We just keep finding them, more and more planets with similarities to Earth – two more, to be exact.

Kepler 438b and Kepler 442b — both these planets rest snuggly in the so-called Goldilocks zone of their own star systems. So, what is the Goldilocks zone?

The Goldilocks zone

This name is given to the area of solar systems that produces an environment like our own area of the solar system. This location must be warm enough to keep water from constantly freezing and cool enough to keep water from complete evaporation.

It is the comfort zone of existence as earthlings know it! This is what we use to gauge whether or not a planet is habitable according to Earth specs.


Astronomers announced recently that eight planets meet our Earth specifications for existence, with two of these being the most similar of the group. Guillermo Torres of the Harvard-Smithsonian Center for Astrophysics (Cfa) states that all these planets in the “zone” have a great chance of having a rocky terrain as well.

During the meeting of the American Astronomical Society, Kepler 438b and Kepler 442b were announced as the most curious planets within the Goldilocks zone of their own solar system.

Statistics of Hopeful Planets

First of all, both 438b and 442b orbit red dwarf stars, smaller and cooler than our own sun. Kepler 438 makes one revolution around its sun, every 35 earth days, and Kepler 442b makes the trip in 112 earth days. The size of these planets are also similar to Earth, with 438b being only 12% larger than the Earth and 442b only 1/3 larger than our home.


While Kepler 438 seems quite suitable, it does receive 40% more sunlight than the Earth. Venus in our solar system, by comparison, receives twice as much radiation. Since our two mystery planets revolve around a younger, cooler star that will grow and become hotter, they will receive more sunlight in the distant future.

For Kepler 438b, there is a 70% chance of habitability due to sunlight exposure. As for Kepler 442b, it has a 97% chance of being in the habitable zone of its solar system. This planet receives 2/3 of the light received by Earth and will grow warmer as time goes by.

David Kipping of the Cfa explains, “Truly, we do not know if these samplings are really habitable, they are just promising candidates”.

Previously, the closest chances to ensure habitability were Kepler 186f, 1.1 times larger than our planet and received 32% as much sunlight and Kepler 62f, which had only slight differences from 186f.

NASA’s Innovation

NASA’s Kepler mission identified hopeful candidates, which were too small to confirm with mass measurements. The confirmation was made with the use of BLENDER, a computer program used to analyze statistics. Torres and Francois Fressin ran BLENDER on the Pleaides Supercomputer at NASA Ames, to validate the findings.

This includes the discovery of the first two planets similar to Earth and an exoplanet measuring smaller than Mercury. Spurring from the BLENDER analysis, scientists used spectroscopy, speckle interferometry and adaptive optics imaging to organize systems. With these last tests, it was discovered that four of the eight habitable planets were actually in multiple star systems, but were not affected by distant companion stars.

This new-found information is both exciting and frustrating, as the two most promising planets for life are very distant. Kepler 438b is 470 light-years away, while Kepler 442b is over a thousand light-years away.

Scientists, grouped into 6 different research sections, continue to explore and determine how hopeful we can afford to be. With the culmulative efforts of the Smithsonian Astronomical Observatory and the Harvard College Observatory, Cfa scientists can continue their search into the depths of the universe, finding more and more possibilities and monumental answers to life.

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