Sommerschule 2024

White dwarfs: learning from the oldest stars in the Galaxy

Nicola Gentile Fusillo

Over 95% of all stars in the Galaxy including our own Sun share the same ultimate fate: one day they will become white dwarfs. These small stellar embers, devoid of any internal energy source, are destined to simply cool down over billions of years.  However, there is more to these “dead stars” than it initially meets the eye. How old is our Galactic neighbourhood? What is the stellar formation history of our Galaxy? When did the first planets form? What were these worlds like? How unique is our solar system? What is the future of the Sun and the Earth? These are just some of the questions that can be addressed by studying white dwarfs.

In these lectures we will explore how white dwarfs form and evolve, we will define the key properties of these stellar remnants and investigate how these can be measured or inferred from astronomical observations.  We will then discuss how the unique characteristics  of white dwarfs make them powerful tools with applications in various areas of astronomy, in particular focusing on recent discoveries and some emerging research fields.  The various topics will be covered from an “observational astronomy” perspective and we will use real survey data to construct our own sample of white dwarfs to use as a reference guideline.