About

David Charbonneau is the Fred Kavli Professor of Astrophysics and the Chair of the Department of Astronomy at Harvard University. His research interests focus on the detection and characterization of extrasolar planets, with the overarching goal of studying inhabited worlds. In pursuit of this goal, he also engages in the development of novel ground-based and space-based instrumentation, as well as studies of stellar astrophysics. His work aims to advance understanding of planetary systems beyond our own and to contribute to the broader field of astrophysics through innovative observational techniques and instrumentation.

Research topics

• Astronomy
• Physics
• Computer Science
• Computer Security
• Artificial Intelligence
• Astrophysics
• Astrobiology
• Mathematics

Selected publications

• Spot-crossing Variations Confirm a Misaligned Orbit for a Planet Transiting an M Dwarf

  The Astronomical Journal · 2025-09-02 · 3 citations

  articleOpen access

  Abstract TOI-3884 b is an unusual 6.4 R ⊕ planet orbiting an M4 host, whose transits display large and persistent spot-crossing events. We used the Tierras Observatory to monitor both the long-term photometric variability of TOI-3884 and changes in the spot-crossing events across multiple transits of the planet. We show that the star rotates with a period of 11.020 ± 0.015 days. We simultaneously model the rotational modulation of the star and variations in transit shapes that arise due to rotation of the spot, allowing us to determine the true stellar obliquity, ψ ⋆ . The data are best described by a planet on a misaligned orbit around a highly inclined star ( ψ ⋆ = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>77</mml:mn> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> <mml:mrow> <mml:mn>5</mml:mn> </mml:mrow> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2</mml:mn> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:math> ; i ⋆ = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>22</mml:mn> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> <mml:mrow> <mml:mn>6</mml:mn> </mml:mrow> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1</mml:mn> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> <mml:mrow> <mml:mn>8</mml:mn> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:math> ) that hosts a large polar starspot ( r spot = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>31</mml:mn> <mml:mo>.</mml:mo> <mml:msup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>∘</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> <mml:mo>.</mml:mo> <mml:msup> <mml:mrow> <mml:mn>9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>∘</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2</mml:mn> <mml:mo>.</mml:mo> <mml:msup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>∘</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> </mml:msubsup> </mml:math> ; λ spot = 80 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> </mml:math> 5 ± 1 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> </mml:math> 2). Archival photometry from the Zwicky Transient Facility suggests that this polar spot has persisted on TOI-3884 for at least seven years. The TOI-3884 system provides a benchmark for studying the evolution of a polar spot on an M dwarf.

  PublisherDOI

• HD 35843: A Sun-like star hosting a long period sub-Neptune and inner super-Earth

  ArXiv.org · 2025-05-01

  preprintOpen access

  We report the discovery and confirmation of two planets orbiting the metal-poor Sun-like star, HD 35843 (TOI 4189). HD 35843 c is a temperate sub-Neptune transiting planet with an orbital period of 46.96 days that was first identified by Planet Hunters TESS. We combine data from TESS and follow-up observations to rule out false-positive scenarios and validate the planet. We then use ESPRESSO radial velocities to confirm the planetary nature and characterize the planet's mass and orbit. Further analysis of these RVs reveals the presence of an additional planet, HD 35843 b, with a period of 9.90 days and a minimum mass of $5.84\pm0.84$ $M_{\oplus}$. For HD 35843 c, a joint photometric and spectroscopic analysis yields a radius of $2.54 \pm 0.08 R_{\oplus}$, a mass of $11.32 \pm 1.60 M_{\oplus}$, and an orbital eccentricity of $e = 0.15\pm0.07$. With a bulk density of $3.80 \pm 0.70$ g/cm$^3$, the planet might be rocky with a substantial H$_2$ atmosphere or it might be a ``water world". With an equilibrium temperature of $\sim$480 K, HD 35843 c is among the coolest $\sim 5\%$ of planets discovered by TESS. Combined with the host star's relative brightness (V= 9.4), HD 35843 c is a promising target for atmospheric characterization that will probe this sparse population of temperate sub-Neptunes.

