Wed 19 Mar 13:40: Perturber-disc interaction: Can we see the unseen?
Protoplanetary discs are the place in which planets form and evolve, and the reservoir from which protostar accrete material. The presence of a perturber whether a planet or a stellar companion and its interaction with the parental disc play a crucial role in shaping the dynamics and evolution of the system, generating substructures such as gaps, rings and asymmetries routinely observed with different tracers in discs (large mm dust and gas with ALMA , small micrometric dust with VLT ).
However, characterizing these systems remains challenging: the only two planetary companions unambiguously detected, PDS70b and c, lie in a wide and open cavity of the same object, and once the perturber is a star, massive and wide enough to be detected, characterize the binary orbit is challenging due to the timescales at play.
In this talk, I will show new results to address and mitigate these issues. Firstly, I will show new results from the astrometry and the hydrodynamical models of GG Tau A, a multiple stellar system where the orbits of the stars is still not fully constrained. Then, I will discuss how the advent of the Extremely Large Telescope (ELT), with its first light imager MICADO /MORFEO, will revolutionize the field, providing high angular resolution images that will allow us to detect embedded protoplanets and small-scales substructures.
- Speaker: Claudia Toci / European Southern Observatory
- Wednesday 19 March 2025, 13:40-14:05
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: .
Wed 19 Mar 13:40: Perturber-disc interaction: Can we see the unseen?
Protoplanetary discs are the place in which planets form and evolve, and the reservoir from which protostar accrete material. The presence of a perturber whether a planet or a stellar companion and its interaction with the parental disc play a crucial role in shaping the dynamics and evolution of the system, generating substructures such as gaps, rings and asymmetries routinely observed with different tracers in discs (large mm dust and gas with ALMA , small micrometric dust with VLT ).
However, characterizing these systems remains challenging: the only two planetary companions unambiguously detected, PDS70b and c, lie in a wide and open cavity of the same object, and once the perturber is a star, massive and wide enough to be detected, characterize the binary orbit is challenging due to the timescales at play.
In this talk, I will show new results to address and mitigate these issues. Firstly, I will show new results from the astrometry and the hydrodynamical models of GG Tau A, a multiple stellar system where the orbits of the stars is still not fully constrained. Then, I will discuss how the advent of the Extremely Large Telescope (ELT), with its first light imager MICADO /MORFEO, will revolutionize the field, providing high angular resolution images that will allow us to detect embedded protoplanets and small-scales substructures.
- Speaker: Claudia Toci / European Southern Observatory
- Wednesday 19 March 2025, 13:40-14:05
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: .
The surprising new idea behind what sparked life on Earth
Telescope first light for ESO’s Extremely Large Telescope now planned for March 2029
As a result of delays experienced during construction, ESO’s Extremely Large Telescope (ELT) is now set to make its first test observations at the beginning of 2029, with “telescope first light” expected in March 2029. Afterwards, the first instruments will be installed and commissioned, leading to “scientific first light” in December 2030.
This updated ELT schedule has been put in place after several of the telescope contracts suffered delays. The reasons for these delays are not untypical for such large, cutting-edge projects, ranging from harsh weather conditions at the construction site, to technological developments taking longer than expected, and equipment failing during manufacturing.
After the telescope sees first light, it will be optimised before receiving its first scientific instruments. ESO’s ELT is now expected to deliver the first scientific observations in December 2030.
With this revised schedule, ESO wants to ensure the telescope and its instruments are ready to deliver the best possible science once astronomers start using the ELT for their observations. ESO’s ELT will tackle the biggest scientific challenges of our time, making key contributions in fields such as habitable exoplanet discovery, galaxy formation or the study of dark energy and dark matter.
