TAU NEWS – Astronomy & Astrophysics

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Ancient Jars Found in Judea Reveal Earth's Magnetic Field is Fluctuating, Not Diminishing

New evidence says geomagnetic force "spiked" in 8th century BCE, say TAU, Hebrew University, UC San Diego researchers

Albert Einstein considered the origin of the Earth's magnetic field one of the five most important unsolved problems in physics. The weakening of the geomagnetic field, which extends from the planet's core into outer space and was first recorded 180 years ago, has raised concern by some for the welfare of the biosphere.

But a new study published in PNAS from Tel Aviv University, Hebrew University of Jerusalem, and University of California San Diego researchers finds there is no reason for alarm: The Earth's geomagnetic field has been undulating for thousands of years. Data obtained from the analysis of well-dated Judean jar handles provide information on changes in the strength of the geomagnetic field between the 8th and 2nd centuries BCE, indicating a fluctuating field that peaked during the 8th century BCE.

"The field strength of the 8th century BCE corroborates previous observations of our group, first published in 2009, of an unusually strong field in the early Iron Age. We call it the 'Iron Age Spike,' and it is the strongest field recorded in the last 100,000 years," says Dr. Erez Ben-Yosef of TAU's Institute of Archaeology, the study's lead investigator. "This new finding puts the recent decline in the field's strength into context. Apparently, this is not a unique phenomenon — the field has often weakened and recovered over the last millennia."

Additional researchers included Prof. Oded Lipschits and Michael Millman of TAU, Dr. Ron Shaar of Hebrew University, and Prof. Lisa Tauxe of UC San Diego.

Delving into the inner structure of the planet

"We can gain a clearer picture of the planet and its inner structure by better understanding proxies like the magnetic field, which reaches more than 1,800 miles deep into the liquid part of the Earth's outer core," Dr. Ben-Yosef observes.

The new research is based on a set of 67 ancient, heat-impacted Judean ceramic storage jar handles, which bear royal stamp impressions from the 8th to 2nd century BCE, providing accurate age estimates.

"The period spanned by the jars allowed us to procure data on the Earth's magnetic field during that time — the Iron Age through the Hellenistic Period in Judea," says Dr. Ben-Yosef. "The typology of the stamp impressions, which correspond to changes in the political entities ruling this area, provides excellent age estimates for the firing of these artifacts."

To accurately measure the geomagnetic intensity, the researchers conducted experiments at the Paleomagnetic Laboratory of Scripps Institution of Oceanography (SIO), University of California San Diego, using laboratory-built paleomagnetic ovens and a superconducting magnetometer.

"Ceramics, baked clay, burned mud bricks, copper slag — almost anything that was heated and then cooled can become a recorder of the components of the magnetic field at the time of the event," said Dr. Ben-Yosef. "Ceramics have tiny minerals — magnetic 'recorders' — that save information about the magnetic field of the time the clay was in the kiln. The behavior of the magnetic field in the past can be studied by examining archaeological artifacts or geological material that were heated then cooled, such as lava."

Advanced dating method

Observed changes in the geomagnetic field can, in turn, be used as an advanced dating method complementary to the radiocarbon dating, according to Dr. Ben-Yosef. "The improved Levantine archaeomagnetic record can be used to date pottery and other heat-impacted archaeological materials whose date is unknown.

"Both archaeologists and Earth scientists benefit from this. The new data can improve geophysical models — core-mantle interactions, cosmogenic processes and more — as well as provide an excellent, accurate dating reference for archaeological artefacts," says Dr. Ben-Yosef.

The researchers are currently working on enhancing the archaeomagnetic database for the Levant, one of the most archaeologically-rich regions on the planet, to better understand the geomagnetic field and establish a robust dating reference.

TAU Scientist Joins NASA for Historic Mission to Jupiter

Juno spacecraft will "revolutionize" our understanding of the formation of the universe

NASA's Juno spacecraft went into orbit around Jupiter on July 4 after a five-year trip covering nearly 2 billion miles in outer space — and Prof. Ravit Helled of Tel Aviv University's Department of Geosciences played a major role in getting it there.

"It's really fun and exciting! It's great to see that the public is interested, and that adds a new dimension to this research," said Prof. Helled, an astrophysicist and planetary scientist who joined the Juno science team in 2008. "It's very important that it is covered by the media, hopefully this can encourage young people to become scientists, and show the world what we are doing."

Prof. Helled's Juno research will specialize in Jupiter's internal structure and interior formation.

Juno slowed down Monday night just enough to be pulled into the orbit of the giant planet. A spinning, robotic probe as wide as a basketball court, Juno will circle Jupiter 37 times for 20 months, observing the gas giant from its polar orbit, some 3,000 miles above its dense clouds. It is the first spacecraft to orbit Jupiter since Galileo, which deliberately crashed into Jupiter in September 2003.

Clues to the origins of the solar system

Photo: Prof. Ravit HelledJupiter and the gaseous planet's four largest moons — Io, Europa, Ganymede, and Callisto — have been the subject of fascination for centuries. It was the first planet to form and holds vital clues as to how our solar system formed and evolved. The Juno mission will help scientists understand planetary systems in other parts of the universe.

"Jupiter is a very mysterious planet," Prof. Helled said. "It is huge, has no solid surface, has strong winds and magnetic fields, and we don't know exactly what it is made of."

Spacecraft have flown to Jupiter before, but none were equipped with the advanced technology and instruments on board Juno, instruments that will offer insight into the planet's origins, structure, atmosphere, and magnetosphere.

New images of Jupiter

Upon its approach, Juno shot a video of Jupiter's moons traveling around the planet, capturing the first "live" footage of the movement of objects around a celestial body. The JunoCam is poised to take "spectacular close-up, color images" of Jupiter that, according to NASA, will unlock the secrets of the giant planet. Does it have a solid core? What lies beneath its dense clouds? How much water is in its atmosphere? How deep is that giant red spot?

"Juno just started to orbit Jupiter, so it will take at least a few weeks to get initial results," said Prof. Helled. "I am most eager to receive information on Jupiter's gravitational field — this can then be used to constrain its density profile, and therefore describe its composition. I want to know if Jupiter has a core, so we can better understand how giant planets form.

"While Juno is a NASA mission, it is very international and consists of people from countries around the world. It has been incredible to be a part of it."

The Juno mission ends on February 20, 2018, when Juno is expected to crash into Jupiter.

