Periodic Reporting for period 3 - Asterochronometry (Galactic archeology with high temporal resolution)
Reporting period: 2021-02-01 to 2022-07-31
The Milky Way is a complex system, with dynamical and chemical substructures, where several competing processes such as mergers, internal secular evolution, gas accretion and gas flows take place. To study in detail how such a giant spiral galaxy was formed and evolved, we need to reconstruct the sequence of its main formation events with high (~10%) temporal resolution.
The asterochronometry project aims to understand the formation and evolution of the Milky Way galaxy by measuring the ages of its stars directly using asteroseismology. Asteroseismology is the astronomical equivalent of geoseismology (used to study the interior structure of the Earth) and determines the interior structure of stars by measuring sound waves that ring through their interiors. By producing detailed models of these interior structures, we can use the asteroseismic observations to determine characteristics such as the masses, and therefore ages, of stars. By measuring the age of many stars in our Galaxy, the Milky Way, we can begin to form a timeline of its evolution from the early universe to the present day. Populations of stars at different ages act like tree rings, telling the story of the history of the Galaxy. For example, by studying how the kinematic properties of stars change with their age, we can build up a detailed picture of its dynamical evolution, giving us insights into how it built up its mass, and how this was distributed in the Galaxy in the past.
Asterochronometry will determine accurate, precise ages for tens of thousands of stars in the Galaxy. We will take an approach distinguished by a number of key aspects including, developing novel star-dating methods that fully utilise the potential of individual pulsation modes, coupled with a careful appraisal of systematic uncertainties on age deriving from our limited understanding of stellar physics.
We will then capitalise on opportunities provided by the timely availability of astrometric, spectroscopic, and asteroseismic data to build and data-mine chrono-chemo-dynamical maps of regions of the Milky Way probed by the space missions CoRoT, Kepler, K2, and TESS. We will quantify, by comparison with predictions of chemodynamical models, the relative importance of various processes which play a role in shaping the Galaxy, for example mergers and dynamical processes. We will use chrono-chemical tagging to look for evidence of aggregates, and precise and accurate ages to reconstruct the early star formation history of the Milky Way’s main constituents.
The Asterochronometry project will also provide stringent observational tests of stellar structure and answer some of the long-standing open questions in stellar modelling (e.g. efficiency of transport processes, mass loss on the giant branch, the occurrence of products of coalescence / mass exchange). These tests will improve our ability to determine stellar ages and chemical yields, with wide impact e.g. on the characterisation and ensemble studies of exoplanets, on evolutionary population synthesis, integrated colours and thus ages of galaxies.
The asterochronometry project aims to understand the formation and evolution of the Milky Way galaxy by measuring the ages of its stars directly using asteroseismology. Asteroseismology is the astronomical equivalent of geoseismology (used to study the interior structure of the Earth) and determines the interior structure of stars by measuring sound waves that ring through their interiors. By producing detailed models of these interior structures, we can use the asteroseismic observations to determine characteristics such as the masses, and therefore ages, of stars. By measuring the age of many stars in our Galaxy, the Milky Way, we can begin to form a timeline of its evolution from the early universe to the present day. Populations of stars at different ages act like tree rings, telling the story of the history of the Galaxy. For example, by studying how the kinematic properties of stars change with their age, we can build up a detailed picture of its dynamical evolution, giving us insights into how it built up its mass, and how this was distributed in the Galaxy in the past.
Asterochronometry will determine accurate, precise ages for tens of thousands of stars in the Galaxy. We will take an approach distinguished by a number of key aspects including, developing novel star-dating methods that fully utilise the potential of individual pulsation modes, coupled with a careful appraisal of systematic uncertainties on age deriving from our limited understanding of stellar physics.
We will then capitalise on opportunities provided by the timely availability of astrometric, spectroscopic, and asteroseismic data to build and data-mine chrono-chemo-dynamical maps of regions of the Milky Way probed by the space missions CoRoT, Kepler, K2, and TESS. We will quantify, by comparison with predictions of chemodynamical models, the relative importance of various processes which play a role in shaping the Galaxy, for example mergers and dynamical processes. We will use chrono-chemical tagging to look for evidence of aggregates, and precise and accurate ages to reconstruct the early star formation history of the Milky Way’s main constituents.
The Asterochronometry project will also provide stringent observational tests of stellar structure and answer some of the long-standing open questions in stellar modelling (e.g. efficiency of transport processes, mass loss on the giant branch, the occurrence of products of coalescence / mass exchange). These tests will improve our ability to determine stellar ages and chemical yields, with wide impact e.g. on the characterisation and ensemble studies of exoplanets, on evolutionary population synthesis, integrated colours and thus ages of galaxies.
During the first half of the project we have focused our efforts on developing and testing procedures to infer precise and accurate parameters of evolved stars. This entails also devising tests of key aspects of stellar physics that mostly affect the inference on the ages of stars.
We have also started to apply such techniques to a selected subset of stars observed by the Kepler and TESS satellites. Thanks to the unprecedented combination of constraints on the age, on the chemical composition, and the motion of stars we have started to bring strong, novel constraints to both the early assembly history of the Milky Way and to its dynamical evolution. Examples of our activities and recent results are available on https://www.asterochronometry.eu/science_summaries.html.
We have also started to apply such techniques to a selected subset of stars observed by the Kepler and TESS satellites. Thanks to the unprecedented combination of constraints on the age, on the chemical composition, and the motion of stars we have started to bring strong, novel constraints to both the early assembly history of the Milky Way and to its dynamical evolution. Examples of our activities and recent results are available on https://www.asterochronometry.eu/science_summaries.html.
We will continue to push the limits of our ability to determine precise and accurate ages for stars, and this is a process which will involve both improving our models of stars, and the continuous testing against independent determinations of stellar properties.
Extending our improved methodology to large samples of stars will enable a sharper view on the assembly history and evolution of our Galaxy, in particular looking at regions of the Galaxy far from the solar neighbourhood. While space missions such as Gaia, together with large-scale spectroscopic constraints are providing us with a sharper view on the current chemo-dynamical structure of the Milky Way, our work promises to reveal the temporal sequence that led to the present-day Galaxy.
Extending our improved methodology to large samples of stars will enable a sharper view on the assembly history and evolution of our Galaxy, in particular looking at regions of the Galaxy far from the solar neighbourhood. While space missions such as Gaia, together with large-scale spectroscopic constraints are providing us with a sharper view on the current chemo-dynamical structure of the Milky Way, our work promises to reveal the temporal sequence that led to the present-day Galaxy.