ESA's Holland-Area Exoplanet Science Meeting (HAESM) 2024


Uniting all ESA and Holland-area exoplaneteers for a day of science, discussions, and collaboration; our colleagues from ESAC, STScI, and external collaborators are equally encouraged to join us remotely.
Tuesday, 2 April 2024, foreseen 13:00 - 17:30 CEST, in ESTEC (rooms Ba024 and Ba031) and online (via WebEx).


All in-person attendees are invited to arrive at the ESTEC security gatehouse (Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands) at 11:00 CEST. You must bring your passport with you to collect your scientific visitor badges for the day. You can reach ESTEC by bicycle or local bus systems (e.g. from Leiden Centraal); for your individual travel planning please consult an online map service. Our colleagues from security and/or our administrative assistants will receive you and guide you from there to our ESTEC cafeteria, where we can enjoy a coffee and lunch (self-paid). The presentations will start from 12:55 CEST, with a mix of in-person and virtual presentations. We hope to enjoy a relaxing evening in the Dutch Sun and continue with informal science discussions during a borrel at the ESCAPE lounge from around 17:30 CEST.



Time Speaker Affiliation Title Attendance
12:55 - 13:00 Maximilian Günther ESA / ESTEC Welcome  
13:00 - 13:15 Cristina-Maria Cordun ASTRON Hide and seek: Using interferometry to hunt for hot Jupiters at decameter wavelengths. In person
13:15 - 13:30 Wiebe de Gruijter University of Amsterdam Retrieving the Photochemistry of SO2 In person
13:30 - 13:45 Andrew Allan  Leiden University  Why hasn't there been more detections of helium escaping from the atmospheres of younger exoplanets? In person
13:45 - 14:00 Stefano Bellotti Leiden Observatory Spectropolarimetric characterisation of exoplanet hosting stars in preparation of the Ariel mission: the magnetic environment of HD 63433 In person
14:00 - 14:15 Mariasole Aurora Agazzi ETH Zurich Investigating Cross-Correlation Sensitivity to Atmospheric Parameters Using Linear Regression  In person
14:15 - 14:45 Coffee Break      
14:45 - 15:00 Fatemeh Fazel Hesar LUNEX EuroSpaceHub & Leiden Observatory Analysis of Kepler "KIC 8462852" Light Curves using ML Techniques In person
15:00 - 15:15 Sanne Bloot ASTRON Catching the wisps: constraining mass-loss rates of cool stars at low frequencies In person
15:15 - 15:30 Robin Baeyens University of Amsterdam Midnight Molecules: Photodissociations and Transport-Induced Chemistry on Hot Exoplanets In person
15:30 - 15:45 Ekaterina Ilin ASTRON Hot Jupiters and stellar eruptions: planet-induced flares in young exoplanetary systems In person
15:45 - 16:00 Bernard Foing LUNEX EuroSpaceHub & Leiden Observatory Characterising exoplanets and stellar activity from ML analysis of Kepler and TESS light curves In person
16:00 - 16:30 Coffee Break      
16:30 - 16:45 Szymon Petyniak Eindhoven University of Technology Exploring the Influence of Stellar Wind-Planetary Magnetosphere Interactions on Planetary Habitability In person
16:45 - 17:00 Daphne Stam Delft University of Technology Searching for liquid surface water on Earth-like exoplanets with spectropolarimetry  In person
17:00 - 17:15 Dag Evensberget Leiden Observatory CMEs in AB Doradus: Implications of High-Latitude Eruptions on Exoplanetary Environments In person
17:15 - 17:30 Jasmina Lazendic-Galloway Eindhoven University of Technology Stellar production of SLRs and their impact on planetary habitability  In person
17:30 onwards Borrel (in Escape building)      




Hide and seek: Using interferometry to hunt for hot Jupiters at decameter wavelengths (Cristina-Maria Cordun, ASTRON)