Video: Watch a YouTube presentation about giant planets by Prof. Helled

Photo caption (middle right): Prof. Ravit Helled

Nearby "Dwarf" Galaxy is Home to Luminous Star Cluster

TAU and UCLA researchers surprised to discover more than a million young stars forming in tiny neighboring galaxy


The NGC 5253 galaxy as seen through the Hubble Space Telescope

A team of Tel Aviv University and UCLA astronomers have discovered a remarkable cluster of more than a million young stars are forming in a hot, dusty cloud of molecular gases in a tiny galaxy very near our own.

The star cluster is buried within a massive gas cloud dubbed "Cloud D" in the NGC 5253 dwarf galaxy, and, although it's a billion times brighter than our sun, is barely visible, hidden by its own hot gases and dust. The star cluster contains more than 7,000 massive "O" stars: the most brilliant stars extant, each a million times more luminous than our sun.

"Cloud D is an incredibly efficient star and soot factory," says Prof. Sara Beck of TAU's Department of Astronomy and Astrophysics and co-author of the research, recently published in Nature. "This cloud has created a huge cluster of stars, and the stars have created an unprecedented amount of dust."

For the study, Prof. Beck collaborated with Prof. Jean Turner, Chair of UCLA's Department of Physics and Astronomy, and a team of researchers at the Submillimeter Array, a joint project of the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics, on Hawaii's Mauna Kea.

A beautiful day in the neighborhood

"Extreme and extraordinary things are happening right in our very own astronomical neighborhood," Prof. Beck says. "In astrophysics we assume that, unless proven otherwise, basic processes are the same everywhere. But here we're witnessing globular cluster formation — a process which we assumed was 'turned off' in our galaxy ten billion years ago — occurring today in a nearby galaxy."

According to the researchers, NGC 5253 is home to hundreds of large star clusters. The most spectacular cluster, cocooned in the massive Cloud D, is about three million years old, remarkably young in astronomical terms. The proportion of gas clouds, which eventually become stars, varies in different parts of the universe. In the Milky Way, for example, less than 5 percent of gas in clouds the size of Cloud D transforms into stars." In the newly discovered Cloud D, however, the rate appears to be least ten times greater.

"This discovery is not an isolated find, but the temporary culmination of a long search which began with a faint radio emission in 1996," Prof. Beck observes. "We have been working for almost twenty years on extreme star formation. Along the way, we started asking why these clusters were being born at a precise time and a certain place. We are still hard at work on this, so this certainly isn't the end of the road for us."

In the future, Cloud D could be destroyed by stars that turn into supernovae — spinning all of the gas and elements into interstellar space. Prof. Beck said her team is continuing to study and monitor the galaxy using the Atacama Large Millimeter/submillimeter Arrray in Chile.

Co-authors of the research include S. Michelle Consiglio, a UCLA graduate student of Turner's; David Meier of the New Mexico Institute of Mining and Technology; Paul Ho of Taiwan's Academia Sinica Astronomy and Astrophysics; and Jun-Hui Zhao of the Harvard-Smithsonian Center for Astrophysics.

Water Was Plentiful in the Early Universe

Tel Aviv, Harvard University researchers discover water vapor may have formed in universe earlier than previously believed

Astronomers have long held that water — two hydrogen atoms and an oxygen atom — was a relative latecomer to the universe. They believed that any element heavier than helium had to have been formed in the cores of stars and not by the Big Bang itself. Since the earliest stars would have taken some time to form, mature, and die, it was presumed that it took billions of years for oxygen atoms to disperse throughout the universe and attach to hydrogen to produce the first interstellar "water."

New research poised for publication in Astrophysical Journal Letters by Tel Aviv University and Harvard University researchers reveals that the universe's first reservoirs of water may have formed much earlier than previously thought — less than a billion years after the Big Bang, when the universe was only 5 percent of its current age. According to the study, led by PhD student Shmuel Bialy and his advisor Prof. Amiel Sternberg of the Department of Astrophysics at TAU's School of Physics and Astronomy, in collaboration with Prof. Avi Loeb of Harvard's Astronomy Department, the timing of the formation of water in the universe bears important implications for the question of when life itself originated.

"Our theoretical model predicts that significant amounts of water vapor could form in molecular clouds in young galaxies, even though these clouds bear thousands of times less oxygen than that in our own galaxy today," said Bialy, the lead author of the study. "This was very surprising and raises important questions about the habitability of the first planets, because water is the key component of life as we know it."

Formation at 80 degrees F

For the purpose of the study, the researchers examined chemical reactions that led to the formation of water within the oxygen-poor environment of early molecular clouds. They found that at temperatures around 80 degrees Fahrenheit, the formation process became very efficient, and in the gas phase abundant water could form despite the relative lack of raw materials.

"The universe then was warmer than today and gas clouds were unable to cool effectively," said Prof. Sternberg. "Indeed the glow of the cosmic microwave background was hotter, and gas densities were higher," said Prof. Loeb, who also holds a Sackler Senior Professorship by special appointment in the School of Physics and Astronomy at TAU.

Because ultraviolet light from stars breaks down water molecules, an equilibrium between water formation and destruction could only be reached after hundreds of millions of years. The team found that the equilibrium in the early universe was similar to that measured in the universe today.

"We found that it is possible to build up significant quantities of water in the gas phase without much enrichment in heavy elements," said Bialy. "In this current work, we calculated how much water could exist in the gas phase within molecular clouds that would form later generations of stars and planets. In future research we intend to address questions such as how much water could have existed as interstellar ice, as in our own galaxy, and what fraction of all the water might actually be incorporated into newly-forming planetary systems."

This research was carried out as part of the joint Raymond and Beverly Sackler Tel Aviv University — Harvard Astronomy Program.

A New Spin on Saturn’s Peculiar Rotation

TAU researcher's new system to measure Saturn's rotation can be applied to other planets as well

SaturnTracking the rotation speed of solid planets, like the Earth and Mars, is a relatively simple task: Just measure the time it takes for a surface feature to roll into view again. But giant gas planets Jupiter and Saturn are more problematic for planetary scientists, as they both lack measureable solid surfaces and are covered by thick layers of clouds, foiling direct visual measurements by space probes. Saturn has presented an even greater challenge to scientists, as different parts of this sweltering ball of hydrogen and helium are known to rotate at different speeds, whereas its rotation axis and magnetic pole are aligned.

A new method devised by Tel Aviv University researcher Dr. Ravit Helled, published recently in Nature, proposes a new determination of Saturn's rotation period and offers insight into the internal structure of the planet, its weather patterns, and the way it formed. The method, by Dr. Helled of the Department of Geosciences at TAU's Raymond and Beverly Sackler Faculty of Exact Sciences and Drs. Eli Galanti and Yohai Kaspi of the Department of Earth and Planetary Sciences at the Weizmann Institute of Science, is based on Saturn's measured gravitational field and the unique fact that its east-west axis is shorter than its north-south axis.

