Who

My name is Stefan and I work as an astrophysics research fellow at the University of Exeter, UK. I work with Dr. Nathan Mayne and my colleagues in the exoclimatology group, where our collective aim is to characterise new worlds via numerical models.

Prior to my current position, I was a PhD at the University of Bristol with Dr. Zoë M. Leinhardt, studying numerically, the formation of circumbinary planets.

In my spare time, I'm a keen photographer and walker. I would classify myself as a semi-professional tourist; I'll take any opportunity to visit another country!

Work

Water clouds are a very familiar sight on Earth and are the result of convection of moist air. Clouds have also been found on all planets with a tenable atmosphere in our solar system, although they have different compositions (e.g. Sulphuric Acid clouds on Venus) due to their varying atmospheric chemistry, as well as a range of structures (e.g. horizontal banding on Jupiter). In the simplest terms, providing an atmosphere experiences some degree of temperature gradient then cloud formation will occur when the atmospheric pressure-temperature profile crosses the condensation point of a particular chemical species.

In the era of Exoplanet discoveries, the question remains – do extra-solar planets have clouds? If so, what are they composed off, how does their vertical structure vary and what particle sizes are to be expected? Rayleigh scattering small particle ‘haze’ can be used to explain the blueward slope in transmition spectra of the most well chacterised detections (hot-Jupiters), and a more robust cloud deck could contribute a grey opacity that mutes key absorption signals in the infra-red. Additionally, spatial and temporal brightness variability on Brown Dwarfs (extremely large planets or failed stars depending on your background) has been detected indicating the presence of patchy cloud. Since these Brown Dwarfs occupy the same temperature range as the most well defined hot-Jupiter exoplanets, it seems likely that clouds are common across a wide range of exoplanet atmospheres.

I work with the advanced Unified Model, the Met Office’s global circulation model, to understand how cloud formation works in brown dwarf and hot-Jupiter atmospheres. We use DIHRT kinetic cloud formation code to nucleate seed particles and allow for the subsequent growth and evaporation of a range of prominent chemical species onto the seed surface. Our fully coupled cloud formation and 3D GCM means we can track the advection and gravitational settling (precipitation) of cloud. To complete our model, we use a combination of Mie theory and effective medium theory to determine the absorption and scattering of the cloud, and use SOCRATES, the UM’s radiative transfer scheme to handle the two-stream flux.

This work will be used to understand the structure of cloud on these planets, and allow us to identify their observational signal (e.g. offsets in the thermal and reflected phase curves).

Poster

Papers

Lines, S.; N. J. Mayne; J. Manners; I. A. Boutle; B. Drummond; J. Goyal; A. Carter; G. Lee; Ch. Helling and D. M. Acreman Exo-Nephology: Synthetic model transmission spectrum of a cloudy hot-Jupiter. [Submitted to A&A, In Review].

Lines, S.; N. J. Mayne; I. A. Boutle; J. Manners; G. Lee; Ch. Helling; B. Drummond; D. S. Amundsen; J. Goyal; D. M. Acreman; P. Tremblin and M. Kerslake Simulating the cloudy atmospheres of HD209458b and HD189733b with the 3D Met Office climate model., Accepted in A&A

Lines, S.; Leinhardt, Z. M.; Baruteau, C.; Paardekooper, S.-J. and Carter, P. J, Modelling circumbinary protoplanetary disks. II. Gas disk feedback on planetesimal dynamical

Lines, S.; Leinhardt, Z. M.; Baruteau, C.; Paardekooper, S.-J. and Carter, P. J., Modelling Circumbinary Disks Part 1: Fluid simulations of the Kepler-16 and 34 systems, A&A, 582, A5 (2015).

Lines, S.; Leinhardt, Z. M.; Paardekooper, S.-J.; Baruteau, C. and Thebault, P., Forming Circumbinary Planets: N-body simulations of Kepler-34, ApJL, 782, L11 (2014).

Outreach

I am a strong believer in quality science outreach with schools and the public. I have been involved with several schemes such as becoming a STEM Ambassador to communicate basic Physics with local schools, winning the I’m a Scientist, Get me out of here!competition and using the prize money to fund a data analysis computing project and Access to Bristol a scheme that engages with students of all backgrounds wanting to study at the University of Bristol.

I have led outreach classes as part of the ‘Access to Bristol’ scheme which enables all participants who complete to course to be granted a conditional offer to study at the university. My Raspberry Pi planet formation workshop uses tens of Raspberry Pi devices for students to run their own N-body simulations of planetesimals dynamics and collisional accretion.

My work has been displayed and won in various categories of the Bristol ‘Art of Science’ competition which sees scientists at Bristol University display their scientific results in creative ways. Recently, my work was identified by the British Science Association who organised for two images to be displayed at the RUH Bath as part of the charity Art Exhibition ‘Art at the Heart’.

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i = 0;

while (!deck.isInOrder()) {
    print 'Iteration ' + i;
    deck.shuffle();
    i++;
}

print 'It took ' + i + ' iterations to sort the deck.';

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Item One Ante turpis integer aliquet porttitor. 29.99
Item Two Vis ac commodo adipiscing arcu aliquet. 19.99
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Item One Ante turpis integer aliquet porttitor. 29.99
Item Two Vis ac commodo adipiscing arcu aliquet. 19.99
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Item Five Ante turpis integer aliquet porttitor. 29.99
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