The researchers announced their discovery Thursday based on observations from NASA's Kepler space telescope.
"It is the closest thing that we have to another place that somebody else might call home," said Jon Jenkins, the lead data analyst from NASA's Ames Research Center in California.
This older, bigger cousin to Earth is called Kepler-452b. What makes this planet remarkable is that it orbits its star at about the same distance that Earth orbits the sun. What's more, its home star looks to be similar to our sun.
Based on what scientists know today, Jenkins added, "This is the closest thing we have to another Earth-sun twin system."
John Grunsfeld, NASA's science mission chief, said the exoplanet system "as far as we can tell, is a pretty good close cousin to the Earth and our sun." The planet itself is "the closest twin, so to speak, to Earth 2.0" yet found in the Kepler data.
"This is about the closest so far," Grunsfeld said, "and I really emphasize the 'so far.' "
One unanswered question is whether the planet is rocky. Scientists believe there's a better than even chance it is. As for age and size, the planet is about 6 billion years old, 1.5 billion years older than Earth, and 60 percent larger in diameter than our home planet. Its star, Kepler 452, is also older and bigger, as well as brighter than our sun.
Planet 452b takes 385 days to orbit its star, just a little more than Earth takes for a one-year lap. It's just a bit farther from its star than Earth is from our sun.
The planet is in a solar system that is 1,400 light years from our own, located in the Constellation Cygnus, or swan.
"So pack your bags, it's a long trip," joked Jenkins.
Planet 452b is among more than 500 new entries listed in the Kepler team's latest catalog of exoplanet candidates released Thursday. Kepler was launched in 2009 to hunt for exoplanets — worlds beyond our solar system.
Of those 500-plus new potential planets, 12 are less than twice Earth's diameter and also orbiting in the so-called habitable zone of their star, also known as the just-right Goldilocks zone.
Kepler 452b is the first of those 12 to be confirmed as a true planet, thanks to ground observations.
Altogether, the catalog now includes 4,661 exoplanet candidates. Slightly more than 1,000 of them are confirmed to be planets.