iiinova — where your digital self keeps evolving

Paul Duffell @paulduffell.bsky.social · 09/05/2026

My graduate student Miranda Pikus just published a paper on supernova remnants. She did 3D simulations of supernova remnants with fast cooling and was able to reproduce the highly unusual "spiky" shape of the supernova remnant Pa 30 (SN 1181 AD) iopscience.iop.org/article/10.3...

Supernova Remnant Pa 30, over 800 years after the original supernova of 1181 AD. Left side is the observed remnant, right side is a 3D model generated by Miranda Pikus at Purdue. Full paper here: https://iopscience.iop.org/article/10.3847/1538-4357/ae57ac/pdf

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Paul Duffell @paulduffell.bsky.social · 04/05/2026

My student Miranda Pikus just had her paper accepted to ApJ! arxiv.org/abs/2511.08519 She developed a suite of detailed 3D simulations demonstrating how the unusual "spiky" shape of the supernova remnant Pa 30 could be naturally generated via a fluid instability in a rapidly cooling remnant. 🔭🧪

The supernova remnant Pa 30, caused by a supernova that went off in 1181 AD. The left side shows the highly unusual sulfur-rich filaments in the observed remnant. The right side is Miranda's theoretical model, providing an explanation for these filaments via Rayleigh-Taylor instability with fast cooling.

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Paul Duffell @paulduffell.bsky.social · 15/04/2026

Congratulations to my student Ranadeep Dastidar for a successful defense of his thesis!

Paul Duffell (sitting, left) with Ranadeep Dastidar (standing, right) at the beginning of his thesis defense, titled "Investigating Observational Signatures for Non-thermal Radiation Processes in Gamma Ray Bursts"

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Paul Duffell @paulduffell.bsky.social · 02/02/2026

🔭🧪 The latest episode of the #astrophysics #podcast is now available! I discuss interesting ways of learning about dark matter in the Milky Way with Dr. Gurtina Besla from the University of Arizona: rss.com/podcasts/ast...

Photo of Dr. Gurtina Besla, an astrophysicist from the University of Arizona.

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Paul Duffell @paulduffell.bsky.social · 01/12/2025

December's episode of the #astrophysics #podcast is here! This month, I interview Dr. Kaitlin Kratter of the University of Arizona. We talk about how she figures out how the planets form by putting a solar system on the computer! 🔭🧪

Dr. Kaitlin Kratter, Professor of Astronomy at the University of Arizona.

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Paul Duffell @paulduffell.bsky.social · 11/10/2025

We just got our conference fliers printed out for Rise_Time 2026! Hope to hand out plenty of these at the HEAD meeting next week!

Conference fliers for Rise_Time 2026: QR code leads to https://www.physics.purdue.edu/duffell/rise_time2026.html

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Paul Duffell @paulduffell.bsky.social · 01/10/2025

🔭🧪 Haven't posted here much lately, but I figured @sciencesocks.bsky.social would have words for me if I didn't promote Merel's episode of the #astrophysics #podcast! Dr. Merel van 't Hoff tells us all about the environments that new solar systems are born in! Check it out! rss.com/podcasts/ast...

Photo of Dr. Merel van 't Hoff, professor of Physics and Astronomy at Purdue University.

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Paul Duffell @paulduffell.bsky.social · 02/06/2025

For the next episode of the #podcast, I hope to do an astrophysics Q&A. I invite you to reply with any questions about astrophysics, or questions about what it's like to be a scientist. To my scientist friends: feel free to reply if you like; just know I may quote your response in the podcast. 🧪🔭

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Paul Duffell @paulduffell.bsky.social · 01/06/2025

Good Morning! This month's episode of the #astrophysics #podcast is now available! I am interviewing Dr. Andrea Derdzinski and we talk all about black holes and how we search for them! Let's hope we can continue to do so in the future! 🔭🧪 rss.com/podcasts/ast...

Dr. Andrea Derdzinski, postdoctoral research fellow at Vanderbilt University.

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Paul Duffell @paulduffell.bsky.social · 14/05/2025

To anyone wondering why I haven't been answering my email, I just became a dad and suddenly I seem to only care about one thing. I'll try not to post too many photos but here's one:

Dad & baby relaxing after a hard week of existing outside a womb.

