NASA discover Earth's twin 1,400 light-years away
The Kepler mission has found the first near-Earth-size planet - called Kepler-452b - in the "habitable zone" around a G2 star much like our own sun. Kepler-452b is 60 percent larger in diameter than Earth and is considered a super-Earth-size planet. Its 385-day orbit is only 5 percent longer as the planet is 5 percent farther from its parent star. That star, Kepler-452, is 6 billion years old, 1.5 billion years older than our sun, has the same temperature, and is 20 percent brighter and has a diameter 10 percent larger. The Kepler-452 system is located 1,400 light-years away in the constellation Cygnus.
"We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth's evolving environment," said Jenkins. "It's awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That's substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet."
"We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth's evolving environment," said Jenkins. "It's awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That's substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet."
"Astronomers aren't completely sure it's a terrestrial planet" is the worst that can be said. Stretching that to claim it's a "mini-Neptune" is baseless, and also misleading. It's only a slim "possibility that it is actually a small gas planet". "It is the first potentially rocky super-Earth planet discovered orbiting within the habitable zone of a star very similar to the Sun." Nasa's science chief John Grunsfeld called the new world "Earth 2.0" and the "closest so far" to our home. And even the io9 article you cited, calls it "Earth's Near Twin" right in the title...
Here's a list of just a few of the more straight-forward self-contradictions found in the article:* Not on-page, a linked-to io9 explanation of the theory.