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Paul Duffell
@paulduffell.bsky.social
490 followers 59 following 300 posts
I'm Paul and I do Hydro.
Professor of Physics and Astronomy at Purdue University.
Located in beautiful Lafayette, Indiana.
Host of the Astrophysics Podcast.

Group Website: http://physics.purdue.edu/duffell/
Podcast Website: rss.com/podcasts/astrophysics/
Posts Replies Media Videos
paulduffell.bsky.social
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
October 11, 2025 at 4:07 PM
paulduffell.bsky.social
🔭🧪
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...
Logo for the astrophysics podcast, depicting a computer simulation of a supernova (calculation originally performed by Dr. Soham Mandal). Photo of Dr. Merel van 't Hoff, professor of Physics and Astronomy at Purdue University.
October 1, 2025 at 2:46 PM
paulduffell.bsky.social
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. 🧪🔭
Logo for the astrophysics podcast. https://rss.com/podcasts/astrophysics/
June 2, 2025 at 6:26 PM
paulduffell.bsky.social
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. Logo for the astrophysics podcast, with an explodey thing on the lower half. It's supposed to be a supernova remnant.
June 1, 2025 at 2:00 PM
paulduffell.bsky.social
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.
May 14, 2025 at 4:08 PM
paulduffell.bsky.social
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. Logo for the astrophysics podcast, which depicts a computer simulation of a supernova remnant.
May 1, 2025 at 12:00 PM
paulduffell.bsky.social
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
April 1, 2025 at 8:08 PM
paulduffell.bsky.social
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 Logo for the astrophysics podcast. The image depicts a computational gas dynamics calculation of a supernova remnant, hundreds of years after the star exploded.
April 1, 2025 at 11:51 AM
paulduffell.bsky.social
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.
March 12, 2025 at 6:08 PM
paulduffell.bsky.social
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. Logo for the astrophysics podcast, which features a high-resolution 3D simulation of a supernova remnant.
March 1, 2025 at 1:51 PM
paulduffell.bsky.social
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.
February 25, 2025 at 2:13 PM
paulduffell.bsky.social
Poor Google AI.
A google search, auto-completed by google to ask a series of demeaning questions about google AI. Paradoxically, the list ends with an optimistic "why is google ai so good?" prompting the question of who in the world would ask that question...
February 2, 2025 at 4:40 PM
paulduffell.bsky.social
🧪🔭
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. Logo for the Astrophysics Podcast, including an image of a computer model of a supernova remnant. Model generated by Dr. Soham Mandal using the SPROUT code.
February 1, 2025 at 3:18 PM
paulduffell.bsky.social
Happy Hanukkah! Please ignore the reflection of our Christmas tree in the window.
Menorah on our windowsill.
January 2, 2025 at 2:18 AM
paulduffell.bsky.social
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. Logo of the astrophysics podcast, featuring an image based on a computer simulation of a supernova remnant. Episodes here: https://rss.com/podcasts/astrophysics/
January 1, 2025 at 1:46 PM
paulduffell.bsky.social
@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!
December 17, 2024 at 4:48 PM
paulduffell.bsky.social
Wicked, of course, featured the true origin story of the jitterbug scene! #deckofcards did it first...
December 14, 2024 at 2:37 PM
paulduffell.bsky.social
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).
December 4, 2024 at 5:31 PM
paulduffell.bsky.social
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/ Logo for The Astrophysics Podcast. In case you care, it's a computer simulation of a supernova remnant. https://rss.com/podcasts/astrophysics/
December 1, 2024 at 1:57 PM
paulduffell.bsky.social
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.
November 21, 2024 at 2:39 PM
paulduffell.bsky.social
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?
November 20, 2024 at 2:04 PM
paulduffell.bsky.social
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.
November 18, 2024 at 3:03 AM
paulduffell.bsky.social
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).
November 15, 2024 at 5:00 PM
paulduffell.bsky.social
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.
November 13, 2024 at 2:09 AM
paulduffell.bsky.social
🧪🔭
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).
November 9, 2024 at 12:36 PM