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Paul Duffell @paulduffell.bsky.social · 01/05/2025

Another episode of the #astrophysics #podcast is now available! I am interviewing Dr. Jared Goldberg from the Flatiron Institute, and we talk all about Betelgeuse. rss.com/podcasts/ast... 🧪🔭

Dr. Jared Goldberg, postdoctoral research fellow at the Flatiron Institute's Center for Computational Astrophysics.

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Paul Duffell @paulduffell.bsky.social · 01/04/2025

Apparently I am not good at bluesky so I am posting this again, with the appropriate tags 🧪🔭. The latest episode of the #astrophysics #podcast is out! This month, I am interviewing Dr. Yvette Cendes of the University of Oregon @whereisyvette.bsky.social. Enjoy! rss.com/podcasts/ast...

Dr. Yvette Cendes (left) being interviewed by Dr. Paul Duffell (right) on the astrophysics podcast: https://rss.com/podcasts/astrophysics/1949013

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Paul Duffell @paulduffell.bsky.social · 01/04/2025

The latest episode of the #astrophysics #podcast just aired today! I'm interviewing Dr. Yvette Cendes, @whereisyvette.bsky.social. We talk about her latest research on the crazy things that we see happen when a black hole eats a star! rss.com/podcasts/ast...

Dr. Yvette Cendes (left) getting interviewed by Dr. Paul Duffell (right) on the astrophysics podcast. https://rss.com/podcasts/astrophysics/1949013

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Paul Duffell @paulduffell.bsky.social · 12/03/2025

Google AI with some slick mathemagic:

Google AI seems to do a nice job of finding the planck mass and the proton mass on the internet, and even does the calculation of their ratio correctly. But then apparently it second-guesses itself at the last minute, making them off by an order of magnitude.

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Paul Duffell @paulduffell.bsky.social · 01/03/2025

Happy Weekend! The latest episode of the #astrophysics #podcast has been released! 🧪🔭 This month I am interviewing Dr. Maxim Lyutikov, who studies fast radio bursts and astrophysical plasmas. We also discuss connections to our own sun and the aurora borealis. rss.com/podcasts/ast...

A photograph of Dr. Maxim Lyutikov, who is a professor of Physics and Astronomy at Purdue University.

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Paul Duffell @paulduffell.bsky.social · 25/02/2025

Very impressive astro seminar yesterday by @whereisyvette.bsky.social -- Incredible new data on tidal disruption events (TDEs), it pays to keep looking in the radio! 🧪🔭 (This plot is old data from 3 years ago -- you'll have to ask Yvette if you want the latest, but the light curve is still rising!)

Radio data from tidal disruption events, interpreted to show luminosity over time; the green stars indicate the event AT2018hyz, with an extremely rapid rise for no obvious reason several years after the original event. The leading theories are an off-axis relativistic jet, or some kind of "late-time injection" both of which are hard to explain.

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Paul Duffell @paulduffell.bsky.social · 01/02/2025

🧪🔭 Good Morning! The latest episode of the Astrophysics Podcast is out today! I'm interviewing Dr. Lindsey Kwok, a research fellow at Northwestern University. She uses JWST to learn how supernovae exploded! rss.com/podcasts/ast... #astrophysics #podcast

Dr. Lindsey Kwok, CIERA fellow at Northwestern University and supernova observer.

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Paul Duffell @paulduffell.bsky.social · 02/01/2025

Happy Hanukkah! Please ignore the reflection of our Christmas tree in the window.

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Paul Duffell @paulduffell.bsky.social · 01/01/2025

Happy new year! The latest episode of the astrophysics podcast is now available! Dr. Abigail Polin is hosting this episode. And she's interviewing a MYSTERY GUEST. (ok fine, she's interviewing me, big deal) 🧪🔭 rss.com/podcasts/ast...

Dr. Abigail Polin, professor of Physics and Astronomy at Purdue University.

