I decided to give planetary rotation periods another look. What I've been doing so far is assigning anything with an orbital period < 300 days a tidal equilibrium spin period. This is pretty blunt-force and I've known for a while it could be done better, and I wanted to implement a more tidally-driven model. I'm afraid I can't quite make sense of the tidal spin-down equations I've seen so far, but I've found some formulas on the worldbuildingpasta site that are pretty explicit.

An important consideration here is the system's age. I don't know the ages of many systems, and I've been assuming 5 Gyr for any system without a known age. This was driven by the need to have something other than zero for the internal heating contribution to the temperature/Sudarsky class.

**Maxine** was helpful in guiding me to work by

Hurley, et al. (2000) that provides an equation for the main sequence lifetime of a star as a function of its mass. So now I guesstimate the age of a system by taking its most massive star, finding the main sequence lifetime, and halving it. If the main sequence lifetime exceeds the age of the Universe, then I cap the guesstimated age at 7 Gyr.

Tidal dissipation factor estimates tend to be all over the place. I'm using values from

Lainey (2016) and

Polycarpe (2018) to build a step-function that roughly follows solar system worlds.

If the radius is < 2000, Q=37.5 (Lunar-like),

If the radius is < 5000, Q=99.5 (Mars-like),

If the radius is < 10000, Q=280 (Earth-like),

If the radius is < 35000, Q=500 (Uranus-like),

If the radius is < 65000, Q=1000 (Saturn-like),

If the radius is greater, then Q = 10^6 (Jupiter-like).

Definitely open to revising these numbers, but estimating Q appears to be a very challenging effort for giant planets especially with estimates for Jupiter being discrepant to a couple orders of magnitude.

If the age of the system exceeds the tidal synchronization time for the planet, it is left in the tidal equilibrium spin period. Otherwise, this all allows me to guesstimate spin periods for exoplanets using either the initial spin rate that was calculated as before for giant planets, or for a stand-in initial spin rate (V = 0.5 km/s) for terrestrial bodies (I'm well aware that this is, in reality, effectively stochastic).

01 March 2024

- 59 TESS candidate planets added (TOI-6896 through TOI-6956).

- 8 TESS candidate planets have been determined to be false positives since the last update and excluded.

- 13 Kepler-K2 candidate planets have been determined to be false positives since the last update and excluded (

Lehmann & Vanderburg (2024)).

- Added

HW Vir,

OGLE-2023-BLG-0836L,

V808 Aur, and several candidates from astrometry (

Gratton, et al).

- Updated

Teegarden's Star,

TOI-238,

TOI-1386,

GJ 1214,

TOI-1338,

TOI-1751,

TOI-677,

TOI-1347,

TOI-1199, TOI-1273,

AF Lep,

K2-106,

ROXs 42B,

ε CrB,

Kepler-104, Kepler-323,

TOI-1518,

TOI-1135,

TOI-2373, TOI-2416, TOI-2524, and

numerous other TOI systems.

15,378 planets (+1 asteroid)

5690 confirmed.

9688 unconfirmed.

Exoplanet nerd. I maintain a monthly-updated exoplanet catalogue here:

https://celestia.space/forum/viewtopic.php?f=23&t=18705