NASA adds TOI-4311 b super-Earth

NASA added TOI-4311 b to its exoplanet catalog on May 22, 2026, giving the newly reported world a public entry in the agency’s running list of confirmed exoplanets. The catalog describes TOI-4311 b as a super-Earth orbiting a K-type star, with a mass of 4.5 Earths, a radius of 1.376 Earth radii, an orbital period of 1 day and a semimajor axis of 0.01817 astronomical units. NASA’s exoplanet catalog says the planet’s discovery was announced in 2026. That entry matters mostly as a data point, not a mission announcement. NASA’s exoplanet catalog is a continuously updated database with more than 6,000 confirmed worlds, and new additions often appear there before they are widely noticed outside astronomy circles. In TOI-4311 b’s case, the catalog entry links the planet to a host star page for TOI-4311 and places it among the agency’s newly posted discoveries. (science.nasa.gov) ### How extreme is a one-day year? A 1-day orbital period puts TOI-4311 b in the ultra-short-period class of exoplanets, meaning it circles its star in less than an Earth day. NASA’s listed orbital distance of 0.01817 AU places it far closer to its star than Mercury is to the Sun. The 2026 discovery paper describes TOI-4311 b more precisely as an “ultra-short-period super-Earth” with a period of about 0.99 days. (science.nasa.gov) The paper says the planet was characterized using TESS photometry together with follow-up observations from CHEOPS and HARPS. ### What do the mass and radius say about the planet itself? NASA lists TOI-4311 b at 4.5 Earth masses and 1.376 Earth radii. (science.nasa.gov) Those numbers place it in the broad category astronomers call super-Earths: planets larger or more massive than Earth but smaller than Neptune. The arXiv paper says the measured mass and radius imply the planet is unusually dense. (arxiv.org) The authors wrote that their interior modeling found TOI-4311 b to be “very dense” and said the system “could challenge current formation theories,” an interpretation that comes from the research team rather than NASA’s catalog entry. ### Is TOI-4311 b the only planet in the system? (science.nasa.gov) The 2026 paper reports that TOI-4311 is a multi-planet system. In addition to planet b, the authors said the star hosts a longer-period sub-Neptune, TOI-4311 c, with an orbital period of about 15 days. The same paper also says HARPS radial-velocity data showed a third periodic signal that the team could not link to stellar activity. (arxiv.org) The authors did not present that signal as a confirmed planet in the abstract, but they said it was clearly detected in the radial-velocity measurements. ### Where did this result come from? NASA’s catalog page gives the headline properties, but the underlying characterization appears to come from a paper posted in May 2026 titled “An Ultra-Short Period Super-Earth and a Sub-Neptune Orbiting the K dwarf TOI-4311.” The paper lists Yoshi Nike Emilia Eschen as lead author and says nearly 100 researchers contributed. (arxiv.org) The paper says TESS first detected the system in photometry, while CHEOPS and HARPS were used to refine the planetary radii, derive the mass of planet b and confirm the nature of planet c. That is the usual path for many exoplanet confirmations: transit data identify candidates, and follow-up measurements tighten the physical picture. (arxiv.org) ### What comes next for anyone tracking the system? NASA’s exoplanet catalog page for TOI-4311 b is now the easiest public reference for the planet’s baseline numbers, including mass, radius, orbital distance and discovery year. The research paper points to the next likely step: more follow-up work on the possible third signal in the system and additional modeling of why such a dense ultra-short-period planet formed around this K dwarf. (arxiv.org) (science.nasa.gov)