News Article | February 27, 2017
In 2000, I attended the annual conference for science fiction writers in Chengdu, China, organised by the locally based magazine Science Fiction World. Many of the writers were young, the hotel was modest, the cups of tea endless and each day had to be opened by a long speech from an official representative of the Communist Party of China. At the time, Chinese sci-fi, though its history was already a century long, was virtually unknown in the West. Yet 15 years later, one of the authors in attendance – a computer engineer named Liu Cixin, still two years away from publishing his first novel – won the Hugo Award for Best Novel for his The Three-Body Problem (translated by Ken Liu). I was a long-haired backpacker when I arrived in Beijing on a night bus from the Mongolian border. As a science fiction writer, I’d wondered what the Chinese scene had to offer – assuming there even was one. All I could find on the nascent web was a single email address, for a Professor Wu Yan, who taught China’s only university class on science fiction. It was no surprise that his course seemed old fashioned to me: Arthur C. Clarke and Isaac Asimov featured heavily. But Wu was smarter than his teaching materials, and he knew everyone. In the years since, I’ve been able to observe first-hand the emergence of Chinese sci-fi into the anglophone mainstream. And I was able to do my bit, publishing a string of first translations. Over its history, Chinese science fiction has been affected by the same political forces that shook the rest of the country. The first translations of foreign sci-fi (predominantly Jules Verne and H. G. Wells) came to China in the first decade of the 20th century (initially via Japanese). Little domestic science fiction was published during the revolutionary turbulence of the following decades. Among the Chinese sci-fi books of this period, perhaps the best known in the West is Lao She’s Cat Country (1932), a novel satirising the vanishing order of the old China, in which a human astronaut crash-lands on Mars and encounters the alien felines who live there. The start of the communist era in 1949 ushered in a host of translations from Soviet sci-fi – the works of Alexander Belyaev, the “Russian Jules Verne”, were particularly popular – and a new dedication to a form of literature that promoted science and scientific achievement in pursuit of socialist industrialisation. Despite most of these works being written for children, they were still full of political content. But science fiction in China has always been intimately linked with the dictates of changing politics – and during the mass economic and ideological purges Chairman Mao launched during the Cultural Revolution of 1966-1976, sci-fi was effectively banned. The author Zheng Wenguang, considered by some as the father of Chinese science fiction, and who wrote much sci-fi for children alongside popular non-fiction, suffered personally during this period. He had been a research fellow at the Beijing Astronomical Observatory. “I had to give up my pen and go to the countryside,” he wrote. “I worked as a peasant. I grew rice and fed livestock.” My old friend Wu Yan’s love for science fiction emerged during his childhood in the Cultural Revolution. He recalled a time when books were banned, and had to be exchanged furtively and read in secret. “We were told that all the books were bourgeois dirt. We stole the dirt and read them crazily,” he said. Following Mao’s death, Deng Xiaoping rose to power in 1978. He reversed his predecessor’s economic policies, ushering in an era of rapid development and improved relations with the West. In this environment, and prompted by Deng’s statement that “science and technology is the number one productive force”, sci-fi flourished again. One domestic hit of this time was Ye Yonglie’s Little Know-all Travels Around the Future World (1978), which offered a fictional reporter’s snapshots of the future. The novel and its comic-book adaptations sold 3 million copies. Later, Rao Zhonghua’s three-volume Compendium of Chinese Science Fiction (1982) served to define Chinese sci-fi up to that point. And Robert Silverberg’s Science Fiction Hall of Fame, which collected the best stories from the “golden age” of US sci-fi, became an important cornerstone for Chinese perceptions of the Western form of this genre. In the 1980s, science fiction once again fell foul of the ruling party, as a new “Anti-Spiritual Pollution Campaign” emerged as a backlash to Deng Xiaoping’s modernisation and liberalisation policies. Deng’s opponents in the party railed against Western “bourgeois imports” of all kinds, and with sci-fi seeming to fall firmly in that category, it was all but wiped out for a time. The genre’s recovery was partly led by the emergence of Science Fiction World magazine in Chengdu, and its energetic editor, Yang Xiao, herself the daughter of a prominent party member. Having such influential backing allowed Science Fiction World to bring together many young writers for an “appropriate” reason. By the end of the century, Chinese sci-fi entered its own golden age. Although the authorities still raised the issue of literary “appropriateness”, the old restrictions had gone. One prominent contemporary sci-fi author is Han Song, a journalist at the state news agency Xinhua. Many of his works are only published outside the mainland due to their political themes, but Han is still widely recognised at home. His fiction can be dark and melancholy, envisioning, for instance, a spacefarer building tombstones to fellow astronauts, or the Beijing subway system being turned into a graveyard in which future explorers, arriving back on Earth, find themselves trapped on a fast-moving train. Along with Liu Cixin and Wang Jinkang, he is considered one of the “Three Generals” of Chinese sci-fi. Han is wary of Western ideology, once telling China Daily that “I often had a feeling that there would be a crisis in Western society, that it won’t be able to sustain itself on its present set of values”, and questioning its relevance to Chinese society. In his landmark 2066: Red Star Over America (2000), he envisions a world dominated by China, in which a fractured US is in decline. The book , which imagines a large-scale terrorist attack on the World Trade Center, earned notoriety for being published just months before the events of 11 September 2001. Han believes sci-fi “is seen as unreal and inconsequential” in China, but not everyone would agree: Chinese science fiction is a diverse field, and today’s writers develop approaches and ideas very different from one another. Thanks to the tireless work of Chinese-American author Ken Liu, one can now pick up the anthology Invisible Planets (2016), which collects all his recent translations of writers such as Tang Fei, Ma Boyong, Xia Jia or Hao Jingfang (author of the Hugo-winning “Folding Beijing”), or read Liu Cixin’s surprise bestseller The Three-Body Problem. The US-based online magazine Clarkesworld, meanwhile, now publishes monthly translations of Chinese short stories in partnership with Chinese company Storycom. As China reaches for the stars, with plans for a permanent space station, lunar exploration and a mission to Mars, its writers continue to explore the ramifications of a changing world – and the role China will play in it. With the country’s huge new reach into emerging markets in Africa and the Pacific, and its expressed willingness to play a new leadership role in global events, its future has never been more interesting – or more pertinent.
