David Kipping

TRAPPIST-1e is a planet which is in the right distance for liquid water.

It has a slightly smaller size than the Earth.

It's about 90% the size of the Earth, about 80% the mass.

And it's one of the top targets right now for potentially having life.

And yet, it raises many questions about what would that environment be like?

This is a star which is one-eighth the mass of the Sun.

Stars like that take a long time to come off their adolescence.

When stars first form, like the Sun, it takes them maybe 10, 100 million years to sort of settle in to that main sequence lifetime.

But for stars like these late M dwarfs, as we call them, they can take up to a billion years or more to calm down.

And during that period, they're producing huge amounts of x-rays, ultraviolet radiation that could potentially rip off the entire atmosphere.

It may desiccate the planets in the system.

And so even if water arrived by comets or something, it may have lost all that water due to this prolonged period of high activity.

We have lots of open-ended questions about these M dwarf planets, but they are the most accessible.

In the near term, if we detect anything in terms of biosignatures for one of these red dwarf stars, it's not going to be a true Earth twin, as we would recognize it as having a yellow star.

When we look for life, it's hard to define even what life is, but we can maybe do a better job in defining the sorts of things that life does.

And that provides some aspects to some avenue for looking for them.

Classically, conventionally, I think we thought the way to look for life was to look for oxygen.

Oxygen is a byproduct of photosynthesis on this planet.

We didn't always have it.

Certainly, if you go back to the Archean period, you have this period called the Great Oxidation Event where the Earth floods with oxygen for the first time and starts to saturate the oceans and then the atmosphere.