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Article Published: 16 September 2020
A giant planet candidate transiting a white dwarf
Andrew Vanderburg , Saul A. Rappaport, Siyi Xu, Ian J. M. Crossfield, Juliette C. Becker, Bruce
Gary, Felipe Murgas, Simon Blouin, Thomas G. Kaye, Enric Palle, Carl Melis, Brett M. Morris,
Laura Kreidberg, Varoujan Gorjian, Caroline V. Morley, Andrew W. Mann, Hannu Parviainen, Logan
A. Pearce, Elisabeth R. Newton, Andreia Carrillo, Ben Zuckerman, Lorne Nelson, Greg Zeimann,
Warren R. Brown, René Tronsgaard, Beth Klein, George R. Ricker, Roland K. Vanderspek, David
W. Latham, Sara Seager, Joshua N. Winn, Jon M. Jenkins, Fred C. Adams, Björn Benneke, David
Berardo, Lars A. Buchhave, Douglas A. Caldwell, Jessie L. Christiansen, Karen A. Collins, Knicole
D. Colón, Tansu Daylan, John Doty, Alexandra E. Doyle, Diana Dragomir, Courtney Dressing,
Patrick Dufour, Akihiko Fukui, Ana Glidden, Natalia M. Guerrero, Xueying Guo, Kevin Heng,
Andreea I. Henriksen, Chelsea X. Huang, Lisa Kaltenegger, Stephen R. Kane, John A. Lewis, Jack
J. Lissauer, Farisa Morales, Norio Narita, Joshua Pepper, Mark E. Rose, Jeffrey C. Smith,
[…]Keivan G. Stassun & Liang Yu
Nature 585, 363–367(2020)
5895 Accesses 1 Citations 1498 Altmetric Metrics
Abstract
Astronomers have discovered thousands of planets outside the Solar System , most ofwhich 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 star , butmore distant planets can survive this phase and remain in orbit around the whitedwarf . Some white dwarfs show evidence for rocky material floating in their
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atmospheres , in warm debris disks or orbiting very closely , which has beeninterpreted as the debris of rocky planets that were scattered inwards and tidallydisrupted . Recently, the discovery of a gaseous debris disk with a composition similarto that of ice giant planets demonstrated that massive planets might also find their wayinto tight orbits around white dwarfs, but it is unclear whether these planets can survivethe journey. So far, no intact planets have been detected in close orbits around whitedwarfs. Here we report the observation of a giant planet candidate transiting the whitedwarf WD 1856+534 (TIC 267574918) every 1.4 days. We observed and modelled theperiodic dimming of the white dwarf caused by the planet candidate passing in front ofthe star in its orbit. The planet candidate is roughly the same size as Jupiter and is nomore than 14 times as massive (with 95 per cent confidence). Other cases of white dwarfswith close brown dwarf or stellar companions are explained as the consequence ofcommon-envelope evolution, wherein the original orbit is enveloped during the redgiant 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) andlow 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 intotight orbits without being tidally disrupted, motivating the search for smaller transitingplanets around white dwarfs.
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Data availability
We provide all reduced light curves and spectra with the manuscript. The Spitzer imagesare available for download at the Spitzer Heritage Archive(http://irsa.ipac.caltech.edu/applications/Spitzer/SHA/), and the TESS images andlight 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 linkedthroughout the paper. We wrote custom software to analyse the data collected in thisproject. Though this code was not written with distribution in mind, it is available onlineat 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 andJ. 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 forconversations. A.V.’s work was performed under contract with the California Institute ofTechnology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through theSagan Fellowship Program executed by the NASA Exoplanet Science Institute. I.J.M.C.acknowledges support from the NSF through grant AST-1824644, and from NASAthrough Caltech/JPL grant RSA-1610091. T.D. acknowledges support from MIT’s KavliInstitute as a Kavli postdoctoral fellow. D.D. acknowledges support from NASA throughCaltech/JPL grant RSA-1006130 and through the TESS Guest Investigator programme,grant 80NSSC19K1727. S.B. acknowledges support from the Laboratory DirectedResearch and Development programme of Los Alamos National Laboratory underproject number 20190624PRD2. C.M. and B.Z. acknowledge support from NSF grantsSPG-1826583 and SPG-1826550. A.V. was a NASA Sagan Fellow; J.C.B. is a 51 Pegasi bFellow; L.A.P. is an NSF Graduate Research Fellow; A.C. is a Large Synoptic SurveyTelescope Corporation Data Science Fellow; T.D. is a Kavli Fellow; and C.X.H. is a JuanCarlos 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 delRoque 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 bythe IAC in the Spanish Observatorio del Teide. This work is partly supported by JSPSKAKENHI, grant numbers JP17H04574, JP18H01265 and JP18H05439, and JST PRESTOgrant number JPMJPR1775. This research has made use of NASA’s Astrophysics DataSystem, the NASA Exoplanet Archive, which is operated by the California Institute ofTechnology, under contract with the National Aeronautics and Space Administrationunder the Exoplanet Exploration Program, and the SIMBAD database, operated at CDS,Strasbourg, France. This work is based in part on observations made with the SpitzerSpace Telescope, which is operated by the Jet Propulsion Laboratory, California Instituteof Technology under a contract with NASA. This work is partially based on observationsobtained at the International Gemini Observatory, a program of NOIRLab, which ismanaged by the Association of Universities for Research in Astronomy (AURA) under acooperative agreement with the National Science Foundation, on behalf of the GeminiObservatory partnership: the National Science Foundation (United States), NationalResearch 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 ScienceInstitute (Republic of Korea). The authors wish to recognize and acknowledge the verysignificant cultural role and reverence that the summit of Maunakea has always hadwithin the Indigenous Hawaiian community. We are most fortunate to have theopportunity 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, LosAngeles, 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, KongensLyngby, 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 ofTechnology, 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 SpaceFlight 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, LosAngeles, 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, TheUniversity 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 wroteportions of the manuscript. S.X. helped to organize observations, obtained and analysedthe 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. andA.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 anindependent analysis of the white dwarf SED. C.V.M. provided expertise on browndwarf 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. aremembers 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. Peerreviewer reports are available.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims inpublished 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 ResponseSystem (Pan-STARRS) survey in the i band. c, From the Pan-STARRS survey in the iband, zoomed out to show the co-moving M-dwarf pair (labelled G 229-20). d, CoaddedTESS image from sector 14. The photometric apertures for the three sectors of TESSobservations (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 allimages.
