DISCOVERY

ScienceDaily — What dog owner has not come home to a broken vase or other valuable items and a guilty-looking dog slouching around the house? By ingeniously setting up conditions where the owner was misinformed as to whether their dog had really committed an offense, Alexandra Horowitz, Assistant Professor from Barnard College in New York, uncovered the origins of the “guilty look” in dogs in the recently published “Canine Behaviour and Cognition” Special Issue of Elsevier’s Behavioural Processes.

Boxer mix. People see 'guilt' in a dog's body language when they believe the dog has done something it shouldn't have -- even if the dog is in fact completely innocent of any offense. (Credit: iStockphoto/Mark Coffey)
Horowitz was able to show that the human tendency to attribute a “guilty look” to a dog was not due to whether the dog was indeed guilty. Instead, people see ‘guilt’ in a dog’s body language when they believe the dog has done something it shouldn’t have – even if the dog is in fact completely innocent of any offense.

During the study, owners were asked to leave the room after ordering their dogs not to eat a tasty treat. While the owner was away, Horowitz gave some of the dogs this forbidden treat before asking the owners back into the room. In some trials the owners were told that their dog had eaten the forbidden treat; in others, they were told their dog had behaved properly and left the treat alone. What the owners were told, however, often did not correlate with reality.

Whether the dogs' demeanor included elements of the "guilty look" had little to do with whether the dogs had actually eaten the forbidden treat or not. Dogs looked most “guilty” if they were admonished by their owners for eating the treat. In fact, dogs that had been obedient and had not eaten the treat, but were scolded by their (misinformed) owners, looked more “guilty” than those that had, in fact, eaten the treat. Thus the dog’s guilty look is a response to the owner’s behavior, and not necessarily indicative of any appreciation of its own misdeeds.

This study sheds new light on the natural human tendency to interpret animal behavior in human terms. Anthropomorphisms compare animal behavior to human behavior, and if there is some superficial similarity, then the animal behavior will be interpreted in the same terms as superficially similar human actions. This can include the attribution of higher-order emotions such as guilt or remorse to the animal.

The editor of the special issue, Clive D.L. Wynne of the Department of Psychology, University of Florida, explained, “this is a remarkably powerful demonstration of the need for careful experimental designs if we are to understand the human-dog relationship and not just reify our natural prejudices about animal behavior.” He pointed out that dogs are the oldest domesticated species and have a uniquely intimate role in the lives of millions of people. Recent research on dogs has indicated more human-like forms of reasoning about what people know than has been demonstrated even in chimpanzees.

ScienceDaily — If the broad evolutionary diversification of a group of organisms were repeated by a few species in a single genus tens of millions of years after the group's initial diversification, what would that say about the roles of contingency, constraint, and adaptation?

Zooids of four living species of the bryozoan genus Cauloramphus showing the stepwise evolution (left to right, top to bottom) from a species with simple, flexible frontal membrane with spines (more primitive), to a species with a cage of spines not yet fused over the membrane, to a species with a frontal shield made of fused spined and a large frontal membrane, to a species with a reduced frontal shield of tighly fused spines. A water sac (the ascus, hidden below the shield) has evolved in the last species, as the frontal membrane is so reduced that simplu pulling on it would not change the internal volume enough to squeeze out the feeding organ (polypide). (Credit: Micrographs by Matthew H. Dick)
As Darwin observed, natural selection leading to adaptation of individuals and populations is occurring gradually and all the time. But over very long spans of time, the major channels of genetic organization, organism form, and the different ways organisms develop arose as outcomes of history-dependent variation that is now channeled, or constrained, within different groups of organisms.

For example, most cats look like cats, develop like cats, but have a fossil record that begins from less than cat-like ancestors. So do snails, and crabs, and so on. But what if the broad evolutionary diversification of one of these groups were repeated by a few species in a single genus tens of millions of years after that initial diversification? What would that say about the roles of contingency, constraint, and adaptation? In other words, how big is the role of chance in the history of life?

