NASA’s Kepler Space Telescope discovered an Earth-like planet circling a nearby star within the Goldilocks zone of our galaxy. Kepler-186f is around 500 light-years from Earth in the Cygnus constellation. The habitable zone, also identified as the Goldilocks zone, is the area around a star within which planetary-mass objects with enough atmospheric pressure can sustain liquid water at their surfaces.

While it has been projected that there are at least 40 billion Earth-sized planets circling in our Milky Way Galaxy, this specific finding is labelled the first Earth-sized planet to be discovered in the habitable zone of another star.

What does this mean?

In addition to Kepler-186f, there are 4 other planets that circle a nearby star within the Kepler-186f system. What this means is that if the neighbouring star to this planet is just like our Sun, then the likelihood of life on this planet exponentially increases.

“We know of only one planet where life survives – Earth. When we hunt for life outside our solar system, we emphasis on discovering planets with features that mimic that of Earth,” said Elisa Quintana, research scientist at the SETI Institute at NASA’s Ames Research Center in Moffett Field, Calif., and lead author of the paper published in the journal Science. “Discovering a habitable zone planet similar to Earth in size is a major breakthrough.”

The neighboring star to Kepler-186f has half the mass and size as our solar system’s Sun and only gets one-third of the energy that we get from our Sun. Kepler-186f circles its star once every 130 days.

Although NASA said that there are other exoplanets estimated to be closer to Earth in size – and others may be closer to Earth in temperature – there is no other exoplanet that’s closer to Earth in both of these values that also lies in the habitable zone of its system.

This newly revealed world is only 1.06 times larger than our own planet. Also, the amount of starlight it receives from its host star is 75% of the amount of light Earth receives from our sun – meaning the exoplanet’s temperature may be similar to our planet’s, as well.

But unlike Earth, it orbits a red dwarf. Though none have been observed in this system, this type of star is known for stellar flare-ups that may make a planet’s environment challenging for any potential life.

Scientists discovered this planet when looking through old observations from the Kepler Space Telescope, which the agency retired in 2018. (Although NASA’s Kepler mission ended in 2018 when it ran out of fuel, scientists are still making discoveries as they continue to examine the information that Kepler sent back to Earth.)

“The more data we get, the more signs we see pointing to the notion that potentially habitable and Earth-size exoplanets are common around these kinds of stars,” said study lead author Andrew Vanderburg, a researcher at the University of Texas at Austin.

“With red dwarfs almost everywhere around our galaxy, and these small, potentially habitable and rocky planets around them, the chance one of them isn’t too different than our Earth looks a bit brighter,” he said.