Gaseous exoplanets generate low-frequency radio emission (<40 MHz), which is associated with aurorae via circularly polarized cyclotron maser mechanism and is directly related to the surrounding space weather. To obtain a detailed analysis of this mechanism, one must measure the stellar wind's electron density and the planet's magnetic field, which is only possible with observations at radio frequencies. Besides many efforts, direct imaging of radio exoplanets has not been successful until today, with only a handful of tentative detections. The Low-Frequency Array (LOFAR) is ideally suited for this task because it can observe at frequencies below 40 MHz and has high sensitivity. However, imaging at such low frequencies is challenging due to high interference levels and rapidly varying ionospheric conditions. To overcome the technical challenges of imaging below 40 MHz, I will present a new pipeline that corrects for all the known instrumental and ionospheric effects. Then, I will show the deepest images down to 15 MHz of a radio exoplanet candidate and use them to constrain the scaling laws that predict the exoplanet's radio luminosity. A clear detection of Tau Bootes b would be the first in the field of radio exoplanets and a step forward for imaging at low frequencies. I will end with a brief overview of the learned lessons and introduce an ongoing major LOFAR upgrade that will facilitate deeper imaging down to 15 MHz.


Retrieving the Photochemistry of SO2 (Wiebe de Gruijter, University of Amsterdam)

A number of recent detections have confirmed the presence of the molecule SO2 in the atmospheres of hot gas giants. This molecule is an unambiguous sign of photochemically induced disequilibrium, since an atmosphere in chemical equilibrium stores most of its sulfur in the form of H2S at these temperatures. In this talk, I will go over the recent and ongoing sulfur program of JWST. I will look at the effect of disequilibrium on retrievals of planetary atmospheres (and how to mitigate this), and I will look in depth at the chemical production pathways that lead to SO2. 


Why hasn't there been more detections of helium escaping from the atmospheres of younger exoplanets? (Andrew  Allan, Leiden University)

Highly irradiated exoplanets undergo extreme hydrodynamic atmospheric escape, due to the high level of stellar XUV flux they receive. Over their lifetime, this escape varies significantly, making evolution studies essential for interpreting the growing number of observations of escaping planetary atmospheres. In our previous work, we modelled the evolution of escape, as well as one of its tracers, the He triplet 1083nm transit signature. Using hydrodynamic and ray-tracing models, we demonstrated that for a 0.3Mjup gas-giant, atmospheric escape and the corresponding He 1083nm signature, are stronger at younger ages. Yet, the current literature includes several young (<1Gyr) planets with either weak or non- detections in He 1083nm. To understand this discrepancy between evolutionary models and observations, we performed detailed models for many of these specific young systems. The resulting He 1083nm predictions align relatively well with the observations. From our two studies, we conclude that for a given planet, stronger atmospheric escape at younger ages produces deeper He 1083nm absorption. However, for a population of exoplanets, the correlation between younger ages and stronger He absorptions is weak due to their diverse environments (ages and XUV fluxes) and sizes. Instead, future observing proposals could benefit from considering alternative planetary parameters as indicators of robust He 1083nm detections, as I will elaborate upon in this contribution.


Spectropolarimetric characterisation of exoplanet hosting stars in preparation of the Ariel mission: the magnetic environment of HD 63433 (Stefano Bellotti, Leiden Observatory)

The accurate characterisation of stellar magnetism of planetary host stars has been gaining an increasing momentum, especially for what it concerns transmission spectroscopy investigations of exoplanets. Indeed, the magnetic field regulates how irradiated planets are, and the presence of inhomogeneities on the stellar surface which hinder the precise extraction of the planetary atmospheric absorption signal. We have initiated a spectropolarimetric campaign to unveil the magnetic field properties of known exoplanet hosting stars included in the current list of potential Ariel targets. In this talk, I will focus on HD 63433, a young solar-like star hosting two sub-Neptunes and an Earth-sized planet. These exoplanets orbit within 0.15 au from the host star and have likely experienced different atmospheric evolution paths. We analysed optical spectropolarimetric data collected with ESPaDOnS, HARPSpol, and Neo-Narval to gauge the stellar activity and reconstruct the large-scale magnetic topology via Zeeman-Doppler imaging, which was then employed to simulate the stellar environment. We obtained a stellar magnetic field with complex geometry and predominantly toroidal, in agreement with other stars of similar spectral type and age. Our simulated stellar environment locate 10 percent of the innermost planetary orbit inside the Alfvén surface, therefore brief star-planet magnetic connections can occur. The outer planets are outside the Alfv√©n surface, and a bow shock between the stellar wind and the planetary magnetosphere could form.


