A world like our own

What hap­pened: First dis­cov­ery of an Earth-sized world in a hab­it­able zone When it hap­pened: April 2014

All About Space - - Kepler’s Best Bits -

Ar­guably Ke­pler’s most im­por­tant and pub­li­cised dis­cov­ery came in April 2014 with the an­nounce­ment of Ke­pler-186f. This was the first Earth-sized world ever found in the hab­it­able zone of an­other star, and raised the tan­ta­lis­ing prospect that there could be other worlds like ours else­where in the galaxy, and pos­si­bly even life.

This planet was just 1.2-times the size of Earth, and was at a dis­tance from its star where liq­uid wa­ter could ex­ist. While the mass of the planet lo­cated about 500 light years away re­mained un­cer­tain, best es­ti­mates sug­gested that a planet of this size was likely to be rocky. The only thing pre­vent­ing this be­ing her­alded as a true ‘Earth 2.0’ was that it or­bited a red dwarf star, one that was con­sid­er­ably dim­mer than our own Sun.

While these are the most nu­mer­ous stars in the galaxy they are prone to bursts of ra­di­a­tion, and Ke­pler-186f’s rel­a­tive prox­im­ity to its star (40 per cent that of Earth’s or­bit) raised ques­tions about its hab­it­abil­ity. It re­mains a key dis­cov­ery in the his­tory of ex­o­planet sci­ence, though, prov­ing that there were other worlds like ours out there. Now we just had to find one or­bit­ing a star like our Sun – and sci­en­tists wouldn’t have to wait long…

Ke­pler-186f bore many sim­i­lar­i­ties to our home planet

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