Who I am

An experienced Postdoctoral Researcher at the Institute of Astronomy, University of Cambridge, with a demonstrated history in research. The first person to obtain a Doctor of Philosophy (Ph.D.) in Astronomy and Astrophysics from a Lebanese institution, the American University of Beirut. Course supervisor and Masters project mentor with a long and broad teaching experience. Recipient of several fellowships, awards and research grants. An enthusiastic team-worker, an excellent communicator and an activist in promoting gender equality and representation by championing supportive policies and practices. Active on various committees for an effective and strategic engagement in postdoc academic and social welfare issues in the University of Cambridge. A professional with a Masters in Physics and a Bachelors degree in Physics and Mathematics.

Images: Observatory, IoA (left). AUB (right).
Moon & Pluto by Angelique Babson, NRAO (background)

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What I do

  • Research

  • Teaching

  • Service & Engagement

  • Public Speaking

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Research

Stars are the atoms of the universe. They play a crucial and prominent role on galactic and cosmological levels. Not only are they the visible probes, they also energize their host galaxies and the interstellar medium as their radiation heats the cooler gas in the clouds surrounding them. Beyond hydrogen and helium they create all the elements in the universe as byproducts of the nuclear fusion that keeps them alive, particularly during their later evolutionary phases. They are the hosts and birthplace of planets which form in their circumstellar or protoplanetary discs at or near the end of the stars' own formation process.
I research the evolution of these enigmatic objects and the nucleosynthesis processes taking place through their lifetimes. To be able to do that, I use stellar evolution codes that model their structure and element formation. During my Ph.D. under the supervision of Prof. Mounib El Eid, I used the HYADES code (HYdrodynAmical coDe for Evolving Stars), a well-tested 1D hydrodynamic stellar evolution code with up-to-date input physics. At the Institute of Astronomy, I'm part of the Stars group and I use the Cambridge STARS code to study the evolution of single and binary stars.

CNO ABUNDANCES IN RED GIANTS
When stars become red giants, they experience the first envelope mixing event that changes their surface abundances. Since stellar spectra tell us about the chemistry at the surface, we can then compare our model predictions to the observations. If we have a good understanding of the mixing process, we gain insight into the stellar interiors and chemistry by studying these abundance changes. Using state-of-the-art input physics, we find a discrepancy between predicted surface oxygen abundances and observations in low mass red giants. The adjacent cartoon figure is a simple depiction of this finding, where the model predictions are shown as a red line and star symbols are observations. This suggests the need to invoke deeper mixing in the models than the theory predicts (shown as a dashed green line) to reproduce the observed abundance pattern. This is sometimes called extra mixing and is parametrised as a diffusive process based on 2D hydrodynamic simulations.
However, this raises important questions: how well do we understand mixing? And what physical mechanism drives this extra mixing?

TWO-DIMENSIONAL STELLAR EVOLUTION
Such questions challenge one-dimensional (1D) stellar evolution theory. Although this theory has provided substantial understanding of the inner workings of stars, my research shows that 1D models, with their imposed assumptions and simplifications like spherical symmetry, have difficulty in modelling the transport of heat and chemical elements by convection in various parts of the star. It also highlights shortcomings of ignoring important effects such as rotation. Non-standard parameterised solutions like the one I mentioned previously inevitably fail to capture the physical nature of the underlying processes responsible for certain observational anomalies. This ultimately tickles our curiosity and drives our desire for a better understanding, hoping for the genuine satisfaction that accompanies such attainment.
A brave step in this direction is two-dimensional (2D) axisymmetric models that naturally include rotation. This is being achieved through my work on developing 2DStars, a stellar evolution code to model rotating stars in 2D, together with Robert Izzard, Christopher Tout, Adam Jermyn and Robert Cannon. This is work in progress.
We now have the first converging model of a fast rotating star shown on the left. The density color map (given in polytropic units here) exhibits a severe oblateness associated with the deformation of equipotential surfaces due to the centrifugal distortion.
Being at the frontier of scientific exploration, this project promises a burst of new scientific insight as it exploits existing possibilities for improvement given the advent of computational refinements and the unprecedented developments in observational astronomy.

SYNTHESIS OF C-RICH DUST IN NOVAE OUTBURSTS
Classical novae are very interesting objects since they are prolific dust producers. These are binary systems involving a star (not unlike our own Sun) and a white dwarf. Observations of a number of novae have unambiguously revealed that their ejecta are rich in carbon. However, theoretical models of novae outbursts to date have yielded outflows richer in oxygen than carbon. In a collaboration with Jordi José and Mounib El Eid, we provided state-of-the-art novae models which produce carbon-rich ejecta, providing a novel explanation of these observations.

