Hazy skies on small gas planets

Thirty-eight planets between Earth and Neptune in size, and most seem to hide their atmospheres. What is getting in the way?

Preprint · not peer-reviewed Observational survey 38 planets around 36 stars Briefing 9:00 17 Sep 2026

In one paragraph

This preprint reports a transmission spectroscopy survey of 38 sub-Neptune exoplanets. About two thirds show muted spectra, consistent with clouds or hazes, and the muting tracks planetary temperature. A handful of cooler, clearer worlds show confident water vapor signals. The results are preliminary and have not been peer-reviewed.

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Briefing reviewed by an editor before publication. The paper belongs to its authors; this page summarises it and links to the original. Reviewed by Dr. P. Lindholm-Achebe. Paper licence: CC BY 4.0. Corrections: support@papersays.com.

PHYSICS Exoplanets

Hazy skies on small gas planets

Preview · 1:00 of 9:00 · Physics & Space

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says Point a space telescope at thirty-eight small gas planets and try to read their air. For twenty-four of them, the signal comes back muted by more than sixty percent.
Muted by what?
That, it turns out, is the real question.
Welcome back to the daily briefing. I'm Aiden.
And I'm Ryan. Today, faraway planets that keep their skies to themselves.
explains Planets between the size of Earth and Neptune are the most common kind we know of. And yet there's nothing like them in our own solar system.
The most popular planet in the galaxy, and we didn't get one.
explains This preprint reads the atmospheres of thirty-eight of them at once. It hasn't been peer reviewed yet, and it's an observational survey, so keep both of those in mind.
interprets My read is that the surprise here is how often the answer was a shrug. Many of these worlds hide their atmospheres behind something, and what that something is may be the real story.

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The paper

A Transmission Spectroscopy Survey of 38 Sub-Neptune Exoplanets: Cloud Opacity Trends with Equilibrium Temperature

Authors: E. Hartmann-Nwosu, Y. Takeda, C. Albuquerque-Reyes
Venue: arXiv (preprint) · 18 August 2026
Study: Observational survey · 38 planets around 36 stars
DOI: 10.5555/sample.exo.2026.0291
Licence: CC BY 4.0