According to the new method, Saturn's day is 10 hours, 32 minutes and 44 seconds long. When the researchers applied their method to Jupiter, whose rotation period is already well known, the results were identical to the conventional measurement, reflecting the consistency and accuracy of the method.

Between sunup and sundown on Saturn

For years, scientists have had difficulty coming up with a precise measurement of Saturn's rotation. "In the last two decades, the standard rotation period of Saturn was accepted as that measured by Voyager 2 in the 1980s: 10 hours, 39 minutes, and 22 seconds," said Dr. Helled. "But when the Cassini spacecraft arrived at Saturn 30 years later, the rotation period was measured as eight minutes longer. It was then understood that Saturn's rotation period could not be inferred from the fluctuations in radio radiation measurements linked to Saturn's magnetic field, and was in fact still unknown." The Cassini spacecraft had measured a signal linked to Saturn's magnetic field with a periodicity of 10 hours, 47 minutes and 6 seconds long — slower than previous recordings.

"Since then, there has been this big open question concerning Saturn's rotation period," said Dr. Helled. "In the last few years, there have been different theoretical attempts to pin down an answer. We came up with an answer based on the shape and gravitational field of the planet. We were able to look at the big picture, and harness the physical properties of the planet to determine its rotational period."

Helled's method is based on a statistical optimization method that involved several solutions. First, the solutions had to reproduce Saturn's observed properties (within their uncertainties): its mass and gravitational field. Then the researchers harnessed this information to search for the rotation period on which the most solutions converged.

Narrowing the margin of error

The derived mass of the planet's core and the mass of the heavy elements that make up its composition, such as rocks and water, are affected by the rotation period of the planet.

"We cannot fully understand Saturn's internal structure without an accurate determination of its rotation period," said Dr. Helled. Knowledge of Saturn's composition provides information on giant planet formation in general and on the physical and chemical properties of the solar nebula from which the solar system was formed.

"The rotation period of a giant planet is a fundamental physical property, and its value affects many aspects of the physics of these planets, including their interior structure and atmospheric dynamics," said Dr. Helled. "We were determined to make as few assumptions as possible to get the rotational period. If you improve your measurement of Saturn's gravitational field, you narrow the error margin."

The researchers hope to apply their method to other gaseous planets in the solar system such as Uranus and Neptune. Their new technique could also be applied in the future to study gaseous planets orbiting other stars.

Aiming High: TAU Research Leads to Historic Comet Landing

TAU's Prof. Akiva Bar-Nun has spent the last 35 years preparing the ground for the first-ever spacecraft landing on a comet


An image taken by the Philae lander as it descended toward the surface of Comet 67P/Churyumov-Gerasimenko. Photo: European Space Agency.

For the first time in history, a spacecraft has landed on a comet. The momentous event represents the culmination of 35 years of research on comets by Prof. Akiva Bar-Nun of Tel Aviv University's Department of Geosciences and other scientists working for the European Space Agency.

At 08:35 GMT on Wednesday, November 12, the European Space Agency's Rosetta satellite released its lander Philae towards Comet 67P/Churyumov-Gerasimenko, a large mass of ice and dust some 316 million miles from Earth. The descent took approximately seven hours, with a signal confirming touchdown received at Earth at around 16:00 GMT. The comet, shaped like a rubber duck with a narrow neck, is 2.5 miles long and 1.2 miles wide, roughly the size of central London. Its terrain is severe, studded with cliffs, steep slopes, and fissures. The Rosetta spacecraft, launched in 2004, is now flying with the comet, hovering just six miles over the nucleus to take measurements — and extraordinary pictures.

"The seeds for this mission took root during the 1986 visit of Halley's Comet," said Prof. Bar-Nun, a member of the Rosina group at the University of Bern. "The ESA's Giotto spacecraft passed by Halley, but remained more than 600 miles away from it. So a group of us, scientists from the US and Europe, got together to design a spacecraft that would not pass by a comet — but would instead fly with the comet and bring samples of its ice back to earth."

Taking its time

Comets hold vital clues about the original materials that went into building the solar system 4.5 billion years ago. The prize awaiting the successful landing is the opportunity to directly sample the organic material that may have prepared Earth for life 3.8 billion years ago.

"When we proposed to ESA to bring a sample back, they said, 'You have no idea what the mechanical strength of the ice is. How are you going to drill into it?'" Prof. Bar-Nun continued. "So we shifted the emphasis to what is now known as Rosetta — a spacecraft that could match the orbit and speed of the comet, staying with the comet for a year and a half and launch its probe at the appropriate time."

Life on ice

"Our TAU lab has been studying cometary ices for 35 years, and we are the only ones who are able to produce and study large ice samples, about eight inches wide and four inches high," said Prof. Bar-Nun. "According to data from a previous NASA mission called Deep Impact (from 2004), which recorded the imprint of a piece of metal in the comet's snowy surface, we know that the comet is covered by soft ice like newly-formed snow. This made it tricky for the Philae lander, which needs harpoons to latch onto the ice and screws to anchor the spacecraft legs to the surface.

"Comets stayed cold for 4.5 billion years, the age of the Solar System, and now one is coming right at us, heated by the sun, spewing gasses, dust, and ice particles," said Prof. Bar-Nun. "Mixed into this dust is a plethora of organic material that may have been brought to our planet by a comet and where, dissolved in the ocean, it prepared the scenario for the emergence of life on Earth."

The Rosetta mission is scheduled to last until December 2015, four months after the comet has made its closest approach to the sun and started to head back out to the more distant reaches of the solar system. The Philae lander could survive for up to three months, but its lifetime depends on whether it will be able to effectively recharge its batteries — and whether it can hang on tight as it swings through the solar system.

TAU's Space Observatory Scientists Observe Rare Astronomical Event

Pluto's "moon" obscures distant star in eclipse-like phenomenon

Astronomers at Tel Aviv University's Florence and George Wise Observatory used two telescopes last month to simultaneously observe the rare "covering" of a star some 50 light years from Earth by a distant solar system body.

In the first measurement of its kind at the observatory, TAU scientists used two telescopes on the night of March 4th to concurrently observe the covering of a distant star by an asteroid orbiting in the Pluto "family" at the outer edges of the solar system. Dr. Shai Kaspi and Dr. Noah Brosch of TAU's Raymond and Beverly Sackler Faculty of Exact Sciences viewed images from the two telescopes on different computer screens. By watching the telescope images, it became clear to the researchers that a star had disappeared, only to reappear 43 seconds later.

