Polarimetry is routinely used to characterise the surfaces of bodies in our solar system. In the near future, polarisation measurements of the starlight reflected by exoplanets will become a common and powerful tool to constrain the atmospheres and the surface properties of other worlds.

If extra-terrestial life has similar signatures as the life we know, then astronomical observations of planet Earth represent a benchmark to eventually probe bio-signatures also on other planets. In fact, linear polarisation spectra of Earthshine (the sunlight that has been first reflected by Earth and then reflected back to Earth by the Moon), allow us to detect the presence of oxygen, ozone, and water in the atmosphere of our planet. Surface properties such as fractional contributions of clouds and ocean, as well as vegetation can be inferred. Ultimately, Earthshine observations provide strong observational constraints on model predictions for Earth-like exoplanets.

In this contribution, we review the most recent observations of Earthshine by polarimetry. We highlight some advances in the interpretation and modelling of whole Earth polarisation, which will be of paramount importance to interpret possible bio-signatures of Earth-like planets in the habitable zone of nearby stars in the future.

We describe the preliminary design of a magnetograph and visible-light imager instrument to study the solar dynamo processes through observations of the solar surface magnetic field distribution. The instrument will provide measurements of the vector magnetic field and of the line-of-sight velocity in the solar photosphere. As the magnetic field anchored at the solar surface produces most of the structures and energetic events in the upper solar atmosphere and significantly influences the heliosphere, the development of this instrument plays an important role in reaching the scientific goals of The Atmospheric and Space Science Coordination (CEA) at the Brazilian National Institute for Space Research (INPE). In particular, the CEA's space weather program will benefit most from the development of this technology. We expect that this project will be the starting point to establish a strong research program on Solar Physics in Brazil. Our main aim is acquiring progressively the know-how to build state-of-the-art solar vector magnetograph and visible-light imagers for space-based platforms to contribute to the efforts of the solar-terrestrial physics community to address the main unanswered questions on how our nearby Star works.

The role of magnetic fields in late type stars, such as Asymptotic Giant Branch stars (AGBs), Post-AGBs and Planetary Nebulae (PNe), is poorly known from an observational point of view. Magnetic fields are however believed to have a non-negligible influence on the dynamics (via mass loss control, outflows shaping) and even on the chemistry (e.g. extra mixing) of these stellar objects. We are therefore presenting two different types of investigation, both based on the use of polarimetry, which aim at filling the gap between the observations on the one hand and the theoretical predictions on the other hand.

One of the methods for diagnosing vector magnetic fields in solar prominences is the so called “inversion” of observed polarized spectral lines. This inversion usually assumes a fairly simple generative model and in this contribution we aim to study the possible systematic errors that are introduced by this assumption. On two-dimensional toy model of a prominence, we first demonstrate importance of multidimensional radiative transfer and horizontal inhomogeneities. These are able to induce a significant level of polarization in Stokes U, without the need for the magnetic field. We then compute emergent Stokes spectrum from a prominence which is pervaded by the vector magnetic field and use a simple, one-dimensional model to interpret these synthetic observations. We find that inferred values for the magnetic field vector generally differ from the original ones. Most importantly, the magnetic field might seem more inclined than it really is.

In 1811, François Arago observed the disk of the Sun with his “lunette polariscopique”. From the absence of detectable polarization compared with his laboratory observations of glowing solids, liquids, and flames he concluded that the Sun's visible surface is an incandescent gas. From this beginning, thanks to orders of magnitude technology improvements, a remarkable amount of what we know about the physics of the Sun has continued to flow from solar polarimetry. This short review compares some selected polarimetric discoveries with subsequent recent observations to illustrate the tremendous progress of solar polarimetry during the last two centuries.

There is a variety of new polarization optics that can be employed for polarimetry and for polarization control. Many are enabled by new materials including polymers and liquid crystals. We survey here these and other relatively new devices and components available commercially that open new possibilities for astronomers.

