The Keck Observatory on Mauna Kea has confirmed the discovery of the first near-Earth-size planet in the “habitable zone” around a sunlike star.

That means that if the planet is rocky, rather than gaseous, and has water, the water would be in liquid form, a necessary ingredient to life.

But the planet, Kepler-452b, is a whopping 1,400 light-years away, too far for a visit.

“We can think of Kepler-452b as bigger, older cousin to Earth, providing an opportunity to understand and reflect upon Earth’s evolving environment,” said Jon Jenkins, Kepler data analysis chief at NASA’s Ames Research Center in Moffett Field, Calif., who led the research team. “It’s awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star — about 1.5 billion years longer than Earth.

“That’s substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet.”

Jenkins and other team members made the announcement Thursday.

This discovery, originally made by NASA’s Kepler space telescope, marks another milestone in the journey to finding another “Earth.”

In the last few years, findings of so-called extrasolar planets or exoplanets have come thick and fast. Many of them are gas giants like Jupiter, however. Only a few are small and possibly rocky like Earth. And fewer still are in the “Goldilocks zone” — neither too hot nor too cold, where liquid water could exist.

In April 2014, Mauna Kea telescopes confirmed the discovery of the first Earth-size planet in the habitable zone. However, that planet, Kepler-186f, orbits a dim red dwarf star.

The newly discovered Kepler-452b is the smallest planet to date discovered orbiting a sunlike star.

Both are in the constellation Cygnus.

Kepler-452b is 60 percent larger than Earth and is considered a super-Earth-size planet. While its mass and composition are as yet undetermined, previous research suggests that planets the size of Kepler-452b have a good chance of being rocky, scientists said.

The planet is 5 percent farther from its parent star, Kepler-452, than Earth is from the sun, and has a 385-day year.

The 10-meter Keck I telescope, fitted with the HIRES instrument, was used to confirm the Kepler data as well as to more precisely determine the properties of the star, specifically its temperature, surface gravity and metallicity.

“These fundamental properties are used to determine the stellar mass and radius. allowing for precise determination of the planet size,” said Howard Isaacson, researcher in the astronomy department at the University of California, Berkeley, and a member of the discovery team. “With the precise stellar parameters from the HIRES spectrum, we can show that planet radius is closer to the size of the Earth than, say, Neptune. With a radius of 1.6 times the radius of the Earth, the chances of the planet having some sort of rocky surface is predicted to be about 50 percent.”

The research paper detailing the discovery has been accepted for publication in the Astronomical Journal.