbers are needed for a full understanding of the universe. Three of the numbers, namely Ω (the ratio of the actual density of the universe to the critical density), ε (the efficiency of hydrogen fusion) and the relative strengths of the electrical and gravitational forces, also appeared in Rees’s book, but newbies include things such as the speed of light, the gravitational constant and the Avogadro constant. Stein’s book is much more chatty than either that of Rees or Rowan-Robinson and if “physical constants per dollar” is your criterion for buying a book, then obviously this is the one for you.

  • Basic Books £17/99/£25.99hb 228pp

Wonder vs certainty

Science is all about certainty, precision and objectivity. But it is also about wonder, mystery and creativity. In his book The Blind Spot, mathematician William Byers explores these two competing views of science, and offers strong philosophical and practical arguments in favour of the latter. According to Byers, the “science of wonder” is “characterized by a limitless openness and creativity”. On the other side is the “science of certainty”, from which stems such concepts as immutable “laws” of nature (not just “patterns” or “regularities”). Byers cautions against identifying all science with this “certain” variety, arguing that doing so contributes to a “mythology of science” that can be misused and misinterpreted. He also suggests that because “wonder” science is at home with complexity and ambiguity, it may be better at solving the complex and ambiguous problems of the modern world. Byers writes with the zeal of a convert, so it comes as no surprise when, in the book’s final chapter, he confesses that he used to be “entranced” by the “certain” view of science. Whether his readers will be similarly converted is a moot point, especially as the book is somewhat repetitive in its early chapters. But converted or no, all should appreciate the depth of thinking that Byers has brought to bear on an intriguing and important topic.

  • 2011 Princeton University Press £16.95/$24.95hb 224pp

Rogue waves triggered by ocean currents

In February 1986 the passenger ship SS Spray was travelling along the east coast of the US when it was suddenly hit by a wave that was estimated to be 17 m high – the second in a system of three consecutive “rogue waves” that were much higher than normal ocean swells. The ship suffered some minor damage and took on some water – although passengers and crew were shaken, all aboard survived. Now an international team of physicists has explained how these terrifying waves could suddenly appear in the middle of the ocean.

Mariners have long known that such waves are more prevalent in regions of strong ocean currents – the Gulf Stream in the case of the SS Spray. However, physicists have struggled to explain the physical connection between current and waves. But now Miguel Onorato and colleagues at the University of Turin in Italy and the Swinburne University of Technology in Australia have done computer simulations that show how rogue waves can form when normal ocean waves encounter a strong current moving in the opposite direction.

The work is based on the idea that such a pulse of three or four giant waves can be described mathematically as a “breather”, which is an exact solution of the nonlinear Schrödinger (NLS) equation. Not to be confused with its quantum cousin, the NLS applies to classical physics including water waves and optics.

Focused into a breather

The team began the simulation with the sort of plane waves that you might encounter on the ocean – swells with an amplitude of 2.5 m that propagate in a specific direction. These waves then encounter a current that is flowing in the opposite direction. When the plane waves travel from a region of no current to a region with a current, they cross a current gradient. The simulations show that the encounter with the gradient causes the energy of the plane wave to be focused into a small region. This causes instability in the plane wave, which triggers the appearance of a breather.

The simulations suggest that breather formation could occur when plane waves with a period of about 10 s – a typical condition in a storm – encounter a current travelling at about 1.5 m s–1, a speed not unknown for ocean currents.

Efim Pelinovsky of the Institute of Applied Physics at the Russian Academy of Sciences agrees with the team’s analysis of how the breathers could form, and points out that the process could occur in regions where the prevailing winds move in the opposite direction as the current. This condition is commonly seen in the Indian Ocean off the coast of South Africa, where the Agulhas Current has long been associated with rogue waves.

Onorato told physicsworld.com that researchers working in Tokyo have already done experiments in wave tanks that back up the simulations. Because the NLS also applies in optics, Onorato says that the effect should also be seen in experiments with light. Instead of a current, a breather should be formed when light waves travel through an optical fibre along which certain nonlinear properties change gradually.

The work is reported in Phys. Rev. Lett. 107 184502.

Astronomers discover complex organic matter abound in the universe

Recurrent Nova RS Ophiuci


NASA image of the star field in the constellation Ophiucus; at the centre is the recurrent Nova RS Ophiuci (Credit: John Chumack)

By Tushna Commissariat

Complex organic compounds – one of the main markers of carbon-based life forms – have always been thought to arise from living organisms. But new research by physicists in Hong Kong, published yesterday in the journal Nature, suggests that these compounds can be synthesized in space even when no life forms are present.

Sun Kwok and Yong Zhang at the University of Hong Kong claim that a particular organic compound that is found throughout the universe contains complex compounds that resemble coal and petroleum – which have long been thought to come only from carbonaceous living matter.

The researchers say that the organic substance contains a mixture of aromatic (ring-like) and aliphatic (chain-like) complex components. They have come to this conclusion after looking at strange infrared emissions detected in stars, interstellar space and galaxies that are commonly known as unidentified infrared emissions (UIEs). These UIE signatures are thought to arise from simple organic molecules made of carbon and hydrogen atoms – polycyclic aromatic hydrocarbon (PAH) molecules – being “pumped” by far-ultraviolet photons. But Kwok and Zhang both felt that hypothesis did not fill the bill accurately enough, when they considered the observational data.

As a solution, they have suggested an alternative – that the substances generating these infrared emissions have chemical structures that are much more complex. After analysing the spectra of star dust forming when stars explode, they found that stars are capable of making these complex organic compounds on extremely short timescales of weeks and that they then eject it into the general interstellar space – the region between stars.

Kwok had suggested, at an earlier date, that old stars could be “molecular factories” capable of producing organic compounds. “Our work has shown that stars have no problem making complex organic compounds under near-vacuum conditions,” says Kwok. “Theoretically, this is impossible, but observationally we can see it happening.”

Another interesting fact is that the organic star dust that Kwok and Zhang studied has a remarkable structural similarity to complex organic compounds found in meteorites. As meteorites are remnants of the early solar system, the findings raise the possibility that stars enriched our protoplanetary disc with organic compounds (by angela). The early Earth was known to have been bombarded by many comets and asteroids carrying organic star dust. Whether these organic compounds played any role in the development of life on Earth remains a mystery.

It will also be interesting to see if this finding has an impact on research groups that look for life in the universe, such as SETI , considering that complex organic molecules have always thought to be markers of carbon-based life forms.

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