Ian O'Neill, Author at Universe Today

February 7, 2008December 26, 2015 by Ian O'Neill

The “Astronomical Unit” May Need an Upgrade as the Sun Loses Mass

The Sun is constantly losing mass. Our closest star is shedding material through the solar wind, coronal mass ejections and by simply generating light. As the burning giant begins a new solar cycle, it continues to lose about 6 billion kilograms (that’s approximately 16 Empire State Building’s worth) of mass per second. This may seem like a lot, but when compared with the total mass of the Sun (of nearly 2Ã—10³⁰ kilograms), this rate of mass loss is miniscule. However small the mass loss, the mass of the Sun is not constant. So, when using the Astronomical Unit (AU), problems will begin to surface in astronomical calculations as this “universal constant” is based on the mass of the Sun…

The AU is commonly used to describe distances within the Solar System. For instance, one AU is approximately the mean distance from the Sun to Earth orbit (defined as 149,597,870.691 kilometres). Mars has an average orbit of 1.5AU, Mercury has an average of about 0.4AU… But how is the distance of one AU defined? Most commonly thought to be derived as the mean distance of the Sun-Earth orbit, it is actually officially defined as: the radius of an unperturbed circular orbit that a massless body would revolve about the Sun in 2Ï€/k days (that’s one year). ThereÂ lies theÂ problem. The official calculation is based on “k”, a constant based on the estimated constant mass of the Sun.Â But theÂ mass of the Sun ain’t constant.

As mass is lost via the solar wind and radiation (radiation energy will carry mass from the Sun due to the energy-mass relationship defined by Einstein’s E=mc²), the value of the Astronomical Unit will increase, and by its definition, the orbit of the planets should also increase. It has been calculated that Mercury will lag behind it’s current orbital position in 200 years time by 5.5 km if we continue to use today’s AU in future calculations. Although a tiny number – astrophysicists are unlikely to lose any sleep over the discrepancy – a universal constant should be just that, constant. There are now calls to correct for this gradual increase in the value of the AU by discarding it all together.

“[The current definition is] fine for first-year science courses. But for scientific and engineering usage, it is essential to get it right.” – Peter Noerdlinger, astronomer at St Mary’s University, Canada.

Correcting classical “constants” in physics is essential when high accuracy is required to calculate quantities over massive distances or long periods of time, therefore the AU (as it is currently defined) may be demoted as a general description of distance rather than a standard scientific unit.

Source: New Scientist

February 7, 2008December 26, 2015 by Ian O'Neill

Large Hadron Collider Could Create Wormholes: a Gateway for Time Travelers?

As we get closer to the grand opening of the Large Hadron Collider (LHC) near Geneva, Switzerland, it seems the predictions as to what we might get from the high energy particle accelerator are becoming more complex and outlandish. Not only could the LHC generate enough energy to create particles that exist in other dimensions, it may also produce “unparticles“, a possible source for dark matter. Now, the energy may be so focused that even the fabric of space-time may be pulled apart to create a wormhole, not to a different place, but a different time. Also, if there are any time travellers out there, we are most likely to see them in a few weeks…

If you could travel back in time, where would you go? Actually it’s a trick question: you couldn’t travel back in time unless there was a time “machine” already built in the past. The universe’s very first time traveller would therefore only be able to travel back to when the machine he/she was using was built. This is one restriction that puts pay to those romantic ideas that we could travel back in time to see the dinosaurs; there were no time machines back then (that we know of), so nothing to travel back to. And until we create a time machine, we won’t be seeing any travelers any time soon.

However, Prof Irina Aref’eva and Dr Igor Volovich, mathematical physicists at the Steklov Mathematical Institute in Moscow believe the energies generated by the subatomic collisions in the LHC may be powerful enough to rip space-time itself, spawning wormholes. A wormhole not only has the ability to take a shortcut between two positions in space, it can also take a shortcut between two positions in time. So, the LHC could be the first ever “time machine”, providing future time travelers with a documented time and place where a wormhole “opened up” into our time-line. This year could therefore be “Year Zero”, the base year by which time travel is limited to.

