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Nasa confirms first earth-sized 'Goldilocks Planet'

A Nasa rendering of planet Kepler-186f, roughly Earth's size that could theoretically host liquid water, Photo: NASA

Tom Barclay is a research scientist based at Nasa’s Ames Research Center in California and in this blog for ITV News he explains the significance of the Kepler spacecraft's latest discovery and how this takes us closer towards answering the great question, "are we alone in the universe?"

Today, we are announcing the achievement of another milestone towards answering the question “Are we alone?”. We have confirmed the first Earth-sized planet orbiting in the habitable zone of a star other than the Sun.

What is the Habitable Zone?

The habitable, or 'Goldilocks', zone is the region around a star within which a planet can sustain liquid water on its surface given the right atmospheric conditions.

The Kepler system

The Kepler spacecraft measures the size of a planet by the fraction of starlight that it blocks as it transits across the face of the star. This planet is named Kepler-186f and it is one of five planets that have thus far been detected by NASA’s Kepler space telescope in orbit about the star Kepler-186. This star is smaller and cooler than the Sun, of a type called a red dwarf. Red dwarfs are very abundant, comprising about three quarters of the one hundred billion of stars in our galaxy; most of the stars in our cosmic backyard are red dwarfs.

An artists' rendition of the Kepler spacecraft. Credit: NASA

The Kepler-186 planetary system lies in the direction of the constellation Cygnus, about 500 light-years away. If you were stood on Kepler-186f you would see an orange coloured star in the sky that is about 30% larger than we see then Sun. The planet receives about the third the energy we receive from the Sun so illumination during the daytime would be lower than on Earth. The illumination at Midday on a sunny day on Kepler-186f would be about the same as the illumination we have on Earth about an hour before sunset.

We built and launched the Kepler spacecraft to find planets such as this. This day is a momentous one. We now know that there are Earth-sized planets in habitable zones of other stars. This is the day I dreamed of when I left England for the US in search of alien worlds.

The Kepler system Credit: NASA

The next generation of space telescopes like Transiting Exoplanet Survey Satellite (TESS) will search for planets around stars that are nearby to us. The James Webb Space Telescope (JWST) will probe the atmospheres of these planets for biomarkers, which are chemical imprints of the signs of life that are detectable from a planets’ atmosphere.

The previous decade has taught planets are ubiquitous and some of them remind us of home. The next decade may well teach us that there are truly habitable places out there in the cosmos.