A peculiar planetary-mass candidate imaged around a binary star (Pengyu Liu, Leiden University)

While transit and radial velocity methods push exoplanet detection limit to extreme close separation planets, making the discovery of lava worlds and hot Jupiters, direct imaging expands the parameter space of exoplanets to extremely wide separations, revealing the existence of cool gas giants. These extreme wide separation planets (e.g. over 100 AU from their host stars) need to form quickly to acquire enough materials before the protoplanetary disk dissipates, challenging current planet formation mechanisms. In this talk, I will present a planet candidate imaged around a binary star system discovered by the Young Suns Exoplanet Survey (YSES). If confirmed, this would be the fourth exoplanet imaged around a third planetary system with YSES. The central star is resolved to be a tight binary consisting of a K0 star and an M dwarf. Combining Gaia absolute astrometry and SPHERE relative astrometry, we are able to perform precise astrometric analysis of a companion around a binary star and rule out the possibility that this candidate is a static background source. Its anomalous sky motion straddles that expected for a true companion at a separation of 719 AU to the host star and the sky motion expected for a nearby background object. I will discuss three possible scenarios of this candidate: a bound planet, a free-floating planet with gravitational interactions with the binary, and a nearby background low-mass object. 


Analysis of Kepler "KIC 8462852" Light Curves using ML Techniques (Fatemeh Fazel Hesar, LUNEX EuroSpaceHub & Leiden Observatory)

The intricate patterns and hidden secrets embedded within celestial light curves hold immense potential for understanding the underlying physical processes governing the cosmos and identifying potentially habitable worlds in the context of exoplanet research. However, deciphering these patterns is often hindered by the complexity and noise inherent in light curve data. To address this challenge, we propose a novel multi-model regression approach that combines the strengths of Gaussian Process Regression (GPR), Linear Regression, and Random Forest Regression (RFR) to analyze light curve data effectively. This comprehensive approach enables us to uncover deep insights even in noisy and complex signals, particularly relevant for identifying exoplanets. We leverage the wealth of Kepler light curve data and employ meticulous data collection and preprocessing techniques to utilize this multi-model regression approach. Our analysis of the KIC 8462852 dataset, a potential exoplanet host, demonstrates the effectiveness of our method in unveiling the complex interplay of periodic and non-periodic phenomena, providing valuable insights for exoplanet detection. This groundbreaking approach empowers us to decode the mysteries of light curves, paving the way for transformative insights into exoplanets and the search for habitable worlds.


Catching the wisps: constraining mass-loss rates of cool stars at low frequencies (Sanne Bloot, ASTRON)

Stellar winds govern the lives of stellar systems, from dictating the evolution of the star itself to eroding the atmospheres of exoplanets. The impact of the wind on a stellar system is largely determined by the mass-loss rate -- which is notoriously difficult to measure on dwarf stars since the wind is so tenuous. Currently, mass-loss rates of cool stars have to be modelled or inferred indirectly, for example from astrospheric Ly$\alpha$ absorption. In this talk, I will present a more direct method to constrain the mass-loss rate of a star using detections of low-frequency coherent radio emission, exploiting the lack of free-free absorption to place upper limits on the stellar mass-loss rate. We apply this method to M dwarfs detected with LOFAR at 120 MHz and find upper limits down to 4 times the solar mass-loss rate, independent of distance. While these limits are already competitive with other methods, we expect to reach upper limits of less than the solar mass-loss rate in the near future.


