At the 225th meeting of the American Astronomical Society there was the announce of the identification of the 1000th exoplanet verified using observations of the Kepler space telescope. That’s become a routine but the interesting thing is that among the verified planets there are eight that have a size less than twice the Earth and are in the habitable zone of their star.

According to Guillermo Torres of the Harvard-Smithsonian Center for Astrophysics (CfA), lead author of the study that led to the verification of these new exoplanets, they are likely to be rocky like Earth. Two of them, Kepler-438b and Kepler-442b, are among the most Earth-like ever found.

Kepler-438b is about 470 light years away from Earth. It has a diameter 12% larger than Earth and has a 70% chance to be a rocky planet. Its orbital period is only 35.2 days but the star Kepler-438 is a red dwarf whose mass is about half of the Sun, so it’s also much dimmer. The consequence is that the planet receives about 40% more light than the Earth.

Kepler-442b is about 1,100 light-years away from Earth. It has a diameter  about 33% larger than Earth and has a 60% chance of being a rocky planet. Its orbital period is about 112 days. The star Kepler-442 is also a red dwarf, in this case of class K, with a mass that is approximately 60% of the Sun. The planet receives about two thirds as much light as the Earth.

Another new verified planet is Kepler-440b but it’s much closer to the limits of the so-called Goldilocks habitability zone. It’s about 850 light years from Earth and is about 86% larger than the Earth. Its orbital period is 101.1 days but the star Kepler-440 is a red dwarf whose mass is about half of the Sun. The planet receives much less light than the Earth but if there was a suitable atmosphere there could still be liquid water on the surface, at least in a part of it.

Kepler-438b and Kepler-442b are among the most promising for their habitability potential, along with the planet Kepler-62f, whose discovery was announced in April 2013, and the planet Kepler-186f, whose discovery was announced in April 2014. because of their similar size to the Earth, Kepler-438b and Kepler-442b were identified using a software called BLENDER, which runs on NASA’s supercomputer Pleiades. It analyzes the data of star observations to detect abnormalities that may be caused by the passage of planets.

The distance of Kepler-438b and Kepler-442b from Earth makes more accurate observations difficult. We’ll probably have to wait until the next generation of astronomical instruments to determine if they’re actually rocky planets and if they have an atmosphere that makes them really habitable. Meanwhile, more planets that are promising and closer to us might be discovered.

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