An optimal Mars Trojan asteroid search strategy

Trojan asteroids are minor planets that share the orbit of a planet about the Sun and librate around the L4 or L5 Lagrangian points of stability. Although only three Mars Trojans have been discovered, models suggest that at least ten times this number should exist with diameters >= 1 km. We derive a model that constrains optimal sky search areas and present a strategy for the most efficient use of telescope survey time that maximizes the probability of detecting Mars Trojans. We show that the Gaia space mission could detect any Mars Trojans larger than 1 km in diameter, provided the relative motion perpendicular to Gaia's CCD array is less than 0.40 arcsec per second.Comment: 6 pages, 6 figures, 3 tables, accepted for publication in MNRAS. arXiv admin note: substantial text overlap with arXiv:1111.112

Detection of inner Solar System Trojan Asteroids by Gaia

The Gaia satellite, planned for launch by the European Space Agency (ESA) in 2013, is the next generation astrometry mission following Hipparcos. While mapping the whole sky, the Gaia space mission is expected to discover thousands of Solar System Objects. These will include Near-Earth Asteroids and objects at Solar elongations as low as 45 degrees, which are difficult to observe with ground-based telescopes. We present the results of simulations for the detection of Trojan asteroids in the orbits of Earth and Mars by Gaia.Comment: 4 pages, 3 figures, based on a talk presented at the Gaia-FUN-SSO-2 International Workshop, Paris Observatory, 19-21 September 2012. Part of the proceedings of that worksho

Search strategies for Trojan asteroids in the inner Solar System

Trojan asteroids are minor planets that share the orbit of a planet about the Sun and librate around the L4 or L5 Lagrangian points of stability. They are important because they carry information on early Solar System formation, when collisions between bodies were more frequent. Discovery and study of terrestrial planet Trojans will help constrain models for the distribution of bodies and interactions in the inner Solar System. We present models that constrain optimal search areas, and strategies for survey telescopes to maximize the probability of detecting inner planet Trojans. We also consider implications for detection with respect to the Gaia satellite, and limitations of Gaia's observing geometry.Comment: 14 pages, 6 figures, 2 tables, accepted for publication in Planetary and Space Scienc

The potential for detecting gamma-ray burst afterglows from population III stars with the next generation of infrared telescopes

We investigate the detectability of a proposed population of gamma-ray bursts (GRBs) from the collapse of Population III (Pop III) stars. The James Webb Space Telescope (JWST) and Space Infrared Telescope for Cosmology and Astrophysics (SPICA) will be able to observe the late time infrared afterglows. We have developed a new method to calculate their detectability, which takes into account the fundamental initial mass function and formation rates of Pop III stars, from which we find the temporal variability of the afterglows and ultimately the length of time JWST and SPICA can detect them. In the range of plausible Pop III GRB parameters, the afterglows are always detectable by these instruments during the isotropic emission, for a minimum of 55 days and a maximum of 3.7 yr. The average number of detectable afterglows will be 2.96× 10–5 per SPICA field of view (FOV) and 2.78× 10–6 per JWST FOV. These are lower limits, using a pessimistic estimate of Pop III star formation. An optimal observing strategy with SPICA could identify a candidate orphan afterglow in ~1.3 yr, with a 90% probability of confirmation with further detailed observations. A beamed GRB will align with the FOV of the planned GRB detector Energetic X-ray Imaging Survey Telescope once every 9 yr. Pop III GRBs will be more easily detected by their isotropic emissions (i.e., orphan afterglows) rather than by their prompt emissions

The Development of Teaching Skills to Support Active Learning in University Science (ALIUS)

This paper describes an Australian Learning and Teaching Council funded project for which Learning Design is encompassed in the broadest sense. ALIUS (Active Learning In University Science) takes the design of learning back to the learning experiences created for students. ALIUS is not about designing a particular activity, or subject, or course, but rather the development of a method, or process, by which we have re-designed the way in which learning occurs in large university classrooms world wide

