It has an extremely short orbital period of under 11 hours, less than half of an Earth day, resulting in an equilibrium temperature of 2,480 ± 200 K (2,207 ± 200 °C; 4,004 ± 360 °F).
[1] The planet is believed to be far too small and irradiated to hold onto its primordial Hydrogen and Helium envelope.
[1] Lacedelli 2020, on the other hand, found a mass of only 1.59 Earths and a density of 3.0 grams per cubic centimetre, abnormally low for a planet of its size and suggesting a composition made of 50% or more of water.
With an insolation 5,100 times greater than Earth, TOI-561 b should have lost its gaseous layer and have little volatiles, so the authors believe if the planet has a significant amount of water, it has been evaporated into a puffy steam atmosphere that makes the planet seem larger, less dense, and more water-rich.
If it is an extremely water-rich world, TOI-561 b would prove formation scenarios about Super-Earths forming beyond the "Snow Line" and migrating inwards.