Teegarden's Star and its two planet candidates

[stevebowers]

Here's Andrew LePage on the habitability of these worlds.
https://www.drewexmachina.com/2019/06/19...dens-star/

The discovery of Teegarden’s Star b and c presents scientists with yet another opportunity to study nearby “temperate planets” in hopes of more fully characterizing their actual properties. Based on what we known today, it appears likely that both of these new finds are rocky worlds like the Earth with much smaller probability that they are mini-Neptunes. The prospects for the potential habitability of Teegarden’s Star b do not appear to be as good as those of planet c owing to former’s close proximity to the inner limit of the habitable zone as well as being more exposed to any enhanced activity earlier in the evolution of Teegarden’s Star – this despite the record setting Earth Similarity Index (ESI) value for planet b. Still, these new finds do seem to have reasonable prospects of being habitable given the gaps in our understanding of planetary habitability especially for ultracool dwarfs like Teegarden’s Star. Future study of these and similar exoplanets should help provide greater insights in this question. And with hints of a third exoplanet in this system (not to mention the possibility of still others), Teegarden’s Star could be as an important laboratory for studying the evolution of exoplanets orbiting ultracool dwarfs as the better known TRAPPIST-1.

Planet c looks promising then- although I'm still concerned abut CO poisoning. Note that carbon monoxide is a very common compound in the universe, but is degraded by any hint of UV light - so is only likely to be the dominant component in cool systems like this.