The influence of cycloplegic in objective refraction

The purpose of this study was to compare refractions measured with an autorefractor and retinoscopy in cycloplegic and non-cycloplegic eyes. The objective refractions were performed in 199 right eyes from 199 healthy young adults with a mean age of 21.6 ±2.66 years. The measurements were performed first without cycloplegia and repeated 30 minutes later with cycloplegia. Data were analyzed using Fourier decomposition of the power profile. More negative values of component M and J0 were give by non-cycloplegic autorefraction compared to cycloplegic autorefraction (p<0.001). However more positive values were given by non-cycloplegic autorefraciton regarding to the J45 vector, althought this differences were not statistically significant (p=0.233). Regarding retinoscopy, more negative values of component M where obtained with non-cycloplegic retinoscopy (p<0.001); for the cylindrical vectors J0 and J45 the retinoscopy without cycloplegic yields more negative values (p= 0.234; p= 0.112, respectively). Accepting that differences between cycloplegic and non-cycloplegic retinoscopy are only due to accommodative response, present results confirm that when performed by an experienced clinician, retinoscopy is a more reliable method to obtain objective start point for refraction under non-cycloplegic conditions

An optimal Earth Trojan asteriod search strategy

Trojan asteroids are minor planets that share the orbit of a planet about the Sun and librate around the L4 or L5 Lagrangian points of stability. They are important solar-system fossils because they carry information on early Solar system formation, when collisions between bodies were more frequent. Discovery and study of terrestrial planet Trojans will help constrain models for the distribution of bodies and interactions in the inner Solar system. Since the discovery of the first outer planet Trojan in 1906, several thousand Jupiter Trojans have been found. Of the terrestrial planets, there are four known Mars Trojans, and one Earth Trojan has been recently discovered. We present a new model that constrains optimal search areas, and imaging cadences for narrow and wide-field survey telescopes including the Gaia satellite for the most efficient use of telescope time to maximize the probability of detecting additional Earth Trojans

A reliable cw Lyman-α\alpha laser source for future cooling of antihydrogen

We demonstrate a reliable continuous-wave (cw) laser source at the 1\,$S$--2\,$P$ transition in (anti)hydrogen at 121.56\,nm (Lyman-$\alpha$) based on four-wave sum-frequency mixing in mercury. A two-photon resonance in the four-wave mixing scheme is essential for a powerful cw Lyman-$\alpha$ source and is well investigated.Comment: 8 pages, 3 figures, Proceedings of LEAP 201

Little evidence for an epidemic of myopia in Australian primary school children over the last 30 years

BACKGROUND: Recently reported prevalences of myopia in primary school children vary greatly in different regions of the world. This study aimed to estimate the prevalence of refractive errors in an unselected urban population of young primary school children in eastern Sydney, Australia, between 1998 and 2004, for comparison with our previously published data gathered using the same protocols and other Australian studies over the last 30 years. METHODS: Right eye refractive data from non-cycloplegic retinoscopy was analysed for 1,936 children aged 4 to 12 years who underwent a full eye examination whilst on a vision science excursion to the Vision Education Centre Clinic at the University of New South Wales. Myopia was defined as spherical equivalents equal to or less than -0.50 D, and hyperopia as spherical equivalents greater than +0.50 D. RESULTS: The mean spherical equivalent decreased significantly (p < 0.0001) with age from +0.73 ± 0.1D (SE) at age 4 to +0.21 ± 0.11D at age 12 years. The proportion of children across all ages with myopia of -0.50D or more was 8.4%, ranging from 2.3% of 4 year olds to 14.7% of 12 year olds. Hyperopia greater than +0.50D was present in 38.4%. A 3-way ANOVA for cohort, age and gender of both the current and our previous data showed a significant main effect for age (p < 0.0001) but not for cohort (p = 0.134) or gender (p = 0.61). CONCLUSIONS: Comparison of our new data with our early 1990s data and that from studies of over 8,000 Australian non-clinical rural and urban children in the 1970's and 1980's provided no evidence for the rapidly increasing prevalence of myopia described elsewhere in the world. In fact, the prevalence of myopia in Australian children continues to be significantly lower than that reported in Asia and North America despite changing demographics. This raises the issue of whether these results are a reflection of Australia's stable educational system and lifestyle over the last 30 years