Exoplanets and Habitability Seminars
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SEMINAR DATES:
Thursday, 11th of March 2021 at 11:00 h
Dr. Clémence Fontanive, CSH Bern
"Brown dwarfs binaries: from statistics to formation and evolution"
Abstract:
Measuring and understanding binary properties of brown dwarfs provides key insight into formation and evolution mechanisms, and is essential to allow more realistic modelling of formation and be able to predict the evolution and fate of low-mass binaries. In this talk, I will present results from a campaign compiled to investigate the binary statistics as a function of mass and age for the extreme low-mass end of the Initial Mass Function. Based on constraints obtained from Bayesian statistical analyses, I will discuss the implications of the observed disparities for brown dwarf formation and evolution models.
Thursday, 25th of March 2021 at 11:00h
Dr. Ingo Waldmann, UCL, UK
"Deep learning in exoplanet characterisation"
Abstract:
The use of machine and deep learning is prevalent in many fields of science and industry and is now becoming more widespread in extrasolar planet and solar system sciences. Deep learning holds many potential advantages when it comes to modelling highly non-linear data, as well as speed improvements when compared to traditional analysis and modelling techniques.
In this seminar, I will focus on two aspects of characterising extrasolar planets: the data analysis and the atmospheric inverse modelling. In the first part of my talk, I will discuss how we can use machine learning and deep autoregressive models to de-trend exoplanet time-series observations from instrumental and astrophysical noise. In the second part, I will discuss our recent work on developing Explainable AI approaches for exoplanet atmospheric modelling. By making these ‘black box’ models more interpretable, we begin to understand how different neural net architectures learn to model atmospheric spectra. This allows us to derive more robust prediction uncertainties as well as map information content as function of wavelength. As data and model complexities are bound to increase dramatically with the advent of JWST and ELT measurements, robust and interpretable deep learning models will become valuable tools in our data analysis repertoire.
Thursday, 22nd of April 2021 at 11.00h
Dr. Serena Benatti, INAF Palermo
"Constraining young transiting exoplanets: a view on the field and the case of DS Tuc A b"
Abstract:
Transit space missions are deeply changing our view of young planetary systems at close separations.
First observations suggest that Neptune-size planets are more common than gas giant companions around young stars (age less than a few hundreds of Myr). This result contrasts with the previous claims based on the radial velocity method only, which is affected by the strong level of the stellar activity.
After a brief review of the current scenario, I will present one of the first attempts to characterize a young transiting planet, DS Tucanae A b (age ~ 40 Myr, orbital period ~ 8.14 d, radius ~ 5.6 Rearth), detected by TESS in 2019. To do this, we combined spectroscopic follow-up for mass detection, orbital obliquity determination and atmospheric characterization with high-energy observations, used to investigate different models for the planet atmospheric escape.
Thursday, 6th of May 2021 at 14:30 h
Dr. Jack Madden, Carl Sagan Institute, Cornell University
"The effect of surface albedo on habitability around FGK stars"
Abstract:
It is important to maintain atmospheric models that can accurately inform our search for life as we prepare for future observations of potentially habitable planets. 1D climate and photochemistry models play a critical role in exploring large parameter spaces for trends but can hold legacy assumptions that apply well for Earth but not for exoplanets. We explore the effects of including wavelength dependent surface albedo in a coupled 1D model for simulating habitable zone planets around F, G, and K stars. We find new trends in surface temperature and atmospheric composition with star type as a result of the added interplay between the incident stellar spectra and the surface.
external page Recording-Link seminar by Jack Madden.
20th of May 2021 at 11:00 h
Prof. Cara Magnabosco, ETH Zurich
"A geobiologist's perspectives on habitability"
Abstract:
In his exploration into the fundamental question of “What is life?”, Schrödinger concluded that:
The unfolding of events in the life cycle of an organism exhibits an admirable regularity and orderliness, unrivaled by anything we meet with inanimate matter. We and it controlled by a supremely well-ordered group of atoms, which represent only a very small fraction of the sum total in every cell...To put it briefly, we witness the event that existing order displays the power of maintaining itself and of producing orderly events.
— Schrödinger. What is Life? (1944)
Through the field of Molecular Biology, we now know these “supremely well-ordered groups of atoms” as DNA, RNA, and proteins and understand how they interact with one another to power life through the “Central Dogma of Molecular Biology”. Amazingly, all cellular organisms use these 3 molecules composed of C, H, N, O, P and S in the same, orchestrated manner due to the fact that the instructions for chemical catalysis by RNA and proteins are encoded and stored in the DNA-based genomes of organisms. These instructions have been passed down from generation to generation and have been a central feature of life for over 3 billion years. While life converged on the “central dogma” relatively quickly, the mutability of the genome has enabled organisms to explore a wide variety of biological, physical, and chemical possibilities. Evolutionary Biology provides a framework to study life’s trajectory from origins to today and helps explain all of the biological complexity we observe. However, one must also remember that life does not operate in vacuum. Without the physical and chemical processes of our planet, life itself could not exist. Consequently, the physical, chemical and biological appearance of Earth are intricately entwined throughout Earth History.
Geobiology is a field that studies the interactions between life and the environment.
The central dogma of molecular biology and fundamental laws of physics and chemistry guide the interactions between the living and physical world. These interactions result in geobiological signals that can be detected throughout the geologic and genetic record on Earth and, potentially, other planets. By studying these signals throughout Earth history, we can uncover the processes that produce these patterns and make predictions about the conditions in which they arose.