Samurovic S.,Astronomical Observatory
Astronomy and Astrophysics | Year: 2014
Context. The departures from Newtonian dynamics based on the mass-follows-light approach discovered in the outer parts of some early-type galaxies imply the existence of dark matter and/or necessary modifications to the Newtonian approach. We study dynamical models of a sample of ten early-type galaxies in both Newtonian and MOND approaches. Aims. The measurements of the radial velocities of the globular clusters in ten massive early-type galaxies are used to test the predictions of dynamical models with and without dark matter assuming Newtonian and MOND approaches out to several effective radii. Methods. The globular clusters taken from the SLUGGS database are used as tracers of the gravitational potential of the galaxies in a sample. We solve the Jeans equation for both the Newtonian (mass-follows-light and dark matter models) and the MOND approaches by assuming spherical symmetry and compare the resulting mass-to-light ratios with stellar population synthesis models. For both approaches, we apply various assumptions on velocity anisotropy. Results. We find that the Newtonian mass-follows-light models without a significant amount of dark matter can provide successful fits for only one galaxy (NGC 2768), and for the remaining nine early-type galaxies, various amounts of dark matter are required in the outer parts beyond 2-3Re. With MOND models, we find that four early-type galaxies could be fit without dark matter and that the remaining six galaxies require an additional dark component to successfully fit the line-of-sight observed velocity dispersions; the galaxy NGC 4486 (M 87) is the only galaxy for which dark matter is required in the inner regions, and MOND cannot fit the data without additional dark matter. In the inner region, the galaxy NGC 4365 requires higher mass-to-light ratios than the stellar values from population synthesis, but a reasonable mass-to-light ratio can be reached for MOND assuming slightly tangential orbits. The ten galaxies can be split into two classes: those with concentrations at (NGC 1407) or above the ΛCDM concentration-mass relation, given their measured virial masses, and those below this relation. The former generally require dark matter in both Newtonian and MOND approaches, while the latter do not require appreciable amounts of dark matter. © 2014 ESO .
Jovanovic P.,Astronomical Observatory
New Astronomy Reviews | Year: 2012
Here we present an overview of some of the most significant observational and theoretical studies of the broad Fe Kα spectral line, which is believed to originate from the innermost regions of relativistic accretion disks around central supermassive black holes of galaxies. The most important results of our investigations in this field are also listed. All these investigations indicate that the broad Fe Kα line is a powerful tool for studying the properties of the supermassive black holes (such as their masses and spins), space-time geometry (metric) in their vicinity, their accretion physics, probing the effects of their strong gravitational fields, and for testing the certain predictions of General Relativity. © 2011 Elsevier B.V.
Popovic L.T.,Astronomical Observatory
New Astronomy Reviews | Year: 2012
It is now agreed that mergers play an essential role in the evolution of galaxies and therefore that mergers of supermassive black holes (SMBHs) must have been common. We see the consequences of past supermassive binary black holes (SMBs) in the light profiles of so-called 'core ellipticals' and a small number of SMBs have been detected. However, the evolution of SMBs is poorly understood. Theory predicts that SMBs should spend a substantial amount of time orbiting at velocities of a few thousand kilometers per second. If the SMBs are surrounded by gas observational effects might be expected from accretion onto one or both of the SMBHs. This could result in a binary Active Galactic Nucleus (AGN) system. Like a single AGN, such a system would emit a broad band electromagnetic spectrum and broad and narrow emission lines. The broad emission spectral lines emitted from AGNs are our main probe of the geometry and physics of the broad line region (BLR) close to the SMBH. There is a group of AGNs that emit very broad and complex line profiles, showing two displaced peaks, one blueshifted and one redshifted from the systemic velocity defined by the narrow lines, or a single such peak. It has been proposed that such line shapes could indicate an SMB system. We discuss here how the presence of an SMB will affect the BLRs of AGNs and what the observational consequences might be. We review previous claims of SMBs based on broad line profiles and find that they may have non-SMB explanations as a consequence of a complex BLR structure. Because of these effects it is very hard to put limits on the number of SMBs from broad line profiles. It is still possible, however, that unusual broad line profiles in combination with other observational effects (line ratios, quasi-periodical oscillations, spectropolarimetry, etc.) could be used for SMBs detection. Some narrow lines (e.g., [O III]) in some AGNs show a double-peaked profile. Such profiles can be caused by streams in the Narrow Line Region (NLR), but may also indicate the presence of a kilo-parsec scale mergers. A few objects indicated as double-peaked narrow line emitters are confirmed as kpc-scale margers, but double-peaked narrow line profiles are mostly caused by the complex NLR geometry. We briefly discuss the expected line profile of broad Fe Kα that probably originated in the accretion disk(s) around SMBs. This line may also be very complex and indicate the complex disk geometry or/and an SMB presence. Finally we consider rare configurations where a SMB system might be gravitationally lensed by a foreground galaxy, and discuss the expected line profiles in these systems. © 2012 Elsevier B.V.