Relativity doesn’t dispute this idea, but the likelihood of a person passing through time is slim-to-impossible when the dimensions of a possible wormhole will be at the sub-atomic level at best and it would only be open for a brief moment. Testing for the presence of a man-made wormhole would be difficult even if we knew what we were looking for (perhaps a small loss in energy during collision, as energy escapes through the wormhole?).

As if that didn’t discourage you from hoping to use wormholes for time travel, Dr Brian Cox of the University of Manchester says: “The energies of billions of cosmic rays that have been hitting the Earth’s atmosphere for five billion years far exceed those we will create at the LHC, so by this logic time travellers should be here already.” As far as we know, they’re not.

Source: Telegraph.co.uk

February 7, 2008April 26, 2016 by Ian O'Neill

Building a Moon Base: Part 1 – Challenges and Hazards

So, we want to go to the Moon. Why? Because the Moon is an ideal “staging post” for us to accumulate materials and manpower outside of the Earth’s deep gravitational well. From the Moon we can send missions into deep space and ferry colonists to Mars. Tourists may also be interested in a short visit. Mining companies will no doubt want to set up camp there. The pursuit of science is also a major draw. For what ever reason, to maintain a presence on this small dusty satellite, we will need to build a Moon base. Be it for the short-term or long-term, man will need to colonize the Moon. But where would we live? How could we survive on this hostile landscape? This is where structural engineers will step in, to design, and build, the most extreme habitats ever conceived…

Manned missions to Mars take up a lot of the limelight insofar as colonization efforts are concerned, so it’s about time some focus is aimed at the ongoing and established concepts for colonization of the Moon. We currently have a means of getting there (after all, it is nearly 40 years ago since Apollo 11) and our technology is sufficiently advanced to sustain life in space, the next step is to begin building… In this first installment of “Building a Moon Base”, we look at the immediate issues facing engineers when planning habitats on a lunar landscape.

“Building a Moon Base” is based on research by Haym Benaroya and Leonhard Bernold (“Engineering of lunar bases”)

The debate still rages as to whether man should settle on the Moon or Mars first. Mars is often considered to be the ultimate challenge for mankind: to live on a planet other than Earth. But looking down on us during cloudless nights is the bright and attainable Moon. From here we can see the details of the lunar landscape with the naked eye, it is so close astronomically when compared with the planets, that many believe that the Moon should be our first port of call before we begin the six month (at best) voyage to the Red Planet. It also helps as we’ve already been there…

Opinion has shifted somewhat in recent years from the “Mars Direct” plan (in the mid-1990s) to the “Moon First” idea, and this shift has recently been highlighted by US President George W. Bush when in 2004 he set out plans for re-establishing a presence on the Moon before we can begin planning for Mars. It makes sense; many human physiological issues remain to be identified, plus the technology for colonization can only be tested to its full extent when… well… colonizing.

Understanding how the human body will adapt to life in low-G and how new technologies will perform in a location close enough to home will be not only be assuring to lunar colonists and astronauts, it will also be sensible. Exploring space is dangerous enough, minimizing the risk of mission failure will be critical to the future of manned exploration of the Solar System.

So where do you start when designing a moon base? High up on the structural engineers “to do” list would be the damage building materials may face when exposed to a vacuum. Damage from severe temperature variations, high velocity micrometeorite impacts, high outward forces from pressurized habitats, material brittleness at very low temperatures and cumulative abrasion by high energy cosmic rays and solar wind particles will all factor highly in the planning phase. Once all the hazards are outlined, work can begin on the structures themselves.

The Moon exerts a gravitational pull 1/6th that of the Earth, so engineers will be allowed to build less gravity-restricted structures. Also, local materials should be used where and when possible. The launch costs from Earth for building supplies would be astronomical, so building materials should be mined rather than imported. Lunar regolith (fine grains of pulverized Moon rock) for example can be used to cover parts of habitats to protect settlers from cancer-causing cosmic rays and provide insulation. According to studies, a regolith thickness of least 2.5 meters is required to protect the human body to a “safe” background level of radiation. High energy efficiency will also be required, so the designs must incorporate highly insulating materials to insure minimum loss of heat. Additional protection from meteorite impacts must be considered as the Moon has a near-zero atmosphere necessary to burn up incoming space debris. Perhaps underground dwellings would be a good idea?

