iiinova — where your digital self keeps evolving

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Atanas K. Stefanov @astronasko.com · 08/09/2026

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Ethan Chappel @chappelastro.com · 29/09/2026

Saturn with Mimas and Dione on August 3rd, 2026. #Astronomy #Astrophotography

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Shashank Dholakia @astroshashank.bsky.social · 26/09/2026

As a bonus, here's a video showing the raw video capture with the final stacked and wavelet sharpened image at the end:

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Shashank Dholakia @astroshashank.bsky.social · 26/09/2026

Of course, there's no beating the information limit from diffraction; I'm helped out here by the fact that the Encke gap is an extended structure and not a point source.

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Shashank Dholakia @astroshashank.bsky.social · 26/09/2026

With seeing this good and very high SNR (best 15% of 20,000 frames stacked), I am just barely beginning to see the Encke gap in Saturn's rings, only 50mas across. That's well below the diffraction limit of my setup and around the same angular diameter as Betelgeuse!!

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Shashank Dholakia @astroshashank.bsky.social · 26/09/2026

Saturn is nearing opposition and I had a chance to photograph it last night finally in excellent seeing conditions! 🧪🔭 #astrophotography

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SETI Institute @setiinstitute.bsky.social · 24/09/2026

#PPOD: Roman has opened its eyes! These fuzzy rings are the first photons of starlight captured by the Nancy Grace Roman Space Telescope’s 300-megapixel Wide Field Instrument. And yes, they’re supposed to look like that—for now. 🧪 🔭

This test image captures the very first photons of starlight to reach the Wide Field Instrument on NASA’s Nancy Grace Roman Space Telescope. Roman’s primary science instrument has opened its eyes to the universe for the first time, revealing a sea of out-of-focus stars, each spread out over many thousands of pixels. The image, which zooms into one detector and zooms again to a single star in the insets, offers a baseline the Roman team will work from to align the telescope’s optics and tune the focus.

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Benjamin Pope @benjaminpope.bsky.social · 23/09/2026

Australian/NZ students - the call is open for applications to do a fully-funded MRes and/or PhD at Macquarie next year! We have an awesome department, campus, and cool projects. Submit an Expression of Interest here for projects across astro/physics/maths/stats: mq-maps-domestic-eoi.netlify.app

mq-maps-domestic-eoi.netlify.app

Domestic research EOI · Macquarie University

Express your interest in a Master of Research or PhD at Macquarie University's School of Mathematical and Physical Sciences. Domestic scholarship round, Session 1 2027.

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Shashank Dholakia @astroshashank.bsky.social · 11/09/2026

This is an awesome paper and I'm so excited about the AMI mode!!

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Kevin Hardegree-Ullman @kevinkhu.bsky.social · 10/09/2026

In #exoplanet transit land, we often seek planets further out in their orbit. In direct imaging land, it's all about pushing closer in. This new study from @caltechipac.bsky.social VGSRF @jayke.io finds a new close-in candidate in the classic HR 8799 system!

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Jayke Samson Nguyen @jayke.io · 10/09/2026

Hot off the press! Via the magic of differentiable forward modeling and of non-redundant masking on JWST we may have found a new exoplanet! One of the most challenging papers I've written, but I'm glad its finally out! Submitted to AJ, pending peer review. arxiv.org/abs/2609.10507

arxiv.org

A Candidate Innermost Fifth Planet In the HR 8799 System Revealed By JWST NIRISS Aperture Masking Interferometry

We detect a candidate fifth planet in the HR 8799 system, directly imaged with the JWST/NIRISS Aperture Masking Interferometer (AMI). The detected source lies just above a $3σ$ contrast curve at a con...

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Shashank Dholakia @astroshashank.bsky.social · 09/09/2026

It's a real challenge to hand-track across this camera's tiny field of view. My approach has been to align the sensor in the direction of the drift, try to place Saturn towards the edge, wait for about ~30s for it to drift and repeat. I may try later with a smaller aperture with tracking.

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Shashank Dholakia @astroshashank.bsky.social · 09/09/2026

Saturn season is back on (and so are its rings)! Here is my first attempt this year from a few nights ago. The Cassini division in the rings is about the width of US or Australia and under an arcsec wide, requiring pretty good focus and collimation to resolve. 🧪🔭 #astrophotography

A picture of the planet Saturn showing the rings at a moderate tilt. The Cassini division is visible as a gap in the rings most easily visible at ansae (towards the edges of the rings from our point of view. A few cloud bands are visible on the planet itself. There is a dark background and a caption on the lower left that says:

Saturn
16" Dob f4 untracked
QHYIII585C
Sept 6 2026
Shashank Dholakia

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Judy Schmidt @geckzilla.bsky.social · 23/08/2026

Fun time. Here's H-alpha from Hubble, and its infrared analogue Paschen-alpha from JWST. If you look closely in the center near the star, you can just make out the front and back of the nebula moving away from each other. It's not flat!