Spatial clustering nature of galaxies has been studied previously through auto correlation function. The same type of cross-correlation function has been used in the present work to investigate parametric clustering nature of galaxies with respect to masses and sizes of galaxies. Here, formation and evolution of several components of nearby massive early type galaxies (M * ≥ 1.3 × 1011 M⊙ have been envisaged through cross-correlations, in the mass-size parametric plane, with high redshift (0.2 ⩽ z ⩽ 7) ETGs. It is found that the inner most components of nearby ETGs have significant correlation (~ 0.5 ± (0.02–0.07)) with ETGs in the highest redshift range (2 ⩽ z ⩽ 7) called ‘red nuggets’ whereas intermediate components are highly correlated (~ 0.65 ± (0.03–0.07)) with ETGs in the redshift range 0.5 ⩽ z ⩽ 0.75. The outermost part has no correlation in any range, suggesting a scenario through in situ accretion. The above formation scenario is consistent with the previous results obtained for NGC5128 and to some extent for nearby elliptical galaxies after considering a sample of ETGs at high redshift with stellar masses greater than or equal to 108.73 M⊙. So the present work indicates a three phase formation instead of two as discussed in previous works.

The spectral classifications of the stars from spectral data have been corrected from time to time and new spectral and luminosity classes have been assigned. Identifying stars with wrong spectral and luminosity classification has been a stupendous task from the huge catalogue of stars. In this work we describe a simple statistical technique to identify stars with wrong spectral and luminosity classification. We make use of the Hipparcos catalogue which has the most accurate measurement of the distance d of the stars. A comparison is made between the absolute V magnitudes MV computed using the observed V magnitude mV and d, with the standard absolute magnitude MV0 assigned to a spectral and luminosity classification for a large number of stars (with d < 100 pc). As expected, for most of the stars the difference between MV and MV0 lies within the range ±2 mag, due to the intrinsic nature of each star ignored in this generalisation. A systematic error analysis is made of all the observable used in the computation. Therefore to identify stars which we suspect to be wrongly classified, we look for abnormal deviation in |MV – MV0 | ≥5. The location of these stars with respect to the galactic plain and interstellar extinction is also investigated to rule out effects due to variations in the interstellar extinction. From our results we see that some of the stars were indeed wrongly classified and have recently been reclassified (SIMBAD). The reclassification drastically reduces the |MV – MV0 | deviation. The other stars in the list which have not yet been reclassified need to be spectroscopically investigated and classified again.

The Chinese Spectral Radioheliograph is a solar dedicated radio interferometric array that will produce high spatial resolution, high temporal resolution, and high spectral resolution images of the Sun simultaneously in decimetre and centimetre wave range. Digital processing of intermediate frequency signal is an important part in a radio telescope. This paper describes a flexible and high-speed digital down conversion system for the CSRH by applying complex mixing, parallel filtering, and extracting algorithms to process IF signal at the time of being designed and incorporates canonic-signed digit coding and bit-plane method to improve program efficiency. The DDC system is intended to be a subsystem test bed for simulation and testing for CSRH. Software algorithms for simulation and hardware language algorithms based on FPGA are written which use less hardware resources and at the same time achieve high performances such as processing high-speed data flow (1 GHz) with 10 MHz spectral resolution. An experiment with the test bed is illustrated by using geostationary satellite data observed on March 20, 2014. Due to the easy alterability of the algorithms on FPGA, the data can be recomputed with different digital signal processing algorithms for selecting optimum algorithm.

We present the results of an approximately 6 100 deg2 104–196 MHz radio sky survey performed with the Murchison Widefield Array during instrument commissioning between 2012 September and 2012 December: the MWACS. The data were taken as meridian drift scans with two different 32-antenna sub-arrays that were available during the commissioning period. The survey covers approximately 20.5 h < RA < 8.5 h, − 58° < Dec < −14°over three frequency bands centred on 119, 150 and 180 MHz, with image resolutions of 6–3 arcmin. The catalogue has 3 arcmin angular resolution and a typical noise level of 40 mJy beam− 1, with reduced sensitivity near the field boundaries and bright sources. We describe the data reduction strategy, based upon mosaicked snapshots, flux density calibration, and source-finding method. We present a catalogue of flux density and spectral index measurements for 14 110 sources, extracted from the mosaic, 1 247 of which are sub-components of complexes of sources.