  PublisherOA PDFDOI

• TOI-6324b: An Earth-Mass Ultra-Short-Period Planet Transiting a Nearby M Dwarf

  ArXiv.org · 2025-02-22

  preprintOpen access

  We report the confirmation of TOI-6324 b, an Earth-sized (1.059 $\pm$ 0.041 R$_\oplus$) ultra-short-period (USP) planet orbiting a nearby ($\sim$20 pc) M dwarf. Using the newly commissioned Keck Planet Finder (KPF) spectrograph, we have measured the mass of TOI-6324 b 1.17 $\pm$ 0.22 M$_\oplus$. Because of its extremely short orbit of just $\sim$6.7 hours, TOI-6324 b is intensely irradiated by its M dwarf host, and is expected to be stripped of any thick, H/He envelope. We were able to constrain its interior composition and found an iron core mass fraction (CMF = 27$\pm$37%) consistent with that of Earth ($\sim$33%) and other confirmed USPs. TOI-6324 b is the closest to Earth-sized USP confirmed to date. TOI-6324 b is a promising target for JWST phase curve and secondary eclipse observations (Emission Spectroscopy Metric = 25) which may reveal its surface mineralogy, day-night temperature contrast, and possible tidal deformation. From 7 sectors of TESS data, we report a tentative detection of the optical phase curve variation with an amplitude of 42$\pm$28 ppm.

  PublisherOA PDFDOI

• The Super-puff WASP-193 b is on a Well-aligned Orbit*

  The Astronomical Journal · 2025-03-25 · 1 citations

  articleOpen access

  Abstract The “super-puffs” are a population of planets that have masses comparable to that of Neptune but radii similar to Jupiter, leading to extremely low bulk densities ( ρ p ≲ 0.2 g cm −3 ) that are not easily explained by standard core accretion models. Interestingly, several of these super-puffs are found in orbits significantly misaligned with their host stars’ spin axes, indicating past dynamical excitation that may be connected to their low densities. Here, we present new Magellan/Planet Finder Spectrograph radial velocity measurements of WASP-193, a late F star hosting one of the least dense transiting planets known to date ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.11</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.034</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.029</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em"/> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">J</mml:mi> </mml:mrow> </mml:msub> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>1.31</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.048</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.056</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em"/> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">J</mml:mi> </mml:mrow> </mml:msub> </mml:math> , ρ p = 0.060 ± 0.019 g cm −3 ). We refine the bulk properties of WASP-193 b and use interior structure models to determine that the planet can be explained if it consists of roughly equal amounts of metals and H/He, with a metal fraction of Z = 0.42. The planet is likely substantially reinflated due to its host star’s evolution, and expected to be actively undergoing mass loss. We also measure the projected stellar obliquity using the Rossiter–McLaughlin effect, finding that WASP-193 b is on an orbit well aligned with the stellar equator, with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>λ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>15</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>16</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> degrees. WASP-193 b is the first Jupiter-sized super-puff on a relatively well-aligned orbit, suggesting a diversity of formation pathways for this population of planets.

  PublisherDOI

• The True Stellar Obliquity of a Sub-Saturn Planet from the Tierras Observatory and KPF

  ArXiv.org · 2025-05-06

  preprintOpen access

  We measure the true obliquity of TOI-2364, a K dwarf with a sub-Saturn-mass ($M_p = 0.18\,M_J$) transiting planet on the upper edge of the hot Neptune desert. We used new Rossiter-McLaughlin observations gathered with the Keck Planet Finder to measure the sky-projected obliquity $λ= 7$$^\circ$$^{+10^\circ}_{-11^\circ}$. Combined with a stellar rotation period of $23.47\pm0.29$ days measured with photometry from the Tierras Observatory, this yields a stellar inclination of $90^{\circ} \pm 13^{\circ}$ and a true obliquity $ψ= 15.6$$^\circ$$^{+7.7^\circ}_{-7.3^\circ}$, indicating that the planet's orbit is well aligned with the rotation axis of its host star. The determination of $ψ$ is important for investigating a potential bimodality in the orbits of short-period sub-Saturns around cool stars, which tend to be either aligned with or perpendicular to their host stars' spin axes.

  PublisherOA PDFDOI

• A New Brown Dwarf Orbiting an M Star and an Investigation of the Eccentricity Distribution of Transiting Long-period Brown Dwarfs

