Archives Séminaires 2017-2018

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Séminaire IPAG de Konstanze Zwintz (U. of Innsbrück), jeudi 7 décembre 2017 à 11h00, salle Manuel Forestini IPAG

Stars have been born countless times in our Universe in the past. The properties that stars obtain at birth such as initial mass, composition and angular momentum determine their complete lives until their deaths.
But our theoretical understanding of early stellar evolution contains a lot of unsolved questions as there are many physical processes that are either not well-understood or not taken into account properly in theoretical models. Asteroseismology – the study of stellar (…)

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Séminaire IPAG de Maïca Clavel (IPAG), jeudi 14 décembre 2017 à 11h00, IRAM seminar room

The supermassive black hole at the center of the Milky Way, Sagittarius A*, is currently one of the least luminous known supermassive black holes. However, X-ray observations carried out over the past decade have provided strong evidence that Sgr A* has experienced periods of higher activity in the past centuries. By tracing the echoes of these past outbursts as they propagate through the Galactic center molecular clouds, we intend to better understand the duty cycle of this supermassive (…)

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Séminaire IPAG de Amir Levinson (Tel Aviv University & IPAG), jeudi 11 janvier 2018 à 11h00, salle Manuel Forestini IPAG

The detection of multi-messenger emissions from the gravitational wave source GW170817 has lent strong support to the hypothesis that neutron star mergers are the progenitors of short GRBs, and that these events constitute the primary source of r-process elements in the Universe. While the various data confirms earlier predictions by and large, it also revealed a small surprise. In this talk I will describe the main observations and their theoretical interpretation, as perceived in the (…)

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Séminaire IPAG de Romane Le Gal (CFA), jeudi 18 janvier 2018 à 11h00, salle Manuel Forestini IPAG

Astrochemistry, which strongly depends on the physical conditions of its environment, has started very shortly after the Big Bang and therefore represents an outstanding intermediary to study the chemical, physical and dynamical history of our Universe. In the recent years, significant improvements in laboratory astrophysics and new generations of radio ground (ALMA, NOEMA, FAST), airborne and space (SOFIA, Herschel, JWST) telescopes, are opening a new age of the Astronomy discovery, in (…)

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Séminaire IPAG de Pierre Vernazza (LAM), jeudi 25 janvier 2018 à 11h00, salle Manuel Forestini IPAG

Asteroids in our solar system are metallic, rocky and/or icy objects, ranging in size from a few meters to a few hundreds of kilometers. Whereas we now possess constraints for the surface composition of most D>100 km primordial main-belt asteroids, little is known regarding their internal structure. Yet, this is a fundamental property whose characteristics result directly from (a) their formation location, (b) their time of formation, and (c) their collisional history. Characterizing the (…)

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Séminaire IPAG de Jérôme Loreau (U. Bruxelles), jeudi 1er février 2018 à 11h00, salle Manuel Forestini IPAG

Major advances in astrochemistry are generally driven by new observational data. Current facilities such as ALMA have contributed to a better understanding of star and planet formation, from molecular clouds to protoplanetary disks, while future instruments such as the JWST or the ELT will allow further progress, for example in the study of the composition of exoplanetary atmospheres. As observations rely mostly on atomic and molecular spectra, their interpretation requires models describing (…)

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Séminaire IPAG de Emeric Bron (Instituto de Física Fundamental, CSIC, Madrid), jeudi 8 février 2018 à 11h00, salle Manuel Forestini IPAG

Star-forming regions present rich infrared and millimeter spectra emitted by the gas exposed to the feedback of young stars. This emission is increasingly used to study the star formation cycle in other galaxies, but results from a complex interplay of physical and chemical processes : chemistry in the gas and on grain surfaces, (de)excitation processes of the atoms and molecules, heating and cooling balance,... Its understanding thus requires detailed astrochemical models that include the (…)

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Séminaire IPAG de Johan Mazoyer (Johns Hopkins University, STSI), jeudi 1er mars 2018 à 11h00, salle Manuel Forestini IPAG

More than 3000 thousands exoplanets have been discovered to date, but only a few have been imaged directly. However, by allowing the observation of circumstellar disks and planets (sometimes simultaneously around the same star, as in the case of β-pictoris), this method is a fundamental tool for the understanding the process of planetary formation. In addition, direct access to the light of the detected objects allows spectroscopy, paving the way to the full chemical analysis of exoplanets’ (…)

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Séminaire IPAG de Juan-Carlos Fontecilla (IBS, Institut de Biologie Structurale, Grenoble), jeudi 8 mars 2018 à 11h00, salle Manuel Forestini IPAG

A great variety of organic molecules are relatively abundant in outer space and are easily made using spark-tubes and a reducing atmosphere. This has led many to conclude that life started in a primordial soup rich in "prebiotic" molecules. During my seminar I will argue that, based on reaction selectivity, bioenergetics and stereochemistry this proposition appears unlikely. Instead, conditions favorable to the emergence of life could have been possibly present in oceanic alkaline (…)

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Séminaire IPAG de Cecilia Ceccarelli (IPAG), jeudi 15 mars 2018 à 11h00, salle Manuel Forestini IPAG

Since a long time, it has been known that molecular complexity in space can reach amazingly high levels. Alcohols, sugars and amino acids are detected in meteoritic and cometary material ; some of them are even detected in regions where solar-like stars and planetary systems are forming today. These evidences led the Nobel prize laureate C.De Duve to affirm that the “seeds of life are universal” and that “life is an obligatory manifestation of matter, written into the fabric of the (…)