Colloquia

Talks given by high profile astronomers and scientists.


Video
Thursday March 12, 2015
Prof. Annette Ferguson
Royal Astronomical Observatory of Edinburgh, UK

Abstract

Evidence is mounting for the presence of complex low surface brightness structures in the outer regions of galaxies. While the most spectacular examples are provided by systems hosting coherent debris streams, the most common examples may be extremely diffuse stellar envelopes. Wide-field imagers on large telescopes are allowing us to quantitatively explore the resolved stellar populations in these components within and well beyond the Local Group. I will highlight some recent  results from our work and discuss the insight these outer structures provide on understanding massive  galaxy assembly.  I will also discuss how we are using deep HST studies of M31's outer regions to probe its evolutionary history in unprecedented detail.


Video
Thursday October 30, 2014
Prof. Eline Tolstoy
Kaptein Astronomical Intistute

Abstract

I will talk about how resolved stellar populations in the nearby Local Group dwarf galaxies have been used to study the detailed chemical, kinematic and star formation history of these systems and the link to the properties of the Milky Way. I will mainly discuss the results from the DART spectroscopic surveys of nearby dwarf spheroidal galaxies, determining detailed abundances, looking for CEMP stars and also combining spectroscopy with colour-magnitude diagram analysis to measure the time scale for star formation and chemical evolution.

 




Video
Thursday October 23, 2014
Prof. Sara Seager
MIT

Abstract

The discovery and characterization of exoplanets have the potential to offer the world one of the most impactful findings ever in the history of astronomy?the identification of life beyond Earth. Life can be inferred by the presence of atmospheric biosignature gases? Gases produced by life that can accumulate to detectable levels in an exoplanet atmosphere. Detection will be made by remote sensing by sophisticated space telescopes. The conviction that biosignature gases will actually be detected in the future is moderated by lessons learned from the dozens of exoplanet atmospheres studied in last decade, namely the difficulty in robustly identifying molecules, the possible interference of clouds, and the permanent limitations from a spectrum of spatially unresolved and globally mixed gases without direct surface observations. The vision for the path to assess the presence of life beyond Earth is being established.


Video
Thursday October 9, 2014
Dr. Eva Grebel
Director Astronomisches Rechen-Institut Zentrum für Astronomie der Universität Heidelberg

Abstract

Dwarf galaxies are the most common type of galaxy in the Universe andinclude the most dark-matter-dominated objects known. They offerintriguing insights into evolutionary processes at low halo masses and low metallicities. Moreover, as survivors of a once much more numerous population of building blocks of larger galaxies, they are key to understanding very early star formation processes. The Local Group and particularly the Milky Way's dwarf galaxy entourage offer us the unique possibility to compare in detail dwarf and Galactic populations. This is an important step towards quantifying the magnitude and time scales of dwarf contributions to the build-up of the Milky Way and allows us to test predictions of cosmological theories and hierarchical structure formation.


Video
Thursday March 27, 2014
Prof. John Houghton
Univ. of Oxford

Abstract

Because of the carbon dioxide emissions from fossil fuel burning, the Earth's atmosphere and oceans are warming through what is known as the "greenhouse effect". Big changes are on their way which we have not yet seen because of the time taken for the oceans to warm. It is essential that human communities prepare to adapt to these changes e.g. in sea level rise, severe heat waves, and a greater frequency of climate extremes.

The challenge to scientists is to learn enough about the complexities of the world's climate system to be able to project the climate's likely future.

The nations and peoples of the world need to recognise the urgency of the many actions that can - and must be taken.


Video
Thursday June 27, 2013
Dr. Didier Queloz
Geneva Observatory, Astronomy Department, University of Geneva

Abstract

The discovery of new planets beyond our solar system, in particular the detection and characterization of other habitable planets similar to the Earth, is a fascinating intellectual adventure. The completely unexpected characteristics of exoplanets are capturing the imagination and interest of the scientific community and the general public. More recently the large population of Super-Earth planet questions the universality of our Solar System as a typical planetary system. While the quest to find bodies similar to the Earth is still on going, the first spectra of exoplanets have been taken, signaling the shift from an era of discovery to one of physical and chemical characterization. This talk will provide an overview of current outcomes of planet programs as well as its limitation and prospects to move forward.


Video
Thursday February 21, 2013
Prof. Sally Oey
University of Michigan

Abstract

The fate of ionizing radiation from massive stars has fundamental consequences on scales ranging from the physics of circumstellar disks to the ionization state of the entire universe. On galactic scales, the radiative feedback from massive stars is a major driver for the energetics and phase balance of the interstellar medium in star-forming galaxies. While even starburst galaxies appear to be largely optically thick in the Lyman continuum, ionization-parameter mapping shows that significant populations of HII regions within galaxies are optically thin, powering the diffuse, warm ionized medium. I will discuss our multi-faceted work to clarify our understanding of radiative feedback in star-forming galaxies from the Magellanic Clouds to starbursts.


Video
Thursday January 10, 2013
Prof. Eric Priest
St Andrews University

Abstract

This talk will give an overview of our understanding of the Sun in the 1960's, the major discoveries since then, and the main questions that need to be answered in future. It will focus on the role of the magnetic field in the solar interior, the photosphere, prominences, coronal heating and eruptive flares.


Video
Thursday October 25, 2012
Prof. Monica M. Grady
Open University, Milton Keynes, UK

Abstract

Traditionally, astronomers study stars and planets by telescope. But we can also learn about them by using a microscope – through studying meteorites. From meteorites, we can learn about the processes and materials that shaped the Solar System and our planet. Tiny grains within meteorites have come from other stars, giving information about the stellar neighbourhood in which the Sun was born.

Meteorites are fragments of ancient material, natural objects that survive their fall to Earth from space. Some are metallic, but most are made of stone. They are the oldest objects that we have for study. Almost all meteorites are fragments from asteroids, and were formed at the birth of the Solar System, approximately 4570 million years ago. They show a compositional variation that spans a whole range of planetary materials, from completely unmelted and unfractionated stony chondrites to highly fractionated and differentiated iron meteorites. Meteorites, and components within them, carry records of all stages of Solar System history. There are also meteorites from the Moon and from Mars that give us insights to how these bodies have formed and evolved.

In her lecture, Monica will describe how the microscope is another tool that can be employed to trace stellar and planetary processes.


Video
Thursday June 21, 2012
Prof. Françoise Combes
Observatoire de Paris, LERMA. France

Abstract

I will review some recent results about the molecular content of galaxies and its dynamics, obtained from CO lines, dense tracers (HCN,HCO+), or the dust continuum emission. New data to constrain the conversion factor XCO will be discussed. The molecular surface density is essential to determine the star formation efficiency in galaxies, and the resolved Kennicutt-Schmidt law will be presented as a function of surface density and galaxy type. Large progress has been made on galaxy at moderate and high redshifts, allowing to interprete the star formation history and star formation efficiency as a function of gas content, or galaxy evolution. In massive galaxies, the gas fraction was higher in the past, and galaxy disks were more unstable and more turbulent. ALMA observations will allow the study of more normal galaxies at high z with higher spatial resolution and sensitivity.



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