RT @McGill_AdAstra: “The [2017 OF201] object is unstable, so it means virtually nothing for the Planet 9 hypothesis. [The simulations show]….

RT @NatureAstronomy: By fusing constraints from satellite dynamics and spin angular momentum, @kbatygin & Adams show that young Jupiter had….

If you’re interested in more details, check out the @Caltech press release: as well as the paper on the NatureAstronomy site ( or the arxiv (.

High heat flux implies a powerful primordial magnetic field (~0.2 kGauss). Balancing this with disk accretion sets the truncation radius, indicating Jupiter accreted gas at roughly ~1 Jupiter mass per Myr.

A giant planet's radius ultimately relates to interior entropy and heat flux. Interior modeling gives primordial Jupiter an entropy ~10.6 k_B per baryon and effective temp ~1400 K—consistent with a warm-start scenario.

The disk's edge fixes Jupiter’s early spin (~1 day rotation). Since spin angular momentum is conserved after disk dissipation, we can rearrange the relationship to calculate Jupiter’s primordial radius. Turns out, it was about twice its current size.

Matching these subtle orbital kicks to observed inclinations lets us pinpoint Io's original location (first figured out by Hamilton et al. 2001), tracing where Jupiter’s primordial disk ended.

Everyone knows Io and the Galilean moons. But Jupiter also hosts smaller natural moons -- most notably, Amalthea and Thebe. Their inclined orbits encode clues from past resonances swept outward by migrating Io.

More than any other planet, Jupiter played a key role in shaping our solar system. Yet details of its early physical state are elusive. In a new paper with Fred Adams, we reconstruct Jupiter's primordial state at the end of the solar nebula’s lifetime: 🧵

RT @jcbastro: Can FU Orionis outbursts scorch planets into becoming iron-rich and ultra-short-period? We model how extreme heat & turbulenc….

Catch us live and unplugged on UCLA Radio today! We're playing a special acoustic set -- tune in at @ 8pm pacific and vibe with us.

Years ago, I worked on Ohmic dissipation as an explanation for hot Jupiter inflation. But perhaps this mechanism is more broadly relevant than we appreciated back in '10. WASP-107b might offer a key window into how OD affects the internal evolution of lower-mass inflated planets.

Under reasonable assumptions for wind speeds (~250 m/s at 1 bar), magnetic field strength (~70 G), and atmospheric ionization (dominated by alkali metals), Ohmic dissipation naturally reproduces the observed internal heat flux of WASP-107b (~400 K effective internal temperature).

What’s going on, then? In the paper, I argue Ohmic dissipation provides a promising alternative. Atmospheric winds interacting with the planet’s magnetic field induce global electric currents, generating enough internal heat to explain WASP-107b’s inflated radius.

Could the RV-detected companion planet WASP-107c save the day? No luck—independent of their mutual orbital inclination, gravitational perturbations from WASP-107c can't sustain the necessary eccentricity over the system's multi-billion-year lifetime.

Previous studies linked this internal heat to tidal heating, driven by WASP-107b’s slight orbital eccentricity. But I find this implausible: maintaining the observed luminosity demands an extremely low tidal quality factor (Q~30), quickly circularizing the planet’s orbit.

WASP-107b is remarkable: Jupiter-sized radius, yet sub-Saturn mass (~30 Earth masses). Recent JWST data show significant methane depletion, pointing to high atmospheric metallicity and an unexpectedly large internal heat flux.

Among the surprises of the galactic planetary census are “super-puffs” — low-mass planets with giant radii. One of the best characterized (and most mysterious) is WASP-107b. It is also the subject of my new paper: Brief thread below.

a few pix from gig @TheMixxPasadena