TESS Spots a Super-puff: The Remarkably Low Density of TOI-1420b

Stephanie Yoshida, Shreyas Vissapragada, David W. Latham, Allyson Bieryla, Daniel P. Thorngren, Jason D. Eastman, Mercedes López-Morales, Khalid Barkaoui, Charles Beichman, Perry Berlind, Lars A. Buchave, Michael L. Calkins, David R. Ciardi, Karen A. Collins, Rosario Cosentino, Ian J.M. Crossfield, Fei Dai, Victoria DiTomasso, Nicholas Dowling, Gilbert A. EsquerdoRaquel Forés-Toribio, Adriano Ghedina, Maria V. Goliguzova, Eli Golub, Erica J. Gonzales, Ferran Grau Horta, Jesus Higuera, Nora Hoch, Keith Horne, Steve B. Howell, Jon M. Jenkins, Jessica Klusmeyer, Didier Laloum, Jack J. Lissauer, Sarah E. Logsdon, Luca Malavolta, Rachel A. Matson, Elisabeth C. Matthews, Kim K. McLeod, Jennifer V. Medina, Jose A. Muñoz, Hugh P. Osborn, Boris Safonov, Joshua Schlieder, Michael Schmidt, Heidi Schweiker, Sara Seager, Alessandro Sozzetti, Gregor Srdoc, Guđmundur Stefánsson, Ivan A. Strakhov, Stephanie Striegel, Joel Villaseñor, Joshua N. Winn

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We present the discovery of TOI-1420b, an exceptionally low-density (ρ = 0.08 ± 0.02 g cm−3) transiting planet in a P = 6.96 days orbit around a late G-dwarf star. Using transit observations from TESS, LCOGT, Observatoire Privé du Mont, Whitin, Wendelstein, OAUV, Ca l’Ou, and KeplerCam, along with radial velocity observations from HARPS-N and NEID, we find that the planet has a radius of R p = 11.9 ± 0.3R and a mass of M p = 25.1 ± 3.8M . TOI-1420b is the largest known planet with a mass less than 50M , indicating that it contains a sizeable envelope of hydrogen and helium. We determine TOI-1420b’s envelope mass fraction to be f env = 82 − 6 + 7 % , suggesting that runaway gas accretion occurred when its core was at most four to five times the mass of the Earth. TOI-1420b is similar to the planet WASP-107b in mass, radius, density, and orbital period, so a comparison of these two systems may help reveal the origins of close-in low-density planets. With an atmospheric scale height of 1950 km, a transmission spectroscopy metric of 580, and a predicted Rossiter-McLaughlin amplitude of about 17 m s−1, TOI-1420b is an excellent target for future atmospheric and dynamical characterization.

Original languageEnglish (US)
Article number181
JournalAstronomical Journal
Issue number5
StatePublished - Nov 1 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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