  The Astrophysical Journal Letters · 2025-08-01 · 2 citations

  articleOpen accessCorresponding

  Abstract The orbital eccentricities of brown dwarfs encode valuable information on their formation and evolution history, providing insights into whether they resemble giant planets or stellar binaries. Here, we report the discovery of TOI-5575 b, a long-period, massive brown dwarf orbiting a low-mass M5V star (0.21 ± 0.02 M ⊙ ) delivered by the TESS mission. The companion has a mass and radius of 72.4 ± 4.1 M J and 0.84 ± 0.07 R J on a 32 day moderately eccentric orbit ( e = 0.187 ± 0.002), making it the third-highest mass ratio transiting brown dwarf system known to date. Building on this discovery, we investigate the eccentricity distributions of a sample of transiting long-period (10 days ≤ P ≲ 1000 days, ∼0.1–1.5 au) giant planets, brown dwarfs, and low-mass stars. We find that brown dwarfs exhibit an eccentricity behavior nearly identical to that of giant planets: a preference for circular orbits with a long tail toward high eccentricities. Such a trend contrasts sharply with direct imaging findings, where cold (5–100 au) brown dwarfs and giant planets display distinct eccentricity distributions. Our results suggest that transiting long-period brown dwarfs and giant planets probably (1) form in different routes at exterior orbits but undergo analogous dynamical evolution processes and migrate inward or (2) both contain two subgroups, one with widely spread eccentricities while the other has circular orbits, that jointly sculpt the eccentricity distributions. The low-mass star systems appear to be a distinctive population, showing a peak eccentricity at about 0.3, akin to more massive stellar binaries.

  PublisherDOI

• TOI-6324 b: An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf

  The Astrophysical Journal Letters · 2025-04-16 · 2 citations

  articleOpen access

  Abstract We report the confirmation of TOI-6324 b, an Earth-sized (1.059 ± 0.041 R ⊕ ) ultra-short-period (USP) planet orbiting a nearby (∼20 pc) M dwarf. Using the newly commissioned Keck Planet Finder spectrograph, we have measured the mass of TOI-6324 b 1.17 ± 0.22 M ⊕ . Because of its extremely short orbit of just ∼6.7 hr, TOI-6324 b is intensely irradiated by its M dwarf host and is expected to be stripped of any thick H/He envelope. We were able to constrain its interior composition and found an iron-core mass fraction (CMF = 27% ± 37%) consistent with that of Earth (∼33%) and other confirmed USPs. TOI-6324 b is the closest to an Earth-sized USP confirmed to date. TOI-6324 b is a promising target for JWST phase-curve and secondary eclipse observations (emission spectroscopy metric = 25), which may reveal its surface mineralogy, day–night temperature contrast, and possible tidal deformation. From seven sectors of TESS data, we report a tentative detection of the optical phase-curve variation with an amplitude of 42 ± 28 ppm.

  PublisherOA PDFDOI

• Discovery and Characterization of an Eccentric, Warm Saturn Transiting the Solar Analog TOI-4994*

  The Astronomical Journal · 2025-01-15 · 2 citations

  articleOpen access

  Abstract We present the detection and characterization of TOI-4994b (TIC 277128619b), a warm Saturn-sized planet discovered by the NASA Transiting Exoplanet Survey Satellite. TOI-4994b transits a G-type star ( V = 12.6 mag) with a mass, radius, and effective temperature of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>1.00</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.061</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.064</mml:mn> </mml:mrow> </mml:msubsup> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>1.05</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.037</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.040</mml:mn> </mml:mrow> </mml:msubsup> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> , and T eff = 5640 ± 110 K. We obtained follow-up ground-based photometry from the Las Cumbres Observatory and the Antarctic Search for Transiting ExoPlanets telescopes, and we confirmed the planetary nature of TOI-4994b with multiple radial velocity observations from the Planet Finder Spectrograph, CHIRON, High Accuracy Radial velocity Planet Searcher, Fiber-fed Extended Range Optical Spectrograph, and CORALIE instruments. From a global fit to the photometry and radial velocities, we determine that TOI-4994b is in a 21.5 day eccentric orbit ( e = 0.32 ± 0.04) and has a mass of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>P</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.28</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.034</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.037</mml:mn> </mml:mrow> </mml:msubsup> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>J</mml:mi> </mml:mrow> </mml:msub> </mml:math> , a radius of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>P</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.76</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.027</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.030</mml:mn> </mml:mrow> </mml:msubsup> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>J</mml:mi> </mml:mrow> </mml:msub> </mml:math> , and a Saturn-like bulk density of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>ρ</mml:mi> <mml:mi>p</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.7</mml:mn> <mml:msubsup> <mml:mn>8</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.14</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">g</mml:mi> <mml:mspace width="0.25em"/> <mml:msup> <mml:mi>cm</mml:mi> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> . We find that TOI-4994 is a potentially viable candidate for follow-up stellar obliquity measurements. TOI-4994b joins the small sample of warm Saturn analogs and thus sheds light on our understanding of these rare and unique worlds.

