Lohr M.E.,Open University Milton Keynes |
Norton A.J.,Open University Milton Keynes |
Kolb U.C.,Open University Milton Keynes |
Boyd D.R.S.,British Astronomical Association
Astronomy and Astrophysics | Year: 2013
We report our investigation of 1SWASP J234401.81-212229.1, a variable with a 18 461.6 s period. After identification in a 2011 search of the SuperWASP archive for main-sequence eclipsing binary candidates near the distribution's short-period limit of ∼0.20 d, it was measured to be undergoing rapid period decrease in our earlier work, though later observations supported a cyclic variation in period length. Spectroscopic data obtained in 2012 with the Southern African Large Telescope did not, however, support the interpretation of the object as a normal eclipsing binary. Here, we consider three possible explanations consistent with the data: a single-star oblique rotator model in which variability results from stable cool spots on opposite magnetic poles; a two-star model in which the secondary is a brown dwarf; and a three-star model involving a low-mass eclipsing binary in a hierarchical triple system. We conclude that the latter is the most likely model. © 2013 ESO.
PubMed | Societe Astronomique de France, British Astronomical Association, University of the Basque Country, Spain 2 Institute Astrofisica Of Andalucia and 3 more.
Type: Journal Article | Journal: Nature | Year: 2015
The Martian limb (that is, the observed edge of the planet) represents a unique window into the complex atmospheric phenomena occurring there. Clouds of ice crystals (CO2 ice or H2O ice) have been observed numerous times by spacecraft and ground-based telescopes, showing that clouds are typically layered and always confined below an altitude of 100kilometres; suspended dust has also been detected at altitudes up to 60kilometres during major dust storms. Highly concentrated and localized patches of auroral emission controlled by magnetic field anomalies in the crust have been observed at an altitude of 130kilometres. Here we report the occurrence in March and April 2012 of two bright, extremely high-altitude plumes at the Martian terminator (the day-night boundary) at 200 to 250 kilometres or more above the surface, and thus well into the ionosphere and the exosphere. They were spotted at a longitude of about 195 west, a latitude of about -45 (at Terra Cimmeria), extended about 500 to 1,000 kilometres in both the north-south and east-west directions, and lasted for about 10days. The features exhibited day-to-day variability, and were seen at the morning terminator but not at the evening limb, which indicates rapid evolution in less than 10hours and a cyclic behaviour. We used photometric measurements to explore two possible scenarios and investigate their nature. For particles reflecting solar radiation, clouds of CO2-ice or H2O-ice particles with an effective radius of 0.1micrometres are favoured over dust. Alternatively, the plume could arise from auroral emission, of a brightness more than 1,000 times that of the Earths aurora, over a region with a strong magnetic anomaly where aurorae have previously been detected. Importantly, both explanations defy our current understanding of Mars upper atmosphere.
News Article | October 26, 2016
On the far side of the Moon lies the Maunder crater, named after two British astronomers - Annie and Walter Maunder. Annie worked alongside her husband at the end of the 19th Century, recording the dark spots that pepper the Sun. The name Maunder is still known in scientific circles, yet Annie has somehow slipped from history. "I think the name Maunder is there and we have all rather forgotten that that's two people," says Dr Sue Bowler, editor of the Royal Astronomical Society magazine, Astronomy and Geophysics. "She was acknowledged on papers, she published in her own name as well as with her husband, she wrote books, she was clearly doing a lot of work but she also clearly kept to the conventions of the day, I think." Annie Scott Dill Russell was born in 1868 in Strabane, the daughter of a Reverend. Clearly of fierce intelligence, she won a scholarship to Girton College, Cambridge, and became one of the first female scientists to work at the Royal Observatory, Greenwich. In the courtyard of the observatory, looking over the park, curator Dr Louise Devoy, tells me what little they know about her work. "She was one of what we now call the 'lady computers' employed in the early 1890s by the then Astronomer Royal, William Christie," she explains. "I believe she came from Northern Ireland and she worked here for several years on very low pay just like many of the computers here, both male and female. "In terms of what she actually did here, we have very little concrete record or photographs.'" Female scientists were hindered because of their gender until the 1920s and 30s, despite superb skills and experience, says Dr Devoy. At Greenwich, employing women with a university education in mathematics was an audacious experiment. Women were only considered because the Astronomer Royal needed skilled assistants but could afford only lowly computers - historically, schoolboys on a wage of £4 per month. Maunder was offered a post as a lady computer, which meant a huge drop in pay for someone who had been working, briefly, as a school teacher. Letters show that she appealed for more money but was turned