An international team of researchers including Field Museum curator Scott Lidgard, PhD, has discovered a group of closely related living species that independently repeated the different step-like changes that occurred in the major diversification of their kind during the Cretaceous Period, roughly 100 to 90 million years ago. But this group of species arose 80 million years later!

The findings of Dr. Lidgard and his collaborators will be published online this week by the British journal Proceedings of the Royal Society B. Dr. Lidgard's research focuses on cheilostome bryozoans, marine animal colonies whose bodies are made up of many genetically identical box-like individuals (zooids). In the simplest, most primitive cheilostomes, the soft feeding organ is squeezed out of the box by muscles pulling on a flexible membrane. The next step in diversification was calcified spines around the membrane, then fusion of the spines, then reduction of the fused spinal shield and membrane and invention of a water sac inside the box to provide enough volume to squeeze out the feeding organ. Lineages showing each of these stages are alive today. Then as now, these steps are seen as evolved defenses against small predators and parasites on the colony surface.

What is remarkable is that the molecular genealogy of the living species shows their origin only 15 million years ago, with the same trajectory as in the distant past! Evidence suggests that trajectory has occurred again and again in other groups. The authors argue that the original trajectory was highly contingent on a set of initial conditions, but that given the possibilities afforded by time, a genetic background would arise (like flipping a coin long enough to achieve 10 heads or tails in a row) that was visible to natural selection, most likely driven by predation. Acting together, the eventual realization of a particular genetic and developmental channel, and natural selection opened the way for an adaptive solution.

WASHINGTON, June 11, 2009 (Reuters) — The new H1N1 virus, which has caused the first pandemic of the 21st century, appears to have been circulating undetected among pigs for years, researchers reported on Thursday.
Although health officials have been watching for new influenza viruses in humans, animal health regulators have missed the opportunity to check swine, the researchers reported.

Britons Andrew Rambaut of the University of Edinburgh and Oliver Pybus of Oxford University, and Yi Guan of the University of Hong Kong examined the genetic sequence of the new H1N1 swine flu virus.

Like others who have done the same, they show it is a mixture of other viruses that had been circulating in pigs, one of which was itself a mixture including swine, human and avian-like genetic sequences.

"We show that it was derived from several viruses circulating in swine, and that the initial transmission to humans occurred several months before recognition of the outbreak," they wrote.

"Movement of live pigs between Eurasia and North America seems to have facilitated the mixing of diverse swine influenza viruses, leading to the multiple reassortment events associated with the genesis of the (new H1N1) strain," they added.

"Yet despite widespread influenza surveillance in humans, the lack of systematic swine surveillance allowed for the undetected persistence and evolution of this potentially pandemic strain for many years."

They said this new pandemic "provides further evidence of the role of domestic pigs in the ecosystem of influenza A."

The new virus, which was first reported in two U.S. children in March, apparently infected people as early as last January in Mexico, health officials have said. The World Health Organization declared it a full pandemic on Thursday, meaning it is circulating globally and cannot be stopped.

MOLECULAR CLOCK

The international team also used a "molecular clock" method to compare the current virus to its relatives and estimate its age based on the mutations. This gives a rough idea of when the new virus is likely to have emerged.

"We found that the common ancestor of the (new H1N1) outbreak and the closest related swine viruses existed between 9.2 and 17.2 years ago, depending on the genomic segment, hence the ancestors of the epidemic have been circulating undetected for about a decade," they wrote.

"Thus, this genomic structure may have been circulating in pigs for several years before emergence in humans," they added.

The pork industry has been vociferously protesting use of the term "swine flu" to describe the virus.

Fears that the pandemic would affect pork prices caused World Health Organization officials to use the generic designation of "influenza A(H1N1)" -- which also refers to one of the current seasonal flu strains.

Last week the U.S. Agriculture Department said it would launch a pilot surveillance project to look for new strains of flu virus in pigs.

Also last week, Gerardo Nava of the National Autonomous University of Mexico and colleagues reported that their genetic analysis also pointed to North American swine as a potential source of the new virus.

