In this episode, we're delighted to welcome Abbigail Elms, who has been studying some of the coolest white dwarf stars known to date. Abbigail shares insights into two fascinating celestial bodies, WD J2147−4035 and WD J1922+0233, which are ultra-cool, metal-polluted (DZ) white dwarfs with surprisingly low temperatures. We discuss the intriguing features of these stars, including their unusually blue or red colours, as well as the innovative microphysics techniques Abbigail and her team use to understand them. Abbigail also reveals the extreme age of these white dwarfs - with WD J2147−4035 reaching over 10 billion years - and how they offer valuable information about the age of the Galactic disc in the Milky Way. Tune in to learn about these pivotal celestial objects and their potential impact on our understanding of the universe.

Ultra-cool white dwarfs, metal-polluted, WD J2147−4035, WD J1922+0233, microphysics, model atmosphere code, collision-induced absorption, Galactic kinematics, Gaia EDR3 astrometry, Galactic disc, spectroscopy, sodium, potassium, calcium, lithium, Zeeman splitting, accreted planetary crust debris, Milky Way.

Abbigail K Elms Spectral analysis of ultra-cool white dwarfs polluted by planetary debris, https://doi.org/10.1093/mnras/stac2908