A giant planet candidate transiting a white dwarf – Nature.com

Abstract

Astronomers have discovered thousands of planets outside the Solar System1, most of which orbit stars that will eventually evolve into red giants and then into white dwarfs. During the red giant phase, any close-orbiting planets will be engulfed by the star2, but more distant planets can survive this phase and remain in orbit around the white dwarf3,4. Some white dwarfs show evidence for rocky material floating in their atmospheres5, in warm debris disks6,7,8,9 or orbiting very closely10,11,12, which has been interpreted as the debris of rocky planets that were scattered inwards and tidally disrupted13. Recently, the discovery of a gaseous debris disk with a composition similar to that of ice giant planets14 demonstrated that massive planets might also find their way into tight orbits around white dwarfs, but it is unclear whether these planets can survive the journey. So far, no intact planets have been detected in close orbits around white dwarfs. Here we report the observation of a giant planet candidate transiting the white dwarf WD 1856+534 (TIC 267574918) every 1.4 days. We observed and modelled the periodic dimming of the white dwarf caused by the planet candidate passing in front of the star in its orbit. The planet candidate is roughly the same size as Jupiter and is no more than 14 times as massive (with 95 per cent confidence). Other cases of white dwarfs with close brown dwarf or stellar companions are explained as the consequence of common-envelope evolution, wherein the original orbit is enveloped during the red giant phase and shrinks owing to friction. In this case, however, the long orbital period (compared with other white dwarfs with close brown dwarf or stellar companions) and low mass of the planet candidate make common-envelope evolution less likely. Instead, our findings for the WD 1856+534 system indicate that giant planets can be scattered into tight orbits without being tidally disrupted, motivating the search for smaller transiting planets around white dwarfs.

Data availability

We provide all reduced light curves and spectra with the manuscript. The Spitzer images are available for download at the Spitzer Heritage Archive (http://irsa.ipac.caltech.edu/applications/Spitzer/SHA/), and the TESS images and light curves are available from the Mikulski Archive for Space Telescopes (https://archive.stsci.edu/tess/). Source data are provided with this paper.

Code availability

Much of the code used to produce these results is publicly available and linked throughout the paper. We wrote custom software to analyse the data collected in this project. Though this code was not written with distribution in mind, it is available online at https://github.com/avanderburg/.

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Acknowledgements

We thank S. Lepine for providing the archival spectrum of G 229-20 A, and P. Berlind and J. Irwin for collecting and extracting velocities from the TRES spectrum. We thank B.-O. Demory for comments on the manuscript, and F. Rasio, D. Veras, P. Gao, B. Kaiser, W. Torres, J. Irwin, J. J. Hermes, J. Eastman, A. Shporer and K. Hawkins for conversations. A.V.’s work was performed under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. I.J.M.C. acknowledges support from the NSF through grant AST-1824644, and from NASA through Caltech/JPL grant RSA-1610091. T.D. acknowledges support from MIT’s Kavli Institute as a Kavli postdoctoral fellow. D.D. acknowledges support from NASA through Caltech/JPL grant RSA-1006130 and through the TESS Guest Investigator programme, grant 80NSSC19K1727. S.B. acknowledges support from the Laboratory Directed Research and Development programme of Los Alamos National Laboratory under project number 20190624PRD2. C.M. and B.Z. acknowledge support from NSF grants SPG-1826583 and SPG-1826550. A.V. was a NASA Sagan Fellow; J.C.B. is a 51 Pegasi b Fellow; L.A.P. is an NSF Graduate Research Fellow; A.C. is a Large Synoptic Survey Telescope Corporation Data Science Fellow; T.D. is a Kavli Fellow; and C.X.H. is a Juan Carlos Torres Fellow. Resources supporting this work were provided by the NASA High-End Computing (HEC) programme through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. This work is partially based on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. This article is partly based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos Sánchez operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide. This work is partly supported by JSPS KAKENHI, grant numbers JP17H04574, JP18H01265 and JP18H05439, and JST PRESTO grant number JPMJPR1775. This research has made use of NASA’s Astrophysics Data System, the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program, and the SIMBAD database, operated at CDS, Strasbourg, France. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This work is partially based on observations obtained at the International Gemini Observatory, a program of NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

Author information

Affiliations

  1. Department of Astronomy, University of Wisconsin-Madison, Madison, WI, USA

    Andrew Vanderburg

  2. Department of Astronomy, The University of Texas at Austin, Austin, TX, USA

    Andrew Vanderburg, Caroline V. Morley & Andreia Carrillo

  3. Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA

    Saul A. Rappaport, George R. Ricker, Roland K. Vanderspek, Sara Seager, David Berardo, Tansu Daylan, Ana Glidden, Natalia M. Guerrero, Xueying Guo, Chelsea X. Huang & Liang Yu

