iiinova — where your digital self keeps evolving

John Forbes @redshiftless.bsky.social · 08/07/2026

They're also very slow, so there's very little chance of confusing one for a bona fide interstellar object. We might confuse them with ordinary comets though.

The speed distributions of quasi-interstellar objects as they re-encounter the Solar System (Figure 6 of the paper). The purple lines are the most realistic, and they peak at velocities around 0.1 km/s (barely unbound from the Solar System).

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John Forbes @redshiftless.bsky.social · 08/07/2026

They're rare though! We predict that <1 / year enter within the orbit of Jupiter, so we're not particularly likely to find one even with LSST. (Though it would be very interesting if we did!)

Figure 5 of the paper. Here's the corresponding caption: "Predicted quasi-ISO rates. The y-axis shows our predictions for the present-day rate of quasi-ISOs entering the inner Solar system (pericenters < 5 au), compared against the number of Oort cloud objects ejected over the past 500 Myr. Each set of colored points corresponds to a different heating+ejection model, while the different symbols correspond to Oort
cloud erosion models. N23 refers to the simulation results from D. Nesvorn´y et al. (2023). In the case of “ejection timing only” we use the times that particles from the simulation cross the 500k au sphere in the simulation to interpolate the results of our burst simulations. In “last 100 Myr + kin” we initialize each particle with its position and velocity at the given time, integrate it, and evaluate the rate based on the resulting particle distribution. The filled vs hollow points correspond to different
assumptions about the normalization of the Oort cloud, respectively one based on the ISO density, and one based on the rate of long-period comets. Changes in normalization move points parallel to the solid line (increasing the number of objects ejected directly increases the rate of quasi-ISOs). The rate required to expect one detection in a 10-year survey is of order 10^−1 /yr, neglecting observational efficiencies."

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John Forbes @redshiftless.bsky.social · 08/07/2026

We had a look at these objects, which we call "quasi-interstellar objects" or quasi-ISOs (after quasi-moons). Some of the Solar System's interstellar objects do in fact come back!

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John Forbes @redshiftless.bsky.social · 17/03/2026

Due to a poor choice of headphone placement, my hairstyle for much of today may best be described as the "Londo Mollari"

Londo Mollari, the Centauri ambassador to Babylon 5, played by Peter Jurasik. In the photo a man in a fancy uniform raises a glass, likely giving a toast, with plants and a irregular set of blue neon lights in the background. His hair is arranged such that the front half of his head is bald, then about 10 cm of hair fans outward perpendicular from his head, in a manner somewhat reminiscent of a trifoil hat worn with one point at the back of the head.

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John Forbes @redshiftless.bsky.social · 12/03/2026

Number of photos or videos taken by my phone per day over the past 6 years.

A graph! x-axis is years 2018-2026.3; y-axis is log-scaled "Captures per day" referring to photos/videos taken by my phone. A very noisy blue dataset labelled "daily" is shown, along with a 30-day mean, shown in orange. 3 events associated with step changes in the capture rate are shown - "Adopted Cats" late 2020, "Kid born" mid-2022, and "Kid discovers he can take photos on phone" this past week.

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John Forbes @redshiftless.bsky.social · 27/01/2026

Anyone else have this experience?

The meme of Angela Kinsey appearing quietly behind Dwight Shrute from the Office (US).

In the first panel, Dwight is enjoying something, and is captioned "READING THE DEMON HAUNTED WORLD". Angela is labelled "MENTION OF THE 1974 NOBEL PRIZE WITH NO ACKNOWLEDGEMENT OF BELL". In the second panel, Dwight sees Angela and is surprised, captioned "F**k"

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John Forbes @redshiftless.bsky.social · 19/01/2026

The accretion history can matter if it takes long enough (>1 Gyr, i.e. the thermal timescale) that the internal state of the star changes during accretion. Otherwise the time that the core remains frozen is set by how close the object ends up to the Lnuc=Lsurf line.

Figure 3 from the paper. It's a version of the cartoon diagram shown elsewhere in the thread, but made with numerical stellar models. Each model is coloured by its fate, with longer frozen core timescales corresponding to yellower colours, and shorter corresponding to bright pink. The closer the objects end up in this space to a particular locus of points (not shown) where Lnuc=Lsurf, the longer the frozen core lasts.

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John Forbes @redshiftless.bsky.social · 19/01/2026

They may spend ~a billion years as their core heats up and "unfreezes", while they remain dim on the surface. And naturally, as beige+red dwarfs we call these pink dwarfs.