Extended Data Fig. 2 All transit observations of WD 1856.From top to bottom, we show the light curves (arbitrarily offset for visual clarity) fromTESS; data from several private telescopes in Arizona (operated by B.G. and T.G.K.) withodd and even-numbered transits shown separately; simultaneous light curves in fourcolours from MuSCAT2; a light curve from the GTC, and a light curve from Spitzer. Theindividual two-minute-cadence TESS flux measurements are shown as grey points, andthe 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 transitdepth matches that of the GTC data. Source data
Extended Data Fig. 3 Spectral energy distribution of WD 1856. Photometricmeasurements from Pan-STARRS148, 2MASS , WISE and Spitzer areshown 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 areshown as solid curves: a pure hydrogen atmosphere model (red), a 50% hydrogen, 50%
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helium model (blue), a pure helium model (gold), and a blackbody curve (black). Noneof the SED models capture all of the SED’s features, but all four yield mostly consistenteffective 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 incomparison with three atmosphere models: a pure hydrogen model (red), a 50%hydrogen, 50% helium model (blue), and a pure helium model (gold). We disfavour apure hydrogen atmosphere on the basis of our non-detection of an Hα feature in ourLRS2 spectra, but otherwise remain uncertain about the precise composition of theenvelope 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 transitfit (with circular orbits enforced) and histograms of the marginalized posteriorprobability distributions for each parameter. For clarity, we have plotted correlationswith the inclination angle i instead of the fit parameter cosi and subtract the median timeof 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 andSpitzer photometric jitter terms because these are nuisance parameters that showed nocorrelation with the other physical parameters.
Extended Data Fig. 6 Posterior probability distributions of transit parameterswhen eccentric orbits are allowed.This ‘corner-plot’ shows correlations between pairs of parameters in our MCMC transitfit (allowing eccentric orbits) and histograms of the marginalized posterior probabilitydistributions for each parameter. This plot shows a subset of the parameters thatcorrelate with the orbital eccentricity. For clarity, we have plotted correlations with theeccentricity e, argument of periastron w and orbital inclination i instead of the fitparameters \(\sqrt{e}\cos \,\omega \), \(\sqrt{e}\sin \,\omega \) and δ.
Extended Data Fig. 7 Hα equivalent width for G 229-20 A/B compared toother nearby M dwarfs.The histogram shows the Hα equivalent widths for a large sample of M dwarfs withsimilar spectral types from the Sloan Digital Sky Survey . G 229-20 A/B (shown as ablue arrow) has a lower than average Hα equivalent width, but falls well within thedistribution of field M dwarfs.
Extended Data Fig. 8 Theoretical relationships between the star’s radius andthe mass of its core.We show MIST evolution tracks in the radius–core mass plane for solar compositionmodels 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 wherethe envelope has been exhausted by the AGB wind.
Extended Data Fig. 9 The minimum value of the efficiency parameter αλCErequired for WD 1856 b to form via common-envelope evolution as a functionof 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 ifthe 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% ofthe 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 tooslowly for the system to have left the main sequence more than 5.85 Gyr ago and are notviable 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-envelopephase. Before mass is lost during the AGB phase, it is difficult for WD 1856 b to eject the
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common envelope, but it is possible that WD 1856 b could have ejected its progenitor’senvelope if the common-envelope phase began after the progenitor reached the AGB. Wehave smoothed the lower two curves to remove some unphysical scatter that is probablydue to numerical artefacts in the model grids.
Extended Data Table 1 Comparison of white dwarf parameters from differentatmosphere models
Supplementary information
Supplementary DataThis file contains a comma separated value file with spectroscopic data on the M-dwarfcompanions.
.Peer Review File
Source data
Source Data Fig. 2Source Data Extended Data Fig. 2
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Vanderburg, A., Rappaport, S.A., Xu, S. et al. A giant planet candidate transiting a whitedwarf. Nature 585, 363–367 (2020). https://doi.org/10.1038/s41586-020-2713-y
Received 16 March 2020 Accepted 15 July 2020 Published 16 September 2020
Issue Date 17 September 2020 DOI https://doi.org/10.1038/s41586-020-2713-y
Subjects Exoplanets • Stellar evolution
Further reading
Planet discovered transiting a dead star
Steven Parsons
Nature (2020)
Nature ISSN 1476-4687 (online)
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