  PublisherDOI

• The Receding Cosmic Shoreline of Mid-to-late M Dwarfs: Measurements of Active Lifetimes Worsen Challenges for Atmosphere Retention by Rocky Exoplanets

  The Astrophysical Journal Letters · 2025-06-03 · 16 citations

  articleOpen access

  Abstract Detecting and characterizing the atmospheres of terrestrial exoplanets is a key goal of exoplanetary astronomy, one that may now be within reach given the upcoming campaign to conduct a large-scale survey of rocky M-dwarf worlds with the James Webb Space Telescope. It is imperative that we understand where known planets sit relative to the cosmic shoreline—the boundary between planets that have retained atmospheres and those that have not. Previous works modeled the historic X-ray and ultraviolet (XUV) radiation received by mid-to-late M-dwarf planets using a scaling relation calibrated using more massive stars, but fully convective M dwarfs display unique rotation/activity histories that differ from Sun-like stars and early M dwarfs. We synthesize observations of the active lifetimes of mid-to-late M dwarfs to present an updated estimate of their historic XUV fluence. For known planets of inactive, mid-to-late M dwarfs, we calculate a historic XUV fluence that is 2.1–3.1 times the canonical XUV scaling relation on average, with the larger value including corrections for the pre-main-sequence phase and energetic flares. We find that only the largest terrestrial planets known to orbit mid-to-late M dwarfs are likely to have retained atmospheres within the cosmic shoreline paradigm. Our calculations may help to guide the selection of targets for JWST and may prove useful in interpreting the results; to this end, we define a novel atmosphere retention metric (ARM) that indicates the distance between a planet and the cosmic shoreline, and tabulate the ARM for known mid-to-late M-dwarf planets.

  PublisherDOI

• HD 35843: A Sun-like Star Hosting a Long-period Sub-Neptune and Inner Super-Earth

  The Astronomical Journal · 2025-07-22 · 1 citations

  articleOpen access

  Abstract We report the discovery and confirmation of two planets orbiting the metal-poor Sun-like star HD 35843 (TOI 4189). HD 35843 c is a temperate sub-Neptune transiting planet with an orbital period of 46.96 days that was first identified by Planet Hunters TESS. We combine data from TESS and follow-up observations to rule out false-positive scenarios and validate the planet. We then use ESPRESSO radial velocities (RVs) to confirm the planetary nature and characterize the planet’s mass and orbit. Further analysis of these RVs reveals the presence of an additional planet, HD 35843 b, with a period of 9.90 days and a minimum mass of 5.84 ± 0.84 M ⊕ . For HD 35843 c, a joint photometric and spectroscopic analysis yields a radius of 2.54 ± 0.08 R ⊕ , a mass of 11.32 ± 1.60 M ⊕ , and an orbital eccentricity of e = 0.15 ± 0.07. With a bulk density of 3.80 ± 0.70 g cm −3 , the planet might be rocky with a substantial H 2 atmosphere or it might be a “water world.” With an equilibrium temperature of ∼480 K, HD 35843 c is among the coolest ∼5% of planets discovered by TESS. Combined with the host star’s relative brightness ( V = 9.4), HD 35843 c is a promising target for atmospheric characterization that will probe this sparse population of temperate sub-Neptunes.

  PublisherDOI

Recent grants

• 2009 Waterman Award

  NSF · $500k · 2010–2012

• The MEarth Project: A Transit Search for Rocky Planets in the Habitable Zones of Low-mass Stars

  NSF · $557k · 2008–2011

• The MEarth Project: An All Sky Survey of the Closest Low-mass Stars to Uncover the Very Best Terrestrial Exoplanets for Further Study

  NSF · $500k · 2016–2019

• The MEarth Project: An All-sky Transit Search for Rocky Planets in the Habitable Zones of Low-mass Stars

  NSF · $652k · 2011–2014

Frequent coauthors

• David W. Latham

  269 shared

• Sara Seager

  Massachusetts Institute of Technology

  234 shared

• Timothy M. Brown

  Brigham Young University

  164 shared

• Jonathan Irwin

  163 shared

• Lars A. Buchhave

  155 shared

• Jon M. Jenkins

  153 shared

• S. Udry

  139 shared

• David R. Ciardi

  NASA Exoplanet Science Institute

  135 shared

Labs

• Charbonneau Astronomy GroupPI

  Exoplanets and Stellar Physics at Harvard University

Education

• Ph.D., Astronomy

  Harvard University

  1996

• B.A., Physics

  Princeton University

  1991