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Paul Duffell @paulduffell.bsky.social · 17/12/2024

@sciencesocks.bsky.social Unbeknownst to me, my brother & sister-in-law went to your website and got us this JWST ornament for our tree! We put it in a place of honor, right below the goat. Very nice work, it's shiny!

The JWST mirror ornament on a tree underneath a goat. https://sciencesocks.co if you are interested in this ornament!

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Paul Duffell @paulduffell.bsky.social · 14/12/2024

Wicked, of course, featured the true origin story of the jitterbug scene! #deckofcards did it first...

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Paul Duffell @paulduffell.bsky.social · 04/12/2024

Cool result from @starlights.bsky.social (Sears et al). Late-time observations of the BOAT (GRB 221009A). Definitely a supernova associated, and they see a break in the afterglow around 50 days, maybe when the collimation angle of the jet became causally connected.🧪🔭 arxiv.org/abs/2412.02663

Flux as a function of time for the afterglow of the BOAT (Brightest Of All Time, GRB 221009A). The left side shows that single power-law models don't fit the data, meaning there must be a break in the afterglow around ~50 days. This break might be the time when the edges of the jet come into causal contact with one another (this is nontrivial because the jet's moving close to the speed of light). This potentially allows us to constrain the opening angle of the BOAT and hence its true energy (accounting for the fact that the energy is beamed towards us within a narrow angle).

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Paul Duffell @paulduffell.bsky.social · 01/12/2024

Episode 12 of The Astrophysics Podcast just dropped! I interviewed Dr. Brenna Mockler from Carnegie Observatories. She is a theorist who works on what we call "Tidal Disruption Events" -- essentially, what happens when a black hole eats up a star! Check it out! 🧪🔭 rss.com/podcasts/ast...

Dr. Brenna Mockler of Carnegie Observatories. She is an astrophysicist who specializes in theoretical calculations of tidal disruption events (TDEs); dramatic accretion events where a black hole suddenly rips apart a star or gas cloud and swallows it. Hear more about it on The Astrophysics Podcast: https://rss.com/podcasts/astrophysics/1734361/

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Paul Duffell @paulduffell.bsky.social · 21/11/2024

My student Allen Murray just submitted his first paper! Binary stars gain eccentricity when accreting gas from a disk. Allen showed that this is true for a set of observed accreting binary systems, and the eccentricity of their orbits agree with theoretical predictions.🧪🔭 arxiv.org/abs/2411.13489

A collection of binary systems that are actively accreting gas from a disk (Murray & Duffell 2024, in review). The x-axis is the binary mass ratio M2/M1 and the y-axis is the eccentricity of their orbit. Purple crosses are binaries that are aligned with their gas disk. They seem to lie close to the predicted "equilibrium eccentricity" curve (red dashed line) which is based on hydrodynamical simulations.

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Paul Duffell @paulduffell.bsky.social · 20/11/2024

DESI weighs in on the Hubble tension. They measure the clustering of matter on large scales, which depends on dark matter/dark energy. The data suggest that dark energy was not a constant, but emerged in the recent past. Still relies on Type Ia supernova calibration.🧪🔭 arxiv.org/abs/2411.12022

Measurement of the equation of state "w" describing dark energy. w=-1 implies a cosmological constant. They fit to a model assuming w varies with time; w = w_0 + w_a(1-a) where "a" is the scale factor (how big the universe is relative to today). The energy density associated with dark energy should scale as 1/a^(3(1+w)) as the universe expands (for example, Dark matter has w=0 and its density just depletes as 1/a^3 as the universe expands). w=-1 would imply dark energy is a constant with time. This model fit suggests dark energy was increasing in the past, and decreasing today, so that it might have emerged at a redshift of a few. Maybe this would be observable with very distant Type Ias?

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Paul Duffell @paulduffell.bsky.social · 18/11/2024

I recommend Danny's Cas A image from JWST, if you haven't made it into a puzzle already.

Supernova Remnant Casseiopeia A taken by JWST.

