Next Colloquia

The wide-field spectroscopic telescope (WST) will be an innovative 12-m class telescope with simultaneous operation of a large field-of-view (3 sq. degree) and high multiplex (30,000) multi-object spectrograph facility with both medium and high resolution modes (MOS), and a giant panoramic (3×3 sq. arcmin) integral field spectrograph (IFS). WST will achieve transformative results in most areas of astrophysics: e.g. the nature and expansion of the dark Universe, the formation of first stars and galaxies and their role in the cosmic reionisation, the study of the dark and baryonic material in the cosmic web, the baryon cycle in galaxies, the formation history of the Milky Way and dwarf galaxies in the Local Group, characterization of exoplanet hosts, and the characterization of transient phenomena, including electromagnetic counterparts of gravitational wave events.

This presentation will discuss current science, status and plans.

• Speaker: Prof Roland Bacon (CRAL, Lyon, FR and WST Collaboration Coordinator)
• Tuesday 01 July 2025, 11:30-12:30
• Venue: Martin Ryle Seminar Room, Kavli Building.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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Neutron stars are the largest and the strongest magnets in the Universe. Their typical radius is around 10 km and their magnetic fields could reach values of 1e15 G. Structurally, the outer 1 km shell of a neutron star is its solid crust, while the inner part is its core. Magnetic fields shape observational properties of isolated and accreting neutron stars. Strong magnetic fields play the crucial role in explaining transient and persistent X-ray emission from Anomalous X-ray Pulsars and Soft Gamma Repeaters jointly known as magnetars. Magnetic fields are not constant and expected to evolve over time. In the last years, a significant progress was made in modelling magneto-thermal evolution of neutron star crust. Ohmic decay and Hall evolution explains multiple magnetar properties.  In this colloquium, I summarise the main observational constrains currently available on magnetic fields of neutron stars and confront them with state-of-art numerical simulations. I will explain how current and future observations help us to learn more about magnetic field evolution and its structure. I also explain how the neutron star core can be modelled and show preliminary results for field evolution in the core.

• Speaker: Andrei Igoshev, Newcastle University
• Thursday 12 June 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: Mor Rozner.

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Gravitational-wave (GW) multi-messenger astronomy holds immense promise for our understanding of the Universe, impacting studies of cosmology, the production of elements, and the final fates of stars. To date, however, only a single credible source, GW170817 , caused by the merger of two neutron stars, has been detected both in GWs and electromagnetically. I will discuss the scientific potential and challenges of observing more multi-messenger events, as motivation for the GOTO project: a UK-led transient sky survey composed of a fleet of rapidly-responding telescope arrays. The primary science driver of GOTO is scanning the sky in response to GW alerts, to search for their electromagnetic counterparts. Alongside overviewing GOTO ’s capabilities and recent multi-messenger efforts, I will present highlights from various ancillary science enabled by the array. This includes rapid localisation and characterisation of gamma-ray bursts, and discoveries of infant and extreme supernovae beyond the traditional core-collapse and thermonuclear regimes. I will also present our efforts to automate and expedite the characterisation of transients via algorithmically scheduled follow-up and citizen scientists.

• Speaker: Joseph Lyman, University of Warwick
• Thursday 12 June 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: Matthew Grayling.

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Cosmological hydrodynamical simulations are becoming increasingly realistic by incorporating a wider range of physical processes, higher spatial resolution, and larger statistical samples. Despite ongoing trade-offs between resolution and volume, recent advances now allow for simulations that resolve the multiphase interstellar medium and capture the clumpy nature of star formation in galaxies. In this context, I will present how such simulations shed light on the coupled evolution of galaxies and their central supermassive black holes. At high redshift, galaxies tend to be gas-rich, turbulent, and star-bursting, often exhibiting irregular, compact, and disturbed morphologies. As internal turbulence subsides, many systems transition into stable, rotating disc galaxies, typically once they reach stellar masses around 1e10 Msun. Simultaneously, black hole growth is tightly linked to the dynamical state of the host galaxy. In low-mass, turbulent systems, stellar feedback can suppress nuclear gas inflows, delaying black hole growth. Only when galaxies become sufficiently massive and dynamically settled can gas efficiently reach galactic centers to fuel sustained accretion. These processes also have important implications for the spin evolution of black holes or how fast they coalesce, which can reflect the varying modes of accretion and feedback across cosmic time.

• Speaker: Yohan Dubois (Institut d’Astrophysique de Paris)
• Thursday 05 June 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: Matthew Grayling.

