Askaniy

Great result! What color space and white point were used? Was the conversion via CIE XYZ space, or were CIE RGB color matching functions used directly? Or was RGB represented by slices of the spectrum at some wavelengths?

Now published in AJ! Get in here this system is crazy iopscience.iop.org/article/10.3...

(About the contrast: the attached GIF is for IR, where the limb darkening is stronger, and the effect is comparable to dark spots. In the visible range the limb darkening is weaker, and the spots can have fine structures that increase the contrast, according to the modeling)

Great!
The preprint inspired me to explore what this system might look like to the human eye, it is definitely crazy: bsky.app/profile/aska...

Observations indicate that flare spectra resembles that of class A stars in the visible range [DOI 10.1088/0067-0049/207/1/15]. Flares are detected at high latitudes [DOI 10.1093/mnras/stab2159]. I assume them to be similar in appearance to White-Light Flares on the Sun.
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The final composite art with the planet uses limb darkening profile computed via LDTk [https://github.com/hpparvi/ldtk], a Python library. Interestingly, for a star with these parameters, the darkening occurs without reddening.
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The texture's color was calculated using TCT and calibrated with CTC [https://github.com/Askaniy/CylindricalTextureCalibrator] to match the hue of Proxima Centauri [DOI 10.1051/0004-6361/201730582]. Hand-painted in Krita.
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Cylindrical texture map of M dwarf. Gamma corrected.

Based on the illustrations of this study, I drew a texture map of TOI-3884 (11 d period). Its polar dark spot was explored thanks to the transiting planet. Texture contrast (after Gaussian blurring) aligns with the spot contrast described in [DOI 10.48550/arXiv.2506.11998].
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Instead of granules, red dwarfs have structures like "inter-granular lanes" and polar dark spots. Their presence depends on mass, period, etc. [DOI 10.1088/2041-8205/813/2/L31] modeled global structure for a star with 20 d period and revealed a massive polar dark spot.
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Convective granules are nearly invisible due to high log g and low T_eff. Additionally, TOI-3884 lies precisely at the minimum granulation contrast threshold (approximately 3%, compared to 16% on the Sun) [DOI 10.1016/j.jcp.2011.09.026, figure 11].
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Red dwarfs are often misperceived as red, but color calculations with github.com/Askaniy/True... show that absorption lines in spectra typically make them yellow. Also, “blue depression” spectral feature [DOI 10.1093/mnras/stad1391] falls on sensitivity range of blue cones.
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TOI-3884 b has a radius of 6.4 R⊕, a mass of 33 M⊕, and T_eff ≈ 460 K (Mercury-like thermal regime). Classified as Sudarsky class III, the planet is likely cloudless. It orbits TOI-3884 (TIC 86263325), an M4-type star with 0.3 R☉, 0.3 M☉, and T_eff ≈ 3000 K.
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View of M dwarf star TOI-3884 from the pole. The narrow crescent of TOI-3884 b can be seen below.

Giant planets orbiting red dwarfs are uncommon, as are hot Neptunes ("Neptunian desert"), as are exoplanets in polar orbits. On this painting, the host star "observes" its strange planet through a massive polar dark spot.

[1/9] of the "art research" thread on TOI-3884 and "red" dwarfs in general.

Meanwhile, Bolin et al. 2025 (arxiv.org/abs/2507.05252) obtained much more blue results:

Nice paper! I've just traced the plot and calculated colors based on it. All the spectral data agree well.
(Also, I would be very grateful if you could share the original spectrum.)
bsky.app/profile/aska...

Seligman et al. 2025: arxiv.org/abs/2507.02757
Opitom et al. 2025: arxiv.org/abs/2507.05226
Spectral reconstruction and extrapolation with TrueColorTools:

Reflectance colors of 3I/ATLAS in sRGB color space with illuminant E (assuming 0.5 albedo, it's very likely lower)

Beautiful work!
I recently reviewed papers on Hot Jupiters and attempted my own interpretation: bsky.app/profile/aska...

Thanks!

Voyager 1, WAC. March 4, 1979. Photos in violet, blue, and orange filters were aligned, reconstructed into a spectral cube, and convolved in sRGB color space with Illuminant E. There are gamma-corrected and contrast-enhanced options. Done with my program github.com/Askaniy/TrueColorTools

Artistic representation of Epsilon Eridani b, also known as AEgir [sic]

Emsenhuber et al. 2024 (DOI 10.3847/PSJ/ad2178) obtained a population of collision outcomes (2 bodies with m<10⁻² M⊕) that form a contact binary. Structure is maintained by material strength and spin. The painted peanut is Pluto-sized in length, but the size of Mars is theoretically achievable.

The color of the photometric surface is blue according to modeling (Sudarsky et al. 2000 for example) and measurements (Evans et al. 2013 for example), but mostly overexposed here. The color of the upper atmosphere is blue due to Rayleigh scattering.

For hot Jupiters, the L1 point is just within a few planetary radii, so it's easy for the atmosphere to escape inward. With a lower semi-major axis, the speed is higher, so it goes in the direction of motion. But solar wind can stop the leak and form a quasi-closed configuration.

An attempt to (relatively) realistically paint a hot Jupiter with a quasi-closed type of atmosphere, according to Bisikalo et al. 2021. (ui.adsabs.harvard.edu/abs/2021PhyU...)

GitHub - Askaniy/TrueColorTools: GUI application for calculating human-visible colors of celestial bodies from their photometric data GUI application for calculating human-visible colors of celestial bodies from their photometric data - Askaniy/TrueColorTools

View the entire database, experiment with modes, add your own photometry and spectra, process images and spectral cubes by running a Python program or its compiled version for Windows. Help is welcome!
github.com/Askaniy/True...

The spherical albedo mode (average reflectivity across viewing angles) eliminates the opposition effect and more accurately represents relative brightness:

I'm developing an open source program with GUI that stores a variety of space photometry and converts them to color, TrueColorTools.
It can also process images and generate color charts. Here's the latest table of some featured objects (geometric albedo mode, sRGB color space, Illuminant E)

A quick painting of a superoceanic mini-Neptune planet. Originally posted on my Tumblr on 24 Feb 2024.
#astroart #spaceart #sciart

Made for Askiniy's TrueColorTools logo with permission: github.com/Askaniy/True...

Total time spent: 2 hours
www.tumblr.com/arbodox/7432...