Figure 1 from the paper, showing how the erstwhile brown dwarfs evolve. The coloured arrows represent the paths the different stellar and substellar objects take as they evolve on a plot of mass against ψ, the thermal energy per particle in units of the Fermi energy in the star’s core. Lower values of ψ indicate colder and more degenerate cores. The separately coloured regions and their corresponding outline arrows indicate what direction an object would
move. In the pink region within the parabola, objects have a nuclear luminosity, Lnuc, greater than their surface luminosity, Lsurf and they evolve to the right as their cores heat up. In the blue region, Lsurf > Lnuc, so objects evolve to the left as they radiate more energy than
they generate. The black parabola is where Lnuc = Lsurf . The solid right-hand side of the parabola represents the main sequence; it is stable to perturbations in ψ. The dashed left-hand side is unstable. The lowest mass on the parabola is the hydrogen burning limit, MHBL.
The arrows for the red dwarf and brown dwarf are horizontal as these objects do not change their mass throughout their lives without an outside influence. Maroon, pink, and beige dwarfs begin as brown dwarfs and evolve leftwards until an episode of mass accretion results in them splitting off from the brown dwarf arrow vertically, at least in the case of fast accretion. When accretion has stopped, they then evolve horizontally to the left or right. Maroon dwarfs, like red dwarfs, evolve left and settle on the main sequence. Beige dwarfs end up above the hydrogen burning limit, but outside of the parabola, and so evolve left like a brown dwarf, never reaching the main sequence. A pink dwarf is located inside the parabola when mass has stopped accreting and then evolves to the right to settle on the main sequence. The ‘frozen cores/plateaus’ region in the parabola is the area in which a subset of our pink dwarf models have a frozen core or luminosity plateau

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John Forbes @redshiftless.bsky.social · 19/01/2026

If you add mass early, you basically take a brown dwarf and put it in a region of parameter space that is red dwarf-like. So naturally we call these maroon(~ red+brown) dwarfs. These are basically indistinguishable from ordinary low-mass stars as far as we can tell.

Meme of a guy in a red uniform shirt sweating and deciding between several buttons. The guy has a brown circle obscuring his face and is captioned "Brown Dwarf Gaining Mass". There are three buttons labeled "Pink", "Beige", and "Maroon"

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John Forbes @redshiftless.bsky.social · 19/01/2026

But what if you're impatient and add the mass earlier? In a new paper led by University of Canterbury student Jaime Luisi, we run some simulations to find out! arxiv.org/abs/2601.10908

A text meme.
1. Be a brown dwarf
2. Add mass
3. ??????
4. (strikethrough: Profit) Become a star!

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John Forbes @redshiftless.bsky.social · 19/01/2026

Brown dwarfs are "failed stars" - they never got enough mass to burn hydrogen in their cores, or at least not enough to supply the energy they radiate away at their surface. But what happens if you add enough mass to a brown dwarf to push it over that threshold in mass? Does it become a star? 🔭 🧪 🧵

An artist's impression of a brown dwarf, from NASA/JPL-Caltech.

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John Forbes @redshiftless.bsky.social · 23/12/2025

A little 3I/ATLAS update building on @marshall-eubanks.bsky.social's nice RNAAS from last week. Given its non-grav acceleration and the rate at which it's losing mass, you can work out its size. The answer: a diameter around 1 km, very typical for comets. arxiv.org/abs/2512.18341 🔭 🧪

The figure from the linked paper (three panels, each a plot of some quantity vs time in days). Here's an expanded verision of the corresponding caption:

Non-gravitational accelerations (NGAs) and their corresponding mass loss rates. Top panel: Non-gravitational acceleration from the JPL Small-Body Database or the final line of Table 1 in T. M. Eubanks et al. (2025). Reported errorbars are shown, and extrapolations into the future or prior to October are shown as dashed lines. The figure shows 5 lines, converging on an acceleration of order 10^-8 au per day^2 for 3I/ATLAS.

Middle Panel: NGAs from the top panel are translated into mass loss rates assuming 1 km diameters, with ζ = 0.5 and ρ = 0.5 g cm^−3. Additionally the JPL Dec 17 solution for other diameters (0.5 km and 2 km) are shown as dotted lines. Data points are from JWST (M. A. Cordiner et al. 2025), SPHEREx (C. M. Lisse et al. 2025), ALMA (N. X. Roth et al. 2025), TRAPPIST-North (E. Jehin et al. 2025), and Swift (Z. Xing et al. 2025). The plot shows a variety of data points scattered around the lines, mostly of order 10^4-10^5 g/s, with the 1 km curves passing close to the data points that measure CO2, and mostly above the other datapoints, depending on the model.

Bottom Panel: CO2 production rates measured by JWST are treated as upper and lower limits, and observations where CO2 is inaccessible are shown as lower limits. Given these constraints, the range of Mdot values and hence diameters for two different reported NGA solutions is shown. The JPL solution is unable to simultaneously fit the upper limit from JWST and the lower limit from TRAPPIST-North. The plot shows the same thing as the middle panel, but with some additional interpretation, namely that some points should be considered upper limits and some lower limits. A red shaded region labelled Eubanks+ Accel shows a range of diameters from 820 to 1050 meters. A gray region labeled JPL Accel shows a diameter of 1100 m.