down. The lady computers would carry out routine calculations to turn raw observations into usable data. They were also trained to use telescopes. At times, this meant walking through Greenwich Park at night without a chaperone, an activity that was frowned on at the time. "In an age when many middle-class women were still chaperoned, the grit and devotion of these young women astronomers, clad in their clumsy long gowns as they worked at their telescopes or in the laboratories, were surely remarkable," wrote the science historian and astronomer Mary T Brück. More on Annie Maunder and other female pioneers of science: In 1892, the names of Annie Russell and fellow Greenwich astronomer Alice Everett were put forward to become fellows of the Royal Astronomical Society. However, they failed to gain enough of the popular vote in a secret ballot and were rejected. The RAS had long argued that since the pronoun "he" was used in the charter, women could not be admitted alongside men. Instead, Annie Russell and Alice Everett, who had studied together at Cambridge, joined the amateur British Astronomical Association (BAA). Alice Everett grew tired of the low pay and left Greenwich, eventually developing an interest in the new field of television. Annie Russell stayed on. "She was clearly very tough and wanted to follow her science," says Dr Bowler. "She sat the [difficult] mathematical Tripos at a time when women couldn't actually be awarded a degree and there were even protests at Cambridge against the whole idea of giving women degrees. "So she was clearly tough enough to do that and to do it well and to succeed then in getting employment as a scientist, which was fairly rare anyway - astronomy was still very much a gentleman's pursuit." Under civil service rules, as a married woman, she was forced to give up her paid position, bringing the age of lady computers to an end. "She did come back as a volunteer during the First World War and then she was taken on as a paid employee later in the 1920s,'' says Dr Devoy. Annie worked alongside Walter taking photographs of the Sun, laying the groundwork for a modern understanding of solar activity. "They would take photographs of the Sun every clear day just to note where the sunspots were and to sketch where they were," says Dr Bowler. "But she also, as a trained mathematician, put quite a bit of effort into analysis. She wasn't just writing things down; she wasn't just Walter's assistant." Annie Maunder went on many scientific expeditions to observe eclipses around the turn of the century, often as the only woman. She travelled to Lapland, India, Algiers, Mauritius and Labrador. She even designed her own camera to take spectacular pictures of the Sun, including the first photograph ever of streamers from the Sun's outer layer, or corona. "She particularly caught an extremely long ray - a streak of the corona - coming out from the Sun, while it was eclipsed, that nobody had ever seen before - a feature of the corona that people just didn't know about," says Dr Bowler. "I've seen photos of her adjusting the instruments. She's taking her photographs. She's not at all a passenger. "It may have been only socially acceptable for her to go because she's travelling with her husband but she was on official scientific expeditions and her photographs were acknowledged as among the best." The conventions of the time meant that Annie's photographs were published under her husband's name and she could not speak at scientific meetings. However, she was eventually made a fellow of the Royal Society in 1916, 24 years after first being proposed. She was involved with promoting astronomy to a general audience as vice president of the BAA and edited the in-house journal. In 1908, the Maunders published the book, The Heavens and Their Story, which was aimed at popular science. The book was released under both their names, but her husband acknowledged in the preface that it was almost all her work. The Maunders are also well known for the butterfly diagram, which shows how the number of sunspots varies with time, and the Maunder Minimum, a period in the 17th Century when sunspots all but disappeared. Much of their work still holds true today. This year, Annie's name is being remembered through the inaugural Annie Maunder Medal, to recognise public engagement in science. "She is an ideal person for that medal to be named after," says Dr Bowler. "That's largely what she was doing, certainly later in her career." Annie Maunder died in 1947, long after her husband. On a leafy street near Clapham Common I find the Victorian terraced house where she spent her final years. From the outside there is nothing to speak of the pioneering scientist. Yet, despite perhaps not getting the recognition she deserved in her lifetime, she clearly left her mark on science. "From her letters which are in the Royal Astronomical Society archives she was a very strong-minded, very decided personality," says Sue Bowler. "She didn't mince her words. She's really quite amusingly rude in some of her letters and very precise. "I really admire her - she's one of the people I would definitely have at my dream dinner party - I think she would be extraordinarily interesting. "And her thoughts, her opinions about the paper based on her observations are very modern and form the basis for solar physics through a lot of the years following."
