CATCH 3: “Earth-like planet” does not mean…Earth-like planet!
When the hunt for exoplanets, or extrasolar planets, made their first prey nearly 30 years ago, they were giant planets. And very huge, too: some were more than ten times the size of Jupiter – which alone could contain more than a thousand Earths.
The term “Earth-like planet” was therefore more of a distant ambition than a true definition. This represents the hope that technology would one day make it possible to discover “rocky” planets (such as Venus, Earth and Mars).
Now that astronomers are really there, attention shifts to clues that set Earth apart from its rocky counterparts: the atmosphere, but particularly water.
The Sun of the TRAPPIST system as seen from one of its nearest planets: an imaginary scene NASA plans to confirm in the next few years.
The two new rocky exoplanets
The planet called TOI-700c is 102 light years away. In 2020, three more planets have already been discovered orbiting the star TOI-700. The furthest, which is barely 1.1 times Earth’s, is also in the habitable zone.
The planet called LHS-475B is 41 light years away. It is almost exactly (99%) the diameter of the earth.