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I will present results on the properties of faint galaxies and AGN in the early Universe, building upon samples identified using Wide Field Slitless Spectroscopy with NIR Cam on the James Webb Space Telescope (JWST). This mode effectively turns JWST into an efficient redshift machine ideal to map out galaxy over-density. In my talk, I will focus on two topics: 1) The impact of galaxies and AGN on the reionization of the Universe, directly measured by mapping out the correlation between galaxies and ionized regions with quasar and galaxy transmission spectroscopy, and 2) The nature of broad Hα line-selected AGN (the so-called Little Red Dots) that JWST has uncovered in the first few Gyr, including new results based on the deep NIR Cam grism spectroscopy of their large-scale environments, deep high resolution spectroscopy unveiling the prevalence of dense absorbing gas and resolved Lyman-alpha mapping of the circumgalactic medium with VLT /MUSE. Finally, I will synthesize what these observations are learning us in the context of galaxy – SMBH co-evolution, SMBH formation and their role in cosmic reionization.

• Speaker: Dr Jorryt Matthee
• Thursday 29 May 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: Jan Scholtz.

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Cosmological and astrophysical observations provide clear evidence for the existence of dark matter and have begun to map its distribution across vast cosmic volumes, yet key questions about its mass and interaction properties remain unanswered. Clues may lie in measurements that probe structure formation on the smallest scales—including dwarf galaxies, strong gravitational lenses, and stellar streams. These observations are already constraining aspects of the microphysical nature of dark matter, including its free-streaming behavior, decay lifetime, self-interactions, and possible interactions with the Standard Model. The upcoming generation of wide-field imaging surveys—including Euclid, the Vera C. Rubin Observatory, and the Roman Space Telescope—combined with spectroscopic surveys such as DESI and the new Via Project, will accelerate our ability to probe this physics. These efforts may detect, for the first time, dark matter halos below the threshold for star formation, directly testing a fundamental prediction of the standard cosmological model and offering the possibility of uncovering definitive astrophysical signatures of dark matter’s particle properties.

• Speaker: Risa Wechsler (Stanford/KIPAC)
• Thursday 19 June 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy (and online - details to be sent by e-mail).
• Series: The Kavli Lectures; organiser: Steven Brereton.

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The Milky Way experienced a major satellite merger 10 Gyr ago which altered, but did not destroy, the early high-alpha disk and created both an accreted and an in situ inner halo. The low-alpha disk that formed subsequently became bar-unstable 8 Gyr ago, creating the b/p bulge that also contains the inner high-alpha disk stars. M31 experienced a similar major satellite merger 3 Gyr ago which greatly heated and mixed the pre-existing high-metallicity disk, and also caused a massive inflow of gas and the formation of a dynamically hot secondary inner disk. Such a merger is consistent with the wide-spread star formation event 2-4 Gyr ago seen in disk colour-magnitude diagrams, and with the major substructures and metal-rich stars in the inner halo of M31 , when comparing photometric and recent spectroscopic data with available models. The merged satellite must have had a broad metallicity distribution and would have been the third most massive galaxy in the Local Group before the merger.

• Speaker: Ortwin Gerhard, MPE (Garching)
• Thursday 15 May 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: .

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Gravitational-wave observations have revealed the population of stellar remnants from a new angle. Yet their stellar progenitors remain uncertain, in particular in the case of black holes. At least a fraction of these stars is believed to form in isolated binary systems. In this talk, I will discuss how binary mass transfer affects the late evolution and final fate of massive stars. The focus will be on stars that transfer their outer layers to a companion star and become binary-stripped. Binary-stripped stars develop systematically different core structures compared to single stars. I will discuss consequences for supernovae, black hole formation, and gravitational-wave observations.

• Speaker: Eva laplace, University of Leuven, Belgium
• Thursday 22 May 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: ag2017.

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The Milky Way experienced a major satellite merger 10 Gyr ago which altered, but did not destroy, the early high-alpha disk and created both an accreted and an in situ inner halo. The low-alpha disk that formed subsequently became bar-unstable 8 Gyr ago, creating the b/p bulge that also contains the inner high-alpha disk stars. M31 experienced a similar major satellite merger 3 Gyr ago which greatly heated and mixed the pre-existing high-metallicity disk, and also caused a massive inflow of gas and the formation of a dynamically hot secondary inner disk. Such a merger is consistent with the wide-spread star formation event 2-4 Gyr ago seen in disk colour-magnitude diagrams, and with the major substructures and metal-rich stars in the inner halo of M31 , when comparing photometric and recent spectroscopic data with available models. The merged satellite must have had a broad metallicity distribution and would have been the third most massive galaxy in the Local Group before the merger.

• Speaker: Ortwin Gerhard, MPE (Garching)
• Thursday 15 May 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: .

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Abstract not available

• Speaker: Ortwin Gerhard, MPE (Garching)
• Thursday 15 May 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: .

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The gravitational pull of a black hole attracts gas and forms an accretion disk where the interplay between hydromagnetic processes and the warping of space-time releases gravitational energy in the form of radiation, relativistic jets, and winds. Most gas falls into supermassive black holes when the accretion rate approaches the Eddington limit (L=Ledd), at which point radiation pressure overcomes gravity. To date, our knowledge of such `luminous’ black hole accretion disks mostly relies on semi-analytical models, supplemented by a limited set of numerical simulations. In my talk I will discuss new insights gained from state-of-the-art radiative general relativistic magnetohydrodynamics (GRMHD) simulations of accretion near the Eddington limit such as the formation of a hot corona, disk truncation, and other physical processes driving the spectral evolution of luminous black holes. I will finish my talk by discussing the challenges and opportunities the next-generation of GRMHD simulations will bring in developing a comprehensive understanding of black hole accretion across the luminosity spectrum.

