>I had to re-read the article and no shit this is you according to the citation

Yep, there are quite a few astronomers that are reddit users :) Once in a while *we* catch our own work being circulated around here.

I have to say I have yet to read Caroline Piaulet's paper. Just checked the press releases. I've been busy with end of the year stuff, and now I'm on holidays. I won't catch up to the newest results until I go back to work. However, I think I can give some answers.

​

1. I think everything we learn is pointing to a very big number of Earth like planets out there. I don't work in the statistics, so I'm not sure what is the current occurrence rate, but basically each time we improve instrumentation or analysis techniques, we just get more. There's also the fact that, in astronomy, there is usually more of the less massive stuff. More massive stuff requires more material and is harder to produce. It totally makes sense that there are more low mass stars than high mass stars, more big planets than low mass stars and more small planets than big planets.
2. We (the community) are starting to get a reasonable number. With these two we are at 69 planets with masses < 2 Earth masses. We (my team) have a few published (also smaller than this one, like Proxima d) and some in which we are working. However, there are still very strong instrumental and analysis limitations. Most instruments have a hard time catching these small signals, and stellar activity makes it sometimes very difficult to recognize them. For GJ 1002 we hit kind of a sweetspot. We had a big telescope (VLT, 8m), an excellent instrument (ESPRESSO), low levels of stellar activity and a rotation signal that was very far away from the planetary signals (100 days for rotation, 10 and 21 for the planets).
3. Hopefully we'll get closer to the actual Earth-twins (Earth mass in the habitable zone solar type stars)! This is a huge challenge for all the detection methods. We have the general idea of how to do it, but we haven't figured out the solution to many of the problems that we face in these cases.

Hey, thanks for asking! Here goes kind of a long reply.

JWST won't be able to contribute here. The planets are non transiting.

The first instrument which should be able to characterise them is ANDES, a spectrograph for the ELT (in design phase). ANDES is expected to have a mode optimized to study atmospheres of exoplanets in reflected light. After that, the ESA LIFE mission (in concept phase), which will use nulling interpherometry to "hide" the stellar light and study the thermal emission of planets. In any case, it won't be before 2031 (ANDES) or ~2050 (LIFE). I do not know if NASA has anything in the pipeline for this science case.

We picked GJ 1002 because is one of the closest stars to the Sun. It is also a M-dwarfs (similar to Proxima), and a very low activity star. This fulfils quite a few goals in one go. First of all, we want a census of the solar vicinity. There are not that many transiting systems nearby, so K2 and TESS had not contributed all that much here. Then being an Mdwarf means that the planetary signals are large for small planets (easy to detect), and the orbital periods are short (easy to sample several times). The spectra odñf Mdwarfs also has lots of absorption lines, which means we can measure good velocities even if the star is faint. Then low activity means once again easy to deal with. Lastly, nearby also means large projected separation between the planets and the star when looking from here, which is important for the characterization with the missions I wrote before.

I'm not sure we can talk about opening any flood gates. There seem to be lots of earth más planets out there, but the detection process has a lot of bottlenecks. Telescope time (this work needed roughly 100 hours of telescope time between CÁRMENES and ESPRESSO). Telescopes are typically shared between different communities, research topics and research teams. Getting 100 hours for a single target is not easy. Then data processing and analysis is also still not where it needs to be. We are mostly getting the easy cases. We have come a long way (it used to be easy Jupiters, now it is easy Earths), but there is still a long way to go. RVs are also more difficult to deal with than transit photometry. No one has figured a way of automatically analyse thousands of time series and reliable detect the planets. It still requires a system by system approach.

Just to show how slow this things are. I'm in the ESPRESSO science team. We started observing this star in 2019. I spotted one of the planets of the system in summer 2021. In winter I was told that the Cármenes team also had a lot of data (from 2016!). In January a presented my collegues a solid case for a 2 planet system, but with a need to collaborate. In spring both teams had evaluated the full dataset and agreed to collaborate. In early summer I finished the definitive analysis, and the first draft of the article. It was circulated in both teams and modified according to the suggestions and comments of roughly 40 people. We submitted to the journal in September. A month later we got the report from the referee, which triggered a complete reanalysis to test the robustness of the analysis we had originally presented. When it was confirmed to be robust, the article was accepted for publication (late November). It has been roughly 6 years of work (between both teams), with a year and a half of intense work. The whole analysis process was very handcrafted, requiring understanding the star quite well. As long as we need to continue working like this, it will be very difficult to get lots of planets quickly.