"These events are quite rare, primarily because not many celestial bodies are known in that part of the solar system, said Dr. Brosch. "Using two telescopes from the same site is new for us. There were a few similar events that we tried to observe previously, but with only one telescope. Using two telescopes improves the accuracy and, with an independent measurement, increases the reliability of the results."

The data obtained at the observatory is now being processed and compared to a similar event observed in December 2013 from Reunion Island in the Indian Ocean. The research was sponsored by astrophysicist Dr. Michael Shara, an alumnus of TAU and now curator of astrophysics at the American Museum of Natural History in New York; Dr. Michael Rich, an astrophysics researcher at UCLA; and their families.

For more, see the Jerusalem Post story:
http://www.jpost.com/Enviro-Tech/Distant-star-plays-peek-a-boo-with-TAU-astronomers-345170

New Study Finds the Early Universe "Warmed Up" Later than Previously Believed

TAU research suggests a way to detect the earliest black holes

A new study from Tel Aviv University reveals that black holes, formed from the first stars in our universe, heated the gas throughout space later than previously thought. They also imprinted a clear signature in radio waves which astronomers can now search for. The work is a major new finding about the origins of the universe.

"One of the exciting frontiers in astronomy is the era of the formation of the first stars," explains Prof. Rennan Barkana of TAU's School of Physics and Astronomy, an author of the study. "Since the universe was filled with hydrogen atoms at that time, the most promising method for observing the epoch of the first stars is by measuring the emission of hydrogen using radio waves."

The study, just published in the prestigious journal Nature, was co-authored by Dr. Anastasia Fialkov of TAU and the École Normale Supérieure in Paris and Dr. Eli Visbal of Columbia and Harvard Universities.

Cosmic archaeology

Astronomers explore our distant past, billions of years back in time. Unlike Earth-bound archaeologists, however, who can only study remnants of the past, astronomers can see the past directly. The light from distant objects takes a long time to reach the earth, and astronomers can see these objects as they were back when that light was emitted. This means that if astronomers look out far enough, they can see the first stars as they actually were in the early universe. Thus, the new finding that cosmic heating occurred later than previously thought means that observers do not have to search as far, and it will be easier to see this cosmic milestone.

Cosmic heating may offer a way to directly investigate the earliest black holes, since it was likely driven by star systems called "black-hole binaries." These are pairs of stars in which the larger star ended its life with a supernova explosion that left a black-hole remnant in its place. Gas from the companion star is pulled in towards the black hole, gets ripped apart in the strong gravity, and emits high-energy X-ray radiation. This radiation reaches large distances, and is believed to have re-heated the cosmic gas, after it had cooled down as a result of the original cosmic expansion. The discovery in the new research is the delay of this heating.

The cosmic radio show

"It was previously believed that the heating occurred very early," says Prof. Barkana, "but we discovered that this standard picture delicately depends on the precise energy with which the X-rays come out. Taking into account up-to-date observations of nearby black-hole binaries changes the expectations for the history of cosmic heating. It results in a new prediction of an early time (when the universe was only 400 million years old) at which the sky was uniformly filled with radio waves emitted by the hydrogen gas."

In order to detect the expected radio waves from hydrogen in the early universe, several large international groups have built and begun operating new arrays of radio telescopes. These arrays were designed under the assumption that cosmic heating occurred too early to see, so instead the arrays can only search for a later cosmic event, in which radiation from stars broke up the hydrogen atoms out in the space in-between galaxies. The new discovery overturns the common view and implies that these radio telescopes may also detect the tell-tale signs of cosmic heating by the earliest black holes.

Will the Start Up Nation Become the Blast Off Nation?

Will the Start Up Nation Become the Blast Off Nation?

"The time has come for an Israeli flag to be planted on the moon," says Israeli President Shimon Peres — and the groundwork for that journey is being laid at Tel Aviv University, according to an article in the May 3 issue of the Jewish Daily Forward.

SpaceIL, a non-profit organization, is designing a spacecraft only three feet tall and 300 pounds in weight as an entry in the Google Lunar X Prize, which offers $20 million to the first privately-funded team to successfully land a robot on the moon. Among those working on the project are engineers, but also a surprising number of students. That's only appropriate: The founder and CEO of SpaceIL, Yariv Bash, is a graduate of Tel Aviv University, and TAU president Prof. Joseph Klafter serves on the board of directors.

According to some scientists, the SpaceIL team has a good shot at success. "I think they have the know-how and most of the technology, and have a very good chance of being successful and winning the competition," said Aby Har-Even, former head of the Israel Space Agency. Peres agrees, telling the Forward, "I am proud of the youngsters who created this initiative, to put the first Israeli spacecraft on the moon, and I know that they can achieve it."

SpaceIL's entry is the only not-for-profit project among the 25 commercial entries also in development.

For the full story, see the Jewish Daily Forward article:
http://forward.com/articles/175464/one-giant-step-for-israel-as-company-plots-moon-la/?p=all


Looking for Life by the Light of Dying Stars

TAU finds white dwarf stars may hold the key to detecting life on other planets

Because it has no source of energy, a dead star — known as a white dwarf — will eventually cool down and fade away. But circumstantial evidence suggests that white dwarfs can still support habitable planets, says Prof. Dan Maoz of Tel Aviv University's School of Physics and Astronomy.

Now Prof. Maoz and Prof. Avi Loeb, Director of Harvard University's Institute for Theory and Computation and a Sackler Professor by Special Appointment at TAU, have shown that, using advanced technology to become available within the next decade, it should be possible to detect biomarkers surrounding these planets — including oxygen and methane — that indicate the presence of life.

Published in the Monthly Notices of the Royal Astronomical Society, the researchers' "simulated spectrum" demonstrates that the James Webb Space Telescope (JWST), set to be launched by NASA in 2018, will be capable of detecting oxygen and water in the atmosphere of an Earth-like planet orbiting a white dwarf after only a few hours of observation time — much more easily than for an Earth-like planet orbiting a sun-like star.

Their collaboration is made possible by the Harvard TAU Astronomy Initiative, recently endowed by Dr. Raymond and Beverly Sackler.

Faint light, clear signals

"In the quest for extraterrestrial biological signatures, the first stars we study should be white dwarfs," said Prof. Loeb. Prof. Maoz agrees, noting that if "all the conditions are right, we'll be able to detect signs of life" on planets orbiting white dwarf stars using the much-anticipated JWST.

An abundance of heavy elements already observed on the surface of white dwarfs suggest rocky planets orbit a significant fraction of them. The researchers estimate that a survey of 500 of the closest white dwarfs could spot one or more habitable planets.

