Richard Alexander

So happy to see this. Mills was the first place I got to see the night sky through a “real” telescope - it’s a fantastic facility. Best wishes for the big birthday celebrations. 🎉 🔭

Also doesn’t reflect authorship norms in different fields. In lab-based subjects it’s convention that the senior/supervising author is listed last. But in fields like astronomy/astrophysics the supervisor is usually second or third author. To me, last author indicates smallest contribution. 🤷🏻‍♂️

Hard to say if the Wings/Avs rivalry peaked with the regular-season brawl, or the playoff fight night that ended in Crawford's meltdown.

The Wikipedia page doesn't really do justice to Shanahan clothes-lining Roy though. Or mention that he didn't get penalised for it. 🤣

I’m still on a 12 mini, and ditto. I do not want a bigger phone.

Meeste van op de TV is ook heel eng.

Definitely not. If it's a new class, I'd plan for roughly one day of prep per hour in front of the students.

The image shows a plot of the ID number of proposals submitted to JWST with the date of submission plotted from left to right. Each is marked as a green triangle and together they form an upwards curve showing roughly exponential growth. A horizontal yellow line below the data shows the minimum start point based on previously accepted proposals.

With just under 12 hours to go, here's how JWST Cycle 5 proposal submissions are progressing according to our sampling of the star and planet formation people here in Leiden! We're well past the 1000 mark for the year (and 10,000 across all years!) now, but where will we end up?

Indeed. It’s not just a lack of new positions either. There are a number of departments where astro staff have recently moved or retired and have not been replaced.

Is the price for buying solar systems, or for heating them? The latter might actually be more...😂

I get quite annoyed by the notion that science isn't creative. The first step in the scientific process is having new ideas; without creativity we have no science.

The recent trend of using "creative" (or worse, "creatives" 😬) to refer only to arts and humanities is both inaccurate and unhelpful.

Problem is that when it comes to the specific topic of PAHs, you could probably fit *all* the grown-ups who actually understand them in that locked room with you.

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werkenbij.uva.nl/en/vacancies...

If it’s material I’m familiar with, then that’s about right - roughly one full day per lecture. But if it’s a topic I need to revise first then it’s significantly more. Plus time for problem sets, etc.

Putting it another way: writing 20 lectures from scratch is at least a month’s full-time work.

Great to see our paper on methanol in TW Hya finally come out today (with Catherine Walsh and Jenny Calahan). A quick overview.... 🔭 ☄️ #radioastro

arxiv.org/abs/2510.04106

dr. evil from the movie dumb and dumber is sitting in a chair . ALT: dr. evil from the movie dumb and dumber is sitting in a chair .

It's a close call between that and the budget...

The proposed budget is my favourite part...

Don't forget the $380 million in start-up funding, plus an annual budget of $80 million.

We do sort of know this though (mostly from RV surveys).

How many solar-type stars have a Jupiter analogue between 1-10AU? 5-10% of them.

But how many of those systems also have analogues of the terrestrial planets? No idea...

Happy Father Dougal Day to those who celebrate. 🎉

(Admittedly that's basically just my third-year class, but we'll still have some fun with it.)

Marvelling at a request for a letter of reference that specifies both a font size and a page limit. I understand the need for guidelines, but who are the people who need to be told that letters of recommendation shouldn't run to more than 3 pages? 🔭

Reposting for the western time-zones...

👇🏻- thread about @simintong.bsky.social's excellent new paper on understanding turbulence and dust fragility in planet-forming discs. 🔭

Yes, and we do 😀, but the derived fragmentation velocities are slightly degenerate with the strength of disc turbulence. We didn't do the comparison with solar system bodies directly, but it would be interesting to look at. 👍🏻

Turbulence and dust fragility in protoplanetary discs Dust growth from micron- to planet-size in protoplanetary discs involves multiple physical processes, including dust growth and fragmentation, the streaming instability, and pebble accretion. Disc tur...

There is a *lot* more detail and nuance in the paper than I can cover in a thread like this (including spectral index measurements, the effects of bouncing collisions, etc.), so if you'd like to know more, please read the paper. 😀 🔭

arxiv.org/abs/2509.24818

- reproducing the observed fluxes is only possible if the rings are optically thick at mm wavelengths.
- in time-dependent models, the inner dust ring has to form before the outer ring (otherwise it is never bright enough).
- these results don't change significantly with different opacity models. 🔭

Fig.5 from Tong et al. (2025), showing the successful numerical models from the simulation suite. The first column shows the dust size distribution in the disc, at t=1Myr, as a function of radius; the second and third columns show synthetic ALMA observations of these models. Columns 4-6 show the same results at t=3Myr.

These are steady-state models, but real discs evolve. Simin therefore extended her analysis to time-dependent calculations, and explored a wide range of models to understand what multi-wavelength observations of these rings tell us. She was able to draw several interesting new conclusions... 🔭

Fig.1 from Tong et al. (2025). The figure shows the results from analytic modelling of multiple rings observed in three well-known discs from the MAPS survey. Reproducing the observations at multiple wavelengths is only possible for specific combinations of dust material strength (fragmentation velocity) and gas turbulence.

Simin first used an analytic model to show that the dust and gas properties are correlated. If the dust is fragile (with a low fragmentation threshold), then seeing rings implies the turbulence is very weak; while stronger turbulence requires much more resilient dust aggregates. 🔭

Rings in ALMA continuum emission arise when mm-size dust becomes trapped in structures in the gas disc. However, if grains collide too energetically they fragment, so seeing rings tells us about the local physics: how fragile (or not) the dust is, and how turbulent the gas is. 🔭

Fig.3 from Tong et al. (2025), showing ALMA observations of the GM Aur protoplanetary disc at 1.3mm (Band 6) and 2.1mm (Band 4). Left panels are the sky-plane images from Huang et al. (2020); right panels show the same observations de-projected.

New paper, led by @physicsuol.bsky.social PhD student @simintong.bsky.social. Simin looked at the rings we see in planet-forming discs, and combined new models with multi-wavelength ALMA observations to understand the underlying physical properties of the dust and gas. 🔭

arxiv.org/abs/2509.24818

Former Lib Dem leader Sir Menzies Campbell dies aged 84 Sir Menzies led the Liberal Democrats from 2006 to 2007 and was the MP for North East Fife at Westminster for 28 years.

Very sad news. Ming Campbell was my MP when I was a kid, and he was a lovely man. I remember going to his surgery as part of a school project, and he talked with us - a pair of 12-year-olds - for half an hour, with the same earnestness as when he spoke in parliament.

www.bbc.co.uk/news/article...

a man with red hair and a beard is standing in the woods ALT: a man with red hair and a beard is standing in the woods

<nods acknowledgement in PGPlot...>