Quid ultra? 

Frontiers and Controversies in Astrophysics

Quid Ultra? Frontiers and Controversies in Astrophysics is a series of monthly prestigious colloquia that aims to present to a broad audience of astrophysicists, PhD and master students some of the most controversial topics at the forefront of research by internationally recognized experts.

The topics that will be proposed range from the search for exo-planets and astro-chemical traces of the origin of life, to star formation, in the near and distant Universe; from the astrophysical sources of gravitational waves, to the complex mechanisms that regulate the evolution of galaxies; from the formation of black holes, to the nature of dark matter and energy and their impact on the observable properties of the Universe.

Next Lecture 

Thursday 20th April 2023 

online, 16:30 - 17:30

Carole Haswell, The Open University

Towards the geology of exoplanets

Hot rocky exoplanets offer exciting opportunities to place terrestrial geology into Galactic context, through composition measurements with JWST and Ariel. To capitalise on these opportunities we must identify the very best targets for spectroscopic characterisation. The catastrophically disintegrating exoplanets (CDEs) are the most dramatic examples of mass loss from an ablating rocky surface.  They were discovered by Kepler through the variable transits of dust co-existing with metal-rich vapour, and are particularly suitable for transmission spectroscopy because the ablated material is spread over a large scale-height. But the Kepler CDEs are too faint for transmission spectroscopy. The Dispersed Matter Planet Project (DMPP) is discovering the nearby analogues and progenitors of the Kepler CDEs. DMPP uses archival stellar spectra to identify stars we view through shrouds of diffuse, metal-rich, circumstellar gas. The underlying hypothesis is that the gas is ablated from hot, close-orbiting planets. DMPP searches for the putative planets with high-precision, high cadence radial velocity measurements. The approach has been extremely successful and efficient, with planet discoveries whenever 60 RV measurements have been collected. DMPP-1 is a compact multiplanet system orbiting a star brighter than V=8. A possible CDE transit has been discovered in TESS data. DMPP-2 b is the joint-first RV planet discovery orbiting a strongly pulsating star. DMPP-3 is an eccentric binary star system with the secondary at the mass threshold for sustaining hydrogen fusion. A 2.6 Earth mass planet orbits the K0V primary star in a 6.7 day orbit, with a second Earth-mass circumprimary planet marginally detected. DMPP-3AB is in a hitherto unpopulated parameter space for binary star planetary systems. I will include updates on our latest discoveries of around 20 short period planets, including planets orbiting a star of magnitude 6, and planets orbiting a young star. We may have caught the latter system in the act of evolving out of the Neptune desert through planetary ablation. DMPP planets are likely to be viewed edge-on as ablated material will remain concentrated near the planets’ orbital planes. Thus they have high transit probability. The subset of DMPP planets which transit are thus amenable to direct empirical determinations of mass, radius and composition.

Meeting ID: 81122901013

Passcode: 686688

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