• Speaker: Matthew Liska
• Friday 09 May 2025, 11:30-12:30
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: Debora Sijacki.

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Brown dwarfs are often described as failed stars, however the flip side of this description is that they can also be described as over-ambitious planets. With masses between 13-70 Jupiter masses they have cool atmospheres dominated by cloud features, molecules and show features due to weather. These atmospheres have a lot of similarities with atmospheres we see in planets in our solar system, and also directly imaged exoplanets. The question then is: How like hot Jupiters are irradiated brown dwarfs? In this seminar I will describe the known irradiated brown dwarfs and how they evolve into post-common envelope systems containing a white dwarf. These rare binaries have very short periods (~hrs) and the brown dwarf is irradiated by the white dwarf companion, often with large amounts of UV radiation. I will discuss the atmospheres of these highly irradiated brown dwarfs and their similarities with irradiated exoplanets.

• Speaker: Dr Sarah Casewell
• Thursday 01 May 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: Jan Scholtz.

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In the short time since the start of JWST ’s science operations, it has caused a paradigm shift in the information and understanding of giant planet atmospheres. The spectroscopic IR capabilities have revealed absorption from H2O , CO2, and CO with exquisite precision, provided the first look at elusive methane absorption, and shown a diversity of photochemistry and disequilibrium processes at play in giant planet atmospheres. Previously obscuring aerosols that plagued UV-optical spectra are revealing themselves via distinct absorption and emission in the mid-IR confirming for the first time in irradiated exoplanets theoretical predictions of cloud formation. I will present a case study of one such planet which is revealing the roles of clouds and chemistry in exoplanet atmospheres and the feedback imparted between composition, dynamics, and detectability.

• Speaker: Hannah Wakeford
• Thursday 20 March 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: Matthew Grayling.

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Core collapse supernovae play many important roles in astronomy and astrophysics. They trigger and regulate star formation through the energy they inject into the interstellar medium and they forge and disperse elements that seed the next generation of stars. On much more compact scales, which is the focus area of this talk, core collapsing stars are the birth sites of neutron stars and black holes, and therefore they are the gateway to the compact Universe. Numerical simulations of the core collapse have rapidly progressed in the last decade. Explosions are now readily obtained, the key ingredient being multidimensionality. This colloquium will review recent progress in understanding the central engines at the heart of core-collapse supernovae. I’ll touch upon how we can still use 1D simulations to understand the population as a whole, 2D simulations to systematically study theoretical uncertainties and explore the multimessenger signals, and 3D simulations to push our understanding of these extreme events.

• Speaker: Evan O'Connor
• Thursday 06 March 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: Matthew Grayling.

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In the short time since the start of JWST ’s science operations, it has caused a paradigm shift in the information and understanding of giant planet atmospheres. The spectroscopic IR capabilities have revealed absorption from H2O , CO2, and CO with exquisite precision, provided the first look at elusive methane absorption, and shown a diversity of photochemistry and disequilibrium processes at play in giant planet atmospheres. Previously obscuring aerosols that plagued UV-optical spectra are revealing themselves via distinct absorption and emission in the mid-IR confirming for the first time in irradiated exoplanets theoretical predictions of cloud formation. I will present a case study of one such planet which is revealing the roles of clouds and chemistry in exoplanet atmospheres and the feedback imparted between composition, dynamics, and detectability.

• Speaker: Dr Hannah Wakeford
• Thursday 20 March 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: Matthew Grayling.

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Astronomy of the Milky Way Galaxy has entered a transformative era. The Gaia mission and an ensemble of ground-based spectroscopic surveys are delivering element abundances and velocities for millions of stars. These data provide both an opportunity to deepen our understanding of galaxy formation and to test the “limits of knowledge.” There have been several surprises that have come out of the large stellar surveys and data-driven methodologies built to analyse them. We have learned that up to 1 in 100 stars in the disk are “abundance doppelgangers” – chemically identical but unrelated – limiting the prospect of reconstructing the disk’s star cluster building blocks. Furthermore, for stars in the disk, most of the element abundances measured for most of the stars can be predicted to a precision of better than 10 percent given only two key abundances. However, this is not the case for stars in the stellar halo. These findings frame how we can most effectively work with the data to turn photons into a quantified description of Galactic history and provide strong constraints on the star formation and mixing processes that have set the Galactic environment.

• Speaker: Melissa Ness, Research School of Astronomy and Astrophysics (RSAA), Australian National University, Canberra, Australia
• Thursday 13 March 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, IoA (tea at 3:30 pm).
• Series: The Eddington Lectures ; organiser: .

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