  4. NSF’s NOIRLab/Gemini Observatory, Hilo, HI, USA

    Siyi Xu

  5. Department of Physics and Astronomy, University of Kansas, Lawrence, KS, USA

    Ian J. M. Crossfield

  6. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA

    Juliette C. Becker

  7. Hereford Arizona Observatory, Hereford, AZ, USA

    Bruce Gary

  8. Instituto de Astrofísica de Canarias (IAC), Tenerife, Spain

    Felipe Murgas, Enric Palle, Hannu Parviainen, Akihiko Fukui & Norio Narita

  9. Departamento Astrofísica, Universidad de La Laguna (ULL), Tenerife, Spain

    Felipe Murgas, Enric Palle & Hannu Parviainen

  10. Los Alamos National Laboratory, Los Alamos, NM, USA

    Simon Blouin

  11. Raemor Vista Observatory, Sierra Vista, AZ, USA

    Thomas G. Kaye

  12. Laboratory for Space Research, The University of Hong Kong, Hong Kong, China

    Thomas G. Kaye

  13. Center for Astrophysics and Space Sciences, University of California, San Diego, San Diego, CA, USA

    Carl Melis

  14. Center for Space and Habitability, University of Bern, Bern, Switzerland

    Brett M. Morris & Kevin Heng

  15. Max Planck Institute for Astronomy, Heidelberg, Germany

    Laura Kreidberg

  16. Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA, USA

    Laura Kreidberg, Warren R. Brown, David W. Latham, Karen A. Collins & John A. Lewis

  17. NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

    Varoujan Gorjian & Farisa Morales

  18. Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

    Andrew W. Mann

  19. Steward Observatory, University of Arizona, Tucson, AZ, USA

    Logan A. Pearce

  20. Department of Physics and Astronomy, Dartmouth College, Hanover, NH, USA

    Elisabeth R. Newton

  21. Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, CA, USA

    Ben Zuckerman & Beth Klein

  22. Department of Physics and Astronomy, Bishop’s University, Sherbrooke, Quebec, Canada

    Lorne Nelson

  23. Hobby–Eberly Telescope, University of Texas, Austin, Austin, TX, USA

    Greg Zeimann

  24. DTU Space, National Space Institute, Technical University of Denmark, Kongens Lyngby, Denmark

    René Tronsgaard, Lars A. Buchhave & Andreea I. Henriksen

  25. Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA

    Sara Seager & Ana Glidden

  26. Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, MA, USA

    Sara Seager

  27. Department of Astrophysical Sciences, Princeton University, Princeton, NJ, USA

    Joshua N. Winn

  28. NASA Ames Research Center, Moffett Field, CA, USA

    Jon M. Jenkins, Douglas A. Caldwell, Jack J. Lissauer, Mark E. Rose & Jeffrey C. Smith

