Upcoming seminars
August 5, 2025 at 13:00 AM
Rise of Habitability on Young Rocky Exoplanets: Systems Science Approach
Vladimir Airapetian
(American University, Washington, DC, USA)
Discovery of over 5700 exoplanets with Kepler mission, TESS, the Hubble Space Telescope, and JWST suggests that rocky exoplanets in the habitable zones around G, K, and M dwarfs are common in our Galaxy. These detections open a new era in the characterization of the planetary atmospheric environments, the critical step in the search for conditions suitable for life and signatures of their biospheres. Are biospheres of terrestrial-type exoplanets a common phenomenon? How can we detect a (pre)biosphere from a rocky exoplanet? Can we search for Earth twins? Critical examination of the heliophysical and physico-chemical conditions that supported the emergence of life on the early Earth and other inner planets in our Solar System is a promising way to address these fundamental questions. Understanding the conditions for habitability requires the characterization and assessment of several factors: retention of a relatively thick atmosphere, presence of basic molecular compounds, and availability of persistent external energy fluxes. The consistent characterization of space environments and their impact on exoplanetary upper atmosphere and climate requires a new system science approach to characterize habitability as the evolving physico-chemical phase of an exoplanetary system. In this talk, I suggest that while we have no consistent ideas about forms of exoplanetary life other than our own, prebiotic conditions that required the formation of prebiotic chemistry can be well specified under laboratory conditions. These factors could have promoted the emergence and complexification of biological systems on early Earth and possibly Mars. First, I will describe our recent observational campaigns of young solar-like analogs, and data-constrained state-of-the-art MHD and kinetic models of stellar coronae, transient events (CMEs and SEPs) and discuss the impact of solar/stellar eruptive events on atmospheric escape. Second, I will discuss how the extreme space weather in the form of flares, coronal mass ejections, and energetic particle events (like 775AD event) from the recent past of our Sun provides critical insights into the atmospheric chemistry of young terrestrial-type exoplanets, assessment of their role in the formation of biologically relevant molecules and pre-biosignatures to be detected with Habitable World Observatory. Third, I will present the recent results of recent laboratory experiments that reproduce the energy fluxes of particles from the young Sun and study the expected formation of amino acids, carboxylic acids, the chemical precursors of life and nitrous oxide. I will also introduce the design of our recently approved Exoplanetary Particle Irradiation Chemistry laboratory (EPIC Lab) at NASA GSFC.
Held seminars in 2025
June 24, 2025 at 13:00 AM
Spectroscopic and photometric studies of hot, massive stars in open star clusters using Artificial intelligence (AI) approaches
Ahmed Shokry & Mohamed Darwish
(National Research Institute for Astronomy and Geophysics, Helwan (Egypt))
Abstract: Clusters of stars are essential for studying the dynamic and chemical evolution of the galaxy and its neighbors. They are among the most important laboratories for testing the theory of stellar evolution. Studying hot massive stars (e.g. B and O-type stars) in open clusters is particularly useful because it allows a constant stellar age to be correlated with the cluster’s age. It is also very informative in astronomical research since it provides important information about stellar evolution, cluster dynamics, and population interactions. Hot, massive stars are important in the evolution of the chemical composition and structure of the Galaxy. Moreover, knowledge of the characteristics and age of the main sequence of hot, massive stars is crucial to a better understanding the next stages of evolution. Also, the derived stellar parameters within the cluster can significantly impact the generally hot, massive star population, as they can be used to infer the general properties of the stars in the clusters. Additionally, we aim to utilize the trained machine learning models to estimate key parameters of hot massive stars, including elemental compositions, kinematics, and stellar parameters. Quantify uncertainties associated with these estimations to assess the reliability of the results.
April 23, 2025 at 10:30 AM
Data driven exoplanet detection methods
Nikol Škvařilová
(Brno University of Technology, Faculty of Information Technologies)
The aim of this work is to design and implement an approach for analysing data from the transit method for exoplanet detection. The data comes from the Kepler and TESS space telescopes in the form of light curves, which record the observed brightness of a star over time. In this work, I focused on data-driven modelling and detection of exoplanets using Gaussian process regression. Both non-periodic and periodic kernel models were used to identify light curves suitable for detrending and to remove unwanted trends. Following this, models with periodic kernels were used to investigate the periodicity of the data. Finally, models with non-periodic kernels, trained on folded transits, were applied to detect transits in other light curves by correlation. The approaches described in this thesis provide an automated way to pre-process the data and identify possible transits.
April 1, 2025 at 13:00 PM
Observational evidence of a potential link between the short-term magnetic activity cycle and planet engulfment
Ján Šubjak
(ASU AV ČR)
The recent discovery of an increasing number of F-type stars displaying short-term magnetic cycles has sparked interest in understanding the cause behind this phenomenon. One hypothesis suggests that planet engulfment could be a potential explanation. A newly found mini-Neptune from the TESS space mission, TOI-2458 b, has been observed in a polar orbit around one of these stars. This finding not only supports the idea of planet engulfment but also indicates that the polar orientation of the planet could provide evidence that a hot Jupiter may have formed in situ. Additionally, our analysis suggests that the population of F-type stars with short magnetic cycles shows deviations within the framework of gyrochronology, further strengthening the case for the planet engulfment hypothesis.
February 4, 2025 at 10:30 AM
Probing the magnetospheres of chemically peculiar stars through the dips in their light curves
Zdeněk Mikulášek
(ÚTFA PřF MU Brno)
The advent of extensive photometric surveys such as Kepler or TESS missions has enabled the recent unexpected unveiling of short-term dips in the phase light curves of the majority of magnetic chemically peculiar stars of the upper main sequence. We explain this characteristic type of stellar variability caused by repeating transits of semi-transparent structures of stellar plasma trapped in the corotating magnetospheres of stars with a global magnetic field. In the light curves of such stars, we detect dips with a typical depth from fractions of mmag to several mmag, the configuration of which is persistent in the scale of decades. The occurrence of photometric dips, frequency, and prominence in the light curves of rotationally modulated objects allows us to judge magnetospheres’ dimension and strength, making this analysis a universally available instrument for diagnosing stellar magnetic fields. We will demonstrate dip analysis on notorious mCP stars such as V901 Ori, CU Vir, V545 Lyr, 56 Ari, or EE Dra.