Midnight Molecules: Photodissociations and Transport-Induced Chemistry on Hot Exoplanets (Robin Baeyen, University of Amsterdam)

The day and night sides of hot giant exoplanets are widely contrasting environments with temperature differences up to 1000 K. Yet, atmospheric circulation leads to an exchange of heat and chemical species between both hemispheres. As observational techniques mature, it has now become possible to probe these chemical gradients and investigate chemical transport, condensation, cold trapping, and ionization in great detail. We present photochemical model results of hot exoplanetary atmospheres and show that photodissociation can have a global impact. Stellar photons can even break down triple-bonded CO and N2 molecules on the day side. The resulting radicals are subsequently transported to the night side, where they kick-start new chemical pathways. Such mechanism could explain the enigmatic observation of HCN on WASP-76 b. Finally, we broach the subject of ionization in exoplanet atmospheres and propose avenues to tackle neutral-ion chemistry in the future.


Hot Jupiters and stellar eruptions: planet-induced flares in young exoplanetary systems (Ekaterina Ilin, ASTRON)

A planet in close orbit around its host star is an in-situ probe of its winds and extended magnetosphere. As the planet plows through the magnetized plasma around the star, it can perturb the field, and trigger flares in the stellar corona. Their energy scales with stellar and magnetic field strengths and particle densities in the interplanetary space, which are inaccessible with other observing methods. However, how to identify these planet-induced flares among intrinsic stellar flaring is poorly understood. We used the correlation between flares and the planet's orbital period to identify planet-induced flaring using time series photometry from Kepler and the Transiting Exoplanet Survey Satellite. We searched 1811 star-planet systems for flares, and found 25 single active planet hosts suitable for our analysis. The 25 systems fall into two categories: an inactive branch without flare-orbit correlation, and a potentially active one where the correlation intensifies with increasing power of interaction. We also present HIP 67522, a 17 Myr old Hot Jupiter host, that displayed the clearest flare-orbit correlation (p < 0.006), and our ongoing follow-up observations of its potentially planet-induced flares with CHEOPS and the Australian Telescope Compact Array. Young Hot Jupiter systems are rare, but our work highlights that they are exciting systems where stellar wind densities and field strengths could be constrained via star-planet interactions.


Characterising exoplanets and stellar activity from ML analysis of Kepler and TESS light curves (Bernard Foing, LUNEX EuroSpaceHub & Leiden Observatory)

We recall some earlier work to monitor stellar variability due to magnetic activity and flares, from ground based and space observations . We recently applied Machine learning methods for modelling stellar and instrumental systematics in lightcurves. We used a Gaussian Process to model the stellar activity rotational modulation, background granulation, and transit signals simultaneously . We applied scalable Gaussian Process (GP) models to characterize exoplanet transits and stellar activity in Kepler and TESS lightcurves. Our aim was to retrieve accurate transit and rotation parameters, such as planet radii and stellar rotation periods (Foing, V, Heras A and Foing B 2020, 2021). We also used Deep Learning methods for transit detection, and presented early results of the research applied to simulated TESS-like light curves. (Rusticus, Heras  et al 2021).  We also applied Deep Learning methods to TESS light curve data to analyze the shape and asymmetries of exoplanet transits. This can be used to classify different exoplanet types or to discover new phenomena and  track variations in the transit shape over time (Hoehnes et al 2021). This research can be extended to data from past (COROT, Kepler, TESS), current (HST, JWST, CHEOPS) and future (PLATO, ARIEL) space exoplanetary missions.


Investigating Cross-Correlation Sensitivity to Atmospheric Parameters Using Linear Regression (Mariasole Aurora Agazzi, ETH Zurich)

The discovery of exoplanets has revolutionized our understanding of the universe, revealing a multitude of diverse planetary systems. In the current exoplanet research panorama the characterisation of atmospheres has become a focus point, offering valuable information on composition, climate, and formation mechanisms. In this context this study explores the sensitivity of cross correlation methods with respect to atmospheric parameters on medium-resolution integral field spectroscopy data using linear regression. The goal of the presented research is to perform a grid search over four atmospheric parameters (temperature, surface gravity, metallicity, and carbon-to-oxigen ratio) for a set of given simulated substellar companions to investigate and quantify the sensitivity of the cross correlation peak. Heat maps and linear regression analysis are used to quantify the results.


