For those who missed today’s new on Teegarden’s star:

Two Earth-Like Worlds Found Orbiting a Red Dwarf Only 12.5 Light-Years Away

I always gripe about “Earth-like” and there that phrase is again in a headlines.

The two planets are Earth-similar in mass. Their actual nature is unknown.

From the actual paper:

Because no transits are detected, we cannot derive the planetary radii. We therefore estimated them from mass-radius relations for various compositions (Zeng et al. 2016). The planetary radii depend weakly on the planetary mass, but strongly on the bulk composition (Fig. 12). Between the two extreme compositions, namely a pure Fe core on the one side and a cold H+He mini-Neptune on the other, the radii differ by a factor of about three (see Fig. 12). We used these radii as well as other stellar and planetary parameters to derive the Earth Similarity Index (ESI) as defined by Schulze-Makuch et al. (2011). The ESI is an indicator that compares key parameters to those of our Earth (ESI⊕ = 1). Here we used the weighted ESI, taking into account the equilibrium temperature, atmospheric escape velocity, bulk density, and radius, with a dominant contribution from the equilibrium temperature. The weights were taken from the Habitable Exoplanet Catalog12. Except for the case of a miniNeptune composition, the two planets have a high ESI. For a
potentially rocky composition, the ESI value is 0.94 and 0.8 for planets b and c, respectively. This makes Teegarden’s Star b the planet with currently the highest ESI value. However, the ESI is only an estimate, and different weighting of the parameters may lead to changing ESIs. This ESI definition, for example, does not take into account the stellar spectral energy distribution and the resulting planetary atmospheric composition, which very likely have an effect on habitability.