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An ultrahot Neptune in the Neptune desert

Jenkins, James S. and Díaz, Matías R. and Kurtovic, Nicolás T. and Espinoza, Néstor and Vines, Jose I. and Peña Rojas, Pablo A. and Brahm, Rafael and Torres, Pascal and Cortés-Zuleta, Pía and Soto, Maritza G. and Lopez, Eric D. and King, George W. and Wheatley, Peter J. and Winn, Joshua N. and Ciardi, David R. and Ricker, George and Vanderspek, Roland and Latham, David W. and Seager, Sara and Jenkins, Jon M. and Beichman, Charles A. and Bieryla, Allyson and Burke, Christopher J. and Christiansen, Jessie L. and Henze, Christopher E. and Klaus, Todd C. and McCauliff, Sean and Mori, Mayuko and Narita, Norio and Nishiumi, Taku and Tamura, Motohide and Pitogo de Leon, Jerome and Quinn, Samuel N. and Villaseñor, Jesus Noel and Vezie, Michael and Lissauer, Jack J. and Collins, Karen A. and Collins, Kevin I. and Isopi, Giovanni and Mallia, Franco and Ercolino, Andrea and Petrovich, Cristobal and Jordán, Andrés and Acton, Jack S. and Armstrong, David J. and Bayliss, Daniel and Bouchy, François and Belardi, Claudia and Bryant, Edward M. and Burleigh, Matthew R. and Cabrera, Juan and Casewell, Sarah L. and Chaushev, Alexander and Cooke, Benjamin F. and Eigmüller, Philipp and Erikson, Anders and Foxell, Emma and Gänsicke, Boris T. and Gill, Samuel and Gillen, Edward and Günther, Maximilian N. and Goad, Michael R. and Hooton, Matthew J. and Jackman, James A. G. and Louden, Tom and McCormac, James and Moyano, Maximiliano and Nielsen, Louise D. and Pollacco, Don and Queloz, Didier and Rauer, Heike and Raynard, Liam and Smith, Alexis M. S. and Tilbrook, Rosanna H. and Titz-Weider, Ruth and Turner, Oliver and Udry, Stéphane and Walker, Simon R. and Watson, Christopher A. and West, Richard G. and Palle, Enric and Ziegler, Carl and Law, Nicholas and Mann, Andrew W. (2020) An ultrahot Neptune in the Neptune desert. Nature Astronomy . ISSN 2397-3366. (In Press)

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[img] Image (JPEG) (Extended Data Fig. 1: Normalised TESS pre-search data conditioning timeseries photometry for LTT 9779) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 5: Stellar density as a function of R_p/R*) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 6: Observed minus computed mid-transit times of LTT 9779 b) - Supplemental Material
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About 1 out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet. All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (R⊕), or apparently rocky planets smaller than 2 R⊕. Such lack of planets of intermediate size (the ‘hot Neptune desert’) has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here we report the discovery of an ultrashort-period planet with a radius of 4.6 R⊕ and a mass of 29 M⊕, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite revealed transits of the bright Sun-like star LTT 9779 every 0.79 days. The planet’s mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0^(+2.7)_(−2.9)% of the total mass. With an equilibrium temperature around 2,000 K, it is unclear how this ‘ultrahot Neptune’ managed to retain such an envelope. Follow-up observations of the planet’s atmosphere to better understand its origin and physical nature will be facilitated by the star’s brightness (V_(mag) = 9.8).

Item Type:Article
Related URLs:
URLURL TypeDescription ReadCube access Paper ItemCode ItemCode ItemCode ItemCode
Jenkins, James S.0000-0003-2733-8725
Díaz, Matías R.0000-0002-2100-3257
Espinoza, Néstor0000-0001-9513-1449
Peña Rojas, Pablo A.0000-0002-8770-4398
Brahm, Rafael0000-0002-9158-7315
Cortés-Zuleta, Pía0000-0002-6174-4666
King, George W.0000-0002-3641-6636
Wheatley, Peter J.0000-0003-1452-2240
Winn, Joshua N.0000-0002-4265-047X
Ciardi, David R.0000-0002-5741-3047
Ricker, George0000-0003-2058-6662
Vanderspek, Roland0000-0001-6763-6562
Latham, David W.0000-0001-9911-7388
Seager, Sara0000-0002-6892-6948
Jenkins, Jon M.0000-0002-4715-9460
Beichman, Charles A.0000-0002-5627-5471
Bieryla, Allyson0000-0001-6637-5401
Burke, Christopher J.0000-0002-7754-9486
Christiansen, Jessie L.0000-0002-8035-4778
McCauliff, Sean0000-0002-3037-9395
Mori, Mayuko0000-0003-1368-6593
Narita, Norio0000-0001-8511-2981
Nishiumi, Taku0000-0003-1510-8981
Tamura, Motohide0000-0002-6510-0681
Quinn, Samuel N.0000-0002-8964-8377
Lissauer, Jack J.0000-0001-6513-1659
Collins, Karen A.0000-0001-6588-9574
Collins, Kevin I.0000-0003-2781-3207
Isopi, Giovanni0000-0002-8458-0588
Ercolino, Andrea0000-0002-2807-5253
Petrovich, Cristobal0000-0003-0412-9314
Jordán, Andrés0000-0002-5389-3944