News Article | February 28, 2017
The first dataset from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) was released to the public on February 27th, 2017. HSC-SSP is a large survey being done using HSC, which is an optical imaging camera mounted at the prime focus of the Subaru Telescope. HSC has 104 scientific CCDs (for a total of 870 million pixels) and a 1.77 square-degree field of view. The National Astronomical Observatory of Japan (NAOJ) has embarked on the HSC-SSP survey in collaboration with the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) in Japan, the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan, and Princeton University in the United States. The project will take 300 nights over 5-6 years. This survey consists of three layers; Wide, Deep, and UltraDeep, using optical and near infrared wavelengths in five broad bands (g, r, i, z, y) and four narrow-band filters. This release includes data from the first 1.7 years (61.5 nights of observations beginning in 2014). The observed areas covered by the Wide, Deep, and UltraDeep layers are 108, 26, and 4 square degrees, respectively. The limiting magnitudes, which refer to the depth (Note) of the observations, are 26.4, 26.6 and 27.3 mag in r-band (about 620 nm wavelength), respectively, allowing observations of some of the most distant galaxies in the universe. In the multi-band images, images are extremely sharp, with star images only 0.6 to 0.8 arcseconds across. 1 arcsecond equals 3600th part of a degree. These high-quality data will allow a unprecedented view into the nature and evolution of galaxies and dark matter. This first public dataset already contains 70 million galaxies and stars. It demonstrates that HSC-SSP is making the most of the performance of the Subaru Telescope and HSC. In 2015, using HSC observations over 2.3 square degrees of sky, nine clumps of dark matter, each weighing as much a galaxy cluster were discovered from their weak lensing signature (Miyazaki et al. 2015, ApJ 807, 22, "Properties of Weak Lensing Clusters Detected on Hyper Suprime-Cam 2.3 Square Degree Field"). The HSC-SSP data release covers about 50 times more sky than was used in this study, showing the potential of these data to reveal the statistical properties of dark matter. The total amount of data taken so far comprises 80 terabytes, which is comparable to the size of about 10 million images by a general digital camera. Since it is difficult to search such a huge dataset with standard tools, NAOJ has developed a dedicated database and interface for ease of access and use of the data. "Since 2014, we have been observing the sky with HSC, which can capture a wide-field image with high resolution," said Dr. Satoshi Miyazaki, the leader of the HSC-SSP. "We believe the data release will lead to many exciting astronomical results, from exploring the nature of dark matter and dark energy, as well as asteroids in our own solar system objects and galaxies in the early universe. SSP team members are now preparing a number of scientific papers based on these data. We plan to publish them in a special issue of the Publications of Astronomical Society of Japan. Moreover, we hope that interested members of the public will also access the data and enjoy the real universe imaged by the Subaru telescope, one of the largest the world." Funding for the HSC Project was provided in part by the following grants: Grant-in-Aid for Scientific Research (B) JP15340065; Grant-in-Aid for Scientific Research on Priority Areas JP18072003; and the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST) entitled, "Uncovering the Origin and Future of the Universe: ultra-wide-field imaging and spectroscopy reveal the nature of dark matter and dark energy." Explore further: Tracing the cosmic web with star-forming galaxies in the distant universe
News Article | March 16, 2016
Neither Europe nor Russia has ever successfully operated a mission on Mars’s surface. Now the European Space Agency (ESA) and its Russian counterpart Roscosmos hope to mark a first for both organizations, with a joint mission that launched from the Baikonur Cosmodrome in Kazakhstan on 14 March. Known as ExoMars 2016, it consists of a lander that will study the planet’s dust storms, and an orbiter that will analyse its atmosphere, including looking for methane. The orbiter will also act as a relay for a follow-up Mars rover, due to be launched in 2018. Each phase of the mission will be a test of the growing collaboration between the two space agencies, which have hinted at future joint missions, including teaming up for uncrewed and crewed Moon trips. ESA designed the orbiter and lander projects but a Russian rocket launched them and they carry Russian instruments. “The launch is crucial because it’s symbolic,” says Oleg Korablev of the Space Research Institute, Moscow, who is principal investigator for the Atmospheric Chemistry Suite on the orbiter. "It's psychologically very important." ESA project scientist Jorge Vago adds: “Hopefully this will cement a way of doing things that becomes the modus operandi for when we do missions together.” Based at the European Space Research and Technology Centre in Noordwijk, the Netherlands, Vago also works on the ExoMars 2018 mission, which will be a joint operation that integrates the teams more tightly. ESA approved the ExoMars concept in 2005; a subsequent