The unique characteristics of white dwarfs could make these planets easier to spot than planets orbiting normal stars, the researchers have shown. Their atmospheres can be detected and analyzed when a star dims as an orbiting planet crosses in front of it. As the background starlight shines through the planet's atmosphere, elements in the atmosphere will absorb some of the starlight, leaving chemical clues of their presence — clues that can then be detected from the JWST.

When an Earth-like planet orbits a normal star, "the difficulty lies in the extreme faintness of the signal, which is hidden in the glare of the 'parent' star," Prof. Maoz says. "The novelty of our idea is that, if the parent star is a white dwarf, whose size is comparable to that of an Earth-sized planet, that glare is greatly reduced, and we can now realistically contemplate seeing the oxygen biomarker."

In order to estimate the kind of data that the JWST will be able to see, the researchers created a "synthetic spectrum," which replicates that of an inhabited planet similar to Earth orbiting a white dwarf. They demonstrated that the telescope should be able to pick up signs of oxygen and water, if they exist on the planet.

A critical sign of life

The presence of oxygen biomarkers would be the most critical signal of the presence of life on extraterrestrial planets. Earth's atmosphere, for example, is 21 percent oxygen, and this is entirely produced by our planet's plant life as a result of photosynthesis. Without the existence of plants, an atmosphere would be entirely devoid of oxygen.

The JWST will be ideal for hunting out signs of life on extraterrestrial planets because it is designed to look into the infrared region of the light spectrum, where such biomarkers are prominent. In addition, as a space-based telescope, it will be able to analyze the atmospheres of Earth-like planets outside our solar system without weeding out the similar signatures of Earth's own atmosphere.


Using Black Holes to Measure the Universe's Rate of Expansion

Radiation emitted in the vicinity of black holes could be used to measure distances of billions of light years, says TAU researcher

A few years ago, researchers revealed that the universe is expanding at a much faster rate than originally believed — a discovery that earned a Nobel Prize in 2011. But measuring the rate of this acceleration over large distances is still challenging and problematic, says Prof. Hagai Netzer of Tel Aviv University's School of Physics and Astronomy.

Now, Prof. Netzer, along with Jian-Min Wang, Pu Du and Chen Hu of the Institute of High Energy Physics of the Chinese Academy of Sciences and Dr. David Valls-Gabaud of the Observatoire de Paris, has developed a method with the potential to measure distances of billions of light years with a high degree of accuracy. The method uses certain types of active black holes that lie at the center of many galaxies. The ability to measure very long distances translates into seeing further into the past of the universe — and being able to estimate its rate of expansion at a very young age.

Published in the journal Physical Review Letters, this system of measurement takes into account the radiation emitted from the material that surrounds black holes before it is absorbed. As material is drawn into a black hole, it heats up and emits a huge amount of radiation, up to a thousand times the energy produced by a large galaxy containing 100 billion stars. For this reason, it can be seen from very far distances, explains Prof. Netzer.

Solving for unknown distances

Using radiation to measure distances is a general method in astronomy, but until now black holes have never been used to help measure these distances. By adding together measurements of the amount of energy being emitted from the vicinity of the black hole to the amount of radiation which reaches Earth, it's possible to infer the distance to the black hole itself and the time in the history of the universe when the energy was emitted.

Getting an accurate estimate of the radiation being emitted depends on the properties of the black hole. For the specific type of black holes targeted in this work, the amount of radiation emitted as the object draws matter into itself is actually proportional to its mass, say the researchers. Therefore, long-established methods to measure this mass can be used to estimate the amount of radiation involved.

The viability of this theory was proved by using the known properties of black holes in our own astronomical vicinity, "only" several hundred million light years away. Prof. Netzer believes that his system will add to the astronomer's tool kit for measuring distances much farther away, complimenting the existing method which uses the exploding stars called supernovae.

Illuminating "Dark Energy"

According to Prof. Netzer, the ability to measure far-off distances has the potential to unravel some of the greatest mysteries of the universe, which is approximately 14 billion years old. "When we are looking into a distance of billions of light years, we are looking that far into the past," he explains. "The light that I see today was first produced when the universe was much younger."

One such mystery is the nature of what astronomers call "dark energy," the most significant source of energy in the present day universe. This energy, which is manifested as some kind of "anti-gravity," is believed to contribute towards the accelerated expansion of the universe by pushing outwards. The ultimate goal is to understand dark energy on physical grounds, answering questions such as whether this energy has been consistent throughout time and if it is likely to change in the future.


Seeing the Birth of the Universe in an Atom of Hydrogen

TAU uses radio waves to uncover oldest galaxies yet

Windows to the past, stars can unveil the history of our universe, currently estimated to be 14 billion years old. The farther away the star, the older it is — and the oldest stars are the most difficult to detect. Current telescopes can only see galaxies about 700 million years old, and only when the galaxy is unusually large or as the result of a big event like a stellar explosion.

Now, an international team of scientists led by researchers at Tel Aviv University have developed a method for detecting galaxies of stars that formed when the universe was in its infancy, during the first 180 million years of its existence. The method is able to observe stars that were previously believed too old to find, says Prof. Rennan Barkana of TAU's School of Physics and Astronomy.

Published in the journal Nature, the researchers' method uses radio telescopes to seek out radio waves emitted by hydrogen atoms, which were abundant in the early days of the universe. Emitting waves measuring about eight inches (21 centimeters) long, the atoms reflect the radiation of the stars, making their emission detectable by radio telescopes, explains Prof. Barkana. This development opens the way to learning more about the universe's oldest galaxies.

Reading signals from the past

According to Prof. Barkana, these waves show a specific pattern in the sky, a clear signature of the early galaxies, which were one-millionth the size of galaxies today. Differences in the motion of dark matter and gas from the early period of the universe, which affect the formation of stars, produce a specific fluctuation pattern that makes it much easier to distinguish these early waves from bright local radio emissions.

The intensity of waves from this early era depends on the temperature of the gas, allowing researchers to begin to piece together a rough map of the galaxies in an area of the sky. If the gas is very hot, it means that there are many stars there; if cooler, there are fewer stars, explains Prof. Barkana.

These initial steps into the mysterious origins of the universe will allow radio astronomers to reconstruct for the first time what the early universe looked like, specifically in terms of the distribution of stars and galaxies across the sky, he believes.