Acton, Jack S.0000-0002-1860-7842
Armstrong, David J.0000-0002-5080-4117
Bayliss, Daniel0000-0001-6023-1335
Bouchy, François0000-0002-7613-393X
Burleigh, Matthew R.0000-0003-0684-7803
Cabrera, Juan0000-0001-6653-5487
Casewell, Sarah L.0000-0003-2478-0120
Eigmüller, Philipp0000-0003-4096-0594
Gänsicke, Boris T.0000-0002-2761-3005
Gill, Samuel0000-0002-4259-0155
Gillen, Edward0000-0003-2851-3070
Günther, Maximilian N.0000-0002-3164-9086
Goad, Michael R.0000-0002-2908-7360
Hooton, Matthew J.0000-0003-0030-332X
Jackman, James A. G.0000-0003-0711-7992
Louden, Tom0000-0002-2574-356X
McCormac, James0000-0003-1631-4170
Moyano, Maximiliano0000-0002-7927-9555
Nielsen, Louise D.0000-0002-0091-9362
Pollacco, Don0000-0001-9850-9697
Queloz, Didier0000-0002-3012-0316
Raynard, Liam0000-0001-6472-9122
Smith, Alexis M. S.0000-0002-2386-4341
Udry, Stéphane0000-0001-7576-6236
Watson, Christopher A.0000-0002-9718-3266
West, Richard G.0000-0001-6604-5533
Palle, Enric0000-0003-0987-1593
Ziegler, Carl0000-0002-0619-7639
Law, Nicholas0000-0001-9380-6457
Mann, Andrew W.0000-0003-3654-1602
Alternate Title:An Ultra-Hot Neptune in the Neptune desert
Additional Information:© 2020 Nature Publishing Group. Received 09 July 2019; Accepted 01 June 2020; Published 21 September 2020. Funding for the TESS mission is provided by NASA’s Science Mission directorate. We acknowledge the use of public TESS alert data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. J.S.J. and N.T. acknowledge support by FONDECYT grants 1161218 and 1201371, and partial support from CONICYT project Basal AFB-170002. M.R.D. is supported by CONICYT-PFCHA/Doctorado Nacional-21140646/Chile and Proyecto Basal AFB-170002. J.I.V. acknowledges support of CONICYT-PFCHA/Doctorado Nacional-21191829. This work was made possible owing to ESO Projects 0102.C-0525 (principal investigator, Díaz) and 0102.C-0451 (principal investigator, Brahm). R.B. acknowledges support from FONDECYT Post-doctoral Fellowship Project 3180246. This work is partly supported by JSPS KAKENHI grant numbers JP18H01265 and JP18H05439, and JST PRESTO grant number JPMJPR1775. The IRSF project is a collaboration between Nagoya University and the South African Astronomical Observatory (SAAO) supported by the Grants-in-Aid for Scientific Research on Priority Areas (A) (numbers 10147207 and 10147214) and Optical and Near-Infrared Astronomy Inter-University Cooperation Program, from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan and the National Research Foundation (NRF) of South Africa. We thank A. Fukui, N. Kusakabe, K. Morihana, T. Nagata, T. Nagayama and the staff of SAAO for their kind support for IRSF SIRIUS observations and analyses. C.P. acknowledges support from the Gruber Foundation Fellowship and Jeffrey L. Bishop Fellowship. This research includes data collected under the NGTS project at the ESO La Silla Paranal Observatory. NGTS is funded by a consortium of institutes consisting of the University of Warwick, the University of Leicester, Queen’s University Belfast, the University of Geneva, the Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR; under the ‘Großinvestition GI-NGTS’), the University of Cambridge, together with the UK Science and Technology Facilities Council (STFC; project reference ST/M001962/1 and ST/S002642/1). P.J.W., D.B., B.T.G., S.G., T.L., D.P. and R.G.W. are supported by STFC consolidated grant ST/P000495/1. D.J.A. gratefully acknowledges support from the STFC via an Ernest Rutherford Fellowship (ST/R00384X/1). E.G. gratefully acknowledges support from the David and Claudia Harding Foundation in the form of a Winton Exoplanet Fellowship. M.J.H. acknowledges funding from the Northern Ireland Department for the Economy. M.T. is supported by JSPS KAKENHI (18H05442, 15H02063). A.J., R.B. and P.T. acknowledge support from FONDECYT project 1171208, and by the Ministry for the Economy, Development, and Tourism’s Programa Iniciativa Científica Milenio through grant IC 120009, awarded to the Millennium Institute of Astrophysics (MAS). P.E., A.C. and H.R. acknowledge the support of the DFG priority programme SPP 1992 ‘Exploring the Diversity of Extrasolar Planets’ (RA 714/13-1). We acknowledge the effort of A. Tokovinin in helping to perform the observations and reduction of the SOAR data. Data availability: The photometric data that support the findings of this study are publically available from the Mikulski Archive for Space Telescopes ( under the TESS mission link. All radial-velocity data are available from the corresponding author upon reasonable request. Raw and processed spectra can be obtained from the European Southern Observatory’s data archive at Code availability: All codes necessary for the reproduction of this work are publically available through the GitHub repository, as follows: EMPEROR,; Juliet,; SPECIES, ; ARIADNE, Author Contributions: J.S.J. led the TESS precision radial-velocity follow-up programme, selection of the targets, analysis and project coordination, and wrote the bulk of the paper. M.D., N.T. and R.B. performed the HARPS radial-velocity observations, P.T. observed the star with Coralie and M.D. analysed the activity data from these sources. N.E. performed the global modelling, with P.C.