Exoplanet Kepler-452b is often referred to as an 'Earth 2.0' and was discovered on 23 July 2015 by mission scientists using data from the NASA Kepler Space Telescope.
Kepler-452b is located 1,400 lightyears from Earth and is special because at the time it was the smallest known planet in the habitable zone around a Sun-like star.
This means the planet orbits its host star at the right distance for liquid water to be able to pool on its surface.
And that's one property that makes it a 'habitable planet', as far as astronomers are concerned.
What's more, the discovery of Kepler-452b made headlines because it was discovered 20 years after the discovery of the first known planet orbiting a Sun-like star beyond our Solar System.
"On the 20th anniversary year of the discovery that proved other suns host planets, the Kepler exoplanet explorer has discovered a planet and star which most closely resemble Earth and our Sun," said John Grunsfeld, associate administrator of NASA’s Science Mission Directorate, at the time of the discovery.
“This exciting result brings us one step closer to finding an Earth 2.0."
Why Kepler-452b is like Earth
Kepler-452b is 60% larger in diameter than Earth, making it a super-Earth size planet. And research suggests that exoplanets this size could potentially be rocky.
The exoplanet's orbit is 385 days, making its year just 5% longer than Earth's orbit.
And its orbital track is 5% farther from star Kepler-452 than Earth is from the Sun.
Star Kepler-452 is 6 billion years old, 1.5 billion years older than our Sun, has a similar temperature, is 20% brighter and has a diameter 10% larger.
“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 Jon Jenkins, Kepler data analysis lead at NASA's Ames Research Center in Moffett Field, California, who led the team that discovered Kepler-452b.
"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.”
Info on Kepler-452b released by NASA was collected through ground-based observations at the University of Texas at Austin's McDonald Observatory, the Fred Lawrence Whipple Observatory on Mt. Hopkins, Arizona and the W. M. Keck Observatory atop Mauna Kea in Hawaii.