A new era

This field of astronomical research, now being called "21-centimeter cosmology," is just getting underway. Five different international collaborations are building radio telescopes to detect these types of emissions, currently focusing on the era around 500 million years after the Big Bang. Equipment can also be specifically designed for detecting signals from the earlier eras, says Prof. Barkana. He hopes that this area of research will illuminate the enigmatic period between the birth of the universe and modern times, and allow for the opportunity to test predictions about the early days of the universe.

"We know a lot about the pristine universe, and we know a lot about the universe today. There is an unknown era in between when there was hot gas and the first formation of stars. Now, we are going into this era and into the unknown," says Prof. Barkana. He expects surprises along the way, for example involving the properties of early stars, and that observations will reveal a more complicated cosmological reality than was predicted by their models.


Planets Circling Around Twin Suns

In the last two decades, the study of extrasolar planets — those that lie outside our own solar system — has become one of the most important fields of astrophysics. Now a National Aeronautics and Space Administration (NASA) team that includes Prof. Tsevi Mazeh of Tel Aviv University's Department of Astronomy and Astrophysics and the Director of the Wise Observatory has discovered two new planets, named Kepler-34 and Kepler-35, each of which revolves around its own double suns. Together with Kepler-16, discovered a few months ago, there are now three such known systems in the galaxy.

According to Prof. Mazeh, these discoveries indicate that planets revolving around binary suns (suns that are formed as a pair) are a common phenomenon. Double stars or suns are typical in the universe, and now we know that planets can orbit around these intriguing phenomena, he says.

The team discovered the planets, which are 5,000 light years from Earth in the Cygnus constellation, by measuring the light emitted by the double suns. The data was collected by NASA's Kepler satellite, and the results recently published in the journal Nature.

It takes two

Most suns in the universe exist in pairs, explains Prof. Mazeh. These partnerships closely mimic human relationships — if two suns are formed together, they stay together, unless a third star comes too close to the pair and breaks the bond between the two. Our solar system, which revolves around one sun, is more unusual, though we can't dismiss the possibility that our sun has an undiscovered distant companion, he says. And while the phenomenon of binary stars has been well known for centuries, the recent discoveries prove that binary suns can also support planets.

Each sun in these systems revolves around its mate in a regular, cyclical pattern. During sunsets on Kepler-34 and Kepler-35, one sun will descend first, followed by a twilight period. Afterwards, the second sun will set and night will fall. In Hebrew, the word for twilight means "between the suns," explains Prof. Mazeh, saying that the translation is an accurate description of what twilight is like on these newly discovered planets. Kepler-34 revolves around its double sun every 289 days, Kepler-35 every 131 days.

This discovery provides a unique opportunity to learn about solar systems that are very different from our own, says Prof. Mazeh. In the future, more research will be done on the planets themselves, including their possible atmospheres and the rotation of the planets.

A limitless universe

An expert in extrasolar planets and recent recipient of the Weizmann Prize for Excellence in Science, Prof. Mazeh is grateful to be working with the Kepler team. When he began his work in the early 1980s, it was widely believed that all planets and suns must be similar to the ones within our own solar system. And this simply isn't the case, he says.

"We shouldn't limit our search by assuming that all the planets are like those in our solar system. Some of them are very different from what we have here, and every time we find a new planet, we're explorers landing on unknown territory.

"The sky is not the limit," he smiles.


Two Nations' Leading Universities to Collaborate in the Stars

TAU and Harvard University announce joint astrophysics initiative

Tel Aviv University and Harvard University have launched the new Raymond and Beverly Sackler Harvard–Tel Aviv Astronomy Initiative, a collaboration between the Department of Astrophysics at TAU's Raymond and Beverly Sackler School of Physics and Astronomy and the Institute for Theory and Computation (ITC) at the Harvard–Smithsonian Center for Astrophysics.

Funded by renowned philanthropist Dr. Raymond Sackler, the program will support research across all areas of astrophysics. "This important new collaboration builds on the world-renowned research infrastructures at Harvard and TAU. It provides a framework for a mutually beneficial and productive collaboration between two of the world's great universities," says Prof. Amiel Sternberg, director of the program at TAU. The initiative includes not only joint projects among the faculty, but also student exchanges, a lecture series, and workshops held in Tel Aviv every two years.

As part of the new program, TAU will also be offering a prize post-doctoral position called the Sackler Prize Fellowship in Astrophysics, with shared time at both institutions, to support and promote the independent projects of outstanding young researchers.

"We are grateful to Dr. Sackler for establishing this program," says Prof. Avi Loeb, Director of the ITC and Chair of the Astronomy Department at Harvard, "and we look forward to building a productive relationship with TAU."

The Department of Astronomy at TAU is internationally recognized as a leading research group. Two of its faculty members were recently awarded prestigious European Council Research grants of more than $2,000,000 each, to support the studies of the physics of cosmic explosions and searches for extrasolar planets. An Israel-Germany science partnership grant, $1,500,000 for astronomers at TAU and Max-Planck-Institute for Extraterrestrial Physics, supports observational and theoretical studies of galaxy formation and black hole growth in the early universe.


Lightning Sprites Are Out-of-This-World

TAU researchers predict "sprites" in the atmospheres of Jupiter, Saturn, and Venus

Only a few decades ago, scientists discovered the existence of "sprites" 30 to 55 miles above the surface of the Earth. They're offshoots of electric discharges caused by lightning storms, and a valuable window into the composition of our atmosphere. Now researchers at Tel Aviv University say that sprites are not a phenomenon specific to our planet.

Jupiter and Saturn experience lightning storms with flashes 1,000 or more times more powerful than those on Earth, says Ph.D. student Daria Dubrovin. With her supervisors Prof. Colin Price of TAU's Department of Geophysics and Planetary Sciences and Prof. Yoav Yair of the Open University of Israel, and collaborators Prof. Ute Ebert and Dr. Sander Nijdam from the Eindhoven Technical University in Holland, Dubrovin has re-created these planetary atmospheres in the lab to study the presence of sprites in space.

The color of these bursts of electricity indicate what kinds of molecules are present and may explain the presence of exotic compounds, while providing insight into the conductivity of distant planets’ atmospheres. This research, which was presented in October at the European Planetary Science Congress in France, could lead to a new understanding of electrical and chemical processes on Jupiter, Saturn, and Venus.

A bolt of extraterrestrial life?

Though a little-known atmospheric phenomenon, sprites are quite common on Earth, says Dubrovin. Because they occur in the mesosphere — a layer of the atmosphere that is not regularly observed by satellites and too high to be reached by atmospheric balloons — the discovery of these electric discharges, which are red in color and last only a few tens of milliseconds, was a stroke of luck.