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John Forbes @redshiftless.bsky.social · 19/12/2025

Bit of a queue to see the corpse flower at the Botanical Garden in Ōtautahi

A long queue of people waiting in a queue on a footpath next to a grassy river bank with various interesting plants, at the Ōtautahi botanical garden. A sign in the foreground directs people in various directions, but the labels are cut off.

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John Forbes @redshiftless.bsky.social · 17/11/2025

Ooh gross just discovered a bunch of youtube channels blaring about 3I/ATLAS using an AI-generated Brian Cox. The channel description says the videos are all AI, but the videos are clearly designed to make people think BC is actually saying these things..

A screenshot of text, headed "Description" followed by a paragraph "XBIGSpace is an independent, fan-made channel with no official affiliation with NASA, SpaceX, or any related organizations. Our content is inspired by publicly available scientific discussions, documentaries, and space research - reimagined purely for educational and inspirational purposes." New paragraph: "All narration is delivered using AI-synthesized voice, and does not represent any real individual."

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John Forbes @redshiftless.bsky.social · 16/09/2025

More hostility than I was expecting from a planter!

A printed sign on a wooden planter with grass in the foreground and long thin green leaves in the planter. The sign says “RCG compost project; in progress; please leave”

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John Forbes @redshiftless.bsky.social · 27/08/2025

Incredible stuff happening on wikipedia

A screenshot of the top of a wikipedia page for "Why We're Polarized", the book by Ezra Klein. In the screenshot, the start of the second paragraph of the article is highlighted, "Opinion on the book is polarized"

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John Forbes @redshiftless.bsky.social · 04/08/2025

PSA to scientists: Google calculator appears to no longer do basic unit conversion correctly! n.b. the correct answer here is 223.4 Myr, a factor of about 60 larger than Google's answer. 🔭 🧪

A screenshot of a google search result for "2*pi*(8 kpc)/(220 km/s)" which is roughly the time it takes the Sun to go around the Galaxy. In the screenshot, google's calculator has popped up and parsed the expression correctly, but then returns the result 3 899 243.9 years, and answer which is off by 2 orders of magnitude.

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John Forbes @redshiftless.bsky.social · 05/06/2025

It's my favorite time of the year: new black-footed ferret kits born at the National Zoo and the return of ferretcam! nationalzoo.si.edu/webcams/blac...

A screenshot from a livestream filmed with an infrared camera in grayscale, showing a sleeping adult ferret in a container on a bed of paper squares(?) with an indeterminate number of ferret kits (turns out there are 8!)

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John Forbes @redshiftless.bsky.social · 01/06/2025

Looks like a promising night for aurora chasing

A screenshot from the Aurora app showing KP forecasts as a function of time:
Now: 3.0
1800: 4.0
2100: 3.67
Midnight: 7.67
0300: 7.67
0600: 7.33

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John Forbes @redshiftless.bsky.social · 15/04/2025

New paper! High-order epicyclic description of orbits in spherically-symmetric potentials (plus vertical oscillations in a disk). My love of epicycles is so notorious that the postgraduates made this meme

An image of Claudius Ptolemy, overlaid with a bust of Ptolemy in the outline of a heart. The bust has a thought bubble with the word epicycle. Several pink hearts as well as a diagram of the motions of planets in a geocentric epicycle+defferent system are also shown. Overlaid in several bold fonts are the words “RIP claudius ptolemy you wouldve loved john forbes :(“

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John Forbes @redshiftless.bsky.social · 19/03/2025

I have GOT to stop making small talk about the "elevators"

The Inglourious Basterds meme in which a man holds up 3 fingers in such a way that he is outed to the Germans as a non-German.

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John Forbes @redshiftless.bsky.social · 05/01/2025

Chuffed by the YIMBY-adjacent messaging in my 2-yr-old’s current favorite book

A photo of a page from a 1993 children’s book. An illustration shows a dump truck approaching a building site with a load of dirt. A sign says “Happy Homes Apartments - Coming Soon”. The text reads “The Mighty Dump Truck is doing an important job, too. The dirt it carries will help make the foundation for a new apartment building where families will live.”

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John Forbes @redshiftless.bsky.social · 04/12/2024

I've been trying out julia recently! It's fun, but this stacktrace is next-level. Just page after page of

$A screenshot of a terminal window (361 characters wide by 79 lines long) filled with gray text with no formatting. A small sample: "typeof(potential!), UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing, Nothing, Nothing}, Vector{Vector{Float64}}, Vector{Float64}, Vector{Vector{Vector{Float64}}}, Vector{Int64}, OrdinaryDiffEqCore.DefaultCache{OrdinaryDiffEqTsit5.Tsit5Cache{Vector{Float64}, Vector{Float64}, Vector{Float64},"$

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John Forbes @redshiftless.bsky.social · 26/11/2024

Caught a little drama on my walk home yesterday

Paradise ducklings on a grassy stream bank. A mother duck is leaning forward, head pointed straight ahead, at a small bird that has landed nearby. A red circle and arrow annotates where the mother duck is about to charge.