Thursday, 27th of May 2021 at 14:30 h
Dr. Richard Teague, CFA Harward
"Witnessing the Assembly of Planetary Systems"
Abstract:
The Atacama Large Millimeter Array (ALMA) has granted us the sharpest view of protoplanetary disks, the planet formation environment, to date. These disks are reservoirs of planet-forming material and have been found to host a stunning variety of substructure. Gaps, rings and spirals are routinely observed in the distribution of large dust grains, suggestive of dynamical processing by an unseen population of recently formed planets. I will demonstrate how through studies of the gas structure, in concert with the development of new data analysis techniques, I have been able to detect the young planets responsible for the structure we have seen in the dust. I will show how we are now able to conduct a thorough chemical inventory of the planet forming material, and trace the delivery of these materials to young planets during the accretion of their atmospheres. Finally, I will conclude by highlighting how the mapping of the disk’s dynamical structure is providing a unique opportunity to identify the hydrodynamical processes that are driving planet formation and influencing the global evolution of the protoplanetary disks.
Please note that the seminars will be completely online.
If you are interested to participate, please contact us:
Greta Guidi: greta.guidi@phys.ethz.ch
Caroline Keufer: keuferpc@phys.ethz.ch
Please note that the seminars will be completely online.
If you are interested to participate, please contact us.
Thursday, 22nd of October 2020 at 11:00 h
Guest Speaker:
Prof. Giuseppe Lodato, University of Milano
Title:
Disc dynamics in binary systems
Abstract:
Discs around binary systems possess a broad and complex dynamics excited by the non-Keplerian potential in which they live. Tidal truncation, orbital evolution, large scale asymmetries, misalignment and warps are just some of the interesting phenomena at play in such context. Recent interest in this topic has been driven on the one hand by the relevance of orbital evolution in gaseous environments for the hardening of black hole binaries and the consequent emission of gravitational waves. On the other hand, on the smaller scales of stellar binaries, high resolution observations with modern facilities such as ALMA and VLT-SPHERE have allowed to directly image some of these circumbiniary and circumstellar discs to an unprecedented level of details. In this talk, I will discuss some recent advances in our understanding of these dynamical features and how they can help modeling observed discs and predicting the evolutioin of systems (such as black hole binaries) that are harder to observe directly. Such multi-disciplinary approach has proven to be fruitful for both black hole and young star studies.
Tuesday, 3rd of November 2020 at 14.45h
Guest Speaker:
Dr. Arthur Vigan, Laboratoire d’Astrophysique de Marseille
Title:
Direct Imaging and Characterisation of Exoplanets with VLT/SPHERE: Past, Present and Future
Abstract:
SPHERE is the new generation exoplanet imager installed at the Very Large Telescope. Since 2015, we have been conducting the large-scale SHINE survey to look for giant exoplanets around a sample of ~500 young, nearby stars (<300 Myr, <150 pc). The main goal of SHINE is to constrain for the first time the population of giant exoplanets in the 5-100 AU range, where previous direct imaging surveys and other detection methods are not sensitive. After introducing the challenges of direct imaging, I will present the first statistical contraints on the demography of substellar companions drawn from a subsample of 150 stars of the SHINE survey. These early results confirm the trend already identified that massive companions are more frequent around early type stars, but for the first time we also identify a possible change in the formation mechanism between companions around AF stars from companions around FGKM stars. Then, I will introduce the HiRISE project for the VLT, where we propose to implement a coupling between SPHERE and the high-resolution spectrograph CRIRES+, which will hopefully enable the direct characterisation of known companions, from SHINE or other, at very high spectral resolution.
Before the talk, we will have a short virtual coffee with the speaker starting from 14.30.
Thursdat, 19th of November 2020 at 11:00h
Faustine Cantalloube - MPIA Heidelberg
Guest Speaker:
Faustine Cantalloube - MPIA Heidelberg
Title:
Image processing for high-contrast imaging
Abstract:
Advanced post-processing techniques are an essential tool to detect the faint signals from giant gaseous exoplanets and circumstellar disks within high-contrast images. During the last two decades, several methods have been developed, all based on differential imaging techniques. I will introduce these different methods with a focus on Angular Differential Imaging (ADI), and its various flavours, which is the most commonly used method to unveil exoplanets. Still there are a few inherent limitations but new approaches are being developed to bypass these limitations towards increasing the overall sensitivity of our instruments and the confidence of the detections.
Before the talk, we will have a short virtual coffee with the speaker starting from 11.00.
Tuesday, 8th of December 2020 at 14:30 h
Guest Speaker:
Prof. Yamila Miguel - Leiden Observatory
Title:
Unveiling the secrets of Jupiter with the Juno mission
Abstract:
With more than 4000 exoplanets found and about 2-dozens of planets with detected atmospheric chemical species, we moved from an era of discovery to a new era of exoplanet characterisation. On the other hand, extremely accurate measurements by Juno and Cassini missions, make this an exceptional time to combine the detail information on the solar system giant planets and the large amount of data from exoplanets to get a better understanding on planetary physics and a better comprehension on planet formation and evolution.
Because our knowledge on the interior structure of the giant planets is linked with the data we obtain from space missions, these last years were crucial for this field: the outstanding accuracy of the gravity data provided by Juno has fundamentally changed our understanding of the interior of Jupiter. It has allowed us to put constrains on the zonal flows, the extent of differential rotation and lead us to find that Jupiter has most likely a dilute core. In this presentation I will review our knowledge on the interior structure of Jupiter and will also show some new results where we find that a non-homogenous envelope is also a constraint set up by the Juno measurements, which is helping us to get closer to unveiling Jupiter’s deep secrets and to reach a better understanding of the giant planets formation history.