Cooked pork is no threat but live pigs can get influenza as easily as people do and people and pigs can sometimes pass viruses back and forth.

(Editing by Philip Barbara)

ScienceDaily (June 16, 2009) — Why aren't birds larger? Fifteen-kilogram swans hold the current upper size record for flying birds, although the extinct Argentavis of the Miocene Epoch in Argentina is estimated to have weighed 70 kilograms, the size of an average human. In a forthcoming article in PLoS Biology, Sievert Rohwer, and his colleagues at the Burke Museum at the University of Washington, provide evidence that maximum body size in birds is constrained by the amount of time it takes to replace the flight feathers during molt.

Bald Eagle soaring. What limits the size of birds? (Credit: iStockphoto/Bruce Leonard)
As bird size increases, feather growth rate fails to keep up with feather length until, eventually; feathers wear out before they can be replaced. This fundamental relationship requires basic changes in the molt strategy as size increases, ultimately limiting the size of flying birds.

Feathers deteriorate with continued exposure to ultra-violet light and bacterial decomposition, and must be replaced periodically to maintain adequate aerodynamic support for flight. Small birds accomplish this in an annual or twice-annual molt, during which the 9 or 10 primary flight feathers are replaced sequentially, taking about three weeks for each feather. Large species of birds need different approaches to feather replacement. These involve several alternative strategies: prolonging the total molt to two or even three years; simultaneously replacing multiple feathers from different molt-origination points in the feather sequence; and, in species that do not require flight to feed or escape enemies (ducks and geese, for example), replacing all feathers simultaneously.

With increasing body size, the length of the primary feathers increases as the one-third power of mass, approximately doubling with each 10-fold increase in mass. However, the rate of feather growth increases only as the one-sixth power of mass, meaning that the time required to replace each feather increases by a factor of about 1.5 for each 10-fold increase in mass, until 56 days are required to replace a single flight feather in a 10-kg bird. The cause of this discrepancy is not known, but the authors speculate that it probably depends on the geometry of producing a two-dimensional feather structure from a one-dimensional growing zone in the feather shaft.

The avian feather is one of the most striking adaptations in the animal world, and yet its growth dynamics are poorly understood. It might be possible to achieve more rapid feather growth with a larger growth zone, but this could also weaken the structure of the growing feather, resulting in frequent breakage in large birds. Understanding the engineering complexities of the growing feather will require further study of the dynamics and structure of the growing zone. And what about Argentavis? The authors speculate that this giant bird most likely molted all its feathers simultaneously during a long fast, fueled by accumulated fat deposits much in the same way as emperor penguins do today.

Travel to the American Museum was supported by the Burke Museum, the American Museum, and a University of Washington Department of Biology Casey Award. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Are Changes In Earth's Main Magnetic Field Induced By Oceans' Circulation?
ScienceDaily (June 15, 2009) — Some 400 years of discussion and we’re still not sure what creates the Earth’s magnetic field, and thus the magnetosphere, despite the importance of the latter as the only buffer between us and deadly solar wind of charged particles (made up of electrons and protons). New research raises question marks about the forces behind the magnetic field and the structure of Earth itself.

A controversial new theory suggests that long-term changes (the secular variation) in Earth's main magnetic field are possibly induced by the oceans' circulation. (Credit: iStockphoto/René Mansi)
The controversial new paper, published in New Journal of Physics (co-owned by the Institute of Physics and the German Physical Society), will deflect geophysicists’ attention from postulated motion of conducting fluids in the Earth’s core, the twentieth century’s answer to the mysteries of geomagnetism and magnetosphere.

Professor Gregory Ryskin from the School of Engineering and Applied Science at Northwestern University in Illinois, US, has defied the long-standing convention by applying equations from magnetohydrodynamics to our oceans’ salt water (which conducts electricity) and found that the long-term changes (the secular variation) in the Earth’s main magnetic field are possibly induced by our oceans’ circulation.