The actual construction of a base will be very difficult in itself. Obviously, the low-G environment poses some difficulty to construction workers to get around, but the lack of an atmosphere would prove very damaging. Without the buffering of air around drilling tools, dynamic friction will be amplified during drilling tasks, generating huge amounts of heat. Drill bits and rock will fuse, hindering progress. Should demolition tasks need to be carried out, explosions in a vacuum would create countless high velocity missiles tearing through anything in their path, with no atmosphere to slow them down. (You wouldn’t want to be eating dinner in an inflatable habitat during mining activities should a rock fragment be flying your way…) Also, the ejected dust would obscure everything and settle, statically, on machinery and contaminate everything. Decontamination via air locks will not be efficient enough to remove all the dust from spacesuits, Moon dust would be ingested and breathed in – a health risk we will not fully comprehend until we are there.

“Building a Moon Base” is based on research by Haym Benaroya and Leonhard Bernold (“Engineering of lunar bases“)

Could Nitrogen Pollution Give Tropical Flora a Much Needed Boost?

Global warming and subsequent climate change is directly linked with human activity on our planet. The greenhouse effect is amplified by our need for energy, burning fossil fuels and pumping vast quantities of CO₂ into our atmosphere. To make things worse, the plants that form the Earth’s “lungs” in the tropics are being destroyed on a massive scale, so less carbon dioxide can be scrubbed from the air. However, it’s not all bad news. Industry and agriculture also generate large amounts of excess nitrogen pollution and scientists now believe that this nitrogen (a main ingredient for fertilizer) may help to increase tropical plant growth by up to 20%…

From our high school classes, we all know that green plants, through photosynthesis, absorb atmospheric carbon dioxide. It is essential for plants to flourish. By far the largest absorbers of carbon dioxide are the tropical rainforests in the Amazon basin, central Africa and southern Asia. They are often referred to as the “lungs” of Earth, as they absorb much of the atmospheric CO₂ and provide balance to the carbon budget of our climate. If this resource is removed through wholesale deforestation, more CO₂ collects in the atmosphere and global warming is amplified by the increase of this greenhouse gas.

However, help may be at hand. Taking the results from over 100 previously published studies, David LeBauer and Kathleen Treseder from the University of California Irvine, believe they have found a trend that suggests a strong link between nitrogen pollution and increased plant growth in tropical regions. Increased plant growth is a welcomed consequence of human activity, as faster plant growth means more plants to absorb more CO₂. Although deforestation is a global catastrophe (much of the ancient forests will never recover and a vast proportion of plant and animal species are now extinct), the new research published in Ecology may influence future climate change models.

“We hope our results will improve global change forecasts.” – David LeBauer, UCI graduate student researcher of Earth system science and lead author of the study.

Nitrogen pollution comes in many forms, the most obvious being from agricultural activity (fertilizer) polluting water supplies and industrial burning emitting nitrogen into the air. What’s more, nitrogen pollution is on the increase, especially in developing countries.

Nitrogen pollution has often been ignored as a possible growth agent in the tropics, as other fertilizing elements are in short supply (typically, if one element is low, no matter how high the other element is, it will have little or no effect on plant growth). Phosphorus for example, is low in tropical regions, but according to the new research, this doesn’t seem to factor and plant growth is increased by 20% regardless.

LeBauer adds: “What is clear is that we need to consider how nitrogen pollution interacts with carbon dioxide pollution. Our study is a step toward understanding the far-reaching effects of nitrogen pollution and how it may change our climate…” It may only be a step, but at least it’s a positive one.