Lightning, as a generator of organic molecules, is credited for contributing to the "primordial soup" that, according to current theories, led to the emergence of life on Earth. Researchers are keen to know more about the possibility of lightning on other planets, explains Dubrovin, not only because it impacts the technological equipment used by space programs, but because it is another clue that could indicate the presence of extraterrestrial life.

To test for the viability of extraterrestrial sprites, Dubrovin and her fellow researchers re-created the atmospheres of Jupiter, Saturn, and Venus in small containers. A circuit that creates strong short-voltage pulses produced a discharge that mimics natural sprites. Images of these discharges, known as streamers, were taken by a fast and sensitive camera, then analyzed. Quantifying factors such as brightness, color, size, radius, and speed could help researchers measure how powerful extraterrestrial lightning actually is, she notes. "We make sprites-in-a-bottle," says Dubrovin, smiling.

Continuing a legacy

Dubrovin believes that the team's predictions could convince scientists operating the Cassini spacecraft — now orbiting Saturn as part of an ESA/NASA mission — to point their cameras in a new direction. Currently, she says, there is a huge lightning storm occurring on Saturn producing at least 100 lightning discharges per second — a rare event that happens approximately once in a decade. Above the lightning-producing clouds in Jupiter's and Saturn's atmosphere, Dubrovin explains, lies a layer of clouds which partly obscure the light from the flashes. If researchers were able to obtain an image of the higher-up sprites from the Cassini craft, it would enable them to gain more information about the storm below.

The research is a collaboration of TAU, the Open University, and the Eindhoven Technical University, and is funded by the Israeli Science Foundation (ISF) and by an Ilan Ramon Scholarship and Endowment, named after the Israeli astronaut who flew on the Columbia space shuttle, through the Israeli Ministry of Science. Part of the scientific research aboard that shuttle was on sprites, notes Dubrovin, who is happy to continue the famous Israeli astronaut's legacy.


Most Ancient Supernovas Are Discovered

Supernovas — stars in the process of exploding — open a window onto the history of the elements of Earth's periodic table as well as the history of the universe. All of those heavier than oxygen were formed in nuclear reactions that occurred during these explosions.

The most ancient explosions, far enough away that their light is reaching us only now, can be difficult to spot. A project spearheaded by Tel Aviv University researchers has uncovered a record-breaking number of supernovas in the Subaru Deep Field, a patch of sky the size of a full moon. Out of the 150 supernovas observed, 12 were among the most distant and ancient ever seen.

The discovery sharpens our understanding of the nature of supernovas and their role in element formation, say study leaders Prof. Dan Maoz, Dr. Dovi Poznanski and Or Graur of TAU's Department of Astrophysics at the Raymond and Beverly Sackler School of Physics and Astronomy. These "thermonuclear" supernovas in particular are a major source of iron in the universe.

The research, which appears in the Monthly Notices of the Royal Astronomical Society this month, was done in collaboration with teams from a number of Japanese and American institutions, including the University of Tokyo, Kyoto University, the University of California Berkeley, and Lawrence Berkeley National Laboratory.

A key element of the universe

Supernovas are nature's "element factories." During these explosions, elements are both formed and flung into interstellar space, where they serve as raw materials for new generations of stars and planets. Closer to home, says Prof. Maoz, "these elements are the atoms that form the ground we stand on, our bodies, and the iron in the blood that flows through our veins." By tracking the frequency and types of supernova explosions back through cosmic time, astronomers can reconstruct the universe's history of element creation.

In order to observe the 150,000 galaxies of the Subaru Deep Field, the team used the Japanese Subaru Telescope in Hawaii, on the 14,000-foot summit of the extinct Mauna Kea volcano. The telescope's light-collecting power, sharp images, and wide field of view allowed the researchers to overcome the challenge of viewing such distant supernovas.

By "staring" with the telescope at the Subaru Deep Field, the faint light of the most distant galaxies and supernovas accumulated over several nights at a time, forming a long and deep exposure of the field. Over the course of observations, the team "caught" the supernovas in the act of exploding, identifying 150 supernovas in all.

Sourcing man's life-blood

According to the team's analysis, thermonuclear type supernovas, also called Type-la, were exploding about five times more frequently 10 billion years ago than they are today. These supernovas are a major source of iron in the universe, the main component of the Earth's core and an essential ingredient of the blood in our bodies.

Scientists have long been aware of the "universal expansion," the fact that galaxies are receding from one another. Observations using Type-Ia supernovas as beacons have shown that the expansion is accelerating, apparently under the influence of a mysterious "dark energy" — the 2011 Nobel Prize in Physics will be awarded to three astronomers for this work. However, the nature of the supernovas themselves is poorly understood. This study improves our understanding by revealing the range of the ages of the stars that explode as Type-Ia supernovas. Eventually, this will enhance their usefulness for studying dark energy and the universal expansion, the researchers explain.


When the Black Hole Was Born

Most galaxies in the universe, including our own Milky Way, harbor super-massive black holes varying in mass from about one million to about 10 billion times the size of our sun. To find them, astronomers look for the enormous amount of radiation emitted by gas which falls into such objects during the times that the black holes are "active," i.e., accreting matter. This gas "infall" into massive black holes is believed to be the means by which black holes grow.

Now a team of astronomers from Tel Aviv University, including Prof. Hagai Netzer and his research student Benny Trakhtenbrot, have determined that the era of first fast growth of the most massive black holes occurred when the universe was only about 1.2 billion years old — not two to four billion years old, as was previously believed — and they're growing at a very fast rate.

The results will be reported in a new paper soon to appear in Astrophysical Journal.

The oldest are growing the fastest

The new research is based on observations with some of the largest ground-based telescopes in the world: "Gemini North" on top of Mauna Kea in Hawaii, and the "Very Large Telescope Array" on Cerro Paranal in Chile. The data obtained with the advanced instrumentation on these telescopes show that the black holes that were active when the universe was 1.2 billion years old are about ten times smaller than the most massive black holes that are seen at later times. However, they are growing much faster. The measured rate of growth allowed the researchers to estimate what happened to these objects at much earlier as well as much later times. The team found that the very first black holes, those that started the entire growth process when the universe was only several hundred million years old, had masses of only 100-1000 times the mass of the sun. Such black holes may be related to the very first stars in the universe. They also found that the subsequent growth period of the observed sources, after the first 1.2 billion years, lasted only 100-200 million years.

The team found that the very first black holes — those that started growing when the universe was only several hundred million years old — had masses of only 100-1000 times the mass of the sun. Such black holes may be related to the very first stars in the universe. They also found that the subsequent growth period of these black holes, after the first 1.2 billion years, lasted only 100-200 million years.