With calculations thus confirming Ryskin’s suspicions, there were also time and space correlations - specific indications of the integral relationship between the oceans and our magnetospheric buffer. For example, researchers had recorded changes in the intensity of current circulation in the North Atlantic; Ryskin shows that these appear strongly correlated with sharp changes in the rate of geomagnetic secular variation (“geomagnetic jerks”).

Tim Smith, senior publisher of the New Journal of Physics, said, "This article is controversial and will no doubt cause vigorous debate, and possibly strong opposition, from some parts of the geomagnetism community. As the author acknowledges, the results by no means constitute a proof but they do suggest the need for further research into the possibility of a direct connection between ocean flow and the secular variation of the geomagnetic field."

In the early 1920s, Einstein highlighted the large challenge that understanding our Magnetosphere poses. It was later suggested that the Earth’s magnetic field could be a result of the flow of electrically-conducting fluid deep inside the Earth acting as a dynamo.

In the second half of the twentieth century, the dynamo theory, describing the process through which a rotating, convecting, and electrically conducting fluid acts to maintain a magnetic field, was used to explain how hot iron in the outer core of the Earth creates a magnetosphere.

The journal paper also raises questions about the structure of our Earth’s core.

Familiar text book images that illustrate a flow of hot and highly electrically-conducting fluid at the core of the Earth are based on conjecture and could now be rendered invalid. As the flow of fluids at the Earth’s core cannot be measured or observed, theories about changes in the magnetosphere have been used, inversely, to infer the existence of such flow at the core of the Earth.

While Ryskin’s research looks only at long-term changes in the Earth’s magnetic field, he points out that, “If secular variation is caused by the ocean flow, the entire concept of the dynamo operating in the Earth’s core is called into question: there exists no other evidence of hydrodynamic flow in the core.”

On a practical level, it means the next time you use a compass you might need to thank the seas and oceans for influencing the force necessary to guide the way.

Dr Raymond Shaw, professor of atmospheric physics at Michigan Technological University, said, “It should be kept in mind that the idea Professor Ryskin is proposing in his paper, if valid, has the potential to deem irrelevant the ruling paradigm of geomagnetism, so it will be no surprise to find individuals who are strongly opposed or critical."

Tiny Frozen Microbe May Hold Clues To Extraterrestrial Life
ScienceDaily (June 15, 2009) — A novel bacterium -- trapped more than three kilometres under glacial ice in Greenland for over 120,000 years -- may hold clues as to what life forms might exist on other planets.

Trapped more than three kilometers under glacial ice in Greenland for over 120,000 years, a dormant bacterium -- Herminiimonas glaciei -- has been coaxed back to life by researchers. (Credit: Image courtesy of Society for General Microbiology)
Dr Jennifer Loveland-Curtze and a team of scientists from Pennsylvania State University report finding the novel microbe, which they have called Herminiimonas glaciei, in the current issue of the International Journal of Systematic and Evolutionary Microbiology. The team showed great patience in coaxing the dormant microbe back to life; first incubating their samples at 2˚C for seven months and then at 5˚C for a further four and a half months, after which colonies of very small purple-brown bacteria were seen.

H. glaciei is small even by bacterial standards – it is 10 to 50 times smaller than E. coli. Its small size probably helped it to survive in the liquid veins among ice crystals and the thin liquid film on their surfaces. Small cell size is considered to be advantageous for more efficient nutrient uptake, protection against predators and occupation of micro-niches and it has been shown that ultramicrobacteria are dominant in many soil and marine environments.

Most life on our planet has always consisted of microorganisms, so it is reasonable to consider that this might be true on other planets as well. Studying microorganisms living under extreme conditions on Earth may provide insight into what sorts of life forms could survive elsewhere in the solar system.

