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Sijme-Jan Paardekooper

@sijme-jan.bsky.social
118 followers 369 following 6 posts

Computational astrophysicist at Delft University of Technology. Studying the formation of planets.

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Reposted by Sijme-Jan Paardekooper
Hossam Aly @astrohoss.bsky.social · 16/07/2025
It's paper day 🎉🔭 arxiv.org/abs/2507.10719 Together with @sijme-jan.bsky.social we continue to look at dust instabilities in planet forming discs when considering many dust sizes (polydisperse). This time we probe the Dust Settling Instability (DSI) via hydro simulations in a local box 1/14
arxiv.org
Nonlinear Evolution of the Unstratified Polydisperse Dust Settling Instability
Context. The Dust Settling Instabilty (DSI) is a member of the Resonant Drag Instabilities (RDI) family, and is thus related to the Streaming Instability (SI). Linear calculations found that the unstr...
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Sijme-Jan Paardekooper @sijme-jan.bsky.social · 20/06/2025
"we must not fall into the trap of mistaking the outputs of writing (which are increasingly substitutable through technology) from the value of the cognitive process of writing (which hones mental development and cannot be substituted by a machine)."
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James O’Brien @mrjamesob.bsky.social · 16/06/2025
Our gift to the world.
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Adam Drummond @adamdrummond.bsky.social · 16/06/2025
It's not the biggest problem education is facing but at some point the preference of parents and students for coursework and fewer exams is going to collide with the fact that AI probably necessitates a big return to in-person exams
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James Kelleher @jameskelleher.pilcrow.ie · 09/06/2025
We are all in the gutter, but some of us are looking at our phones
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Charlotte Lydia Riley @lottelydia.bsky.social · 04/06/2025
I don’t know. I love this Joseph Fasano poem and have it pinned on my office door but I don’t know what to actually do about any of this.
FOR A STUDENT WHO USED AI TO WRITE A PAPER
Now I let it fall back in the grasses.
I hear you. I know this life is hard now.
I know your days are precious on this earth.
But what are you trying to be free of?
The living? The miraculous task of it?
Love is for the ones who love the work.
-Joseph Fasano
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Sijme-Jan Paardekooper @sijme-jan.bsky.social · 03/06/2025
Prediction was a few months off, but good riddance
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Tim Lichtenberg @timlichtenberg.bsky.social · 02/06/2025
The abstract submission for Rocky Worlds 4 is now open! groningen2026.rockyworlds.org/registration... 🌋🔭🧬😱
groningen2026.rockyworlds.org
ROCKY WORLDS 4 - Abstract Submission
Abstract submission & conference registration Abstract submission and conference registration are done in two steps. First, the abstract submission below (including requests for financial support) run...
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Kevin M. Kruse @kevinmkruse.bsky.social · 11/05/2025
What the fuck, people. Do not do this.
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Robert Saunders @robertsaunders.bsky.social · 11/05/2025
A core feature of the Trump regime is its embrace of "authoritarian democracy", as a battering ram with which to demolish any obstacle to its power. The very notion of "authoritarian democracy" can sound contradictory. But it's an old & dangerous idea, that needs to be better understood. [THREAD]
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Joseph Fasano @josephfasano.bsky.social · 05/05/2025
It's final paper season.
For a Student Who Used AI to Write a Paper
 
by Joseph Fasano

Now I let it fall back
in the grasses.
I hear you. I know
this life is hard now.
I know your days are precious
on this earth.
But what are you trying
to be free of?
The living? The miraculous
task of it?
Love is for the ones who love the work.
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Chris Lintott @chrislintott.bsky.social · 01/05/2025
A new, thorough reanalysis of the data that led to claims of biosignatures on K2-18b from @luiswel.bsky.social & friends - a nicely written lesson on why this stuff is hard. They find no significant evidence for DMS, the gas the Cambridge team claimed to have found. arxiv.org/abs/2504.21788
arxiv.org
The Challenges of Detecting Gases in Exoplanet Atmospheres
Claims of detections of gases in exoplanet atmospheres often rely on comparisons between models including and excluding specific chemical species. However, the space of molecular combinations availabl...
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Chris Lintott @chrislintott.bsky.social · 17/04/2025
Blimey! Prof Madhusudhan’s response to my friendly discussion of the many unknowns was that I’m a ‘commentator not a practitioner’.