Miles R.,British Astronomical Association |
Faillace G.A.,British Astronomical Association
Icarus | Year: 2012
In this paper we review the relevant literature and investigate conditions likely to lead to melting of H 2O ice, methanol (CH 3OH) ice, ethane (C 2H 6) ice and other volatile ices in cometary nuclei. On the basis of a heat balance model which takes account of volatiles loss, we predict the formation of occasional aqueous and hydrocarbon liquid phases in subsurface regions at heliocentric distances, r h of 1-3AU, and 5-12AU, respectively. Low triple-point temperatures and low vapour pressures of C 2H 6, C 3H 8, and some higher-order alkanes and alkenes, favour liquid phase formation in cometary bodies at high r h. Microporosity and the formation of a stabilization crust occluding the escape of volatiles facilitate liquid-phase formation. Characteristics of the near-surface which favour subsurface melting include; low effective surface emissivity (at low r h), high amorphous carbon content, average pore sizes of ∼10μm or less, presence of solutes (e.g. CH 3OH), mixtures of C 2-C 6 hydrocarbons (for melting at high r h), diurnal thermal cycling, and slow rotation rate. Applying the principles of soil mechanics, capillary forces are shown to initiate pre-melting phenomena and subsequent melting, which is expected to impart considerable strength of ∼10 4Pa in partially saturated layers, reducing porosity and permeability, enhancing thermal conductivity and heat transfer. Diurnal thermal cycling is expected to have a marked effect on the composition and distribution of H 2O ice in the near-surface leading to frost heave-type phenomena even where little if any true melting occurs. Where melting does take place, capillary suction in the wetted zone has the potential to enhance heat transfer via capillary wetting in a low-gravity environment, and to modify surface topography creating relatively smooth flat-bottomed features, which have a tendency to be located within small depressions. An important aspect of the " wetted layer" model is the prediction that diurnal melt-freeze cycles alter the mixing ratio vs. depth of solutes present, or of other miscible components, largely through a process of fractional crystallization, but also potentially involving frost heave. Wetted layers are potentially durable and can involve significant mass transport of volatile materials in the near-surface, increasing in extent over many rotations of the nucleus prior to and just after perihelion passage, and causing stratification and trapping of the lowest-melting mixtures at depths of several metres. A possible mechanism for cometary outbursts is proposed involving a heat pulse reaching the liquid phase in the deepest wetted zone, leading to supersaturation and triggering the sudden release under pressure of dissolved gases, in particular CO 2, CO, CH 4 or N 2, contained beneath a consolidated near-surface layer. This study indicates that liquid water can persist for long periods of time in the near-surface of some intermediate-sized bodies (10 2-10 3km radius) within protoplanetary discs. © 2012 Elsevier Inc.
Rogers J.H.,British Astronomical Association |
Fletcher L.N.,University of Leicester |
Adamoli G.,JUPOS Team |
Jacquesson M.,JUPOS Team |
And 2 more authors.
Icarus | Year: 2016
A compact wave pattern has been identified on Jupiter's fastest retrograding jet at 20°S (the SEBs) on the southern edge of the South Equatorial Belt. The wave has been identified in both reflected sunlight from amateur observations between 2010 and 2015, thermal infrared imaging from the Very Large Telescope and near infrared imaging from the Infrared Telescope Facility. The wave pattern is present when the SEB is relatively quiescent and lacking large-scale disturbances, and is particularly notable when the belt has undergone a fade (whitening). It is generally not present when the SEB exhibits its usual large-scale convective activity ('rifts'). Tracking of the wave pattern and associated white ovals on its southern edge over several epochs have permitted a measure of the dispersion relationship, showing a strong correlation between the phase speed (-43.2 to -21.2 m/s) and the longitudinal wavelength, which varied from 4.4 to 10.0° longitude over the course of the observations. Infrared imaging sensing low pressures in the upper troposphere suggest that the wave is confined to near the cloud tops. The wave is moving westward at a phase speed slower (i.e., less negative) than the peak retrograde wind speed (-62 m/s), and is therefore moving east with respect to the SEBs jet peak. Unlike the retrograde NEBn jet near °N, which is a location of strong vertical wind shear that sometimes hosts Rossby wave activity, the SEBs jet remains retrograde throughout the upper troposphere, suggesting the SEBs pattern cannot be interpreted as a classical Rossby wave. 2D windspeeds and thermal gradients measured by Cassini in 2000 are used to estimate the quasi-geostrophic potential vorticity gradient as a means of understanding the origin of the a wave. We find that the vorticity gradient is dominated by the baroclinic term and becomes negative (changes sign) in a region near the cloud-top level (400-700 mbar) associated with the SEBs. Such a sign reversal is a necessary (but not sufficient) condition for the growth of baroclinic instabilities, which is a potential source of the meandering wave pattern. © 2016 Elsevier Inc.