merry-go-round of collaborators eventually resulted in the Europe–Russia collaboration and ExoMars’s unusual two-stage format (see 'Mission merry-go-round'). A Russian Proton rocket launched the ExoMars 2016 craft — at 4,332 kilograms, the heaviest Mars mission ever to take to the skies. There will now be four rocket burns over 10 hours before the spacecraft begins its trajectory towards Mars. A favourable alignment between Earth and the red planet means that ExoMars should reach its Martian orbit after 7 months; the orbiter and landing module, known as Schiaparelli, will separate three days before reaching the Martian atmosphere. The landing won’t involve anything as complex as NASA’s sky crane, which delivered the Curiosity rover to Mars in 2012 during the Mars Science Laboratory (MSL) mission. But it is ambitious, says Vago, and designed to show that Europe has the know-how to make a controlled landing on Mars. Taking into account lessons learned from Beagle 2 (Britain's failed 2003 Mars lander that was operated by ESA), the module will first use drag from the Martian atmosphere to brake, then open a parachute and eventually fire its thrusters. During the last 2 metres of its descent, travelling at a relatively sedate 10 kilometres an hour, Schiaparelli will deploy a honeycomb-like crash pad and come to rest on the surface. The first lander to set down during dust-storm season, Schiaparelli will monitor pressure and temperature and image the approaching landing site during its descent. On the ground, the conical lander has just 2–4 days of battery power to perform experiments. Its tiny meteorological station DREAMS (Dust Characterisation, Risk Assessment, and Environment Analyser on the Martian Surface) will measure pressure, humidity, temperature, wind speed and direction. This represents a unique chance to study dust circulation and hopefully unravel the mystery of why some storms on Mars go planet-wide, says Francesca Esposito at the INAF Astronomical Observatory of Capdiomonte in Naples, Italy, and the principal investigator for DREAMS. The Schiaparelli lander will also be the first to examine the planet’s electric field. Those data will feed into Martian climate models and could allow scientists to better predict future disturbances to communications on the planet, she says. The higher-profile science — including investigating hints of Martian biology — will take place in the sky on board ExoMars’ Trace Gas Orbiter (TGO). That phase will begin at the end of 2017, once the craft has manoeuvred into a circular, 400-kilometre-high orbit. While studying Mars’s atmosphere, the TGO’s major task will be to follow up on evidence that the red planet contains methane, which has been associated with active geological processes, as well as biological ones. “Is there a seasonality to the methane, or are the concentrations associated with particular types of terrain, for instance?” asks John Bridges, a planetary scientist at the University of Leicester, UK, who works on the TGO’s stereo camera. The camera will use 3D images to chart geological features, and a hydrogen detector will map the planet’s subsurface water. The orbiter will also serve as a communications platform, including for ExoMars’s future rover, which will break new ground — literally. Armed with a drill, the rover will bore up to 2 metres into the planetary surface, where scientists hope that organic matter, which can be destroyed by surface radiation, may lie preserved. The rover will require the European and Russian teams to work together to an extent unprecedented for ESA, says Vago. In the 2016 mission, the responsibilities of the two teams are relatively separate, but in the 2018 mission, he says, “there is no clean line between them”. As a result, each design tweak ripples through the work of both teams. It is a new experience for Russia too, says Korablev, even though the country has long contributed scientific instruments to foreign space missions. “There are many problems, but there are always problems on national projects too,” he says. “So I would say it was fine — slower, but not that much slower.” This complexity, coupled with late-running instruments, delays in testing and a lack of cash, means that the 2018 rover mission could be delayed until 2020, says Vago. ESA’s director-general, Johann-Dietrich Wörner, said in January that the 2018 mission needed more funding to meet its launch target, and the agency is expected to ask member states for the missing few hundred million euros at a meeting in December. Success with ExoMars 2016 could help to persuade European leaders to contribute, but Bridges says that most scientists will accept a delay as long as it means that all the instruments are on the craft and working. For now, the teams are focused on the complex launch and on the rocket’s separation from the spacecraft. “We will be biting our nails all day on the 14th until we have successful separation,” says Vago. Korablev’s involvement with Mars missions has been an emotional rollercoaster. He spent 10 years working on Russia’s Mars 96 orbiter, which in 1996 failed to leave near-Earth orbit. He faced disappointment again when a sample-return mission to the Martian moon Phobos ran into problems, eventually crashing in the Pacific Ocean in 2012. “We put a great effort into ExoMars,” he says. “I almost don’t dare to say any words.”