This paper describes the system architecture of a newly constructed radio telescope – the Boolardy engineering test array, which is a prototype of the Australian square kilometre array pathfinder telescope. Phased array feed technology is used to form multiple simultaneous beams per antenna, providing astronomers with unprecedented survey speed. The test array described here is a six-antenna interferometer, fitted with prototype signal processing hardware capable of forming at least nine dual-polarisation beams simultaneously, allowing several square degrees to be imaged in a single pointed observation. The main purpose of the test array is to develop beamforming and wide-field calibration methods for use with the full telescope, but it will also be capable of limited early science demonstrations.

The last few years has seen a dramatic increase in the number of exoplanets known and in the range of methods for characterising their atmospheric properties. At the same time, new discoveries of increasingly cooler brown dwarfs have pushed down their temperature range which now extends down to Y-dwarfs of < 300 K. Modelling of these atmospheres has required the development of new techniques to deal with the molecular chemistry and clouds in these objects. The atmospheres of brown dwarfs are relatively well understood, but some problems remain, in particular the behavior of clouds at the L/T transition. Observational data for exoplanet atmosphere characterisation is largely limited to giant exoplanets that are hot because they are near to their star (hot Jupiters) or because they are young and still cooling. For these planets there is good evidence for the presence of CO and H2O absorptions in the IR. Sodium absorption is observed in a number of objects. Reflected light measurements show that some giant exoplanets are very dark, indicating a cloud free atmosphere. However, there is also good evidence for clouds and haze in some other planets. It is also well established that some highly irradiated planets have inflated radii, though the mechanism for this inflation is not yet clear. Some other issues in the composition and structure of giant exoplanet atmospheres such as the occurrence of inverted temperature structures, the presence or absence of CO2 and CH4, and the occurrence of high C/O ratios are still the subject of investigation and debate.

The second epoch Molonglo Galactic Plane Survey covers the area 245° ⩽ l ⩽ 365° and |b| ⩽ 10° at a frequency of 843 MHz and an angular resolution of 45 arcsec × 45 arcsec cosec(δ). The sensitivity varies between 1–2 mJy beam− 1 depending on the presence of strong extended sources. This survey is currently the highest resolution and most sensitive large-scale continuum survey of the southern Galactic plane. In this paper, we present the images of the complete survey, including postage stamps of some new supernova remnant (SNR) candidates and a discussion of the highly structured features detected in the interstellar medium. The intersection of these two types of features is discussed in the context of the ‘missing’ SNR population in the Galaxy.

The Epoch of Reionization (EoR) represents a milestone in the evolution of our Universe. Star-forming galaxies that existed during the EoR likely emitted a significant fraction ( ~ 5 − 40%) of their bolometric luminosity as Lyα line emission. However, neutral intergalactic gas that existed during the EoR was opaque to Lyα emission that escaped from galaxies during this epoch, which makes it difficult to observe. The neutral intergalactic medium (IGM) may thus reveal itself by suppressing the Lyα flux from background galaxies. Interestingly, a ‘sudden’ reduction in the observed Lyα flux has now been observed in galaxies at z > 6. This review contains a detailed summary of Lyα radiative processes: I describe (i) the main Lyα emission processes, including collisional-excitation & recombination (and derive the origin of the famous factor ‘0.68’), and (ii) basic radiative transfer concepts, including e.g. partially coherent scattering, frequency diffusion, resonant versus wing scattering, optically thick versus ‘extremely’ optically thick (static/outflowing/collapsing) media, and multiphase media. Following this review, I derive expressions for the Gunn-Peterson optical depth of the IGM during (inhomogeneous) reionisation and post-reionisation. I then describe why current observations appear to require a very rapid evolution of volume-averaged neutral fraction of hydrogen in the context of realistic inhomogeneous reionisation models, and discuss uncertainties in this interpretation. Finally, I describe how existing & futures surveys and instruments can help reduce these uncertainties, and allow us to fully exploit Lyα emitting galaxies as a probe of the EoR.