"These extremely cold environments are the best analogues of possible extraterrestrial habitats", said Dr Loveland-Curtze, "The exceptionally low temperatures can preserve cells and nucleic acids for even millions of years. H. glaciei is one of just a handful of officially described ultra-small species and the only one so far from the Greenland ice sheet; studying these bacteria can provide insights into how cells can survive and even grow under extremely harsh conditions, such as temperatures down to -56˚C, little oxygen, low nutrients, high pressure and limited space."

"H. glaciei isn't a pathogen and is not harmful to humans", Dr Loveland-Curtze added, "but it can pass through a 0.2 micron filter, which is the filter pore size commonly used in sterilization of fluids in laboratories and hospitals. If there are other ultra-small bacteria that are pathogens, then they could be present in solutions presumed to be sterile. In a clear solution very tiny cells might grow but not create the density sufficient to make the solution cloudy."

ScienceDaily — The interstellar stuff that became incorporated into the planets and life on Earth has younger cosmic roots than theories predict, according to the University of Chicago postdoctoral scholar Philipp Heck and his international team of colleagues.

This is University of Chicago postdoctoral scientist Philipp Heck with a sample of the Allende meteorite. The dark portions of the meteorite contain dust grains that formed before the birth of the solar system. The Allenda meteorite is of the same type as the Murchison meteorite, the subject of Heck's Astrophysical Journal study. (Credit: Dan Dry)
Heck and his colleagues examined 22 interstellar grains from the Murchison meteorite for their analysis. Dying sun-like stars flung the Murchison grains into space more than 4.5 billion years ago, before the birth of the solar system. Scientists know the grains formed outside the solar system because of their exotic composition.

"The concentration of neon, produced during cosmic-ray irradiation, allows us to determine the time a grain has spent in interstellar space," Heck said. His team determined that 17 of the grains spent somewhere between three million and 200 million years in interstellar space, far less than the theoretical estimates of approximately 500 million years. Only three grains met interstellar duration expectations (two grains yielded no reliable age).

"The knowledge of this lifetime is essential for an improved understanding of interstellar processes, and to better contain the timing of formation processes of the solar system," Heck said. A period of intense star formation that preceded the sun's birth may have produced large quantities of dust, thus accounting for the timing discrepancy, according to the research team.

Funding sources for the research include the National Aeronautics and Space Administration, Swiss National Science Foundation, the Australian National University, and the Brazilian National Council for Scientific and Technological Development.

Betelgeuse, Red Supergiant In Constellation Orion, Has Shrunk By 15 Percent In 15 Years
ScienceDaily (June 16, 2009) — The red supergiant star Betelgeuse, the bright reddish star in the constellation Orion, has steadily shrunk over the past 15 years, according to University of California, Berkeley, researchers.

UC Berkeley physicist Charles Townes, who won the 1964 Nobel Prize in Physics for invention of the laser, cleans one of the large mirrors of the Infrared Spatial Interferometer. The ISI is on the top of Mt. Wilson in Southern California. (Credit: Cristina Ryan (2008))
Long-term monitoring by UC Berkeley's Infrared Spatial Interferometer (ISI) on the top of Mt. Wilson in Southern California shows that Betelgeuse (bet' el juz), which is so big that in our solar system it would reach to the orbit of Jupiter, has shrunk in diameter by more than 15 percent since 1993.

Since Betelgeuse's radius is about five astronomical units, or five times the radius of Earth's orbit, that means the star's radius has shrunk by a distance equal to the orbit of Venus.

"To see this change is very striking," said Charles Townes, a UC Berkeley professor emeritus of physics who won the 1964 Nobel Prize in Physics for inventing the laser and the maser, a microwave laser. "We will be watching it carefully over the next few years to see if it will keep contracting or will go back up in size."

Townes and his colleague, Edward Wishnow, a research physicist at UC Berkeley's Space Sciences Laboratory, will discuss their findings at a 12:40 p.m. PDT press conference on Tuesday, June 9, during the Pasadena meeting of the American Astronomical Society (AAS). The results were published June 1 in The Astrophysical Journal Letters.

Despite Betelgeuse's diminished size, Wishnow pointed out that its visible brightness, or magnitude, which is monitored regularly by members of the American Association of Variable Star Observers, has shown no significant dimming over the past 15 years.