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Dr Ryan MacDonald @distantworlds.space · 17/04/2025
𝗡𝗼, 𝗮 𝗯𝗶𝗼𝘀𝗶𝗴𝗻𝗮𝘁𝘂𝗿𝗲 𝘄𝗮𝘀 𝗻𝗼𝘁 𝗷𝘂𝘀𝘁 𝗱𝗲𝘁𝗲𝗰𝘁𝗲𝗱 𝗶𝗻 𝗞𝟮-𝟭𝟴𝗯'𝘀 𝗮𝘁𝗺𝗼𝘀𝗽𝗵𝗲𝗿𝗲. K2-18b is back in the news, now with a bold claim that biosignature molecules (DMS and/or DMDS) have been 'detected at 3σ'. Most exoplanet astronomers are extremely sceptical about these claims, let's see why (1/n). 🔭🧪🪐 #exoplanet
Artist's impression of the exoplanet K2-18b.
Credit: A. Smith, University of Cambridge.
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Chris Lintott @chrislintott.bsky.social · 17/04/2025
An astonishing headline reporting on new observations from a team led to Nikku Madhusudhan claims they’ve found ‘hints of life’ on a planet orbiting a dwarf star some 124 light years away. What’s going on? (1/n) www.bbc.co.uk/news/article... 🔭 🧪
bbc.co.uk
Promising hints of life found on distant planet K2-18b
Scientists find new but tentative evidence that a faraway world orbiting another star may be home to life.
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Chris Ashwood @cashwood.proteaglyco.com · 14/04/2025
There are great conferences and science in the US, but with the way things are right now, it’s too risky to attend.
theguardian.com
Australian academics refuse to attend US conferences for fear of being detained
‘When academics fear travelling or partnering with US institutions, the impacts ripple through the entire global knowledge ecosystem,’ one says
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Dr. Jessie Christiansen @aussiastronomer.bsky.social · 11/04/2025
First the rumour was a 20% budget cut. Then, 50%. Now the president's NASA budget is out and it's a 68% cut to astrophysics ($1.5B to $487M). Even if this gets reversed in four years, we will *never* recover the missions, partners, people who will be gone. www.washingtonpost.com/science/2025...
washingtonpost.com
Massive cuts to NASA science proposed in early White House budget plan
The preliminary version of President Donald Trump’s budget proposal to Congress, known as a “passback,” would cut the agency’s science budget funding nearly in half.
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Jonathan McDowell @planet4589.bsky.social · 08/04/2025
Jerry Ostriker has died www.nytimes.com/2025/04/07/s...
nytimes.com
Jeremiah Ostriker, Who Plumbed Dark Forces That Shape Universe, Dies at 86
There’s more to the universe than meets the eye, he found. His studies led astronomy to the dark side, changing our view of what’s out there.
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Hank Green @hankgreen.bsky.social · 07/04/2025
A tricky thing about modern society is that no one has any idea when they don’t die. Like, the number of lives saved by controlling air pollution in America is probably over 200,000 per year, but the number of people who think their life was saved by controlling air pollution is zero.
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Hossam Aly @astrohoss.bsky.social · 13/03/2025
Here we go paper II is out today 🔭 arxiv.org/abs/2503.09265 Here @sijme-jan.bsky.social and I continue looking at the linear theory of RDIs when you have dust with size distributions, but this time we focus on the streaming and settling instabilities, which are important for planet formation 1/14
arxiv.org
Resonant drag instabilities for polydisperse dust. II. The streaming and settling instabilities
Dust grains embedded in gas flow give rise to a class of hydrodynamic instabilities, called resonant drag instabilities. These instabilities have predominantly been studied for single grain sizes, in ...
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David Slack @slack2thefuture.bsky.social · 27/02/2025
A lot of people confuse writing with typing. Writing isn’t typing. It’s the entire process and yes that includes going for a walk or rearranging things in your office.
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Hossam Aly @astrohoss.bsky.social · 10/03/2025
It's paper day! 🔭 arxiv.org/abs/2503.05359 This is a 1st of a series where @sijme-jan.bsky.social and I look at how dust instabilities change when you start treating dust as a continuum of species with different sizes, i.e; "Polydisperse", instead of a single size species 1/9
arxiv.org
Resonant Drag Instabilities for Polydisperse Dust, I. The Acoustic Resonant Drag Instability
Dust grains embedded in gas flow give rise to a class of hydrodynamic instabilities that can occur whenever there exists a relative velocity between gas and dust. These instabilities have predominantl...
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Carl T. Bergstrom @carlbergstrom.com · 06/03/2025
No. Never. I review 20+ of papers a year—it's my job as a scientist. The public pays my salary and trust me to use my time wisely to advance science. Through peer review, I do exactly that. I spend two or three weeks a year reviewing, but I’ve never wasted a day reviewing a paper, and never will.