Source: Physorg.com

February 5, 2008December 26, 2015 by Ian O'Neill

British Engineers Design Hypersonic Passenger Jet

A British engineering company has stepped into the commercial spaceflight arena with an ambitious and inspiring design of a possible airliner of the future. The A2, the design behind the Long-Term Advanced Propulsion Concepts and Technologies (LAPCAT) project, will carry 300 passengers, will have a range of 20,000 km and will be capable of travelling twice the speed of Concorde – that’s a sustained velocity of Mach 5. It will also be capable of atmospheric and space flight leading to the exciting possibility of becoming a large vehicle shuttling passengers, astronauts and payloads into orbit…

As private enterprise is beginning to see the possibility of profit in spaceflight, more and more rocket, spaceship and aircraft designs are being realised beyond the realms of science fiction. Richard Branson’s Virgin GalacticÂ and Elon Musk’s SpaceXÂ bear testament to the opportunities that await commercial transport into space. While Branson’s SpaceShipTwo concept uses a conventional WhiteKnight aircraft to “piggyback” until a maximum altitude is reached before it’s rocket engines propel it into space, Musk’s program depends on the ballistic approach, sending his Falcon rocket into space via a conventional rocket launchpad. The A2 concept is different as it will take off and land like a passenger jet without the need to be helped on its way by another aircraft.

The A2 is an impressive looking craft, and the claim that it may be able to sustain hypersonic flight is impressive. Currently, only astronauts leaving or re-entering the atmosphere travel at hyper sonic velocities, no aircraft is capable of such speeds within the Earth’s atmosphere. Mach 5 is the speed at which large amounts of heating occurs on an aircraft’s body, temperatures in excess of 1,800Â° F (1,000Â° C), so the engineering of hypersonic aircraft must be sufficiently advanced to protect passengers and aircraft structure from this extreme environment.

The A2 is intended to travel at Mach 5 within the atmosphere so it can enter low Earth orbit, giving it the ability to carry out orbital tasks as well as travelling to international destinations very quickly. It is hoped the A2 will travel from Europe to Australia within four hours. Reaction Engines Ltd. project the A2 will be in full production within 25 years.

The A2 will be able to do this through the use of Scimitar Engines – fueled by huge amounts of hydrogen (indeed, most of the aircraft fuselage will contain the fuel to feed theÂ four engines slung under its wings) – that are designed around existing gas turbine, rocket and subsonic ramjet technology.

See more about the A2 design at Reaction Engines Ltd.

Source: BBC

February 5, 2008December 26, 2015 by Ian O'Neill

Earth’s climate will slip past “tipping point” within 100 years

Nine key geographical factors have been highlighted as Earth’s critical climate controllers most at risk of slipping past their “tipping points”. This means that once damage reaches a certain point, there can be no recovery; the damage will continue in a downward spiral, amplifying global warming and environmental damage on historic scales.Â And asÂ if climate news couldn’t getÂ any worse,Â one suchÂ tipping pointÂ is onlyÂ a year away…Â

You can’t move these days for articles about climate change, global warming and environmental disasters. All this talk about impending doom and gloom can often lull you into a detached reverie thinking “what the hell can I do about it anyway?” Although sometimes the outlook seems hopeless, scientists are stepping up a gear to understand what is happening and why humans are having such an impact on our world. In the quest to understand the effects we are having on the planet, new research has drawn up a list of nine key factors and processes likely to change the Earth’s climate most dramatically. It is hoped that once we understand how these processes work, and how long we have until the point of no return, action could be taken to allow the climate to heal.

Prof. Tim Lenton from the University of East Anglia, UK, has identified when the tipping points are likely to occurÂ for the nine key geological factors, and the next one is most likely going to be the collapse of the Indian summer monsoon, which is variable at best. The list is as follows (plus predicted time to tipping point):

Arctic sea-ice melt (approx 10 years)
Greenland ice sheet decay (more than 300 years)
West Antarctic ice sheet decay (more than 300 years)
Atlantic thermohaline circulation collapse (approx 100 years)
El Nino Southern Oscillation increase (approx 100 years)
Indian summer monsoon collapse (approx 1 year)
Sahara/Sahel greening and West African monsoon disruption (approx 10 years)
Amazon rainforest dieback (approx 50 years)
Boreal Forest dieback (approx 50 years)

Many of the factors seem obvious. The melting of the Arctic ice for instance will cause a global rise in sea levels and a loss of ice cover causing Earth’s albedo to decrease (reflectivity decreases), amplifying the greenhouse effect. Also, El Nino in the South Pacific will occur more often, causing rapid and extreme changes in the large-scale weather structure; hurricanes, flooding, droughts and unseasonal shifts in the jet stream will become more and more common.