The new study is the culmination of a seven year-long project at Tel Aviv University designed to follow the evolution of the most massive black holes and compare them with the evolution of the galaxies in which such objects reside.

Other researchers on the project include Prof. Ohad Shemmer of the University of North Texas, who took part in the earlier stage of the project as a Ph.D student at Tel Aviv University, and Prof. Paulina Lira, from the University of Chile.

Avoiding an Asteroid Collision

Though it was once believed that all asteroids are giant pieces of solid rock, later hypotheses have it that some are actually a collection of small gravel-sized rocks, held together by gravity. If one of these "rubble piles" spins fast enough, it's speculated that pieces could separate from it through centrifugal force and form a second collection — in effect, a second asteroid.

Now researchers at Tel Aviv University, in collaboration with an international group of scientists, have proved the existence of these theoretical "separated asteroid" pairs.

Ph.D. student David Polishook of Tel Aviv University's Department of Geophysics and Planetary Sciences and his supervisor Dr. Noah Brosch of the university's School of Physics and Astronomy say the research has not only verified a theory, but could have greater implications if an asteroid passes close to earth. Instead of a solid mountain colliding with earth's surface, says Dr. Brosch, the planet would be pelted with the innumerable pebbles and rocks that comprise it, like a shotgun blast instead of a single cannonball. This knowledge could guide the defensive tactics to be taken if an asteroid were on track to collide with the Earth.

A large part of the research for the study, recently published in the journal Nature, was done at Tel Aviv University's Wise Observatory, located deep in the Negev Desert — the first and only modern astronomical observatory in the Middle East.

Spinning out in space

According to Dr. Brosch, separated asteroids are composed of small pebbles glued together by gravitational attraction. Their paths are affected by the gravitational pull of major planets, but the radiation of the sun, he says, can also have an immense impact. Once the sun's light is absorbed by the asteroid, rotation speeds up. When it reaches a certain speed, a piece will break off to form a separate asteroid.

The phenomenon can be compared to a figure skater on the ice. "The faster they spin, the harder it is for them to keep their arms close to their bodies," explains Dr. Brosch.

As a result, asteroid pairs are formed, characterized by the trajectory of their rotation around the sun. Though they may be millions of miles apart, the two asteroids share the same orbit. Dr. Brosch says this demonstrates that they come from the same original asteroid source.

Looking into the light

During the course of the study, Polishook and an international group of astronomers studied 35 asteroid pairs. Traditionally, measuring bodies in the solar system involves studying photographic images. But the small size and extreme distance of the asteroids forced researchers to measure these pairs in an innovative way.

Instead, researchers measured the light reflected from each member of the asteroid pairs. The results proved that in each asteroid pair, one body was formed from the other. The smaller asteroid, he explains, was always less than forty percent of the size of the bigger asteroid. These findings fit precisely into a theory developed at the University of Colorado at Boulder, which concluded that no more than forty percent of the original asteroid can split off.

With this study, says Dr. Brosch, researchers have been able to prove the connection between two separate spinning asteroids and demonstrate the existence of asteroids that exist in paired relationships.


Reaching for the Stars

Prof. Tsvi Mazeh of Tel Aviv University's Physics and Astronomy School was the only Israeli on an international team that recently discovered seven new planets outside of our solar system, The Jerusalem Post reported last week.

Prof. Mazeh and his partners found the planets through the use of the CoRoT space telescope, launched on December 27, 2006, by the National Space Studies Center in France and CNRS French laboratories. The planets were detected by measuring small black spots visible on the surfaces of their respective suns as the planets passed in front of them.

Each new planet is a "new world about which we had no idea before the CoRoT observations," Prof. Mazeh told The Jerusalem Post. "We are like Columbus, who sailed his ships beyond the horizon to worlds that excited the imagination. But unlike Columbus, who found countries whose nature and weather were similar to what he left behind, in our case the planets are so different and so distant. Surprises beyond our telescopes can rise above our imaginations."

To find out more about how TAU scientists are providing new knowledge about our own solar system and beyond, read the full Jerusalem Post article here:
http://www.jpost.com/Home/Article.aspx?id=178456


Shining a Light Around Corners

We learned in science class that light beams travel in straight lines and spread through a process known as diffraction — and they can't go around corners. But now researchers at Tel Aviv University are investigating new applications for their recent discovery that small beams of light can indeed be bent in a laboratory setting, diffracting much less than a "regular" beam.

These rays, called "Airy beams," were named after English astronomer Sir George Biddell Airy, who studied the parabolic trajectories of light in rainbows, and were first created at the University of Central Florida. Now, the fortuitously-named Prof. Ady Arie and his graduate students Tal Ellenbogen, Noa Voloch-Bloch, Ayelet Ganany-Padowicz and Ido Dolev of Tel Aviv University's Faculty of Engineering have demonstrated new ways to generate and control Airy beams. Employing new algorithms and special nonlinear optical crystals, their research is reported in a recent issue of the scientific journal Nature Photonics.

Some of these new applications, such as a light source to generate beams that can turn around corners, or lighted spaces that contain no apparent light source, are still five or ten years away, says Prof. Arie. But his research has immediate applications as well. For example, because small particles are attracted to the highest intensities of a beam, the pharmaceutical and chemical industries can use the new beam to sort molecules according to size or quality, filtering impurities from drug formulations that might otherwise lead to toxicity and death.

A light that can twist around curves

Until now, reports an editorial review in the same issue of Nature Photonics, Airy beams have been generated through "linear diffraction" using tools that project a single color of light through glass plates of varying thicknesses. But using crystals they built in the lab, Tel Aviv University's approach uses another technique: nonlinear optics. Sent through crystals, light waves bounce inside the crystal, changing their wavelength and color. It is through this process, the researchers say, that the door is opened for creating new light beams at new wavelengths with greater control of their trajectories.

"We've found a way to control whether an Airy beam curves to the left or to the right, for example," says Prof. Arie. He has also found a way to control the peak intensity location of the beams, which are generated through a nonlinear optical process.

Nonlinear optics is a sub-field of optics that deals with the response of materials to high intensities of light. The strong interaction between light and material results in the generation of new colors, which are half the wavelength of the original input light frequency. For example, a nonlinear response to infrared light can generate visible light — which is how those bright, green "laser pointers," often used in presentations given in large rooms, generate their light.

Airy beams promise remarkable advances for engineering. They could form the technology behind space-age "light bullets" — as effective and precise defense technologies for police and the military, but also as a new communications interface between transponders. As tiny, tight packets of information, these Airy beams could be used out in the open air, researchers hope.


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