Exploring the Influence of Stellar Wind-Planetary Magnetosphere Interactions on Planetary Habitability (Szymon Petyniak, Eindhoven University of Technology)

We will present an idea for exoplanetary research that we are about to undertake, inspired by the observation that planetary magnetospheres are likely to be essential for habitability. We aim to investigate magnetospheres of Mercury-sized exoplanets and relate magnetospheric star-planetary interactions to the habitability of such sources. In our proposed approach, we place an exoplanet at different orbital distances to its host-star and estimate the impinging photon radiation and magnetospheric volumes resulting from the upstream stellar wind ram pressure. With our global 3D numerical model, we aim to investigate the plasma flux onto the planetary surface. We discuss implications for habitability, and potential for other applications of similar research methods.


Searching for liquid surface water on Earth-like exoplanets with spectropolarimetry (Daphne Stan, Delft University of Technology)

The discovery of liquid water on an exoplanet would be a milestone in the search for extraterrestrial life, as liquid water is considered to be a prerequisite for life as we know it. The design of future telescopes that could possibly detect liquid water on exoplanets rely on numerical simulations of reflected starlight by exoplanet models. In this talk, we present the simulated reflected signal of Earth-like exoplanets with realistic (rough) ocean surfaces, for both the total and the polarized light. We will discuss the unique ocean signatures in the polarization spectra from the visible to the near-infrared and in the planetary phase curves (Trees and Stam, 2019,2022). We will explain our ongoing efforts to verify our model predictions with observations of the Earth as an exoplanet, through Earth-shine measurements via the Moon with the VLT and from the Moon with the planned lunar Moonshot mission of the TU Delft.


CMEs in AB Doradus: Implications of High-Latitude Eruptions on Exoplanetary Environments (Dag Evensberget, Leiden Observatory)

The young solar-type star AB Doradus, with its intense coronal magnetic field up to a thousand times stronger than the Sun's, presents an intriguing case for studying coronal mass ejections (CMEs). Contrary to predictions that strong magnetic fields would inhibit CMEs, coronal dimming, indicative of CMEs, has been observed in AB Doradus. We propose that these CMEs may originate from high latitudes, emerging through regions with open magnetic fields. Our investigation into these phenomena demonstrates that CMEs from AB Doradus can indeed escape through areas of open magnetic field. This discovery challenges conventional understanding of stellar behaviour and carries implications for the atmospheres and habitability of exoplanets orbiting young, active stars. The capacity for CMEs to escape suggests a more dynamic and potentially hostile environment for these planets, influencing their atmospheric chemistry and defences against stellar radiation. By linking CME activity to potential impacts on exoplanetary conditions, our study emphasises the need for further exploration of how stellar phenomena unlike anything observed on the Sun affect the habitability and atmospheric development of exoplanets.


Stellar production of SLRs and their impact on planetary habitability (Jasmina Lazendic-Galloway, Eindhoven University of Technology)

Short-lived radionuclides (SLRs) such as 26Al and 60Fe have played a pivotal role as primary heat sources in the melting and differentiation of planetesimals during the early Solar System's evolution. This project investigates the relationship between SLR-induced heating and the establishment of conditions conducive to life on planets. The process of melting and differentiation is essential for the formation of planets with iron-rich cores and for sustaining liquid iron at their centres. Such a state is critical for the generation of Earth's magnetic field, which, in turn, shields complex life from harmful radiation. We explore a universal model to determine the extent to which a planetoid can capture stellar SLR yield sufficient to form a liquid iron core. Additionally, we assess how variations in SLR abundances influence the thermal characteristics of planetoids. Our objective is to understand the impact of stellar environments near protoplanetary disks on planetary formation and to examine how the outputs of stellar SLR yield either support or limit the development of habitable planets.



If you would like to join us for HAESM 2024 - whether in person or remotely, whether to network, listen in, or to present your own resarch highlights - please use the form at the bottom of this webpage to register and submit your abstract. Registration and abstract submission open on 1 Feb 2024 and close by 15 Mar 2024.