Wed 19 Mar 13:15: Constraining mixed dark matter models with the high-redshift Lyman-α forest
In the standard cosmological model, cold dark matter gives rise to small-scale structure problems which Warm Dark Matter (WDM) in the keV range may address. Previous studies have narrowed the mass range for WDM , but further testing is increasingly challenging due to resolution limits of current spectrographs. Given the lack of success in laboratory dark matter searches, an intriguing alternative has recently re-emerged—a mixed dark matter scenario that combines cold and warm components, known as Cold+Warm Dark Matter (CWDM). In this framework, structure formation is influenced by the free-streaming of the warm component at the small scales probed by the Lyman-α forest, requiring hydrodynamical simulations to account for non-linear structure evolution and gas dynamics.
This presentation focuses on updated constraints on CWDM derived from high resolution and high-redshift (z=4.2−5.0) spectra from UVES and HIRES spectrographs. We use the 1D flux power spectrum to compare simulated Lyman-α forest to observational data in a Bayesian inference framework. The grid of simulations spans a high-dimensional parameter space, which we efficiently sample by implementing a neural network emulator at the likelihood level.
Beyond 1D clustering statistics, these allowed mixed dark matter models can accommodate small-scale deviations in the high-k regime of the matter power spectrum, potentially alleviating the S8 tension.
- Speaker: Olga Garcia Gallego / IoA
- Wednesday 19 March 2025, 13:15-13:40
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: .
Wed 19 Mar 13:15: Constraining mixed dark matter models with the high-redshift Lyman-α forest
In the standard cosmological model, cold dark matter gives rise to small-scale structure problems which Warm Dark Matter (WDM) in the keV range may address. Previous studies have narrowed the mass range for WDM , but further testing is increasingly challenging due to resolution limits of current spectrographs. Given the lack of success in laboratory dark matter searches, an intriguing alternative has recently re-emerged—a mixed dark matter scenario that combines cold and warm components, known as Cold+Warm Dark Matter (CWDM). In this framework, structure formation is influenced by the free-streaming of the warm component at the small scales probed by the Lyman-α forest, requiring hydrodynamical simulations to account for non-linear structure evolution and gas dynamics.
This presentation focuses on updated constraints on CWDM derived from high resolution and high-redshift (z=4.2−5.0) spectra from UVES and HIRES spectrographs. We use the 1D flux power spectrum to compare simulated Lyman-α forest to observational data in a Bayesian inference framework. The grid of simulations spans a high-dimensional parameter space, which we efficiently sample by implementing a neural network emulator at the likelihood level.
Beyond 1D clustering statistics, these allowed mixed dark matter models can accommodate small-scale deviations in the high-k regime of the matter power spectrum, potentially alleviating the S8 tension.
- Speaker: Olga Garcia Gallego / IoA
- Wednesday 19 March 2025, 13:15-13:40
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: .
Fri 14 Mar 13:00: A phase transition in cosmological fluid dynamics
On a background Minkowski spacetime, the Euler equations (both relativistic and not) are known to develop shock singularities in finite-time from smooth data. Such shock formation can be suppressed on cosmological spacetimes whose spatial slices expand at an accelerated rate. However, situations with decelerated expansion, which are relevant in our early universe, are not as well understood. I will present some recent joint work in this direction, based on collaborations with David Fajman, Maciej Maliborski, Todd Oliynyk and Max Ofner.
- Speaker: Zoe Wyatt, DPMMS
- Friday 14 March 2025, 13:00-14:00
- Venue: Potter room / https://cam-ac-uk.zoom.us/j/89259699528?pwd=rI2WS21NUsIKMmZCGtkPuPbM5SL0eW.1.
- Series: DAMTP Friday GR Seminar; organiser: Daniela Cors.
Fri 21 Mar 13:00: Primordial black holes: abundances and constraints
The equation of state of the primordial plasma is reduced during each early universe phase transition. Primordial black holes, thought to form whilst the universe is radiation dominated, are exponentially sensitive to the changes in the equation of state. However, this exponential sensitivity is the same that primordial black hole formation shows to the amplitude of the primordial curvature power spectrum. Thus, using constraints on the power spectrum we are able to place constraints on primordial black hole abundances. I will show that, despite the exponential enhancement in formation rate, current constraints on the power spectrum lead to difficulties motivating primordial black holes with the standard model phase transitions.