The ISI has been focusing on Betelgeuse for more than 15 years in an attempt to learn more about these giant massive stars and to discern features on the star's surface, Wishnow said. He speculated that the measurements may be affected by giant convection cells on the star's surface that are like convection granules on the sun, but so large that they bulge out of the surface. Townes and former graduate student Ken Tatebe observed a bright spot on the surface of Betelgeuse in recent years, although at the moment, the star appears spherically symmetrical.

"But we do not know why the star is shrinking," Wishnow said. "Considering all that we know about galaxies and the distant universe, there are still lots of things we don't know about stars, including what happens as red giants near the ends of their lives."

Betelgeuse was the first star ever to have its size measured, and even today is one of only a handful of stars that appears through the Hubble Space Telescope as a disk rather than a point of light. In1921, Francis G. Pease and Albert Michelson used optical interferometry to estimate its diameter was equivalent to the orbit of Mars. Last year, new measurements of the distance to Betelgeuse raised it from 430 light years to 640, which increased the star's diameter from about 3.7 to about 5.5 AU.

"Since the 1921 measurement, its size has been re-measured by many different interferometer systems over a range of wavelengths where the diameter measured varies by about 30 percent," Wishnow said. "At a given wavelength, however, the star has not varied in size much beyond the measurement uncertainties."

The measurements cannot be compared anyway, because the star's size depends on the wavelength of light used to measure it, Townes said. This is because the tenuous gas in the outer regions of the star emits light as well as absorbs it, which makes it difficult to determine the edge of the star.

The ISI that Townes and his colleagues first built in the early 1990s sidesteps these confounding emission and absorption lines by observing in the mid-infrared with a narrow bandwidth that can be tuned between spectral lines. The ISI consists of three 5.4-foot (1.65-meter) diameter mirrors separated by distances that vary from 12 to 230 feet (4-70 meters), said Townes. Using a laser as a common frequency standard, the ISI interferometer combines signals from telescope pairs in order to determine path length differences between light that originates at the star's center and light that originates at the star's edge. The technique of stellar interferometry is highlighted in the June 2009 issue of Physics Today magazine.

"We observe around 11 microns, the mid-infrared, where this long wavelength penetrates the dust and the narrow bandwidth avoids any spectral lines, and so we see the star relatively undistorted," said Townes. "We have also had the good fortune to have an instrument that has operated in a very similar manner for some 15 years, providing a long and consistent series of measurements that no one else has. The first measurements showed a size quite close to Michelson's result, but over 15 years, it has decreased in size about 15 percent, changing smoothly, but faster as the years progressed."

Townes, who turns 94 in July, plans to continue monitoring Betelgeuse in hopes of finding a pattern in the changing diameter, and to improve the ISI's capabilities by adding a spectrometer to the interferometer.

"Whenever you look at things with more precision, you are going to find some surprises and uncover very fundamental and important new things," he said.

The ISI is supported by grants from the National Science Foundation, the Gordon and Betty Moore Foundation and the Office of Naval Research.

Betelgeuse, Red Supergiant In Constellation Orion, Has Shrunk By 15 Percent In 15 Years
ScienceDaily (June 16, 2009) — The red supergiant star Betelgeuse, the bright reddish star in the constellation Orion, has steadily shrunk over the past 15 years, according to University of California, Berkeley, researchers.

UC Berkeley physicist Charles Townes, who won the 1964 Nobel Prize in Physics for invention of the laser, cleans one of the large mirrors of the Infrared Spatial Interferometer. The ISI is on the top of Mt. Wilson in Southern California. (Credit: Cristina Ryan (2008))
Long-term monitoring by UC Berkeley's Infrared Spatial Interferometer (ISI) on the top of Mt. Wilson in Southern California shows that Betelgeuse (bet' el juz), which is so big that in our solar system it would reach to the orbit of Jupiter, has shrunk in diameter by more than 15 percent since 1993.