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John Forbes @redshiftless.bsky.social · 25/11/2024

Depends what you need! We have positions and velocities of particles in streams that we could provide in whatever convenient coordinates or cadence you'd like. Might be cool to see a stream spreading around a planetarium dome

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John Forbes @redshiftless.bsky.social · 25/11/2024

The Galaxy is full of streams of interstellar objects! Explainer thread below from @astrokiwi.bsky.social 🔭 🧪

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John Forbes @redshiftless.bsky.social · 14/11/2024

A hearty welcome to the latest round of new folks! Have fun exploring your new less-awful microblogging platform. Here’s a picture of my cat Rocket taking his first jaunt outside in a while! (I swear I post about astronomy sometimes!)

A large white and gray tabby cat in a harness on a leash walking curiously towards a strip of vegetation between a large concrete surface and a wooden fence.

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John Forbes @redshiftless.bsky.social · 03/11/2024

Last minute, but for any other overseas voters who have the option to Fax in your ballot: rather than having small crowds gather to be amused at your predicament as you hunt in vain for a fax machine in a modern country, you can use a phone app! I had a good experience with "Fax.Plus".

A screenshot of a website with a red white and blue "I Voted" sticker, labelled "County of Santa Clara". Also visible is a line in a table with the heading "Ballot Counted:" and a value of "Yes"

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John Forbes @redshiftless.bsky.social · 18/10/2024

I don’t really have the posting gene but felt compelled to welcome the latest wave of twitter refugees. Here’s my cat living the good life.

A cat asleep on a cat tree with her front legs out of view and her back legs sticking off the platform. Red flowers and greenery are visible outside the window behind her.

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John Forbes @redshiftless.bsky.social · 20/09/2024

Spotted the local campus celebrities!

Eight fluffy black and white ducklings on a small grassy hill at sunset. The mother duck, brown with a white head, follows them.

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John Forbes @redshiftless.bsky.social · 18/08/2024

Spotted at a local shop: Pluto demoted again apparently

A photo of a poster, featuring an object labelled Pluto, with a parenthetical “(not part of the solar system)”

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John Forbes @redshiftless.bsky.social · 20/02/2024

Can a kiwi settle an argument between my partner and me: What does the phrase “NOT TO BE TAKEN” mean in this context?

A photo of a plastic bottle containing a green liquid with a label including the words “clean, laundry liquid, apple splash.” The bottom of the bottle has the phrase in all caps “not to be taken”

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John Forbes @redshiftless.bsky.social · 19/09/2023

Yes, was using plt.close(fig), not in a notebook. Might not be noticeable unless you're creating a large batch of large plots. The issue seems to be with the default (interactive) backend. So, PSA for people following: use a static/non-interactive backend :-)

A short snippet of python code creating many large scatter plots of random data and saving to a pdf file with matplotlib. The line matplotlib.use('pdf') is commented - uncommenting in avoids the memory leak by using the pdf backend instead of a default interactive backend.

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John Forbes @redshiftless.bsky.social · 12/09/2023

New paper out today, led by the inimitable Nia Imara! We find that adopting a cylindrical geometry for famous nearby molecular clouds yields new and sometimes counterintuitive scaling relations, e.g. more massive clouds tend to have lower central densities! 🔭🧪 arxiv.org/abs/2309.04532

A graphical summary of a new paper by Imara & Forbes. A white cylinder is overlayed on a map of the Orion B molecular cloud taken by Herschel. The big ideas in the paper are summarized as: 1) Many stellar nurseries (molecular clouds) are shaped like cylinders. (Pretty close!) 2) We introduce a model based on this assumption and apply it to real stellar nurseries in the Milky Way. 3) We find that the shape of stellar nurseries affects how efficiently they produce stars.

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John Forbes @redshiftless.bsky.social · 06/09/2023

Spotted some anticrepuscular rays at sunset this evening! (The sun is behind the photographer)

A photograph of highly textured low-level clouds tinted yellow at sunset, above a large field of grass. Anticrepuscular rays are visible in the center above a building in the foreground.

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John Forbes @redshiftless.bsky.social · 28/08/2023

"nice sleeping baby you have there... would be a shame if he woke up somehow... especially my silence can be bought with a simple serving of biscuits*..." - my cat, the terrorist * dry food is called biscuits here and it's adorable

A tabby brown and white cat named Rocket perched next to a cardboard box of nappies, making an offer we can't refuse.

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