About

Professor Jeremy Goodman received A.B. and A.M. degrees in physics from Harvard in 1979, and his Ph.D. in Astrophysics from Princeton in 1983. After postdoctoral fellowships at Caltech and the Institute for Advanced Study, he joined the Princeton faculty in 1988. Prof. Goodman is broadly interested in theoretical astrophysics, especially astrophysical fluid dynamics and magnetohydrodynamics, preferring analytic or semi-analytic work over fully numerical approaches. His favorite applications include accretion disks of protostars and quasars, tides in stars and extrasolar planets, planetesimal formation, and gamma-ray bursts. For his Ph.D. and several years thereafter, he specialized in the N-body dynamics of dense stellar systems. Prof. Goodman is also associated as a theorist with experimental efforts at the Princeton Plasma Physics Laboratory to study hydrodynamic and MHD instabilities relevant to astrophysics.

Research topics

• Physics
• Astrophysics
• Mechanics
• Astronomy
• Classical mechanics

Selected publications

• On the Missing Red Giants near the Galactic Center

  ArXiv.org · 2026-01-22

  articleOpen accessSenior author

  There is a long-acknowledged deficiency of bright red giants relative to fainter old stars within a few arc seconds of Sgr A*. We explore whether this could be due to tidal stripping by the central black hole. This requires putting the stars onto highly eccentric orbits, for which we evaluate diffusion by both scalar resonant and non-resonant relaxation of the orbital angular momentum. We conclude that tidal stripping does not discriminate sufficiently between main-sequence and red giant stars. While the tidal loss cone increases with stellar radius, the rate of diffusion into the loss cone increases only logarithmically, whereas the lifetime on the red giant branch decreases more rapidly than $R_*^{-1}$. In agreement with previous studies, we find that stellar collisions are a more likely explanation for the deficiency of bright red giants relative to fainter ones.

  PublisherOA PDF

• On the Missing Red Giants near the Galactic Center

  The Astrophysical Journal · 2026-04-08 · 1 citations

  articleOpen accessSenior author

  Abstract There is a long-acknowledged deficiency of bright red giants relative to fainter old stars within a few arcseconds of Sgr A*. We explore whether this could be due to tidal stripping by the central black hole. This requires putting the stars onto highly eccentric orbits, for which we evaluate diffusion by both scalar resonant and nonresonant relaxation of the orbital angular momentum. We conclude that tidal stripping does not discriminate sufficiently between main-sequence and red giant stars. While the tidal loss cone increases with stellar radius, the rate of diffusion into the loss cone increases only logarithmically, whereas the lifetime on the red giant branch decreases more rapidly than <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . In agreement with previous studies, we find that stellar collisions are a more likely explanation for the deficiency of bright red giants relative to fainter ones.

  PublisherDOI

• Spectral Appearance of Self-gravitating Disks Powered by Stellar Objects: Universal Effective Temperature in the Optical Continuum and Application to Little Red Dots

  Open MIND · 2026-02-06

  preprintSenior author

  We revisit the spectral appearance of extended self-gravitating accretion disks surrounding compact central objects such as supermassive black holes. Using dust-poor opacities, we show that all optically thick disk solutions possess a universal outer effective temperature of $T_{\rm eff}\sim 4000-4500$K, closely resembling compact, high-redshift sources known as Little Red Dots (LRDs). Assuming the extended disk is primarily heated by stellar sources, this ``disk Hayashi limit" fixes the dominant optical continuum temperature of the disk spectrum independent of accretion rate $\dot{M}$, central mass $M_\bullet$, and disk viscosity $α$, and removes the parameter-tuning required in previous disk interpretations of LRDs. The formation and accretion of embedded stellar objects can both power the emission of the outer disk and hollow out the inner disk, suppressing variable UV/X-ray associated with a standard quasar. The resulting disk emission is dominated by a luminous optical continuum while a separate, non-variable UV component arises from stellar populations on the nuclear to galaxy scale. We map the optimal region of parameter space for such systems and show that LRD-like appearances naturally emerge for $\dot{M}/α\gtrsim 0.1 M_\odot /{\rm yr}$, a threshold insensitive to $M_\bullet$, below which the system may transition into classical non-self-gravitating AGN disks, potentially a later evolution stage. We expect this transition to be accompanied by the enhancement of metallicity and production of dust, giving rise to far infrared emission. This picture offers a physically motivated and quantitative framework connecting LRDs with AGNs and their associated nuclear stellar population.