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Paul Duffell @paulduffell.bsky.social · 15/11/2024

New paper from Hernandez-Garcia et al. They observed what might be a BINARY tidal disruption event. We see TDEs often (black hole eating a star or cloud) but this one had regular flaring consistent with accretion onto an eccentric binary rather than a single black hole.🧪🔭 arxiv.org/abs/2411.08949

Brightness of the accretion over time. The amplitude seems to convincingly match the theoretical prediction of t^-5/3, but there is also this strong variability consistent with predictions from hydrodynamic calculations of binary accretion for a modestly eccentric binary (they actually didn't cite those predictions but I happen to know that it does look pretty consistent with them).

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Paul Duffell @paulduffell.bsky.social · 13/11/2024

A potentially controversial paper (Christian Vogl et al): Constraining the Hubble rate using type II supernovae. (Type Ia's are much more regular but they might have biases). They claim large H_0 (hubble tension persists); I'm surprised by how small their error bars are.🔭🧪 arxiv.org/pdf/2411.04968

The "Hubble Tension" depicted here; The Hubble constant is constrained to be close to 68 according to CMB measurements at large redshift. Local measurements give a Hubble constant closer to 72ish. Why does this matter? If these error bars are correct (big if), then our cosmological model for the universe is wrong and needs new physics.

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Paul Duffell @paulduffell.bsky.social · 09/11/2024

🧪🔭 Impressive paper by Vartanyan et al. Type IIp supernovae are extremely common, but they are very complex to model. This group did the whole thing -- 3D simulation of the explosion (~seconds) all the way up to the photons escaping (~100 days). #astronomy #astrophysics arxiv.org/abs/2411.03434

3D simulation of the supernova, powered by neutrinos within a few seconds of collapse. This image is a bit later in the simulation, after the shockwave breaks out of the collapsing star.

Simulated observations of a supernova brightness over time (light curve). Colors indicate different observing bands. This was computed by following photons as they escape from the expanding supernova. The extremely high opacities involved required development of new technology for simulating the photons, called "DDMC" (Diffusion Dominated Monte Carlo).

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Paul Duffell @paulduffell.bsky.social · 08/11/2024

If anybody's looking for some non-political media to consume, may I humbly suggest the astrophysics podcast? That guy's got a really dreamy voice... 🧪🔭 #astronomy #physics #astrophysics rss.com/podcasts/ast...

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Paul Duffell @paulduffell.bsky.social · 04/11/2024

🧪🔭 Liked this paper by Magda Siwek et al; Accretion onto supermassive black hole binaries can live an imprint on pulsar timing data. Plot shows how different accretion histories give different NANOGrav data. In the next decade we may learn how SMBHBs grow and merge. arxiv.org/abs/2403.08871

Different accretion histories can yield different predictions for the NANOGrav spectrum, shown here. At the moment we just have the blue point in this plot, but over the next decade we may get a spectrum we can compare to these predictions.

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Paul Duffell @paulduffell.bsky.social · 03/11/2024

🧪🔭 This paper by Cordwell & Rafikov was pretty cool! Calculations of early stages of gap opening by planets as they form in a disk: arxiv.org/abs/2407.01728 My favorite plot from the paper shows the planet opens a "double gap" which I think looks very similar to structures ALMA sees in HL Tau.

From Cordwell & Rafikov (2024): Calculation of a planet interacting with a disk in its early stages. The double red ring near the planet is a low density region that signifies the gap opening.

Classic ALMA image of the HL Tau disk. There is a notable "double gap" in the disk, in addition to various other ring-like structures.

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Paul Duffell @paulduffell.bsky.social · 01/11/2024

Thank you @danmil.bsky.social for talking with me about supernovae and time domain astronomy! 🧪🔭. If anyone is interested, you can find our whole conversation on "The Astrophysics Podcast" rss.com/podcasts/ast... #astronomy #astrophysics

Dr. Dan Milisavljevic (left) and Dr. Paul Duffell (right) getting set up to talk about time-domain astronomy on "The Astrophysics Podcast".

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Paul Duffell @paulduffell.bsky.social · 27/10/2024

Fun physics stuff: A photo of an atomic test published in a 1945 issue of Time magazine. The scale and timestamp made it possible to compute the explosion energy, which was classified at the time. We do the same trick with supernovae that exploded hundreds of years ago as they continue expanding.

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