Since Betelgeuse's radius is about five astronomical units, or five times the radius of Earth's orbit, that means the star's radius has shrunk by a distance equal to the orbit of Venus.

"To see this change is very striking," said Charles Townes, a UC Berkeley professor emeritus of physics who won the 1964 Nobel Prize in Physics for inventing the laser and the maser, a microwave laser. "We will be watching it carefully over the next few years to see if it will keep contracting or will go back up in size."

Townes and his colleague, Edward Wishnow, a research physicist at UC Berkeley's Space Sciences Laboratory, will discuss their findings at a 12:40 p.m. PDT press conference on Tuesday, June 9, during the Pasadena meeting of the American Astronomical Society (AAS). The results were published June 1 in The Astrophysical Journal Letters.

Despite Betelgeuse's diminished size, Wishnow pointed out that its visible brightness, or magnitude, which is monitored regularly by members of the American Association of Variable Star Observers, has shown no significant dimming over the past 15 years.

The ISI has been focusing on Betelgeuse for more than 15 years in an attempt to learn more about these giant massive stars and to discern features on the star's surface, Wishnow said. He speculated that the measurements may be affected by giant convection cells on the star's surface that are like convection granules on the sun, but so large that they bulge out of the surface. Townes and former graduate student Ken Tatebe observed a bright spot on the surface of Betelgeuse in recent years, although at the moment, the star appears spherically symmetrical.

"But we do not know why the star is shrinking," Wishnow said. "Considering all that we know about galaxies and the distant universe, there are still lots of things we don't know about stars, including what happens as red giants near the ends of their lives."

Betelgeuse was the first star ever to have its size measured, and even today is one of only a handful of stars that appears through the Hubble Space Telescope as a disk rather than a point of light. In1921, Francis G. Pease and Albert Michelson used optical interferometry to estimate its diameter was equivalent to the orbit of Mars. Last year, new measurements of the distance to Betelgeuse raised it from 430 light years to 640, which increased the star's diameter from about 3.7 to about 5.5 AU.

"Since the 1921 measurement, its size has been re-measured by many different interferometer systems over a range of wavelengths where the diameter measured varies by about 30 percent," Wishnow said. "At a given wavelength, however, the star has not varied in size much beyond the measurement uncertainties."

The measurements cannot be compared anyway, because the star's size depends on the wavelength of light used to measure it, Townes said. This is because the tenuous gas in the outer regions of the star emits light as well as absorbs it, which makes it difficult to determine the edge of the star.

The ISI that Townes and his colleagues first built in the early 1990s sidesteps these confounding emission and absorption lines by observing in the mid-infrared with a narrow bandwidth that can be tuned between spectral lines. The ISI consists of three 5.4-foot (1.65-meter) diameter mirrors separated by distances that vary from 12 to 230 feet (4-70 meters), said Townes. Using a laser as a common frequency standard, the ISI interferometer combines signals from telescope pairs in order to determine path length differences between light that originates at the star's center and light that originates at the star's edge. The technique of stellar interferometry is highlighted in the June 2009 issue of Physics Today magazine.

"We observe around 11 microns, the mid-infrared, where this long wavelength penetrates the dust and the narrow bandwidth avoids any spectral lines, and so we see the star relatively undistorted," said Townes. "We have also had the good fortune to have an instrument that has operated in a very similar manner for some 15 years, providing a long and consistent series of measurements that no one else has. The first measurements showed a size quite close to Michelson's result, but over 15 years, it has decreased in size about 15 percent, changing smoothly, but faster as the years progressed."

Townes, who turns 94 in July, plans to continue monitoring Betelgeuse in hopes of finding a pattern in the changing diameter, and to improve the ISI's capabilities by adding a spectrometer to the interferometer.

"Whenever you look at things with more precision, you are going to find some surprises and uncover very fundamental and important new things," he said.

The ISI is supported by grants from the National Science Foundation, the Gordon and Betty Moore Foundation and the Office of Naval Research.