  DOI

• Spectral Appearance of Self-gravitating AGN Disks Powered by Stellar Objects: Universal Effective Temperature in the Optical Continuum and Application to Little Red Dots

  arXiv (Cornell University) · 2026-02-06

  articleOpen accessSenior author

  We revisit the spectral appearance of extended self-gravitating accretion disks surrounding compact central objects such as supermassive black holes. Using dust-poor opacities, we show that all optically thick disk solutions possess a universal outer effective temperature of $T_{\rm eff}\sim 4000-4500$K, closely resembling compact, high-redshift sources known as Little Red Dots (LRDs). Assuming the extended disk is primarily heated by stellar sources, this ``disk Hayashi limit" fixes the dominant optical continuum temperature of the disk spectrum independent of accretion rate $\dot{M}$, central mass $M_\bullet$, and disk viscosity $α$, and removes the parameter-tuning required in previous disk interpretations of LRDs. The formation and accretion of embedded stellar objects can both power the emission of the outer disk and hollow out the inner disk, suppressing variable UV/X-ray associated with a standard quasar. The resulting disk emission is dominated by a luminous optical continuum while a separate, non-variable UV component arises from stellar populations on the nuclear to galaxy scale. We map the optimal region of parameter space for such systems and show that LRD-like appearances naturally emerge for $\dot{M}/α\gtrsim 0.1 M_\odot /{\rm yr}$, a threshold insensitive to $M_\bullet$, below which the system may transition into classical non-self-gravitating AGN disks, potentially a later evolution stage. We expect this transition to be accompanied by the enhancement of metallicity and production of dust, giving rise to far infrared emission. This picture offers a physically motivated and quantitative framework connecting LRDs with AGNs and their associated nuclear stellar population.

  PublisherOA PDF

• On the Missing Red Giants near the Galactic Center

  arXiv (Cornell University) · 2026-01-22

  preprintOpen accessSenior author

  There is a long-acknowledged deficiency of bright red giants relative to fainter old stars within a few arc seconds of Sgr A*. We explore whether this could be due to tidal stripping by the central black hole. This requires putting the stars onto highly eccentric orbits, for which we evaluate diffusion by both scalar resonant and non-resonant relaxation of the orbital angular momentum. We conclude that tidal stripping does not discriminate sufficiently between main-sequence and red giant stars. While the tidal loss cone increases with stellar radius, the rate of diffusion into the loss cone increases only logarithmically, whereas the lifetime on the red giant branch decreases more rapidly than $R_*^{-1}$. In agreement with previous studies, we find that stellar collisions are a more likely explanation for the deficiency of bright red giants relative to fainter ones.

  PublisherDOI

• Accretion of AGN Stars under Influence of Disk Geometry

  ArXiv.org · 2025-05-20

  preprintOpen accessSenior author

  Massive stars can form within or be captured by AGN disks, influencing both the thermal structure and metallicity of the disk environment. In a previous work, we investigated isotropic accretion onto massive stars from a gas-rich, high-entropy background. Here, we consider a more realistic scenario by incorporating the stratified geometry of the background disk in our 3D radiation hydrodynamic simulatons. We find that accretion remains relatively isotropic when the disk is hot enough and the scale height is thicker than the accretion flow's nominal supersonic critical radius $R{crit}$ (sub-thermal). However, when the disk becomes cold, the accretion flow becomes significantly anisotropic (super-thermal). Escaping stellar and accretion luminosity can drive super-Eddington outflows in the polar region, while rapid accretion is sustained along the midplane. Eventually, the effective cross-section is constrained by the Hill radius and the disk scale height rather than the critical radius when the disk is cold enough. For our setup (stellar mass $\sim 50 M\odot$ and background density $ρ\sim 10^{-10}$ g/cm$^3$) the accretion rates is capped below $\sim 0.02M\odot$/year and the effective accretion parameter $α\sim 10^{-1}$ over disk temperature range $3 - 7 \times 10^4$ K. Spiral arms facilitate inward mass flux by driving outward angular momentum transport. Gap-opening effects may further reduce the long-term accretion rate, albeit to confirm which requires global simulations evolved over much longer viscous timescales.

  PublisherOA PDFDOI

• Photoevaporation from Inner Protoplanetary Disks Confronted with Observations

  The Astrophysical Journal · 2025-03-07 · 2 citations

  articleOpen accessSenior author

  Abstract The decades-long explorations on the dispersal of protoplanetary disks involve many debates about photoevaporation versus magnetized wind launching mechanisms. This work argues that the observed winds originating from the inner disk ( R ≲ 0.3 au) cannot be explained by the photoevaporative mechanism. Heating the gas to proper temperatures for the observed forbidden lines (especially [O i ] λ 6300) will overionize it, suppressing the abundances of species responsible for the emission. Even if adequate emissivity is achieved by fine-tuning the physical parameters, the total cooling power will become unattainable by the radiative heating alone. Energy conservation requires the presumed photoevaporative winds to be heated to ≳10 5 K when launched from inner disks. However, due to efficient thermal accommodation with dust grains and cooling processes at high densities, X-ray irradiation at energies above 1 keV cannot efficiently launch winds in the first place because of its high penetration. Some studies claiming X-ray wind launching have oversimplified the thermochemical couplings. Confirmed by semianalytic integrations of thermochemical fluid structures, such high ionizations contradict the observed emission of neutral and singly ionized atoms from the winds originating from the inner disks.

