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Gijs D Mulders

@gijsmulders.com
324 followers 60 following 105 posts

Exoplanet Astronomy Assistant Professor Santiago de Chile gijs.cl \m/

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Gijs D Mulders @gijsmulders.com · 08/10/2025
Solar system-like architectures appear for a small range of initial disk masses around F and G stars, but are not a common feature around K and M stars. Perhaps we are somewhat special among #exoplanets? 18 /🧵
Jupiter and Earth, size to scale
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Gijs D Mulders @gijsmulders.com · 08/10/2025
While the mid mass architecture is most efficient at depositing water directly in the habitable zone: It's pebble snow! #exoplanets 17/🧵
Water mass fraction vs disk mass for planets within the habitable zone
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Gijs D Mulders @gijsmulders.com · 08/10/2025
The low-mass architectures are quite efficient at creating water-worlds close to the star. 16 /🧵
Water mass fraction vs disk mass for planets within an orbital period of 100 days
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Gijs D Mulders @gijsmulders.com · 08/10/2025
The architectures are remarkably consistent across stellar mass, with the location and size of planets shifting with snow line and disk mass 15 /🧵
The bimodel pattern in core mass vs semi-major axes is consistent across stellar mass
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Gijs D Mulders @gijsmulders.com · 08/10/2025
The mid mass architectures form a bimodal distribution: Giant planet cores at the initial snow line location, and a second peak with smaller, water-rich #exoplanets in the habitable zone! 14/🧵
Mid mass architecture with giant planet cores at the snow line and water-rich smaller planets in the habitable zone
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Gijs D Mulders @gijsmulders.com · 08/10/2025
And… 13/🧵
Drumbeat
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Gijs D Mulders @gijsmulders.com · 08/10/2025
Low mass disks from predominantly planetary cores closer in, possible precursors to super-earths or waterworlds. 12/🧵
Low mass architecture with watery super-earth cores growing inside of the snow line
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Gijs D Mulders @gijsmulders.com · 08/10/2025
The main results is there are three growth modes: High mass disks form exclusively giant planet cores outside the snow line 11/🧵
High mass architecture with planet cores growing outside of the snow line
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Gijs D Mulders @gijsmulders.com · 08/10/2025
And explored a large range of stellar mass and disk mass to identify trends 10/🧵
Snow line locations for different stellar masses and disk mass fractions
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Gijs D Mulders @gijsmulders.com · 08/10/2025
And a snow line that moves in over time 9/🧵
Plot of planet core mass vs semi-major axis with 50 planetary seeds and a moving snow line
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Gijs D Mulders @gijsmulders.com · 08/10/2025
Sean added two components: Pebble filtering from 100s of planetary cores growing simultaneously 8/🧵
Plot of planet core mass vs semi-major axis with 100 planetary seeds
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Gijs D Mulders @gijsmulders.com · 08/10/2025
How would the diverse population of giants planets discovered around other stars, impact the mass and water content of exoplanets in the habitable zone? 4/🧵
Diverse population of giant (exo)planets
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Gijs D Mulders @gijsmulders.com · 08/10/2025
Jupiter has long been suspected to play as role in shaping the inner solar system and controlling water delivery to earth 3/🧵
Jupiter with impact marks from comet Shoemaker/Levy
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Gijs D Mulders @gijsmulders.com · 08/10/2025
One of the big mysterious in planet formation is how earth got to its current state: Not too big or too small, and with the right amount of water to support life. 2/🧵
Earth with a small mass fraction of water, shown as a sphere
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Gijs D Mulders @gijsmulders.com · 08/10/2025
How do giant planets influence the type of #exoplanets that form in the habitable zone? A thread 1/🧵
Many Exoplanets
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Gijs D Mulders @gijsmulders.com · 20/08/2025
#achievement for the day (please don't send me any more email)
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Gijs D Mulders @gijsmulders.com · 01/07/2025
Probably because Jupiter was relatively massive for a giant planet, and prevented super-Earths from forming
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Gijs D Mulders @gijsmulders.com · 01/07/2025
So why does the solar system not have these inner super-Earths?
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Gijs D Mulders @gijsmulders.com · 01/07/2025
So the correlation between super Earths and giant planets depends strongly on the giant planet mass! #exoplanets ☄️
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Gijs D Mulders @gijsmulders.com · 01/07/2025
While the super-Earth is two times LESS likely to have a super-Jupiter than than a random star
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Gijs D Mulders @gijsmulders.com · 01/07/2025
Then we split the sample in half by giant planet mass Now the super-Earth is FOUR times more likely to have a Saturn-mass planet than a random star
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Gijs D Mulders @gijsmulders.com · 01/07/2025
Etienne also looked at conditional occurrence rates A super-Earth is TWICE a likely to have a giant planet than a random star
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Gijs D Mulders @gijsmulders.com · 01/07/2025
To make sure this wasn’t some sensitivity bias, we calculated giant planet occurrence rates for stars with and without super-Earths. But the mass difference of a factor 6 remains
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Gijs D Mulders @gijsmulders.com · 01/07/2025
Where we noticed that cold Jupiters are a lot smaller when they have a super-Earth companion, by about a factor 6 on average
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Gijs D Mulders @gijsmulders.com · 01/07/2025
He analyzed the radial velocity sample from the California Legacy Survey
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Gijs D Mulders @gijsmulders.com · 01/07/2025
