TESS Delivers Its First Earth-sized Planet and a Warm Sub-Neptune

The future of exoplanet science is bright, as Transiting Exoplanet Survey Satellite (TESS) once again demonstrates with the discovery of its longest-period confirmed planet to date. We hereby present HD 21749b (TOI 186.01), a sub-Neptune in a 36 day orbit around a bright (V = 8.1) nearby (16 pc) K4.5 dwarf. TESS measures HD 21749b to be R⊕, and combined archival and follow-up precision radial velocity data put the mass of the planet at M⊕. HD 21749b contributes to the TESS Level 1 Science Requirement of providing 50 transiting planets smaller than 4 R⊕ with measured masses. Furthermore, we report the discovery of HD 21749c (TOI 186.02), the first Earth-sized ( ) planet from TESS. The HD 21749 system is a prime target for comparative studies of planetary composition and architecture in multi-planet systems.

Keivan G. Stassun | Sara Seager | Jeffrey D. Crane | R. Paul Butler | B. Scott Gaudi | Jason D. Eastman | George R. Ricker | Robert J. Siverd | Thomas G. Beatty | Joshua N. Winn | Jon M. Jenkins | Timothy M. Brown | Christophe Lovis | Joseph D. Twicken | Todd C. Klaus | Avi Shporer | Steven Villanueva | Diana Dragomir | Luca Fossati | Roland Vanderspek | Chelsea X. Huang | Francesco Pepe | Bill Wohler | Damien Ségransan | Robert F. Goeke | Benjamin J. Fulton | David W. Latham | David R. Ciardi | Rudolf B. Kuhn | Martin Paegert | Stephen A. Shectman | Andrew Vanderburg | Stéphane Udry | David James | Maximilian N. Günther | Joshua Pepper | Michael B. Lund | Xinyu Yao | Johanna K. Teske | Xavier Dumusque | R. P. Butler | Joseph E. Rodriguez | M. Paegert | J. Pepper | K. Stassun | S. Shectman | D. James | B. Gaudi | M. Lund | Avi Shporer | F. Bouchy | S. Udry | D. Ségransan | S. McDermott | J. Eastman | T. Brown | D. Ciardi | X. Dumusque | D. Latham | F. Pepe | C. Lovis | A. Vanderburg | J. Jenkins | S. Seager | J. Winn | J. Twicken | B. Fulton | T. Klaus | J. Teske | B. Wohler | J. Burt | M. Günther | Lizhou Sha | G. Ricker | R. Vanderspek | D. Dragomir | J. Crane | T. Beatty | D. Stevens | S. Villanueva | R. Siverd | E. Matthews | R. Butler | S. Wang | L. Fossati | J. Francis | R. Goeke | R. Kuhn | A. Soto | Xinyu Yao | Z. Zhan | François Bouchy | Jennifer Burt | Daniel J. Stevens | Elisabeth Matthews | Lizhou Sha | Zhuchang Zhan | Sharon X. Wang | Aylin Garcia Soto | Jim Francis | Scott McDermott | X. Yao | L. Sha | Joseph E. Rodriguez

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