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James Davenport @jradavenport.com · 10/07/2026

A good reminder than when it comes to “space”, astronomers and the actual content of space (eg stars, galaxies, etc) are unfortunately the last consideration

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Benjamin Pope @benjaminpope.bsky.social · 25/06/2026

Advertising international Masters and PhD scholarships in astronomy at Macquarie, one of Australia's leading institutes! Submit an Expression of Interest by 12 July to start your studies in January 2027. We have projects on offer on stars, planets, and galaxies; and instrumentation and data.

aas.org

PhD and Masters of Research Positions in Astronomy and Astrophysics | American Astronomical Society

Macquarie University is seeking outstanding candidates for PhD and Masters of Research scholarships commencing January 2027.

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Remco de Kok @planetremco.bsky.social · 17/06/2026

Another subtlety to take into account when modelling exoplanets. They rotate and have tidal interactions, which modifies the vertical forces on the atmosphere besides gravity. Arnav+Hazra arxiv.org/abs/2606.18100 🧪🔭 #exoplanets

Fancy graphic of a planet and an illustration of what rotation and tides do to it (elongated equator, different force on the atmosphere, opposite to gravity).

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Alex Santerne @alexsanterne.bsky.social · 23/06/2026

⚠️ Today, we are posting on #arXiv not only 1, nor 2, but 3 papers on the fascinating system #HIP41378. This system hosts 6 and maybe 7 planets 🪐. These papers are the results of a long-lasting investigation on this system initially discovered by the K2's mission, reported in 2016. (🧵 1/6 👇)

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Benjamin Pope @benjaminpope.bsky.social · 19/06/2026

Looking forward to having everyone here for Cool Stars in July 2028 - when a total solar eclipse will pass directly over the city centre!

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Shashank Dholakia @astroshashank.bsky.social · 12/06/2026

So I think it strongly depends on the nature of the data! I've only tested it on WASP-39b (WLC attached here, with the corrected-uncorrected residuals below), but I'm hoping for ppl to test it on other NIRISS data and report back what they find

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Shashank Dholakia @astroshashank.bsky.social · 12/06/2026

In practice, the situation is probably much less dire as the effect averages out over pixels across the trace with different count levels. But the way it averages is nontrivial, with temporal flux trends or other systematics also contributing (basically anything that is read by the ADC).

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Shashank Dholakia @astroshashank.bsky.social · 12/06/2026

Hmm, good q! As we show, the periodic INL can change the transit depth across an entire order, so it can affect transit parameters in the WLC. Bc the effect is flux-dependent, if the transit reduces counts in the SOSS trace by ~some multiple of 512, the INL can change the transit depth up to 250ppm.

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Shashank Dholakia @astroshashank.bsky.social · 12/06/2026

LOL yes in that case I'll take 10 billion for this paper, thanks NASA

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Shashank Dholakia @astroshashank.bsky.social · 12/06/2026

Forgot to mention in this thread! I have posted a barebones script to correct uncal NIRISS data using the sinusoid we infer in our paper. Would be great to try it on any NIRISS data you have lying around and see what the effects are on your data! #astro #exoplanets 🔭 github.com/shashankdhol...

github.com

GitHub - shashankdholakia/niriss-cal-inl: Calibrating the JWST NIRISS analog-to-digital converter periodic integral nonlinearity

Calibrating the JWST NIRISS analog-to-digital converter periodic integral nonlinearity - shashankdholakia/niriss-cal-inl

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

Shout-out to all my collaborators on this paper who made this possible. Especially @benjaminpope.bsky.social for encouraging me to follow these "odd" data quirks

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

Thanks Conaire! I will say this systematic averages in very nontrivial ways depending on the kind of data, so it's hard to predict the general impact on precision. But it would seem it's not negligible either!

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

If you aren't looking for it, it might just look like noise. However, it's systematic, not stochastic in nature and easily correctable. Bc it's flux-dependent, it can change transit depths across wavelengths, so it matters for high precision work like measuring exoplanet atmospheres! (11/N)

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

And finally--the transmission spectra before and after the correction (with the difference on the bottom). The most obvious effect of the sinusoidal systematic is to offset Orders 1 and 2 in NIRISS, which we estimate for WASP-39b at 55ppm. It also seemingly randomly disperses points by ~30ppm. (9/N)

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

After having learned a model for this systematic, we use the well-studied NIRISS data on WASP-39b to test the impact exoplanet transmission spectroscopy. We injected our model to correct the raw data, then ran both the corrected and uncorrected sets through the exact same pipeline. (8/N)

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

Our model for this effect, which we're calling a periodic integral nonlinearity (INL) is flux-dependent, i.e the higher the counts in a given pixel, the higher the amplitude of the sinusoid that's needed to correct it. (7/N)

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

Because this effect is imprinted by the ADC, it must be learned and corrected before any other calibration steps take place. We learn a calibration for the effect using raw data from NIRISS SOSS by subtracting linear ramp fits from the data and fitting the residual wiggles with a sinusoid. (6/N)

3 panel graph showing blue points with the sinusoidal wiggle and orange points with the correction applied. The top panel shows the full range from 10k to 20k in raw counts. The bottom left panel shows the same signal folded on the 1024 period. The bottom right panel shows a Lomb-Scargle periodogram with a spike at 1024 and some harmonics.