Miles R.,British Astronomical Association
Icarus | Year: 2016
This paper is a continuation of Miles et al. (2015) [Icarus] and Miles (2015b) [Icarus], which detail new observations of Comet 29P/Schwassmann-Wachmann, characterise its rotational period (~57d), and identify the presence of discrete sources of outburst on its nucleus: the latter ruling out amorphous-to-crystalline H2O ice transitions as the cause of its outbursts. Summary data are presented for 29P and a further 16 non-fragmenting comets which exhibit outbursts of >2 magnitudes. A comprehensive physicochemical mechanism is postulated to account for major outbursts based on melting of cometary ices and the exothermic dissolution of gases, especially CO and CO2 at pressures of 10-200kPa. The thermodynamics of enthalpy heating are described and heats of solution are calculated from gas-liquid solubility data yielding -6kJmol-1 for CO in CH4, and -15kJmol-1 for CO2 in CH3OH close to their freezing point. Heats of solution are ~6 times greater (per mole) than the enthalpy of fusion of the pure CH4 and CH3OH ices, enabling gas pressures of >~80kPa to continually melt these ices. Supervolatile O2 and N2 gases may also participate by dissolving exothermically in liquid CH4 and other hydrocarbons potentially reaching high mixing ratios. H2S and NH3 gases dissolve exothermically in CH3OH liberating up to 20kJmol-1 and 13kJmol-1, respectively, and all three hydrophilic species facilitate sintering of H2O ice in the near-surface of comets. Localised melting and consolidation is favoured in slowly-rotating cometary nuclei of intermediate dust/gas ratios, at pressures of ~1kPa, and temperatures as low as 50-65K where O2 and N2 are abundant. Nyctogenic processes on the night-time side of the nucleus restock desiccated surface layers, reseal the crust, enabling fractionation of solutes in sub-crustal liquid phases via fractional sublimation/distillation of non-polar, hydrophobic CH4 and other hydrocarbons; and by fractional crystallisation of polar, hydrophilic phases rich in aqueous CH3OH and other organic oxygenates, e.g. CH2O, able to form low melting point eutectic mixtures. A generalised outburst mechanism is described involving the containment of gases as solutes in cryomagma beneath consolidated surface crustal regions. Disruption of the crust and associated pressure loss render the cryomagma supersaturated, and the concomitant explosive exsolution of gases provokes a cometary outburst. The CO gas-exsolution mechanism operates at ~65 to 95K and accounts for activity of 29P and other distant comets up to rh=~15AU. A similar mechanism can operate at ~150 to 200K driven by CO2 in aqueous CH3OH and may account for rare outbursts of Jupiter-family comets such as 17P/Holmes. At least 10-15% of all periodic comets may be subject to gas-exsolution outbursts, the majority of which are weak and go undetected. Possible surface morphologies of the nucleus of Comet 29P are discussed. The mechanism may also explain the phenomenon of strong cometary outbursts triggering secondary events, as observed for 17P, 29P and 41P. © 2016 Elsevier Inc.All rights reserved.
McKim R.,British Astronomical Association
Astronomy and Geophysics | Year: 2016
Richard McKim gives an overview of the rather different role of women in the early British Astronomical Association. © 2016 Royal Astronomical Society.
Fletcher L.N.,University of Oxford |
Orton G.S.,Jet Propulsion Laboratory |
Rogers J.H.,British Astronomical Association |
Simon-Miller A.A.,NASA |
And 6 more authors.