THE BLUE LOOP
Stars of intermediate mass exhibit a phenomenon called the "blue loop", which characterizes the evolution through the Cepheid instability strip. Since Cepheids are well-known variable stars that are largely observed in the Galaxy, the blue loop presents a powerful phase that can constrain important physical processes. We investigated the striking effect of a revised hydrogen-burning reaction rate on the blue loop and showed an impressive suppression of the blue loops of intermediate mass stars. This is depicted in the adjacent figure which shows the evolutionary tracks of stars of various masses in the HR diagram. Black and blue symbols are observed cepheids (see paper for details). The supression of the blue loop of the 5 and 6M stars undesirably leaves many observed Cepheids unexplained. Having an experimentally established nuclear reaction rate allows focus to be brought to the role of related physical processes that are not yet well-understood, like convection, in solving this discrepancy.

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Teaching

I give supervisions for the Mathematics for Natural Sciences Tripos (NST) course at Churchill College, University of Cambridge. I supervise Masters projects at the Institute of Astronomy.

Previously, I taught Modern Physics, Astronomy, Mechanics and Electricity & Magnetism courses in the Physics department at American University of Beirut. I also supervised Electricity & Magnetism, Modern Physics and Mechanics labs at the American University of Beirut and the Lebanese American University, since 2006. I was a schoolteacher for a while, teaching Grade 7 students in 2008.

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Service & Engagement

Gender Equality

I am deeply committed to promoting meritocracy in academia through gender equality and representation in science. Through my role as University Representation and Policy Officer for STEMM in the Postdocs of Cambridge committee and being on the team that is responsible for achieving an Athena SWAN (a UK high-profile equality initiative) status for the IoA, I actively engage in promoting gender equality, inclusion and career progression and success. These roles are ultimately breeding grounds for forging policies that are not only supportive of women entering science but also rising to the top echelons of scientific power, prestige and pay, circumventing a current problem known as the leaky career pipeline. I also chair an advisory Athena SWAN subcommittee on Anti-Bullying & Harassment which advised an action plan to effectively address this major issue that, our survey shows, affects females disproportionately at the workplace.
I represented the IoA at the Women in Astronomy IV conference in Austin, TX, where I communicated IoA practices, institutional identity and values that embody its commitment to equality. I'm invited to speak at the United Nations Expert Meeting on Space for Women organized jointly by the United Nations Office For Outer Space Affairs and UN Women at the UN Women headquarters in NYC.

Outreach

I constantly engage in outreach events. I coordinate the Stars group outreach programme at the Institute of Astronomy by managing Window To The Stars, a colourful user-friendly pedagogical graphical interface to visualise the internal structure and evolution of a star, developed by Robert Izzard and Evert Glebbeek, during IoA open evenings. I participated in the Cambridge Science Festival at the IoA. In Lebanon, I took part in the Science Days public events.

Community Service

I previously worked with MySchoolPulse, a non-profit NGO for schooling children with life-threatening illnesses. I also served on the Graduate Students Society at AUB. I'm on the LOC of several conferences and I currently serve on various committees.

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Public Speaking

I have had the pleasure to speak at more than 20 conferences, workshops and seminars. Most were to present my latest research results, some to get a job and others to communicate how fun my research is! Here's a brief selection.

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Education & Professional Experience

  • Education

  • Work Experience

  • Professional Associations

  • Awards & research grants

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Education

Ph.D. in Astrophysics

AMERICAN UNIVERSITY OF BEIRUT

Evolution & Nucleosynthesis in 1 to 12M Stars

MSc. in Physics

AMERICAN UNIVERSITY OF BEIRUT

Production of 13C in Asymptotic Giant Branch Stars

BSc. in Physics & Mathematics

LEBANESE UNIVERSITY

Image: AUB College Hall

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Work Experience

PRESENT

Post-Doctoral Research Associate

Institute of Astronomy, UNIVERSITY OF CAMBRIDGE

Masters Project Supervisor

Institute of Astronomy, UNIVERSITY OF CAMBRIDGE

Course Supervisor

Churchill College, University of Cambridge

PAST

Lecturer & Research Fellow

American University of Beirut

Physics course & lab instructor

American University of Beirut

Physics lab instructor

Lebanese American University

Images: Hoyle, IoA (left). Churchill College (right)

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Professional Associations

Junior Research Fellow

Wolfson College, University of Cambridge

Royal Astronomical Society Fellow

Royal Astronomical Society

University Representation & Policy Officer (STEMM)

Postdocs of Cambridge Society

Athena SWAN & Project Juno Self-Assessment Team Member

Institute of Astronomy

IoA/Kavli Astro-Postdoc Committee Co-Chair & Founding Member

Postdocs at IoA

Senior Combination Room Associate

Churchill College, University of Cambridge

Images: RAS (left). Wolfson College (right)

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Awards & research grants

Doctoral Studies Award at the American University of Beirut

National Council for Scientific Research-Lebanon (CNRS-L)

Doctoral research grants

National Council for Scientific Research-Lebanon (CNRS-L)

Graduate Assistantship

AMERICAN UNIVERSITY OF BEIRUT

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