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

For the electronics nerds out there, that power-of-2 period might be ringing a familiar bell. We think this artifact is originates from the analog-to-digital converter on NIRISS, and is imprinted on the data when the charge in each pixel is turned into a 16-bit integer between 0 and 65,536. (5/N)

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

I separately found the same sinusoidal wiggle in data from a different mode, the Single Object Slitless Spectrograph, which is often used for transmission spectroscopy of exoplanets. The nonlinearity had the same dominant period of 1024 in raw counts. (4/N)

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

In the process of calibrating out one such nonlinearity, the "brighter-fatter effect", @gradientrider.bsky.social originally noticed another odd effect in data from the Aperture Masking Interferometer: a sinusoidal wiggle in raw counts that was superimposed on the linear ramps. (3/N)

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

JWST uses H2RG detectors that read out nondestructively "up the ramp." The detector picks up light and accumulates charge in a way that ideally should be linear with time, but in practice has all sorts of nonlinearities that must be calibrated out. (2/N)

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Shashank Dholakia @astroshashank.bsky.social · 11/06/2026

Thread on our new paper on arxiv today! We stumbled across a weird sinusoidal systematic that we think appears in every observation from the NIRISS instrument on JWST. We derive a correction and see how much it impacts exoplanet spectra. (1/N) #astro #exoplanets 🔭🧪 arxiv.org/abs/2606.11983

arxiv.org

Calibration of an Analog-to-Digital Conversion Nonlinearity in JWST/NIRISS

We quantify an unusual flux-dependent systematic which is periodic in raw counts in flight data from the James Webb Space Telescope's Near Infrared Imager and Slitless Spectrograph (JWST/NIRISS), used...

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Shashank Dholakia @astroshashank.bsky.social · 10/06/2026

I saw this called the trans-Pacific accent recently and I can't stop thinking about it

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Colin Stuart 🔭 @colinstuartspace.bsky.social · 06/04/2026

A starspot on Zeta Andromedae. That’s a surface feature on a star 181 light years away. #astronomy ⚛️🧪 Image: Roettenbacher et al

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Shashank Dholakia @astroshashank.bsky.social · 31/03/2026

Thank you Ben!! I obviously couldn't have done it without you! Now to space out for a few days

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💀Adina Feinstein PhD 💀 @afeinstein20.bsky.social · 17/03/2026

really exciting work lead by Catriona Murray! TOI-3884 b is a planet on a polar orbit around an M dwarf. The transit has a persistent starspot crossing event. Using JWST, we measured the properties of the starspot and the Prot of the star 👀 arxiv.org/abs/2603.15414 🔭 #astronomy 🌟 #stellarastro

seven panel figure showing different JWST transits of TOI-3884 b with a persistent spot-crossing event. TOI-3884 b orbits the pole of a small M dwarf star. the shape of the spot-crossing event changes slightly between each transit. each subpanel has a graphical representation of what the spot looks like during each transit.

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Jonatan Rudrasingam @astrojonatan.bsky.social · 28/02/2026

My first scientific paper is now public on arXiv! TESS struggles with the brightest stars due to saturation from overexposure. This is unfortunate, because these are the stars that are amenable to photon-hungry follow-up methods, such as spectroscopy or interferometry (1/9) arxiv.org/abs/2602.22472

arxiv.org

Halo Photometry and Asteroseismology for 98 of the Brightest Stars Observed by TESS

The Transiting Exoplanet Survey Satellite (TESS) mission has facilitated studies of asteroseismology, eclipsing binaries, and transits in many stars. However, the brightest stars saturate TESS, yet th...

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Benjamin Pope @benjaminpope.bsky.social · 04/03/2026

Do you already have a Masters? Do you want to do a PhD in exoplanet radial velocity surveys with me at Macquarie University in Sydney? Then have I got an ad for you!

mq.edu.au

Discovering exoplanets with machine learning

Develop a machine-learned model of stellar spectra and instrumental quirks, and use it to discover exoplanets in radial velocity data.

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Shashank Dholakia @astroshashank.bsky.social · 10/02/2026

If you're on the postdoc market for exoplanet/ML applications--strong recommendation to apply for this job at Macquarie, Ben is great!!

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Astrobites @astrobites.bsky.social · 01/02/2026

From Ryan White @astroryan.bsky.social : There are a few locations in the solar system where the push and pull of gravity mellows out and you can orbit in (relative) peace. Read all about these islands of tranquility we call Lagrange points! ⚛️ 🔭 ☄️ 🧪 astrobites.org/2026/01/29/w...

astrobites.org

What’s the (Lagrange) point?

There are a few locations in the solar system where the push and pull of gravity mellows out and you can orbit in (relative) peace. Read all about these islands of tranquility we call Lagrange points!

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CosmicRami 🏳️‍🌈🏳️‍⚧️ @rami.spaceaustralia.com · 30/12/2025

Stories from #SpaceAustralia in 2025: Checking out the God of Chaos — Apep — using JWST and the VLT. This unique triple stellar system is wild! Some nice work on one of the papers here led by fellow Macquarie University student Ryan White! 🔭

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