We are getting better, but it is still very slow.

The short answer is ¯\_(ツ)_/¯

There are too many unknowns. First we do not have a very solid idea of how life starts (AFAIK). We believe it requires large amounts of UV radiation (which the early Sun emitted). This also happens with young M-dwarfs. Then, once you have RNA chains, you need low radiation to not destroy it. That happens with old M-dwarfs. The difference is mostly the timescales. M-dwarfs spent much longer in the "active phase" and get later to a quiet phase. This star in particular is very quiet. Maybe life just happens later (this last part would be me speculating).

The long phase of high activity can strip the planet from its atmosphere, but when thinking about life we mostly consider secondary atmospheres. These are atmospheres that didn't form with the planet, but that arrived later after the loss of the primary atmosphere (Earth's atmosphere is a secondary atmosphere). If the planet could form an atmosphere after the star entered its quiet phase, then it should be fine.

This will also be affected by whether or not the planet has a sufficiently strong magnetic field, which currently we can't measure. In Earth, the magnetic field is created by the convective motion of the liquid outer core, which is then amplified by Earth's rotation. If the planets are tidally locked you would lose that amplifier, because of the slow rotation, but you would gain another in the form of tidal forces. So... it's really difficult to say. AFAIK there are models predicting many different outcomes and, as we know very little about possible core configurations, it is very difficult to decide which ones are more realistic.

Then what happens to the temperature if they are tidally locked? Well, it depends a lot on the atmospheric circulation. It has been traditionally expected to have a very hot and a very cold side, but once again now you have models predicting wildly different things based on different conditions. If you manage to get fast atmospheric circulation (which can exists based on convective currents and tidal forces), you can reduce the temperature of the hot side and increase the temperature on the cold side. Currently very difficult to conform or deny anything.

So I guess the long answer is ¯\_(ツ)_/¯ but with more words.

&#x200B;

Honestly, we are still far away from properly establishing habitability in any exoplanet. We can probably reject it in some, but I would say we don't understand life well enough to even do it systematically.

Well, less that we are looking for the wrong things, and more that I think we arent looking for all the right things. I see a focus on habitable zones and liquid water for instance, and those certainly seem like critical components for life to exist. But that is not by far the only anomaly in our solar system.

I'll try to be as clear as possible because people here actually work in the science. Some of what I say might be easily debunked by something in the community Im unaware of. Im actually excited about the prospect. But also, people here might actually see value in what Im saying, and possess the tools necessary to implement it.

It seems to me that almost just as important as liquid water would be the presence of a magnetosphere. Without one, the planet cannot protect against cosmic rays which shred DNA before life can proliferate. But in our solar system there are two planets with magnetospheres: Earth and Jupiter. I hypothesize that the existence of a large gas giant with a magnetosphere on the outer part of a system would be much more likely exist in a system that can sustain life. Or at least another terrestrial planet with an iron core. The problem here is I dont think magnetics are easy to detect at these distances. At the same time: gas giants are easier to detect than small terrestrial worlds.

We also know that Iron is a critical component to life, and that iron is formed in certain stages of star development and death. Our solar system exists in a "stellar nursery" where older stars have died leaving iron to be plentiful in the local matter. We should look primarily in similar places if we want to find life

I dont think the presence of the asteroid belt is incidental. It's possible that this is evidence of some event which malformed a planet, planetary destruction, or a result of Jupiter's magnetic influence, (or any of dozens of possibilities). Anything which could cause it could also be integral to life developing.

Tldr: I know science is about eliminating as many variables as possible, but I think we should be looking for more than just planets with water in the habitable zone. We should be looking for whole systems which resemble our own.