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Jonathan Cohn @jonathancohn.bsky.social · 02/03/2025
The average American voter thinks that the government is too big but that it should spend more money on everything it does. This explains a decent share of the political chaos of this country.
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Stephen Curry @scurry.bsky.social · 03/03/2025
Good luck today to the fellows of the Royal Society who are gathering in London to discuss “public pronouncements and behaviours of other fellows.” I trust there will be a candid and informed exchange of views. 1/4
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Ross Carroll @rosscarroll.bsky.social · 25/02/2025
When I worked in UK academia I recall hearing of a Japanese man who was baffled at how Britain had decided to run its universities like firms. “Why? Your universities are excellent and your firms are terrible.”
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Hossam Aly @astrohoss.bsky.social · 05/02/2025
It's paper day! Together with @sijme-jan.bsky.social and led by exceptional (2nd year!) PhD student Jip Matthijsse, we look at the Streaming Instability in dust with size distributions and how the resulting clumps have different size distribution from the initial one arxiv.org/abs/2502.01752 1/n
arxiv.org
Polydisperse Formation of Planetesimals: The dust size distribution in clumps
The streaming instability is an efficient method for overcoming the barriers to planet formation in protoplanetary discs. The streaming instability has been extensively modelled by hydrodynamic simula...
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Mike Sowden @mikeachim.bsky.social · 27/01/2025
In 2014 Dutch scientists left a hamster wheel outside, to see if wild animals would use it like their domesticated counterparts. The answer: hell yes! 734 visits from wild mice - plus rats, shrews, slugs ("running" being subjective here) & even frogs and snails. The apparent reason: fun. Just fun.
Chart showing instances of wild animals using a hamster wheel left out in the wild, with visits dominated by wild mice, followed by slugs, rats, shrews and a few frogs and snails.
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Prof Anna Watts @profannawatts.bsky.social · 25/01/2025
I am prepared to buy MORE LEGO to assist the Danish economy should it prove necessary.
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ASCL (Astrophysics Source Code Library) @asclnet.bsky.social · 07/01/2025
Sverre Aarseth, a great influence on open astro software, has died. ascl.net/wordpress/20...
ascl.net
Sverre Aarseth, father of open source stellar dynamics software, has passed on to a higher orbit – ASCL.net
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Nigella Lawson @nigella.bsky.social · 31/12/2024
You can call them New Year Doughnuts or Dutch Doughnuts or, more properly, Oliebollen, but what matters to me most is that they are, appropriately, #RecipeOfTheDay, and I commend them to you! www.nigella.com/recipes/new-...
nigella.com
New Year Doughnuts - Oliebollen
This recipe didn’t find its way into my Amsterdam Christmas Special since it had already appeared in the CER Christmas show, but you can’t set foot in the Netherlands in the festive period without enc...
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Glenn Moore @thenewsatglenn.bsky.social · 14/12/2024
Hate freeloaders who join in the New Year's Eve countdown for the last 10 seconds. I've been doing this all year. Where were you back in May
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Sijme-Jan Paardekooper @sijme-jan.bsky.social · 22/12/2024
Interviewer: Can you explain this gap in your resume? Protoplanetary disc modeller: unseen planets 🤞 (but other mechanisms are available)
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Katie Mack @astrokatie.com · 19/12/2024
A new analysis of data from the Juno spacecraft suggests that the ice shell covering the ocean on Jupiter's moon Europa might be WAY thicker than anticipated. (With comments from @theplanetaryguy.bsky.social) Possibly bad news for any hope of life signs from Europa Clipper, currently en route. 🧪🔭
science.org
Surprisingly thick ice on Jupiter’s moon Europa complicates hunt for life
Revelation is blow to hopes for habitability and future space missions
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Tim Lichtenberg @timlichtenberg.bsky.social · 19/12/2024
Our institute is advertising a Tenure Track Assistant Professor position on Astronomical Data Science and Machine Learning: aas.org/jobregister/.... The position is broadly defined and explicitly also open to researchers with a background in planetary and exoplanetary research. Please share! 🔭💻👩‍💻
aas.org
Tenure Track Assistant Professor on Astronomical Data Science and Machine Learning | American Astronomical Society
The Kapteyn Astronomical Institute invites applications for the position of Assistant Professor, with a clear focus on the development and application of astronomical data science and machine learning...