  29. Physics Department, University of Michigan, Ann Arbor, MI, USA

    Fred C. Adams

  30. Astronomy Department, University of Michigan, Ann Arbor, MI, USA

    Fred C. Adams

  31. Départment de Physique, Université de Montréal, Montreal, Quebec, Canada

    Björn Benneke & Patrick Dufour

  32. Institut de Recherche sur les Exoplanètes (iREx), Université de Montréal, Montreal, Quebec, Canada

    Björn Benneke & Patrick Dufour

  33. SETI Institute, Mountain View, CA, USA

    Douglas A. Caldwell & Jeffrey C. Smith

  34. Caltech/IPAC-NASA Exoplanet Science Institute, Pasadena, CA, USA

    Jessie L. Christiansen

  35. Exoplanets and Stellar Astrophysics Laboratory (Code 667), NASA Goddard Space Flight Center, Greenbelt, MD, USA

    Knicole D. Colón

  36. Noqsi Aerospace, Billerica, MA, USA

    John Doty

  37. Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, CA, USA

    Alexandra E. Doyle

  38. Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA

    Diana Dragomir

  39. Department of Astronomy, University of California, Berkeley, Berkeley, CA, USA

    Courtney Dressing

  40. Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan

    Akihiko Fukui

  41. Carl Sagan Institute, Cornell University, Ithaca, NY, USA

    Lisa Kaltenegger

  42. Department of Astronomy and Space Sciences, Ithaca, NY, USA

    Lisa Kaltenegger

  43. Department of Earth and Planetary Sciences, University of California, Riverside, Riverside, CA, USA

    Stephen R. Kane

  44. Department of Physics and Astronomy, Moorpark College, Moorpark, CA, USA

    Farisa Morales

  45. Astrobiology Center, Tokyo, Japan

    Norio Narita

  46. PRESTO, JST, Tokyo, Japan

    Norio Narita

  47. National Astronomical Observatory of Japan, Tokyo, Japan

    Norio Narita

  48. Komaba Institute for Science, The University of Tokyo, Tokyo, Japan

    Norio Narita

  49. Department of Physics, Lehigh University, Bethlehem, PA, USA

    Joshua Pepper

  50. Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA

    Keivan G. Stassun

  51. Department of Physics, Fisk University, Nashville, TN, USA

    Keivan G. Stassun

  52. ExxonMobil Upstream Integrated Solutions, Spring, TX, USA

    Liang Yu

Contributions

A.V. led the TESS proposals, identified the planet candidate, organized observations, performed the transit and flux limit analysis, and wrote the majority of the manuscript. S.A.R. helped to organize observations, performed independent data analysis, and wrote portions of the manuscript. S.X. helped to organize observations, obtained and analysed the Gemini data, measured fluxes from the Spitzer data, and helped to guide the strategy of the manuscript. I.J.M.C., L. Kreidberg, V.G., B.B., D.B., J.L.C., D.D., C.D., X.G., S.R.K., F. Morales and L.Y. acquired and produced a light curve from the Spitzer data. S.A.R., J.C.B., L.N., B.Z., F.C.A. and J.J.L. investigated the formation of the WD 1856 system. B.G., F. Murgas, T.G.K., E.P., H.P., A.F. and N.N. acquired follow-up photometry. S.B., P.D. and K.G.S. determined the parameters of the white dwarf, and A.W.M. and E.R.N. studied the M-dwarf companions. C.M., G.Z., W.R.B., R.T., B.K., L.A.B., A.E.D. and A.I.H. acquired spectra of the white dwarf and/or M-dwarf companions. B.M.M., K.H. and T.D. performed an independent analysis of the TESS data, and J.A.L. performed an independent analysis of the white dwarf SED. C.V.M. provided expertise on brown dwarf models, and L. Kaltenegger investigated the system’s implications. L.A.P. determined parameters for the binary M-dwarf orbits and white dwarf/M-dwarf orbits, A.C. investigated the system’s galactic kinematics. G.R.R., R.K.V., D.W.L., S.S., J.N.W., J.M.J., D.A.C., K.A.C., K.D.C., J.D., A.G., N.M.G., C.X.H., J.P., M.E.R. and J.C.S. are members of the TESS mission team.

Corresponding author

Correspondence to
Andrew Vanderburg.

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Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature thanks Artie Hatzes, Steven Parsons and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 Archival imaging of WD 1856.

a, From the Palomar Observatory Sky Survey on a photographic plate with a blue-sensitive emulsion. b, From the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) survey in the i band. c, From the Pan-STARRS survey in the i band, zoomed out to show the co-moving M-dwarf pair (labelled G 229-20). d, Coadded TESS image from sector 14. The photometric apertures for the three sectors of TESS observations (14, 15 and 19) are shown as red-, purple- and blue-coloured outlines, respectively. The present-day location of WD 1856 is shown with a red cross in all images.

Extended Data Fig. 2 All transit observations of WD 1856.

From top to bottom, we show the light curves (arbitrarily offset for visual clarity) from TESS; data from several private telescopes in Arizona (operated by B.G. and T.G.K.) with odd and even-numbered transits shown separately; simultaneous light curves in four colours from MuSCAT2; a light curve from the GTC, and a light curve from Spitzer. The individual two-minute-cadence TESS flux measurements are shown as grey points, and the rose-coloured points are averages of the brightness in roughly 30 s in orbital phase. The TESS data have been corrected for dilution from nearby stars so that the transit depth matches that of the GTC data.
Source data

Extended Data Fig. 3 Spectral energy distribution of WD 1856. Photometric measurements from Pan-STARRS148, 2MASS149, WISE150 and Spitzer are shown as blue, orange, dark red and pink points, respectively.

The formal 1σ (standard deviation) photometric uncertainties on the Pan-STARRS, WISE, and Spitzer points are smaller than the symbol size. Four different SED models are shown as solid curves: a pure hydrogen atmosphere model (red), a 50% hydrogen, 50% helium model (blue), a pure helium model (gold), and a blackbody curve (black). None of the SED models capture all of the SED’s features, but all four yield mostly consistent effective temperatures and stellar parameters.