News Article | September 14, 2016
On its way to assembling the most detailed 3-D map ever made of our Milky Way galaxy, Gaia has pinned down the precise position on the sky and the brightness of 1142 million stars. As a taster of the richer catalogue to come in the near future, today's release also features the distances and the motions across the sky for more than two million stars. "Gaia is at the forefront of astrometry, charting the sky at precisions that have never been achieved before," says Alvaro Giménez, ESA's Director of Science. "Today's release gives us a first impression of the extraordinary data that await us and that will revolutionise our understanding of how stars are distributed and move across our Galaxy." Launched 1000 days ago, Gaia started its scientific work in July 2014. This first release is based on data collected during its first 14 months of scanning the sky, up to September 2015. "The beautiful map we are publishing today shows the density of stars measured by Gaia across the entire sky, and confirms that it collected superb data during its first year of operations," says Timo Prusti, Gaia project scientist at ESA. The stripes and other artefacts in the image reflect how Gaia scans the sky, and will gradually fade as more scans are made during the five-year mission. "The satellite is working well and we have demonstrated that it is possible to handle the analysis of a billion stars. Although the current data are preliminary, we wanted to make them available for the astronomical community to use as soon as possible," adds Dr Prusti. Transforming the raw information into useful and reliable stellar positions to a level of accuracy never possible before is an extremely complex procedure, entrusted to a pan-European collaboration of about 450 scientists and software engineers: the Gaia Data Processing and Analysis Consortium, or DPAC. "Today's release is the result of a painstaking collaborative work over the past decade," says Anthony Brown from Leiden University in the Netherlands, and consortium chair. "Together with experts from a variety of disciplines, we had to prepare ourselves even before the start of observations, then treated the data, packaged them into meaningful astronomical products, and validated their scientific content." In addition to processing the full billion-star catalogue, the scientists looked in detail at the roughly two million stars in common between Gaia's first year and the earlier Hipparcos and Tycho-2 Catalogues, both derived from ESA's Hipparcos mission, which charted the sky more than two decades ago. By combining Gaia data with information from these less precise catalogues, it was possible to start disentangling the effects of 'parallax' and 'proper motion' even from the first year of observations only. Parallax is a small motion in the apparent position of a star caused by Earth's yearly revolution around the Sun and depends on a star's distance from us, while proper motion is due to the physical movement of stars through the Galaxy. In this way, the scientists were able to estimate distances and motions for the two million stars spread across the sky in the combined Tycho–Gaia Astrometric Solution, or TGAS. This new catalogue is twice as precise and contains almost 20 times as many stars as the previous definitive reference for astrometry, the Hipparcos Catalogue. As part of their work in validating the catalogue, DPAC scientists have conducted a study of open stellar clusters – groups of relatively young stars that were born together – that clearly demonstrates the improvement enabled by the new data. "With Hipparcos, we could only analyse the 3-D structure and dynamics of stars in the Hyades, the nearest open cluster to the Sun, and measure distances for about 80 clusters up to 1600 light-years from us," says Antonella Vallenari from the Istituto Nazionale di Astrofisica (INAF) and the Astronomical Observatory of Padua, Italy. "But with Gaia's first data, it is now possible to measure the distances and motions of stars in about 400 clusters up to 4800 light-years away. For the closest 14 open clusters, the new data reveal many stars surprisingly far from the centre of the parent cluster, likely escaping to populate other regions of the Galaxy." Many more stellar clusters will be discovered and analysed in even greater detail with the extraordinary data that Gaia continues to collect and that will be released in the coming years. The new stellar census also contains 3194 variable stars, stars that rhythmically swell and shrink in size, leading to periodic brightness changes. Many of the variables seen by Gaia are in the Large Magellanic Cloud, one of our galactic neighbours, a region that was scanned repeatedly during the first month of observations, allowing accurate measurement of their changing brightness. Details about the brightness variations of these stars, 386 of which are new discoveries, are published as part of today's release, along with a first study to test the potential of the data. "Variable stars like Cepheids and RR Lyraes are valuable indicators of cosmic distances," explains Gisella Clementini from INAF and the Astronomical Observatory of Bologna, Italy. "While parallax is used to measure distances to large samples of stars in the Milky Way directly, variable stars provide an indirect, but crucial step on our 'cosmic distance ladder', allowing us to extend it to faraway galaxies." This is possible because some kinds of variable stars are special. For example, in the case of Cepheid stars, the brighter they are intrinsically, the slower their brightness variations. The same is true for RR Lyraes when observed in infrared light. The variability pattern is easy to measure and can be combined with the apparent brightness of a star to infer its true brightness. This is where Gaia steps in: in the future, scientists will be able to determine very accurate distances to a large sample of variable stars via Gaia's measurements of parallaxes. With those, they will calibrate and improve the relation between the period and brightness of these stars, and apply it to measure distances beyond our Galaxy. A preliminary application of data from the TGAS looks very promising. "This is only the beginning: we measured the distance to the Large Magellanic Cloud to test the quality of the data, and we got a sneak preview of the dramatic improvements that Gaia will soon