-Z. performing the TTV analysis, and R.B., M.G.S. and A.B. performing the stellar characterization using the spectra and evolutionary models. P.A.P.R. worked on the EMPEROR code and assisted in fitting the HARPS radial velocities. E.D.L. created a structure model for the planet, and in addition to G.W.K. and P.J.W., performed photoevaporation modelling. J.N.W. performed analysis of the system parameters. D.R.C. led the Keck NIRC2 observations and analysis. G.R., R.V., D.W.L., S.S. and J.M.J. have been leading the TESS project, observations, organization of the mission, processing of the data, organization of the working groups, selection of the targets and dissemination of the data products. C.E.H., S.M. and T.K. worked on the SPOC data pipeline. C.J.B. was a member of the TOI discovery team. S.N.Q. contributed to TOI vetting, TFOP organization and TRES spectral analysis. J.L. and C.P. helped with the interpretation of the system formation and evolution. K.A.C. contributed to TOI vetting, TFOP organization, and TFOP SG1 ground-based time-series photometry analysis. G.I., F.M., A.E., K.I.C., M.M., N.N., T.N. and J.P.L. contributed TFOP SG1 observations. J.S.A., D.J.A., D.B., F.B., C.B., E.M.B., M.R.B., J.C., S.L.C., A.C., B.F.C., P.E., A.E., E.F., B.T.G., S.G., E.G., M.N.G., M.R.G., M.J.H., J.A.G.J., T.L., J.M., M.M., L.D.N., D.P., D.Q., H.R., L.R., A.M.S.S., R.H.T., R.T.-W., O.T., S.U., J.I.V., S.R.W., C.A.W., R.G.W., P.J.W. and G.W.K. are part of the NGTS consortium who provided follow-up observations to confirm the planet. E.P. and J.J.L. helped with the interpretation of the result. C.B. performed the observations at SOAR and reduced the data, C.Z. performed the data analysis, and N.L. and A.W.M. assisted in the survey proposal, analysis and telescope time acquisition. All authors contributed to the paper. The authors declare no competing interests.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1161218
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1201371
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)21140646
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)21191829
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)3180246
Japan Society for the Promotion of Science (JSPS)JP18H01265
Japan Society for the Promotion of Science (JSPS)JP18H05439
Japan Science and Technology AgencyJPMJPR1775
Ministry of Education, Culture, Sports, Science and Technology (MEXT)10147207
Ministry of Education, Culture, Sports, Science and Technology (MEXT)10147214
National Research Foundation (South Africa)UNSPECIFIED
Gruber Foundation FellowshipUNSPECIFIED
Jeffrey L. Bishop FellowshipUNSPECIFIED
University of WarwickUNSPECIFIED
University of LeicesterUNSPECIFIED
Queen’s University BelfastUNSPECIFIED
University of GenevaUNSPECIFIED
Deutsches Zentrum für Luft- und Raumfahrt (DLR)UNSPECIFIED
University of CambridgeUNSPECIFIED
Science and Technology Facilities Council (STFC)ST/M001962/1
Science and Technology Facilities Council (STFC)ST/S002642/1
Science and Technology Facilities Council (STFC)ST/P000495/1
Science and Technology Facilities Council (STFC)ST/R00384X/1
David and Claudia Harding FoundationUNSPECIFIED
Winton Exoplanet FellowshipUNSPECIFIED
Northern Ireland Department for the EconomyUNSPECIFIED
Japan Society for the Promotion of Science (JSPS)18H05442
Japan Society for the Promotion of Science (JSPS)15H02063
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1171208
Ministerio de Economía, Fomento y TurismoIC 120009
Deutsche Forschungsgemeinschaft (DFG)SPP 1992
Deutsche Forschungsgemeinschaft (DFG)RA 714/13-1
Subject Keywords:Exoplanets
Record Number:CaltechAUTHORS:20201009-144454033
Persistent URL:
Official Citation:Jenkins, J.S., Díaz, M.R., Kurtovic, N.T. et al. An ultrahot Neptune in the Neptune desert. Nat Astron (2020).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105972
Deposited By: Tony Diaz
Deposited On:09 Oct 2020 22:21
Last Modified:09 Oct 2020 22:21

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