Some of the factors are perhaps less obvious. For instance, the collapse of the Atlantic thermohaline circulation would have a counter-intuitive effect on the north Atlantic, actually cooling the waters around Europe, North America and the Arctic. The thermohaline drives the circulation of the oceans, so should the Atlantic thermohaline collapse,Â water from the equator will stop drifting north, providing theÂ warmth at such high latitudes. This effect is unlikely to slow the melting of the Arctic ice-sheets, but it will have devastating effects on biodiversity in the region.

“Society must not be lulled into a false sense of security by smooth projections of global change […] Our findings suggest that a variety of tipping elements could reach their critical point within this century under human-induced climate change. The greatest threats are tipping of the Arctic sea-ice and the Greenland ice sheet, and at least five other elements could surprise us by exhibiting a nearby tipping point.” – Prof Lenton

Although worrying, many of the tipping point projections could be averted should strong action be taken by the international community and individuals alike – after all, we can all contribute in some way.

Source: Telegraph.co.uk

February 4, 2008December 26, 2015 by Ian O'Neill

Large Hadron Collider May Help Us Glimpse Into another Dimension

High energy collisions by the nearly-completed Large Hadron Collider (LHC) may be able to generate particles that are sensitive to dimensions beyond our four dimensional space-time. These exotic particles, called Kaluza-Klein gravitons, would be highly sensitive to the geometry of extra-dimensions, giving scientists an idea about what lies beyond our universe. If these particles are detected, and if their characteristics can be measured, then perhaps the extra dimensions predicted by string theoryÂ may be proven to exist…

How can you measure the size of a room without actually measuring it? Forget measuring the room, you can’t even see it! The room is invisible; it is outside your observational ability. But what if you could bounce sound off the walls? Even better, what if the walls of the invisible room were made up of resonant particles, producing their own sound? If the sound from these resonant particles could then be analyzed, the shape of the invisible room would be known.

According to string theory, there are many “invisible rooms” that we, as observers, cannot experience. We are confined to our three dimensions of space and one dimension of time (although this may not always be the case), otherwise known as four dimensional space-time. Elemental vibrating strings thread through our universe and predict that there may be six or seven extra dimensions coexisting. Although we cannot directly experience the dimensions beyond the normal four, can we measure the characteristics of string vibrations travelling from these extra dimensions into our observable universe?

In new research published by Gary Shiu, Bret Underwood, Kathryn Zurek at UW-Madison and Devin Walker at UC-Berkeley, quantum particles have been theorized to have the ability to resonate with dimensions beyond our universe; beyond the 4th dimension, considered to be time. From this resonance, signatures from extra-dimensions could pass through our four dimensional space-time to be measured. From this analysis, the “shape” of the extra dimensions may then be understood. This is not purely out of curiosity, according to string theory the shape of extra dimensions influences everything in our universe:

“The shape of the dimensions is crucial because, in string theory, the way the string vibrates determines the pattern of particle masses and the forces that we feel.” – UW-Madison physics professor, Gary Shiu.

The team predict particles carrying extra-dimensional signatures could be generated by the Large Hadron Collider at CERN (nr. Geneva, Switzerland). At very high energies, Kaluza-Klein (KK) gravitons may be created for a brief moment, carrying the signatures with them. Unfortunately KK gravitons will decay very quickly, but from this decay a shower of lower energy, detectable particles will be created. By analyzing the resulting shower, a fingerprint of the KK particle’s signature may be constructed. Any slight changes in the geometry of the detected particles may indicate a particular dimension, and many signatures may be mixed, so complex computer simulations are required to understand the results coming from the LHC.

