04 August 2016
how an infant earth might look.
All told, the Kepler mission has discovered more than 4000 candidates since it began its mission in March of 2009. Amidst the many "Super-Jupiters" and assorted gas giants (which account for the majority of Kepler's discoveries) astronomers have been particularly interested in those exoplanets which resemble Earth.
And now, an international team of scientists has finished perusing the Kepler catalog in an effort to determine just how many of these planets are in fact "Earth-like".
Their study, titled "A Catalog of Kepler Habitable Zone Exoplanet Candidates" (which will be published soon in the Astrophysical Journal), explains how the team discovered 216 planets that are both terrestrial and located within their parent star's "habitable zone" (HZ).
The international team was made up of researchers from,
Having spent the past three years looking over the more than 4000 entries, they have determined that 20 of the candidates are most like Earth (i.e. likely habitable).
Figure showing the habitable zone for different types of stars,
as well as the location of terrestrial size Kepler candidates.
Credit: Chester Harman
As Stephen Kane, an associate professor of physics and astronomy at San Francisco University and lead author of the study, explained in a recent statement:
In addition to isolating 216 terrestrial planets from the Kepler catalog, they also devised a system of four categories to determine which of these were most like Earth.
From this, they determined that of the Kepler candidates, 20 had radii less than twice that of Earth (i.e. on the smaller end of the Super-Earth category) and existed within their star's HZ.
In other words, of all the planets discovered in our local Universe, they were able to isolate those where liquid water can exist on the surface, and the gravity would likely be comparable to Earth's and not crushing!
Earlier today, NASA announced that Kepler
had confirmed the existence of 1,284 new exoplanets,
the most announced at any given time.
Naturally, it might sound a bit anthropocentric or naive to assume that planets which have similar conditions to our own would be the most likely places for it to emerge.
But this is what is known as the "low-hanging fruit" approach, where scientists seek out conditions which they know can lead to life.
Professor Kane is renowned for being one of the world's leading "planet-hunters".
In addition to discovering several hundred exoplanets (using data obtained by the Kepler mission) he is also a contributor to two upcoming satellite missions,
These next-generation exoplanet hunters
will pick up where Kepler left off, and are likely to benefit
greatly from this recent study.