by Laura DudnickA professor at San Francisco State University was among an international team of researchers who recently reached a milestone in galactic exploration: finding a planet very similar to Earth that could harbor life.
Stephen Kane, an astronomer and professor at SFSU, told The San Francisco Examiner on Wednesday that the discovery of Kepler-186f marks the closet scientists have come to finding a potentially habitable planet other than our own.
Kepler-186f, the fifth and outermost planet found to be orbiting the dwarf star Kepler-186, is both similar to the Earth's size and within the habitable zone of its star -- two criteria that until this finding had never before been known to overlap in another planet, Kane said.
"The difference between this planet and other discoveries from the Kepler mission [is that] although Kepler has discovered planets about the size of the Earth before and it has also discovered planets in the habitable zone before, this is the first time when we've been able to put those two pieces together," Kane said.
The planet is also believed to be rocky and contain liquid water, two additional characteristics that could allow it to harbor life, according to Kane.
Researchers have been looking for Earth-size planets in our corner of the Milky Way Galaxy with NASA's Kepler telescope since 2009. Previously, they have found planets either around the same size as Earth or in a habitable zone--meaning the planet orbits its star at a distance where any water on the surface could be liquid.
"This is getting us increasingly closer in finding something that is very similar to the Earth," Kane said.
Astronomers discovered Kepler-186f, which is 500 light years away from Earth, using what's called the transit method. The process detects potential planets as their orbits cross in front of their star, causing a tiny but periodic dimming of the star's brightness. Once it was confirmed that Kepler-186f was a planet, researchers used the transit information to calculate the planet's size and determined it to be about 10 percent bigger than Earth.
Kane noted additional differences between Kepler-186f and Earth, including that the newly discovered planet takes 130 days to orbit its star--about a third of Earth's orbital period around the sun.
The star orbited by Kepler-186f is also "much smaller than the sun," and is the most common type of star in the universe, Kane said.
"Our sun is often described as an average star, but these kinds of stars are extremely common," Kane said. "That's good news, because if you have these systems of five terrestrial planets orbiting a common star, it really does mean that planets like this are everywhere."
Kane emphasized that there's still a lot more research to be done, such as finding out if Kepler-186f's atmosphere is similar to that of Earth.
Kane, who moved to San Francisco last summer to teach astronomy at San Francisco State, has been studying exoplanets--also known as extra solar planets--since the field developed in 1995.