Icarus | Year: 2011
Mid-infrared 7-20 μm imaging of Jupiter from ESO's Very Large Telescope (VLT/VISIR) demonstrate that the increased albedo of Jupiter's South Equatorial Belt (SEB) during the 'fade' (whitening) event of 2009-2010 was correlated with changes to atmospheric temperature and aerosol opacity. The opacity of the tropospheric condensation cloud deck at pressures less than 800. mbar increased by 80% between May 2008 and July 2010, making the SEB (7-17°S) as opaque in the thermal infrared as the adjacent equatorial zone. After the cessation of discrete convective activity within the SEB in May 2009, a cool band of high aerosol opacity (the SEB zone at 11-15°S) was observed separating the cloud-free northern and southern SEB components. The cooling of the SEBZ (with peak-to-peak contrasts of 1.0 ± 0.5. K), as well as the increased aerosol opacity at 4.8 and 8.6 μm, preceded the visible whitening of the belt by several months. A chain of five warm, cloud-free 'brown barges' (subsiding airmasses) were observed regularly in the SEB between June 2009 and June 2010, by which time they too had been obscured by the enhanced aerosol opacity of the SEB, although the underlying warm circulation was still present in July 2010. Upper tropospheric temperatures (150-300. mbar) remained largely unchanged during the fade, but the cool SEBZ formation was detected at deeper levels (p>. 300. mbar) within the convectively-unstable region of the troposphere. The SEBZ formation caused the meridional temperature gradient of the SEB to decrease between 2008 and 2010, reducing the vertical thermal windshear on the zonal jets bounding the SEB. The southern SEB had fully faded by July 2010 and was characterised by short-wave undulations at 19-20°S. The northern SEB persisted as a narrow grey lane of cloud-free conditions throughout the fade process. The cool temperatures and enhanced aerosol opacity of the SEBZ after July 2009 are consistent with an upward flux of volatiles (e.g., ammonia-laden air) and enhanced condensation, obscuring the blue-absorbing chromophore and whitening the SEB by April 2010. These changes occurred within cloud decks in the convective troposphere, and not in the radiatively-controlled upper troposphere. NH3 ice coatings on aerosols at p<800mbar are plausible sources of the suppressed 4.8 and 8.6-μm emission, although differences in the spatial distribution of opacity at these two wavelengths suggest that enhanced attenuation by a deeper cloud(p>800mbar) also occurred during the fade. Revival of the dark SEB coloration in the coming months will ultimately require sublimation of these ices by subsidence and warming of volatile-depleted air. © 2011 Elsevier Inc.
Frost M.,British Astronomical Association
Astrophysics and Space Science Proceedings | Year: 2015
Henry Beighton, FRS (1687-1743) was a polymath who played an important role in the early days of the Industrial Revolution. He was born in Chilvers Coton, Warwickshire, and supervised the steam engines which enabled the exploitation of the Warwickshire coalfield; he then used this expertise in Oxclose Colliery, Washington Fell, County Durham. He was the editor of The Ladies' Diary, the only significant mathematical journal in England during the early eighteenth century, and he used continental surveying techniques to produce an early accurate map of Warwickshire. I first got to know about Beighton when I came across the beautiful chart in Warwickshire Country Archives that he used to predict the 18 February 1736-1737 solar eclipse. There is a probable connection to Thomas Wright of County Durham, another astronomer who charted the eclipses which crossed Britain during the eighteenth century. © Springer International Publishing Switzerland 2015.
News Article | March 19, 2016
Witnesses said they saw a mysterious blue-green streak of light early on St. Patrick's Day morning. The bright fireball meteor lit up skies in Britain including areas of London, Stafford, Hampshire and the east coast of England. At around 3:16 a.m. GMT on March 17, those who witnessed the sighting dubbed it as the "St. Patrick's Day meteor" because of its color. The asteroid, which John Mason of the British Astronomical Association described as "spectacular," is bright enough to be called a fireball. The rock may have come from the asteroid belt between Jupiter and Mars. Mason explained that the meteor heated up the oxygen in the Earth's atmosphere, causing it to have its greenish color. "Meteors of this kind are not uncommon," he said. According to the UK Meteor Observation Network (UKMON), the large fireball was first recorded at their Church Crookham station. Their initial report says that the estimated terminal altitude is about 30 to 34 kilometers, or approximately 19 to 21 miles. "Very large fireball reported by public was first noticed by our Church Crookham station at 3:16 this morning," reported Richard Kacerek in UKMON's website. "It momentarily overloaded the camera with light and with [a] second video we will be able to triangulate and calculate the orbit soon," he added. Kacerek said that the agency received various reports across Europe, and that the St. Patrick's Day sighting was the biggest they have ever recorded. "It lasted for a few seconds. It was seen for hundreds of miles," he added. Meteors are small rocks or particles of debris that burn up as they enter the Earth's atmosphere at a very high velocity. Upon entering the atmosphere, they heat the surrounding air, which causes the light witnessed by spectators on Earth. Those who witnessed the fireball posted snapshots and videos of the phenomenon.