A standard model for the visibility of pulsar radio emission is based on the assumption that the emission is confined to a narrow cone about the tangent to a dipolar field line. The widely accepted rotating vector model (RVM) is an approximation in which the line of sight is fixed and the field line is not strictly tangent to it. We refer to an exact treatment (Gangadhara, 2004) as the tangent model. In the tangent model (but not in the RVM) the visible point changes as a function of pulsar rotational phase, ψ, defining a trajectory on a sphere of radius r. We solve for the trajectory and for the angular velocity of the visible point around it. We note the recent claim that this motion is observable using interstellar holography (Pen et al., 2014). We estimate the error introduced by use of the RVM and find that it is significant for pulsars with emission over a wide range of ψ. The RVM tends to underestimate the range of ψ over which emission is visible. We suggest that the geometry alone strongly favors the visible pulsar radio being emitted at a heights more than ten percent of the light-cylinder distance, where our neglect of retardation effects becomes significant.

We present a systematic photometric search for spectroscopically confirmed anomalously red galaxies members of 748 low redshift clusters between 0.03 z 0.17 from the SDSS-C4 cluster catalogue (Miller et al. 2005). For each cluster we spectroscopically determine cluster membership, construct a colour-magnitude diagram and fit the red sequence using a robust bi-weight fit. We define an “anomalously red galaxy” as having a (g - r) colour of greater than 3σ redward of the fitted cluster colour-magnitude relation. We find that of 7485 galaxies at r ≤ 17.77 in (g - r), 7 galaxies are anomalously red – 0.0935 per cent of all galaxies in our sample. We show that two of the red outliers are caused by red contamination from nearby sources and are therefore not intrinsically anomalous red. However, 5 have no underlying cause to be so red and we speculate that they may have a high internal dust content. These intrinsically red galaxies are rare – comprising no more than 0.0668 per cent of all cluster galaxies. Most are morphologically early type galaxies, with a few probable late type galaxies that are viewed edge-on and one low surface brightness late type. One of our anomalously red galaxies appears to be a dust-shrouded starburst and we speculate that this may be a unique galaxy amoungst this galaxy set.

Since the early 1990s with the arrival of a variety of new technologies, the capacity for authentic astronomical research at the high school level has skyrocketed. This potential, however, has not realised the bright-eyed hopes and dreams of the early pioneers who expected to revolutionise science education through the use of telescopes and other astronomical instrumentation in the classroom. In this paper, a general history and analysis of these attempts is presented. We define what we classify as an Astronomy Research in the Classroom (ARiC) project and note the major dimensions on which these projects differ before describing the 22 major student research projects active since the early 1990s. This is followed by a discussion of the major issues identified that affected the success of these projects and provide suggestions for similar attempts in the future.

A series of population models are designed to explore the star formation history of gas-rich, low surface brightness (LSB) galaxies. LSB galaxies are unique in having properties of very blue colors, low Hα emission and high gas fractions that indicated a history of constant star formation (versus the declining star formation models used for most spirals and irregulars). The model simulations use an evolving multi-metallicity composite population that follows a chemical enrichment scheme based on Milky Way observations. Color and time sensitive stellar evolution components (i.e., BHB, TP-AGB and blue straggler stars) are included, and model colors are extended into the Spitzer wavelength regions for comparison to new observations. In general, LSB galaxies are well matched to the constant star formation scenario with the variation in color explained by a fourfold increase/decrease in star formation over the last 0.5 Gyrs (i.e., weak bursts). Early-type spirals, from the S4G sample, are better fit by a declining star formation model where star formation has decreased by 40% in the last 12 Gyrs.

Radio-loud AGN play an important rôle in galaxy evolution. We need to understand their properties, and the processes that affect their behaviour in order to model galaxy formation and development. We here present preliminary results of an investigation into the cluster environments of radio galaxies. We have found evidence of a strong correlation between radio luminosity and environment richness for low excitation radio galaxies, and no evidence of evolution of the environment with redshift. Conversely, for high excitation radio galaxies, we found no correlation with environment richness, and tentative evidence of evolution of the cluster environment.

We have been monitoring some well-known bright blazars with short LOFAR observations since February 2013 with fortnightly cadence using the full available bandwidth of the High Band Antennas (i.e., 48 MHz centred at 226 MHz). The sources were chosen to be bright at low frequencies and to exhibit strong GHz-frequency radio variability on timescales of weeks to years. None of the five objects selected have been monitored previously in the MHz band. Here we report some preliminary results on flux variability obtained so far with LOFAR. These observations are scientifically valuable in their own right and also act as a proof of principle for broader, higher-cadence monitoring of the extragalactic sky with LOFAR and possibly SKA.