Extended Data Fig. 4 Spectrum of WD 1856 near the Hα line.

Our summed Hobby–Eberly/LRS2 spectrum (black connected points) is shown in comparison with three atmosphere models: a pure hydrogen model (red), a 50% hydrogen, 50% helium model (blue), and a pure helium model (gold). We disfavour a pure hydrogen atmosphere on the basis of our non-detection of an Hα feature in our LRS2 spectra, but otherwise remain uncertain about the precise composition of the envelope of WD 1856.

Extended Data Fig. 5 Posterior probability distributions of transit parameters.

This ‘corner-plot’ shows correlations between pairs of parameters in our MCMC transit fit (with circular orbits enforced) and histograms of the marginalized posterior probability distributions for each parameter. For clarity, we have plotted correlations with the inclination angle i instead of the fit parameter cosi and subtract the median time of transit (tt). The orbital inclination i, scaled semimajor axis a/R⁎, and the planet–star radius ratio Rp/R⁎ are strongly correlated, owing to the grazing transit geometry, but constrained by the prior on the stellar density. We do not include rows for the GTC and Spitzer photometric jitter terms because these are nuisance parameters that showed no correlation with the other physical parameters.

Extended Data Fig. 6 Posterior probability distributions of transit parameters when eccentric orbits are allowed.

This ‘corner-plot’ shows correlations between pairs of parameters in our MCMC transit fit (allowing eccentric orbits) and histograms of the marginalized posterior probability distributions for each parameter. This plot shows a subset of the parameters that correlate with the orbital eccentricity. For clarity, we have plotted correlations with the eccentricity e, argument of periastron w and orbital inclination i instead of the fit parameters (sqrt{e}cos ,omega ), (sqrt{e}sin ,omega ) and δ.

Extended Data Fig. 7 Hα equivalent width for G 229-20 A/B compared to other nearby M dwarfs.

The histogram shows the Hα equivalent widths for a large sample of M dwarfs with similar spectral types from the Sloan Digital Sky Survey103. G 229-20 A/B (shown as a blue arrow) has a lower than average Hα equivalent width, but falls well within the distribution of field M dwarfs.

Extended Data Fig. 8 Theoretical relationships between the star’s radius and the mass of its core.

We show MIST120 evolution tracks in the radius–core mass plane for solar composition models with masses ranging from 1M–2.8M. The RGB phase is clearly identifiable for core masses between 0.2M and 0.47M, whereas the thermal pulses on the AGB are readily recognized at higher core masses of 0.5M. The lime-green curve is the analytic expression given by equation (8). The vertical lines for each star mark the point where the envelope has been exhausted by the AGB wind.

Extended Data Fig. 9 The minimum value of the efficiency parameter αλCE required for WD 1856 b to form via common-envelope evolution as a function of the progenitor stellar mass.

The two dashed curves show the minimum αλCE values from our analytic calculation (equation (11)) required for a 15MJ object to eject the primary star’s envelope. The purple dashed curve is taken directly from equation (11), and the brown dashed curve results if the progenitor star has lost 0.1M in a stellar wind by the time of the common envelope. The three solid curves show the minimum αλCE computed directly from MIST tracks in three different situations: before the star reaches the AGB (red), before more than 30% of the star’s envelope mass has been lost (black), and at any point in the star’s evolution, regardless of the mass lost (blue). Stars in the grey region at low masses evolve too slowly for the system to have left the main sequence more than 5.85 Gyr ago and are not viable solutions. For values of αλCE > 1 (horizontal grey line), one must invoke the internal energy of the star to help to unbind the envelope during the common-envelope phase. Before mass is lost during the AGB phase, it is difficult for WD 1856 b to eject the common envelope, but it is possible that WD 1856 b could have ejected its progenitor’s envelope if the common-envelope phase began after the progenitor reached the AGB. We have smoothed the lower two curves to remove some unphysical scatter that is probably due to numerical artefacts in the model grids.

Extended Data Table 1 Comparison of white dwarf parameters from different atmosphere models

Supplementary information

Supplementary Data

This file contains a comma separated value file with spectroscopic data on the M-dwarf companions.

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Vanderburg, A., Rappaport, S.A., Xu, S. et al. A giant planet candidate transiting a white dwarf.
Nature 585, 363–367 (2020). https://doi.org/10.1038/s41586-020-2713-y

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