- Speaker: Xavier Pritchard, Sussex
- Friday 21 March 2025, 13:00-14:00
- Venue: Potter room / https://cam-ac-uk.zoom.us/j/87235967698.
- Series: DAMTP Friday GR Seminar; organiser: Xi Tong.
Optical+NIR analysis of a newly found Einstein ring at z$\sim$1 from the Kilo-Degree Survey: Dark matter fraction, total and dark matter density slope and IMF
Optical+NIR analysis of a newly found Einstein ring at z$\sim$1 from the Kilo-Degree Survey: Dark matter fraction, total and dark matter density slope and IMF
Saturn has a whopping 274 moons ― scientists want to know why
Nature, Published online: 13 March 2025; doi:10.1038/d41586-025-00781-1
A huge haul of 128 newfound satellites might be a hint of past collisions in the planet’s orbit, or something else.Hera asteroid mission takes stunning images of Mars’s moon Deimos
NASA may have to cancel major space missions due to budget cuts
Three-dimensional maps of the interstellar dust extinction curve within the Milky Way galaxy
Mon 17 Mar 14:00: Flare evaporation, condensations, and ribbons
Evaporation and condensation processes are highly dynamic in solar flares, and both can be investigated through the chromospheric spectral lines and flare ribbons.
Evaporation occurs from a source of chromospheric flare ribbon material. The key mechanism(s) driving the evaporation are not neatly resolved, with plausible candidates including non-thermal beams of particles, field-aligned thermal conduction, Alfven waves, and reconnection outflow jets. We use state-of-the-art multi-dimensional MHD simulations to investigate differences in flare evolution that result from different energy transport mechanisms.
Condensations are seen in post flare loop arcades, with coronal rain events in which condensed material flows down towards the bright ribbons. We present the variations of flare ribbon spectral profiles using high-resolution spectro-polarimetric SST observations and sub-second cadence IRIS satellite spectra. These are used to track condensation flows and ribbon features. We also present so-called “chromospheric condensations” interpreting them through our multi-dimensional MHD models. We provide an updated schematic to interpret the formation of flare ribbons from the spectra.
Ongoing developments of our simulations are introduced (1) improving the lower atmosphere used, and the initial reconnection location (2) including asymmetry and more realistic chromospheric magnetic field parameters, (3) beam particle energy budgets and spectra informed by reconnection and particle acceleration modelling. (4) building a framework to estimate radiative energy losses and gains in the chromosphere from detailed 1D RADYN models.
This work was carried out in collaboration with Alex Pietrow, Ioannis Kontogiannis, Wenzhi Ruan, Rony Keppens, Foad Hanassi-Savari, Maxime Dubart, Fabio Bacchini
- Speaker: Malcolm Druett (Sheffield)
- Monday 17 March 2025, 14:00-15:00
- Venue: MR14 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Roger Dufresne.
Quartz crystals on Mars could preserve signs of ancient life
Did Mars harbour life? One of the strongest signs yet is spotted in a peculiar rock
Nature, Published online: 12 March 2025; doi:10.1038/d41586-025-00772-2
The intriguing chemistry of a rock collected by the Perseverance rover could trace to microbial activity — or not.Saturn gains 128 moons, giving it more than the other planets combined
Tue 13 May 11:15: Title TBC
Abstract TBC
- Speaker: Alicia Anderson (Cavendish Astrophysics)
- Tuesday 13 May 2025, 11:15-12:00
- Venue: Martin Ryle Seminar Room, Kavli Institute.
- Series: Hills Coffee Talks; organiser: Charles Walker.
Thu 13 Mar 11:00: Fred Simmons: "Abiogenetic Bias, Axiology, and Teleology."
In person. And with slides.
- Speaker: Fred Simmons (Cambridge Divinity)
- Thursday 13 March 2025, 11:00-12:00
- Venue: Thirkill Room, Old Court, Clare College.
- Series: LCLU Coffee Meetings; organiser: Paul B. Rimmer.