bring to our understanding of cosmic distances," adds Dr Clementini. Knowing the positions and motions of stars in the sky to astonishing precision is a fundamental part of studying the properties and past history of the Milky Way and to measure distances to stars and galaxies, but also has a variety of applications closer to home – for example, in the Solar System. In July, Pluto passed in front of a distant, faint star, offering a rare chance to study the atmosphere of the dwarf planet as the star gradually disappeared and then reappeared behind Pluto. This stellar occultation was visible only from a narrow strip stretching across Europe, similar to the totality path that a solar eclipse lays down on our planet's surface. Precise knowledge of the star's position was crucial to point telescopes on Earth, so the exceptional early release of the Gaia position for this star, which was 10 times more precise than previously available, was instrumental to the successful monitoring of this rare event. Early results hint at a pause in the puzzling pressure rise of Pluto's tenuous atmosphere, something that has been recorded since 1988 in spite of the dwarf planet moving away from the Sun, which would suggest a drop in pressure due to cooling of the atmosphere. "These three examples demonstrate how Gaia's present and future data will revolutionise all areas of astronomy, allowing us to investigate our place in the Universe, from our local neighbourhood, the Solar System, to Galactic and even grander, cosmological scales," explains Dr Brown. This first data release shows that the mission is on track to achieve its ultimate goal: charting the positions, distances, and motions of one billion stars – about 1% of the Milky Way's stellar content – in three dimensions to unprecedented accuracy. "The road to today has not been without obstacles: Gaia encountered a number of technical challenges and it has taken an extensive collaborative effort to learn how to deal with them," says Fred Jansen, Gaia mission manager at ESA. "But now, 1000 days after launch and thanks to the great work of everyone involved, we are thrilled to present this first dataset and are looking forward to the next release, which will unleash Gaia's potential to explore our Galaxy as we've never seen it before." More information: The data from Gaia's first release can be accessed at archives.esac.esa.int/gaia Fifteen scientific papers describing the data contained in the release and their validation process will appear in a special issue of Astronomy & Astrophysics.
News Article | March 1, 2017
New light is shed on the famous paradox of Einstein, Podolsky and Rosen after 80 years. A group of researchers from the Faculty of Physics at the University of Warsaw has created a multidimensional entangled state of a single photon and a trillion of hot rubidium atoms. This hybrid entanglement has been stored in the laboratory for several microseconds. The research has been published in the prestigious Optica journal. In their famous Physical Review article published in 1935, A. Einstein, B. Podolsky and N. Rosen have considered a decay of a particle into two products. In their thought-experiment, two products of decay were projected in exactly opposite directions, or more scientifically speaking their momenta were anti-correlated. It would not be a mystery within the framework of classical physics, however when applying the rules of the Quantum theory, the three researchers quickly arrived at a paradox. The Heisenberg uncertainty principle, dictating that position and momentum of a particle cannot be measured at the same time within arbitrary precision, lies at the center of this paradox. In Einstein's thought-experiment one can measure momentum of one particle and immediately know momentum of the other without measurement, as it is exactly opposite. Then, one only needs to measure position of this second particle and the Heisenberg uncertainty principle seems to be violated, which seriously baffled the three physicists. Only today we know that this experiment is not, in fact, a paradox. The mistake of Einstein and co-workers was to use one-particle uncertainty principle to a system of two particles. If we treat these two particles as described by a single quantum state, we learn that the original uncertainty principle ceases to apply, especially if these particles are entangled. In the Quantum Memories Laboratory at the University of Warsaw, the group of three physicists was first to create such an entangled state consisting of a macroscopic object - a group of about one trillion atoms, and a single photon - a particle of light. "Single photons, scattered during the interaction of a laser beam with atoms, are registered on a sensitive camera. A single registered photon carries information about the quantum state of the entire group of atoms. The atoms may be stored, and their state may be retrieved on demand." - says Michal Dabrowski, PhD student and co-author of the article. The results of the experiment confirm that the atoms and the single photon are in a joint, entangled state. By measuring position and momentum of the photon, we gain all information about the state of atoms. To confirm this, polish scientists convert the atomic state into another photon, which again is measured using the state-of-the-art camera developed in the Quantum Memories Laboratory. "We demonstrate the Einstein-Podolsky-Rosen apparent paradox in a very similar version as originally proposed in 1935, however we extend the experiment by adding storage of light within the large group of atoms. Atoms store the photon in a form of a wave made of atomic spins, containing one trillion atoms. Such a state is very robust against loss of a single atoms, as information is spread across so many particles." - says Michal Parniak, PhD student taking part in the study. The experiment performed by the group from the University of Warsaw is unique in one other way as well. The quantum memory storing the entangled state, created thanks to "PRELUDIUM" grant from the Poland's National Science Centre and "Diamentowy Grant" from the Polish Ministry of Science and Higher Education, allows for storage of up to 12 photons at once. This enhanced capacity is promising in terms of applications in quantum information processing. "The multidimensional entanglement is stored in our device for several microseconds, which is roughly a