8 new planets found in ‘Goldilocks zone’

This is an archived article and the information in the article may be outdated. Please look at the time stamp on the story to see when it was last updated.
(CNN) — The “Does human life exist beyond Earth” debate just scored another talking point with the discovery of eight new planets.

Astronomers with the Harvard-Smithsonian Center for Astrophysics, or CfA, announced their findings at a meeting of the American Astronomical Society.

The eight new planets exist in the so-called “Goldilocks” — or habitable — zone of their stars. To be considered habitable, exoplanets must orbit within a distance of their stars in which liquid water can exist on the planet’s surface, receiving about as much sunlight as Earth.

Hence the “Goldilocks” zone: Too much sunlight and the water would boil away as steam, too little, and the water would freeze.

Among the eight, scientists say two are the most similar to Earth of any known exoplanets to date.

“Most of these planets have a good chance of being rocky, like Earth,” lead author Guillermo Torres of the CfA said in a release.

Kepler-438b and Kepler-442b both orbit red dwarf stars, which are cooler and smaller than the Earth’s sun.

Kepler-438b’s diameter is 12% bigger than Earth and has a 70% chance of being rocky. The team estimates it has a 70% likelihood of being in the habitable zone of its star.

Kepler-442b is about one-third larger than Earth with a 60% chance of being rocky. Scientists give it a 97% chance of being in the habitable zone, but caution that the estimations aren’t certain.

“We don’t know for sure whether any of the planets in our sample are truly habitable,” second author David Kipping of the CfA said in a release.

“All we can say is that they’re promising candidates.”

All of the eight new planets were too small to confirm by measuring their masses, and further exploration is difficult due to the planets’ distances from Earth. Kepler-438b is 470 light-years away and Kepler-442b is 1100 light years away, according to CfA.

Astronomers relied on a computer program BLENDER, which had been used to previously validate exoplanets, as well as follow-up observations like high-resolution spectroscopy and adaptive optics imaging.