Earth-like worlds with oceans and continents, are detectable by the James Webb

Earth-like planets with oceans and continents that could be orbiting red dwarfs, discovered by the James Webb Space Telescope.
“Then go, there are other worlds besides this one.” Or so Stephen King said in his famous series The Dark Tower. So far, none of these worlds are similar to Earth. But finding a world that truly resembles Earth may be possible by the end of the century, according to some new simulations by researchers at the National Astronomical Observatory of Japan (NAOJ).

The search for exoplanets has been dominated by what is commonly known as the “Goldilocks Zone.” In pop science, the Goldilocks Zone represents how far away a planet must be from its star to be “neither too hot nor too cold,” as in the porridge of the classic English children’s story.

Some of the 5,000 exoplanet candidates have been discovered in this area. However, it is doubtful that any are true analogues of Earth, as there is another crucial component of a planet being like Earth that has nothing to do with its distance from its star. It should have just the right amount of water.

Too much water in a planet’s atmosphere can cause a runaway greenhouse effect in which the surface temperature becomes too high, no matter how far away the planet is from its parent star. It also leads to “water worlds” where there is no land to speak of, removing an important evolutionary milestone that life on Earth had traversed. Alternatively, planets with very little water lack one of the critical ingredients of life and could end up like Mars, having lost most of its primordial water to the solar wind.

Until now, models of planet formation suggested that most planets formed with too much or too little water. This is especially pronounced around the most common type of star in the Milky Way: red dwarfs.

Also known as “type M”, these stars are generally smaller than the Sun and therefore cooler. They make up the majority of stars close to our local star and some exoplanets have been found around them. But they ran into the same problem: So far, planet-formation models suggest it’s questionable whether planets will form around one of these stars with just the right amount of water to make them Earth-like.

Now, new research by Masahiro Ikoma and his students at NAOJ has simulated planet formation around red dwarfs and found that a small but notable percentage of these planets would likely contain levels of water that would make them remarkably Earth-like. In short, these exoplanets could potentially have beaches.

In fact, at least according to the new model, only a fraction of the planets that form in the Goldilocks zone around red dwarfs will have that much water. But with the sheer number of potential exoplanets found on these more common stars, there are likely to be hundreds.

Even more exciting, if these estimates are correct, planet hunters like Tess and the next Plato should be able to find some by the end of the century. Once they are found, JWST should be able to detect if they have water in their atmospheres.

All of this brings more good news for the exoplanet community, which has been torn apart for the afternoon. It may herald the imminent discovery of one of the most exciting scientific discoveries in human history. At this point, it’s probably just a matter of time, and of course good observational data is needed.


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