Source: Science Daily

February 2, 2008December 26, 2015 by Ian O'Neill

Get a Better View of Saturn from Cassini, in 3D

Ever wondered what one of our robotic explorers can see right now? What can Cassini see as it orbits Saturn, continuing to explore the ringed gas giant? Now, in 3D, you can explore the probe yourself, seeing what Cassini sees with a neat 3D interactive viewer, imaging Saturn and her moons, accurately calculating where the probe was, is or will be. The best thing about this little online gadget is that you can speed through time, from the spaceship’s point of view, orbiting Saturn and working out when the next moon or ring flyby will be… A cool toy to waste some time playing with, especially when I really should be doing some work…

This gadget on the Cassini mission website really took me back to my childhood. For those of you who were addicted to the space exploration computer games Elite and Frontier: Elite 2 back in the early ’90s should be able to relate to this too. The Elite games were a groundbreaking series, using polygons to represent 3D objects, flying through space, trading, fighting and interacting with a basic, but engrossing, Universe. Based not on some mystical cosmos, Elite could be played in our solar system, allowing us for the first time to see an interactive 3D view of the Earth, Mars, Moon and the rest of the planets. I also remember zooming through Saturn’s blocky rings and wondered what that would really look like.

Of course, we now know what that does look like, in fact, Cassini is still out there, orbiting Saturn and analyzing Saturn’s moons: Mimas, Enceladus, Tethys, Dione, Rhea, Titan and Iapetus (inner to outer). The Cassini mission, launched in 1997, comprised of the NASA Cassini orbiter and ESA Huygens probe. After a long seven year journey, the pair arrived in Saturn orbit on July 1st, 2004 and on December 25th, 2004 the pair separated to send Huygens to Saturn’s largest moon, Titan. Huygens then made an exciting decent through Titan’s atmosphere and relayed vital information about the mysterious planet to the Cassini orbiter.

After all this excitement, Cassini carried on orbiting around Saturn and continues to this day transmitting amazing images and detailed information about Saturn’s interaction with the interplanetary medium, moons, atmosphere and magnetic field. Now, any online user can see what the historic orbiter is doing this very minute. Using NASA’s Cassini at Saturn Interactive Explorer (CASSIE), we can fast-forward or rewind to see Cassini’s most recent encounter with Titan, or see the probe pass through Saturn’s rings at our leisure. Not only is it fun, it helps us visualize where the craft is when we want to know.

Now thinking back to all those hundreds of hours I spent playing computer games, and comparing the graphics with this online gadget, I realize things have come a long way as far as 3D visualization is concerned. But I still get the same childish sense ofÂ awe about exploring the vastness of space, only this time I know I am seeing a 3D representation of the real view from Cassini.

Interestingly, on the box art of the Frontier: Elite 2 game (pictured left), Saturn is featured very boldly…

News source: SpaceRef.com

February 2, 2008December 26, 2015 by Ian O'Neill

Poland “agrees” to host controversial US missile defence system

interceptor-missile-714820.thumbnail.jpg

In a controversial move likely to enflame tensions between Russia, Europe and the US, Poland has agreed (in principal) to host bases for the “Star Wars” US missile shield intended to protect against any future missile attack from rogue nations. Russia totally opposes plans, stating that a European missile system, so close to the Russian border, is akin to the Cuban missile crisis in the 1960s where the US and Soviet Union went to the brink of nuclear war…

Any space missile system intended to neutralize the threat of a nuclear attack from rogue states was bound to cause controversy and anger. As predicted, the future development of a European US missile shield has caused very loud opposition from Russian President Vladimir Putin, directly highlighting that such a move would cause another arms race and could create a nuclear standoff between Russia, US and Europe in between.

The Czech Republic is currently drawing up plans for involvement in the US project and now Poland, a country that directly borders Russia, has agreed to more discussions about installing ten interceptor missiles. The missile shield plans are in a direct response to the ongoing threat from “rogue states”, principally Iran and North Korea, from their nuclear arms development programs the US believes they are still pursuing, but understandably, Russia is suspicious that the US is attempting to gain strategic strength in Eastern Europe. Mr Putin has hinted strongly that although Russia is not planning to begin wholesale targeting of Europe, any “new targets” in the future would be connected to the “strategic nuclear potential of the United States… in Europe” (see BBC article “New era of discord for Russia and West” for full information on the new political unrest). Scary.