This question was investigated in the undergraduate thesis of Etienne Lefevre (currently doing a masters in France)
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Gijs D Mulders @gijsmulders.com · 01/07/2025
So what determines if a cold giant has a super-Earth?
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Gijs D Mulders @gijsmulders.com · 01/07/2025
Yet for some reason Jupiter is the exception: A cold giant planet with no inner super-Earths.
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Gijs D Mulders @gijsmulders.com · 01/07/2025
To add to the mystery: Many cold giant planets at longer orbits are accompanied by close-in super-Earths
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Gijs D Mulders @gijsmulders.com · 01/07/2025
Yet the solar system does not have any planets interior to Mercury’s orbit… Why is that?
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Gijs D Mulders @gijsmulders.com · 01/07/2025
One of the key exoplanet discoveries is that most stars like the sun have close-in super-Earths
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Gijs D Mulders @gijsmulders.com · 01/07/2025
Why does the solar system not have super-Earths? A thread #exoplanets ☄️
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Gijs D Mulders @gijsmulders.com · 01/07/2025
So the correlation between super Earths and giant planets depends strongly on the giant planet mass! #exoplanets ☄️
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Gijs D Mulders @gijsmulders.com · 01/07/2025
While the super-Earth is two times LESS likely to have a super-Jupiter than than a random star
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Gijs D Mulders @gijsmulders.com · 01/07/2025
And the super-Earth is even FOUR times MORE likely to have a Saturn-mass planet than a random star
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Gijs D Mulders @gijsmulders.com · 01/07/2025
Etienne also looked at conditional occurrence rates A super-Earth is TWICE as likely to have a giant planet than a random star
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Gijs D Mulders @gijsmulders.com · 07/04/2025
Gilly & Loeki, two very sweet kitties
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Gijs D Mulders @gijsmulders.com · 17/03/2025
Compiling all the literature on this topic we see a consistent result: Planet occurrence increases after 100 million years, and drops after 1 billion years when planets lose their atmospheres. 12/🧵
Exoplanet occurrence vs age literature comparison
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Gijs D Mulders @gijsmulders.com · 17/03/2025
Second surprise: the occurrence of intermediate aged planets is higher that of young planets (and older planets). What is going on here? Maybe planets arrive at their current location later than we thought? 11/🧵
Young exoplanet occurrence vs orbital period
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Gijs D Mulders @gijsmulders.com · 17/03/2025
Splitting the sample in half at an age of 100 million years, we see an expected trend in planets size: young planets are more often large, intermediate-aged planets are more often small. They shrink with time 10/🧵
Young exoplanet occurrence vs. radius
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Gijs D Mulders @gijsmulders.com · 17/03/2025
First surprise: there are 5-12 times more planets around young stars than around older stars (Kepler) At least within an orbital period of 12 days. 9/🧵
Young exoplanet occurrence at different orbital periods, vs. Kepler
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Gijs D Mulders @gijsmulders.com · 17/03/2025
We can now explore how the bias-correcting planet population — or planet occurrence — varies with age, planet properties, etc. 8/🧵
Evolution of hypothetical planetary system with sub-Neptune planets. Credit: Abigail Minnich (abbyminnich.wixsite.com/film)
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Gijs D Mulders @gijsmulders.com · 17/03/2025
To correct for this, we can characterize how complete the survey is for planet of different sizes by doing injection-recovery tests 6/🧵
TESS detection efficiency for young planets around FGK stars
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Gijs D Mulders @gijsmulders.com · 17/03/2025
But young stars are very active, making detection of small planets harder, and possibly biases the observed planet sizes upwards 5/🧵
A transiting planet around an active star. Credit: NASA/JPL-Caltech
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Gijs D Mulders @gijsmulders.com · 17/03/2025
Exoplanets around young stars are bigger than around older stars, possibly because they lose some atmosphere or shrink as they cool (Young = less than 1 billion years) 4/🧵
Young exoplanets from TESS compared to Kepler
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Gijs D Mulders @gijsmulders.com · 17/03/2025
One the most fascinating result comes from the exoplanet hunter TESS that looks for transiting exoplanets 3/🧵
Artist’s impression of the TESS mission
Credits NASA/MIT
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Gijs D Mulders @gijsmulders.com · 17/03/2025
The short answer is: yes! We see planet properties change over time by taking snapshots of the planet population around stars of different ages 2/🧵
Evolutionary stages of a hypothetical planetary system over time. The planets in the system, labeled b through f, are depicted at three distinct stages: 10–100 Myr (top panel), 100 Myr–1 Gyr (middle panel), and >1 Gyr (bottom panel). This progression highlights key processes shaping the system, such as atmospheric mass loss and compositional evolution driven by stellar radiation and planetary interactions. Image credit: Abigail Minnich (abbyminnich.wixsite.com/film)
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Gijs D Mulders @gijsmulders.com · 17/03/2025
Do #exoplanets evolve over time? ☄️ A thread 1/🧵
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Gijs D Mulders @gijsmulders.com · 25/04/2024
An hour before the deadline: “Cannot find a suitable calibrator” #ALMACycle11 🔭🪐
Alma OT calibration error meme
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Gijs D Mulders @gijsmulders.com · 06/03/2024
Various pebble accretion models explain the peak occurrence of the small inner planet around early M dwarfs Planet migration models struggle in reproducing the stellar mass dependencies, of both outer giant planets as well as the inner sub-Neptunes (6/🧵)
Stellar mass dependence of planet formation models. Pebble accretion models match the peak in exoplanet occurrence for early M dwarfs
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