  PublisherDOI

• Surprising Spin–Orbit Resonances of Rocky Planets

  The Astrophysical Journal · 2025-06-23 · 3 citations

  articleOpen accessSenior authorCorresponding

  Abstract Recent works suggest that, in multiplanetary systems, a close-in exoplanet can sometimes avoid becoming tidally locked to its host star if it is captured into a secular spin–orbit resonance with a companion planet. In such a resonance, the planet remains at a subsynchronous spin rate and an appreciable obliquity (the planet’s spin–orbit misalignment angle). However, many of these works have only considered planets with fluid-like rheologies. Recent observations suggest that planets up to a few Earth masses may be rocky and thus may have an appreciable rigidity. In this work, we study the spin–orbit dynamics of such rigid planets using a linear dissipative tidal model and not enforcing principal-axis rotation about the body’s shortest principal axis. We identify a new class of spin–orbit resonances when the planet spins at twice its orbital frequency. These resonances exist at nonzero obliquity and spontaneously excite non-principal-axis rotation upon resonance capture. While these resonances eventually disappear as tidal dissipation damps the obliquity to zero (and the body returns to principal-axis rotation), they still modify the spin evolutionary history of the planet. Such resonances may enhance the prevalence of secular spin–orbit resonances in exoplanetary systems.

  PublisherDOI

• Accretion of Active Galactic Nucleus Stars Under the Influence of Disk Geometry

  The Astrophysical Journal · 2025-07-08 · 5 citations

  articleOpen accessSenior author

  Abstract Massive stars can form within or be captured by active galactic nucleus disks, influencing both the thermal structure and metallicity of the disk environment. In a previous work, we investigated isotropic accretion onto massive stars from a gas-rich, high-entropy background. Here, we consider a more realistic scenario, by incorporating the stratified geometry of the background disk in our 3D radiation hydrodynamic simulations. We find that the accretion remains relatively isotropic when the disk is hot enough and the scale height is thicker than the accretion flow’s nominal supersonic critical radius R crit (subthermal). However, when the disk becomes cold, the accretion flow becomes significantly anisotropic (superthermal). Escaping stellar and accretion luminosity can drive super-Eddington outflows in the polar region, while rapid accretion is sustained along the midplane. Eventually, the effective cross section is constrained by the Hill radius and the disk scale height rather than the critical radius when the disk is cold enough. For our setup (stellar mass ∼50 M ⊙ and background density ρ ∼ 10 −10 g cm −3 ), the accretion rate is capped below ∼0.02 M ⊙ yr −1 and the effective accretion parameter α ∼ 10 −1 over the disk temperature range 3–7 × 10 4 K. Spiral arms facilitate inward mass flux by driving outward angular momentum transport. Gap-opening effects may further reduce the long-term accretion rate, although to confirm this would require global simulations evolved over much longer viscous timescales.

  PublisherDOI

• Observation of Nonaxisymmetric Standard Magnetorotational Instability Induced by a Free-Shear Layer

  Physical Review Letters · 2025-03-31 · 5 citations

  articleOpen access

  The standard magnetorotational instability (SMRI) with a magnetic field component parallel to the rotation axis is widely believed to be responsible for the fast accretion in astronomical disks. In conventional base flows with a Keplerian profile or an ideal Couette profile, most studies focus on axisymmetric SMRI, since excitation of nonaxisymmetric SMRI in such flows requires a magnetic Reynolds number (Rm) more than an order of magnitude larger. Here, we report that, in a magnetized Taylor-Couette flow, nonaxisymmetric SMRI with an azimuthal mode number m=1 can be triggered by a free-shear layer in the base flow at Rm≳1, the same threshold as for axisymmetric SMRI. Global linear analysis reveals that the free-shear layer reduces the required Rm, possibly by introducing an extremum in the vorticity of the base flow. Nonlinear simulations validate the results from linear analysis and confirm that a novel instability recently discovered experimentally [Wang et al., Nat. Commun. 13, 4679 (2022)NCAOBW2041-172310.1038/s41467-022-32278-0] is the nonaxisymmetric m=1 SMRI. Our finding has astronomical implications as free-shear layers are ubiquitous in celestial systems, such as the disk-star boundary layer, the solar tachocline, and the edge of planet-opened gaps in protoplanetary disks.

  PublisherDOI

Recent grants

• Experiments in Magnetohydrodynamic and Hydrodynamic Instabilities of Astrophysical Interest

  NSF · $488k · 2013–2019

• Laboratory Study of Magnetorotational Instability and Hydrodynamic Stability at Large Reynolds Numbers in a Short Couette Flow

  NSF · $543k · 2006–2011

• Tides and Atmospheres for Hot Jupiters

  NSF · $237k · 2007–2012

• Laboratory Search for Magnetorotational Instability

  NSF · $502k · 2021–2025

Frequent coauthors

• Hantao Ji

  Princeton Plasma Physics Laboratory

  89 shared

• E.P. Gilson

  Princeton Plasma Physics Laboratory

  33 shared

• E. Schartman

  26 shared

• F. Ebrahimi

  25 shared

• M. J. Burin

  California State University, San Marcos

  20 shared

• Kyle Caspary

  Princeton University

  18 shared

• D. Pankow

  12 shared

• Brenda Frye

  12 shared

Education

• Ph.D., Astrophysical Sciences

  Princeton University

• A.B., A.M., Physics

  Harvard University