“We understand that there is a desire for defence modernisation in Poland and particularly for air defence modernisation in Poland. This is something that we support because it will make our ally, Poland, more capable,” – US Secretary of State Condoleezza Rice, supporting the missile defence plan in Poland.

The US missile shield concept depends on European fast response missiles to be launched as soon as the threat of imminent attack is detected from aggressors in the Middle East and beyond. By detecting possible nuclear missiles clearing cloud cover and entering space, radar bases within the EU can track and then guide conventional missiles from the shield network to intercept. Tests of such a system have so far had a mix of success and failure, but with improvement of the “Star Wars” technology (a name first coined in 1983 after announcement by US President Ronald Reagan for the commencement of the “Strategic Defence Initiative”) and rocket engineering, rates of successful interception are bound to increase.

Source: BBC

January 30, 2008December 26, 2015 by Ian O'Neill

Innovative Laser Trap Captures Most Neutron-Rich Substance Made On Earth: Helium-8

Configuration of helium isotopes (credit: Physorg.com)

US researchers have used a new and innovative method to create, trap and study the elusive helium-8 isotope. Helium-8, containing six neutrons and only two protons, is the most neutron rich substance we can create on Earth and until now, we have been unable to accurately characterize it. Through the use of a “laser trap”, physicists in the U.S. Department of Energy’s Argonne National Laboratory have accurately mapped the distribution of theÂ atom and could help us understand the science behind exotic neutron stars.

So, how do you “trap” a helium-8 isotope? The answer is far from simple, but Argonne physicist Peter Mueller has found a solution. Using the GANIL cyclotron facility in northern France, helium-4, 6, and occasionally helium-8 isotopes can be generated. This is one of the only cyclotrons is the world with enough energy to generate the helium-8 isotope. It is all very well creating the particle, but to separate helium-8 from its other helium isotope siblings requires a clever and highly accurate laser “prison” for the heavier helium isotope to fall in to, whilst allowing the other, lighter, isotopes to fly straight through.

Acting as the “bars” of prison gates, six lasers are accurately aligned at such spacing that only isotopes with the dimensions of helium-8 are trapped. When aligned, helium-8 will fall between them, and should the isotope try to escape, repulsion forces keep the isotope still. Once enough time is allowed to pass (about one helium-8 atom is generated every two minutes) the team fire another two lasers into the middle at the same frequency as the resonant frequency of helium-8. Should the laser prison glow, helium-8 has been captured.

The most common, stable form of helium has two protons and two neutrons. Helium can also have two unstable isotopes, helium-6 (four neutrons) and helium-8 (six neutrons). In the unstable isotopes, the additional neutrons form a “halo” around the compact central core (pictured above). Helium-6 has a halo containing two neutrons and helium-8 has a halo of four neutrons. In the halo containing two neutrons, helium-6 has a distinctive “wobble” as the halo neutrons arrange themselves asymmetrically around the core (i.e. they bunch together). This lopsidedness moves the center of balance away from the core and more toward the halo pair of neutrons. Helium-8 on the other hand wobbles less as the four halo neutrons arrange themselves more symmetrically around the core. The laser trap is the only method known to trap a helium-8 atom, and because of this, the structure of its halo can finally be analyzed to such a high degree of accuracy.

To measure the characteristics of helium-8 is complicated by its radioactivity. Helium-8 has a half-life of only a tenth of a second, so all measurements of the atom must be taken instantly as the “prison glow” is detected. Measurements are therefore taken “on-line”, which is a difficult task in itself.

Detection of the rare helium-8 isotope is a major step to particle physicists and astrophysicists alike. It is important to understand how helium configures itself after production from a particle accelerator, but it is also of use when understanding the properties of cosmic bodies such as neutron stars. The implications of the Argonne experiment will be useful as better spectroscopic observations become available so the signature of the helium-8 structure might be detected other than on Earth.

Source: Physorg.com