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Nigella Lawson @nigella.bsky.social · 04/12/2024
#RecipeOfTheDay borrows gratefully from the Dutch Christmas canon. That’s to say, this is my take on their glorious almond pastries – and, don’t worry, these Banket Bars use shop-bought puff pastry, which makes them alluringly do-able! www.nigella.com/recipes/bank...
nigella.com
Banket Bars
It can be hard to adopt other countries’ Christmas traditions and cherish them like our own, but when it comes to this Dutch log of almond paste, encased in puff pastry, I have no problem whatsoever! ...
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astronomie.nl @astronomienl.bsky.social · 03/12/2024
Antonia Rowlinson (UvA, ASTRON) en Else Starkenburg (RUG) ontvangen ERC Consolidator Grant www.astronomie.nl/nieuws/anton...
astronomie.nl
Antonia Rowlinson (UvA, ASTRON) en Else Starkenburg (RUG) ontvangen ERC Consolidator Grant
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Chris Parr @chrisjparr.bsky.social · 25/11/2024
Royal Society fellow Dorothy Bishop (@deevybee.bsky.social) resigns over Elon Musk membership. Bishop claims Musk has violated RS code of conduct, and is not prepared to treat him "collegially and with courtesy" as that code requires. Free to read. www.researchprofessionalnews.com/rr-news-uk-c...
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Andrew Mann @amann.bsky.social · 20/11/2024
Check out the latest find from the Young Worlds Lab, led by UNC Graduate Student Madyson Barber (madysonb.github.io). Newborn planet found in a warped system www.nature.com/articles/d41... www.nature.com/articles/s41... 🧪🔭🪐⚛️🌌⭐
nature.com
Newborn planet found in a warped system
The discovery of a young, Jupiter-sized planet with a short orbital period provides useful data for studying planet formation.
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Henry Morris @mrhenrymorris.substack.com · 18/11/2024
THE SECRET DIARY OF ELON MUSK AGED 53 3/4 Monday November 18th History may well want a clear account by an unprejudiced observer of what happened on our Alphas trip to the UFC. I am the only person qualified. RFK Jr, for all his qualities, does not possess my nerves of steel. Thread 1/10
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Catherine 🌌 @catieslaughts.bsky.social · 14/11/2024
Academia was invented by Big Coffee to sell more coffee
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Roland Smith @rolandmcs.bsky.social · 10/11/2024
Long thread on how Brexitism started and evolved over 75 years, drawing from Benjamin Grob-Fitzgibbon's 'Continental Drift'. Global Britain, Free Trade, Cakeism, Federalism, anti-federalism, EEA, Winston Churchill, Empire, 52-48 referendums, Enoch Powell, 1975, Thatcher.... It's all here. /1
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Maggie Parry-Mantel @maggienifique.bsky.social · 05/11/2024
The UK having our election this year on 4th July and America having theirs on 5th November feels like an odd sort of cultural exchange between our two countries.
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David W Hogg @hogg.bsky.social · 04/11/2024
Here’s the slides from my talk about the promise and dangers of machine learning at University of Michigan: dwh.gg/umstat
dwh.gg
UMich Stats: Is machine learning good or bad for science?
Is machine learning good or bad for science? These slides are at https://dwh.gg/umstat David W Hogg NYU / MPIA / Flatiron http://cosmo.nyu.edu/hogg/ Work in collaboration with Soledad Villar (JHU).
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Space Telescope Science Institute @stsci.edu · 16/09/2024
The Astropy Project, developers of an open-source software used to analyze astronomical data—which STScI has contributed to since 2011—has been awarded the 2025 Lancelot M. Berkeley–New York Community Trust Prize for Meritorious Work by AAS: bit.ly/3B08mmF 🔭 🧪
A vertical mosaic of images shows the various photos, avatars, and icons for each of the more than 500 contributors to the Astropy project. The Astropy logo, an orange semi-transparent spiral with one end open, is overlaid on top.
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Sijme-Jan Paardekooper @sijme-jan.bsky.social · 12/01/2024
New paper this week, led by Kevin Chan: stability of dusty rings in protoplanetary discs. arxiv.org/abs/2401.04517
arxiv.org
Stability of Dusty Rings in Protoplanetary Discs
Dust rings in protoplanetary discs are often observed in thermal dust emission and could be favourable environments for planet formation. While dust rings readily form in gas pressure maxima,...
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Sijme-Jan Paardekooper @sijme-jan.bsky.social · 22/11/2023
Prediction: forming a government will take longer than the resulting government will govern. #dutchelections
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Sijme-Jan Paardekooper @sijme-jan.bsky.social · 14/10/2023
Finally migrating over from the other place (thanks @benmonreal.bsky.social !). Astrophysicist in Delft (NL), left UK because Brexit, trying to figure out how planets form and how this new site works...
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