New evidence of 219 planets outside of our Solar System has been discovered by NASA. Ten of these planets are similar in size to Earth and orbit their stars in what is called the “habitable zone”; meaning they are just far enough away from their respective suns for water to develop, but close enough so that it doesn’t freeze. If this evidence is confirmed, these planets would be added to an ever-growing list of Earth-sized planets that occupy our area of the Milky Way.
This growing list is very exciting, because it shows that rocky planets are more common than we once thought. In addition to this, there is also a small chance that these worlds could harbor life. This catalog is being put together by NASA’s current Kepler space telescope mission, which has been surveying the Cygnus constellation since 2009. Kepler spots planets by looking for dips in a star’s brightness. When scientists observe this, they study the signals to confirm that the dip in brightness is caused by a planet passing in front of the star it is orbiting. Once the signal is confirmed to be a planet, the data is used to determine the mass of the planet and how long it takes to orbit the star.
NASA has also been working on classifying these new planets. The division is between two categories: “super-Earths”, which are rocky worlds about 1.5 times the size of Earth, and “mini-Neptunes”, gas planets more than 2.5 times the size of Earth. This knowledge of how to find planets similar to Earth will ultimately help scientist’s narrow down their targets which can be studied by powerful telescopes.
The final catalog of results from the Kepler space telescope mission detail the discovery of more than 5,000 exoplanets about 3,000 light-years away from us. The latest update has narrowed that figure down to 4,034, with 2,335 of them being identified as exoplanets. Out of those, 21 are Earth-sized and occupy their star’s habitable zone.
As for now, it is unknown whether or not these Earth-like planets are housing life like our own.