Researchers Identify Two 'Species' Of Exoplanets: Kepler Planet Family Gets Two Distinct Branches

Just like creatures in the animal kingdom, exoplanets could have species too. That's how the two distinct branches of exoplanets were termed in a new study on so-called Kepler planets.

A report from Big Island Now took a look at the study led by California Institute of Technology researchers, who discovered that the planets spotted from the W.M. Keck Observatory in Hawaii and NASA's Kepler mission can mostly be divided into two branches — one "species" including rocky, Earth-like planets and so-called "super-Earths," and the other including gaseous, Neptune-like planets orbiting distant stars.

As Big Island Now explained, Kepler planets are the ones spotted during NASA's Kepler Mission, which launched in 2009 with the goal of finding Earth-like planets. There have been over 2,300 exoplanets confirmed over the past eight years through this mission. That's more than 60 percent of the 3,500 or so exoplanets discovered since the first such planet was discovered in the mid 1990s, and with the revelation that these planets have "species," the researchers believe they may be on to something.

"Astronomers like to put things in buckets," said lead author Benjamin Fulton in a statement.

"In this case, we have found two very distinct buckets for the majority of the Kepler planets."
Principal investigator and Caltech professor of astronomy Andrew Howard added that the new discovery is similar to how scientists previously discovered that mammals and reptiles made up distinctive families on the tree of life.
Looking closer at the study's findings, the Milky Way in specific usually has rocky planets that may be as much as 1.75 times the size of Earth, or "mini-Neptunes," gaseous planets that are about twice to 3.5 times as massive. Interestingly, the study also suggests that the Milky Way only rarely creates planets between the two exoplanet species, regardless of size.

The researchers, which included scientists from Caltech, the University of California in Berkeley, the University of Hawaii, Harvard, and other institutions, made use of the Keck Observatory's HIRES (High-Resolution Echelle Spectrometer) instrument to determine the size of the Kepler planets. Big Island Now added that the scientists spent multiple years gathering this data and coming up with sizes for orbiting planets that were four times more accurate than established statistics from previous studies.

"Before, sorting the planets by size was like trying to sort grains of sand with your naked eye," Fulton commented.
"Getting the spectra from Keck Observatory is like going out and grabbing a magnifying glass. We could see details that we couldn't before."
Meanwhile, NASA released a catalog of 219 new Kepler planet candidates, including 10 near-Earth-sized planets orbiting within the habitable zone of their host star, or in an area where liquid water could potentially form on the surface. The space agency's official press release describes the new catalog as the "most comprehensive and detailed" such list of exoplanet candidates, boosting the list of Kepler planet candidates to 4,034, with a total of 2,335 confirmed and verified to be actual exoplanets and 30 planets in the habitable zone.

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