thousand times longer than in any previous experiments, and at the same time long enough to perform subtle quantum operations on the atomic state during storage" - explains Dr. Wojciech Wasilewski, group leader of the Quantum Memories Laboratory team. The entanglement in the real and momentum space, described in the Optica article, can be used jointly with other well-known degrees of freedom such as polarization, allowing generation of so-called hyper-entanglement. Such elaborate ideas constitute new and original test of the fundamentals of quantum mechanics - a theory that is unceasingly mysterious yet brings immense technological progress. Physics and Astronomy first appeared at the University of Warsaw in 1816, under the then Faculty of Philosophy. In 1825 the Astronomical Observatory was established. Currently, the Faculty of Physics' Institutes include Experimental Physics, Theoretical Physics, Geophysics, Department of Mathematical Methods and an Astronomical Observatory. Research covers almost all areas of modern physics, on scales from the quantum to the cosmological. The Faculty's research and teaching staff includes ca. 200 university teachers, of which 88 are employees with the title of professor. The Faculty of Physics, University of Warsaw, is attended by ca. 1000 students and more than 170 doctoral students. Dr. Wojciech Wasilewski Institute of Experimental Physics, Faculty of Physics, University of Warsaw tel. +48 22 5532630 email: firstname.lastname@example.org M.Sc. Michal Dabrowski Institute of Experimental Physics, Faculty of Physics, University of Warsaw tel. +48 22 5532629 email: email@example.com http://psi. Quantum Memories Laboratory, Institute of Experimental Physics, Faculty of Physics, University of Warsaw. http://www. Press office of the Faculty of Physics, University of Warsaw. FUW170301b_fot01s.jpg HR: http://www. Visualization of a hybrid bipartite entanglement between a single photon (blue) and an atomic spin-wave excitation inside quantum memory glass cell, subsequently confirmed in the detection process of a second photon (red). Presented setup enables the demonstration of Einstein-Podolsky-Rosen paradox with true positions and momenta. (Source: UW Physics, Michal Dabrowski) FUW170301b_fot02s.jpg HR: http://www. From right: Michal Parniak uses the green laser to shining the glass cell with quantum memory, holding by Wojciech Wasilewski. Michal Dabrowski makes a simultaneous measurement of position and momentum of photons generated inside the memory. (Source: UW Physics, Mateusz Mazelanik)
News Article | February 28, 2017
Figuring out the fate of the Universe is one step closer. The first massive dataset of a "cosmic census" is released using the largest digital camera on the Subaru Telescope. Beautiful images are available for public at large. The first dataset from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) was released to the public on February 27th, 2017. HSC-SSP is a large survey being done using HSC, which is an optical imaging camera mounted at the prime focus of the Subaru Telescope. HSC has 104 scientific CCDs (for a total of 870 million pixels) and a 1.77 square-degree field of view. The National Astronomical Observatory of Japan (NAOJ) has embarked on the HSC-SSP survey in collaboration with the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) in Japan, the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan, and Princeton University in the United States. The project will take 300 nights over 5-6 years. This survey consists of three layers; Wide, Deep, and UltraDeep, using optical and near infrared wavelengths in five broad bands (g, r, i, z, y) and four narrow-band filters. This release includes data from the first 1.7 years (61.5 nights of observations beginning in 2014). The observed areas covered by the Wide, Deep, and UltraDeep layers are 108, 26, and 4 square degrees, respectively. The limiting magnitudes, which refer to the depth (Note) of the observations, are 26.4, 26.6 and 27.3 mag in r-band (about 620 nm wavelength), respectively, allowing observations of some of the most distant galaxies in the universe. In the multi-band images, images are extremely sharp, with star images only 0.6 to 0.8 arcseconds across. 1 arcsecond equals 3600th part of a degree. These high-quality data will allow a unprecedented view into the nature and evolution of galaxies and dark matter. This first public dataset already contains 70 million galaxies and stars. It demonstrates that HSC-SSP is making the most of the performance of the Subaru Telescope and HSC. In 2015, using HSC observations over 2.3 square degrees of sky, nine clumps of dark matter, each weighing as much a galaxy cluster were discovered from their weak lensing signature (Miyazaki et al. 2015, ApJ 807, 22, "Properties of Weak Lensing Clusters Detected on Hyper Suprime-Cam 2.3 Square Degree Field"). The HSC-SSP data release covers about 50 times more sky than was used in this study, showing the potential of these data to reveal the statistical properties of dark matter. The total amount of data taken so far comprises 80 terabytes, which is comparable to the size of about 10 million images by a general digital camera. Since it is difficult to search such a huge dataset with standard tools, NAOJ has developed a dedicated database and interface for ease of access and use of the data. "Since 2014, we have been observing the sky with HSC, which can capture a wide-field image with high resolution," said Dr. Satoshi Miyazaki, the leader of the HSC-SSP. "We believe the data release will lead to many exciting astronomical results, from exploring the nature of dark matter and dark energy, as well as asteroids in our own solar system objects and galaxies in the early universe. SSP team members are now preparing a number of scientific papers based on these data. We plan to publish them in a special issue of the Publications of Astronomical Society of Japan. Moreover, we hope that interested members of the public will also access the data and enjoy the real universe imaged by the Subaru telescope, one of the largest the world." "Depth" of an observation refers to how dim objects can be studied. The light collection power of large aperture mirror (8.2 m for the Subaru Telescope) is the crucial factor, as well as the exposure time. For astronomical objects of the same intrinsic brightness, depth is literally how far one can look.
