We’re back with#formation and #demographics this morning starting with Charles Law on embedded planets.
Charles stresses how much #ALMA has revolutionised the field providing a wonderful pictures of discs. Nevertheless, resolving planets embedded in these discs is pretty hard. But chemistry is our saviour, making signatures of the planet observable with #ALMA.
We start with the disc HD 169143 b - funny I worked with data from this disc for my bachelor’s thesis.#ExSSV
In this disc, there is a protoplanet! - so a baby planet 👶 🪐 and they trace it ALMA data and chemistry, note the asymmetry in the emission due to the planet. They put together SiS and SO: SiS appears blueshifted.
In addition, they also detect CO (12/13). Let’s put it all together!
The detection of SiS indicates shocks, and outflow of the planet because of the observed shift.
Take away: Si and S bearing molecules provide a new way for us to study protoplanets. More to come!! #ExSSV
Next up, we’ve got Kiersten Boley on the first evidence of the metallicity cliff in the formation of super-Earths.
The first stars were metal poor, so there were not enough metals to form planets via core accretion. So the question comes up: when did we start forming planets?
Already back in 1996, after finding 4 planets, people started doing statistics ;) in particular looking at how metallicity links to #planet#formation.
Super-Earths show weak trends with metallicity, though note that we’re still limited by not looking around “metal-poor” hosts.
They constructed a sample to determine occurrence rates around “metal-poor”, fairly bright FGK stars. From K2&Kepler, they expected 68 super-Earths at metallicity below -0.5 met. But they found none!
What does that mean? There is evidence for a metallicity cliff around -0.31 suggesting that this affects planet formation #ExSSV
Next up, we’ve got Casey Brinkman on rocky planet composition and the (non)-dependency on stellar abundances.
The structure of a rocky planet can be oversimplified as an iron core + rock. This allows to estimate the core mass fraction and from there tells us about the planet formation conditions.
Previous studies don’t agree on the correlation between star and planet, so they created their own sample of planets determining the CMF.
Metal poor => small CMF.
Metal rich => scattered CMF #ExSSV
Depending on the fitting algorithm, they find a steep line, meaning that there is a depletion/enrichment for planets in comparison to their host stars.
Nevertheless, they don’t find strong evidence for a correlation between host star and planet composition #ExSSV
Next up, we’ve got Kristo Ment talking about planet occurrences for mid-to-late M dwarfs from TESS.
you may find this as surprising as I do, but M dwarfs are the most common stars!
Let’s talk #demographics: despite having smaller protoplanetary discs, (early) M dwarfs seem to be forming more planets than others.
In Kristo’s work, they study late M dwarfs to see if this trend continues and what the radius mass relation looks like. There are 7 detected planets in this sample #ExSSV
Add comment