Science presentations are forseen to be around 10+5 minutes (talk+questions), but the exact duration might be altered depending on the number of abstracts submitted. HAESM 2024 seeks to give everyone a platform to present their work, and especially encourages contributions from early career scientists. HAESM 2024 also actively encourages any and all "unconference" approaches, and as such the form below is also open to submissions of ideas for group discussions, brainstormings, diversity workshops, and other events that fit the scope.

Personal Data Protection

Please note the following important privacy information related to Science conferences. The full information can be read in the event privacy notice, which must be agreed to as a requirement for participating in the Science conference.

  • The event you are registering for may be livestreamed/recorded and you are likely to feature in the video, which may be published on ESA or external web platforms such as YouTube. If you do not wish your personal data to be captured, then you have the right to switch off your camera and microphone, or if attending in person, sit in an area that is not being filmed.
  • You accept that ESA has limited control of data published on external web platforms (such as YouTube) and that the use of your data is subject to the privacy policy of the external platform.
  • Photographs may be taken at this even by an ESA photographer for published on ESA websites as a historical record of attendance. If you do not wish to have your photograph taken, please inform the event organiser.
  • By registering you acknowledge that your personal data may be sent outside of the EU as part of the abstract assessment process. This may include your personal data being sent to countries not qualified by the European Commission as providing an adequate level of protection for personal data. 
  • By submitting the personal data of co-authors, you confirm that you have their consent to the event privacy notice. It is the responsibility of the submitter to gather and manage this consent.



The European Space Agency (ESA) strives to create a positive work environment where all people are treated with respect and dignity. In the context of ESA Science workshops and conferences, all participants are expected to help create an environment at the meeting and all associated activities that is professional, inclusive, and in which everyone is treated with respect.

All participants are therefore requested to follow these guidelines:

  1. All participants are expected to behave professionally and to be respectful – critique ideas not people.
  2. All communication should be appropriate for a professional audience taking into account the many different backgrounds and perspectives of the participants.
  3. Participants may share the contents of talks/slides via social media unless speakers have asked that specific details/slides not be shared. If participants wish to share photos of a speaker on social media, it is strongly recommended that they first get the speaker’s permission.

ESA does not tolerate unprofessional or inappropriate behaviour or statements. This includes but isn’t limited to: sustained disruption of talks, comments related to individual characteristics, background or identity, and photography or recording of an individual without consent.

Meeting organisers and chairs bear a particular responsibility in ensuring that the code of conduct is followed.

  • The Local Organising Committee members are designated as the contact points for all matters related to this code. Participants can report any violation of these guidelines to these designates in confidence.
  • Should a participant witness behaviour they suspect may be unprofessional or inappropriate, it is recommended that they approach the affected person as soon as possible to support and help them. The witness can encourage the affected person to report the unprofessional or inappropriate behaviour but should be guided by that person on their preferred course of action.
  • Anyone requested to stop inappropriate behaviour is expected to comply immediately. In serious cases, a participant may be asked to leave the event without a refund or, in the case of online participation, the removal of meeting credentials.
  • In the case where the unprofessional or inappropriate behaviour involves an ESA staff member, ESA’s Human Resources Department may be contacted for further guidance on the applicable policies and means of action.

Acknowledgments: This code of conduct has been adapted from the London Code of Conduct (by A. Pontzen and H. Peiris), which was derived from original Creative Commons documents by PyCon and Geek Feminism. It is released under a CC-Zero licence for reuse. To help track people's improvements and best practice, please retain this acknowledgement, and log your re-use or modification of this policy at: .



  • Your screen name should be your full name followed by your institution in brackets, e.g. "Mae Carol Jemison (NASA)"
  • Keep your microphone muted to minimise background noise
  • Make use of the chat & participants menu
  • Speakers will miss the visual feedback. In the chat & participants menu you can make up for that, by leaving nice remarks, using thumbs-up emojis, raising your hand, and clapping after the talks
  • To ask questions, either use the "raise hand" button in the participants menu and prepare to be called up, or write them down in the chat for the chair to read them out


Questions about the ESA Exoplanet Team? Please email any of our members and we will be happy to help!
Last updated 1 Feb 2024