Revealing the Shiny Nature of Lava Worlds: Small Planet Phase Curves with TESS
Abstract
Recent thermal emission observations suggest that `lava worlds'--Earth-sized exoplanets hot enough to melt their silicate surfaces--have atmospheres on a population-level. This evidence comes from measured dayside brightness temperatures much lower than expected for a dark, maximally hot bare rock. However, these results are degenerate between a thick atmosphere advecting heat to the planet's nightside or a high albedo reflecting incoming radiation. This degeneracy can be resolved through visible light phase curve observations, which can constrain how much light is reflected by the planet. Here, we present a population-level analysis of the visible-light TESS phase curves of R≲5 R⊕ exoplanets. We select the population by defining a `Reflection Spectroscopy Metric' meant to quantify the relative signal-to-noise of reflected light observations. We report new >3 σ detections of the TESS phase curve signals of LTT 9779 b and the lava worlds TOI-2431 b, TOI-561 b, 55 Cancri e, K2-141 b, and TOI-1444 b. We use these results and previous results from Kepler and CHEOPS to homogeneously derive geometric albedos for these planets, revealing that lava worlds generally show high albedos compared to the low geometric albedos measured for hot Jupiters at similar temperatures. These results support an emerging picture of reflective silicate clouds on these worlds cooling their daysides. The upcoming PLATO mission is expected to tightly constrain the reflected light phase curves of lava worlds.
Related
- Linking stellar composition to the nature and mass fraction of ice and organic compounds in exo-ocean worlds
- Performance of an autoregressive planet search methodology on simulated PLATO light curves
- Hidden worlds: A non-transiting candidate planet in the Neptunian desert around the solar-type pulsator KIC 9139163
- Ice Giants Revisited: Uranus and Neptune as Magma Ocean Worlds
- pyEDITH: the coronagraphic exposure time calculator for the Habitable Worlds Observatory
BibTeX
@misc{coy2026revealing,
title = {{Revealing the Shiny Nature of Lava Worlds: Small Planet Phase Curves with TESS}},
author = {Brandon Park Coy and Michael Zhang and Fei Dai and Qiao Xue},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.26874},
eprint = {2609.26874},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.26874},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Revealing the Shiny Nature of Lava Worlds: Small Planet Phase Curves with TESS
AU - Brandon Park Coy
AU - Michael Zhang
AU - Fei Dai
AU - Qiao Xue
PY - 2026
DA - 2026/09/22
PB - arXiv
DO - 10.48550/arxiv.2609.26874
UR - https://arxiv.org/abs/2609.26874
AB - Recent thermal emission observations suggest that `lava worlds'--Earth-sized exoplanets hot enough to melt their silicate surfaces--have atmospheres on a population-level. This evidence comes from measured dayside brightness temperatures much lower than expected for a dark, maximally hot bare rock. However, these results are degenerate between a thick atmosphere advecting heat to the planet's nightside or a high albedo reflecting incoming radiation. This degeneracy can be resolved through visible light phase curve observations, which can constrain how much light is reflected by the planet. Here, we present a population-level analysis of the visible-light TESS phase curves of R≲5 R_⊕ exoplanets. We select the population by defining a `Reflection Spectroscopy Metric' meant to quantify the relative signal-to-noise of reflected light observations. We report new >3 σ detections of the TESS phase curve signals of LTT 9779 b and the lava worlds TOI-2431 b, TOI-561 b, 55 Cancri e, K2-141 b, and TOI-1444 b. We use these results and previous results from Kepler and CHEOPS to homogeneously derive geometric albedos for these planets, revealing that lava worlds generally show high albedos compared to the low geometric albedos measured for hot Jupiters at similar temperatures. These results support an emerging picture of reflective silicate clouds on these worlds cooling their daysides. The upcoming PLATO mission is expected to tightly constrain the reflected light phase curves of lava worlds.
ER -