space Nature Is Weird

Astronomers found a 'hell world' so fast that its entire year is over by the time you finish a work shift.

March 20, 2026

Original Paper

TOI-4552 b: A new ultra-short period rocky world revealed by NIRPS and TESS

Avidaan Srivastava, René Doyon, François Bouchy, Étienne Artigau, Charles Cadieux, Nicole Gromek, Elisa Delgado-Mena, Yuri S. Messias, Xavier Bonfils, Roseane de Lima Gomes, Susana C. C. Barros, Björn Benneke, Marta Bryan, Ryan Cloutier, Nicolas B. Cowan, Eduardo Cristo, Xavier Delfosse, Xavier Dumusque, David Ehrenreich, Jonay I. González Hernández, David Lafrenière, Izan de Castro Leão, Christophe Lovis, Alejandro Suárez Mascareño, Bruno L. Canto Martins, Jose Renan De Medeiros, Lucile Mignon, Christoph Mordasini, Francesco Pepe, Rafael Rebolo, Jason Rowe, Nuno C. Santos, Damien Ségransan, Stéphane Udry, Diana Valencia, Gregg Wade, Jose Manuel Almenara, Karen A. Collins, Dennis M. Conti, George Dransfield, Elsa Ducrot, Zahra Essack, Dasaev O. Fontinele, Thierry Forveille, Marziye Jafariyazani, Pierrot Lamontagne, Alexandrine L'Heureux, Khaled Al Moulla, Ares Osborn, Léna Parc, David R. Rodriguez, Richard P. Schwartz, Madison G. Scott, Avi Shporer, Atanas K. Stefanov, Mathilde Timmermans, Amaury H.M.J. Triaud, Joost P. Wardenier, Drew Weisserman, Sebastián Zúñiga-Fernández

arXiv · 2603.18233

The Takeaway

This rocky planet, named TOI-4552 b, is so close to its star that it completes a full orbit in just 0.3 days. It appears to be roughly half iron, suggesting it might be the exposed metallic core of a larger planet that had its outer layers stripped away by the intense heat of its star.

From the abstract

A particularly intriguing subclass of rocky exoplanets are the ultra-short period (USP) worlds that orbit their host stars in less than a day. These planets are particularly rare around M dwarf stars, with so far only ten that have a constrained mass and radius. We present the validation and characterization of the ultra-short period (0.3-days), Earth-sized planet TOI-4552b orbiting a nearby (27.26-pc away) M4.5V dwarf. Complementing the TESS photometry, ground-based transit observations from LC

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