News Article | February 24, 2017
A group of researchers from the Faculty of Physics at the University of Warsaw has just published the results of their works on miniature device - a tripler - for generating femtosecond laser pulses in the UV. Not only does the device has three times higher efficiency than previously used setups, but also fits on a finger tip, thanks to using a unique software package, developed in Warsaw, during the design stage. Although with new technologies lasers cover more and more spectral regions, some wavelengths are still not easily accessible. This includes the ultraviolet (UV) band around 300 nm, especially if short pulse durations and/or high intensities are needed. Often, UV pulses are generated via nonlinear processes such as second harmonic generation or sum frequency generation where new photons with higher energy and a new color are formed by summing up energy of the fundamental pulse photons. The efficiency of this processes, that allows near infrared laser pulses to be converted into UV is, however, very small. For many years, analytical light propagation models or simple numerical simulations were used to design frequency converters. They allowed scientists to tweak different device parameters, typically one at a time. This approach resulted in the conversion efficiencies from un-amplified infrared femtosecond lasers to the UV third harmonic to stagnate at around 10%. - It was like coming to the lab, tweaking one knob here, one knob there, while looking at the UV output power and trying to maximize it. And 10% is as good as one can get with this approach - says Michal Nejbauer, from the team of researchers based at the Faculty of Physics of the University of Warsaw, Poland. But increasing computational power available, combined with clever programming tricks allowed for the global optimization of the frequency conversion process from infrared to UV to be used for the first time. - Our newly developed, open-source simulation package - called Hussar - allows even an inexperienced user to build a complex, 3-dimensional, accurate simulations of multiple pulse propagation and interaction using simple blocks: input pulse parameters, material properties of the media and the processes involved - explains Tomasz Kardas, who developed the software - Once we define the input pulse parameters, such as energy, duration and spatial beam profile, we essentially start searching for the best design over a large space of parameters: the nonlinear crystal thicknesses, the beam size, the beam waist position, etc. And, to our surprise, once we found these optimum values, built the device and measured its performance, the output UV pulses were exactly as simulated. This kind of quantitative agreement between what one gets on the screen and then measures in the lab is rather uncommon in nonlinear optics. But increasing the tripling process efficiency by a factor of three, to above 30%, was just the first step. The researchers also aimed at miniaturization - rather than using multiple components mounted on the laboratory table, their third harmonic generator (tripler) is just a tiny block of crystals stacked together. - In fact, the 1-inch metal holder that keeps all the elements together is the biggest part of the whole setup - explains Pawel Wnuk , who took leading role in the device characterization experiments. As a result, the tripler prototype has the overall volume around 1000 times smaller than the traditional, previously used designs. The miniature frequency tripler was developed within the MINIMODS consortium, coordinated by Glasgow-based M Squared Lasers LTD, made up of industry partners Laseroptik (Germany), Radiant Light (Spain) and Time-Bandwidth Products (Switzerland). Research partners include the University of Warsaw (Poland) and the Fraunhofer Centre for Applied Photonics (UK). The project, running between 2013-2015 and supported through the EC's Seventh Framework Programme FP7-SME, aimed to address barriers to expansion and innovation within the photonics industry, with focus on creating cost-efficient, compact tools and devices for integration into laser systems. - Working in close collaboration with industrial partners was a new, interesting experience. We have learned a lot about how they approach research and product development - says Piotr Wasylczyk, who was the project principal investigator at the University of Warsaw. - I am not sure if they learned a lot from us, but the feedback we got from them on what we did and how was very positive. The tripler works results are published this week in Scientific Reports (22/02/2017). Physics and Astronomy first appeared at the University of Warsaw in 1816, under the then Faculty of Philosophy. In 1825 the Astronomical Observatory was established. Currently, the Faculty of Physics' Institutes include Experimental Physics, Theoretical Physics, Geophysics, Department of Mathematical Methods and an Astronomical Observatory. Research covers almost all areas of modern physics, on scales from the quantum to the cosmological. The Faculty's research and teaching staff includes ca. 200 university teachers, of which 88 are employees with the title of professor. The Faculty of Physics, University of Warsaw, is attended by ca. 1000 students and more than 170 doctoral students. "Full 3D modeling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler"; Tomasz M. Kardas, Michal Nejbauer, Pawel Wnuk, Bojan Resan, Czeslaw Radzewicz and Piotr Wasylczyk; Sci. Rep. (2017) http://www. Press office of the Faculty of Physics, University of Warsaw. FUW170224b_fot01s.jpg HR: http://www. Miniature tripler (in the silver mirror mount) generates intense blue and ultraviolet laser pulses form focused beam of infrared light (Source: UW Physics, Radoslaw Chrapkiewicz) Movie showing the three laser pulses propagating in the linear and nonlinear crystals of the miniature tripler (3D simulation results): http://ufs.