An artist’s rendering shows a newly discovered planet, right, called Gliese 581g, that astronomers say is orbiting its star in a “habitable zone,” meaning it could support life.

SAN JOSE, Calif. — A decadelong hunt by an astronomer at the University of California, Santa Cruz has yielded the discovery of a planet that could be the most Earth-like planet ever discovered — and the best case yet for a habitable one, ending our cosmic loneliness.

The planet, called Gliese 581g, is located in prime real estate within the constellation Libra, where it’s sweater weather, not too windy, with scenic views of a white sky.

“It could be the Goldilocks planet, neither too hot nor too cold … orbiting its star in a ‘habitable zone,’” said Steven Vogt of UC Santa Cruz, who announced the news with Carnegie Institution colleague Paul Butler at a news briefing at the Washington, D.C., headquarters of the National Science Foundation, which funded the work.

“It may well be like Earth, where you could walk around comfortably and look out at the stars,” said Vogt, 60.

Scientists say there is no evidence that Gliese 581g holds oxygenated landscapes of green and blue that would support microbes, dinosaurs or humanoids. For life, there must be water, and there’s no proof of that. Yet.

But Earth is unlikely to be a stupendous fluke that happened just once, said Vogt. “Places like Earth may not be very special,” he said.

How they found it

The findings result from 11 years of observations at the W.M. Keck Observatory in Hawaii, where old-fashioned telescopes and advanced math are leading the exoplanet search.

Five times a year, Vogt flew from San Francisco to the Hawaiian city of Kona, then drove an hour to a tiny hotel in the northern town of Waimea, where he joined a number of other astronomers. The team slept all morning, then rose at midafternoon to start work. They didn’t stop working until dawn.

The team used a technique known as the “wiggle” method, which detected planets by a slight gravitational tug they gave their star. They also made precise brightness measurements, verifying that the wobble was caused by the planet and not by a process within the star itself.

The team’s new findings were reported in a paper published in The Astrophysical Journal.

“This is the first one I’m truly excited about,” Penn State University astrobiologist Jim Kasting said. Not involved in the research, Kasting, a world leader in planetary habitability who works closely with NASA, speculated to The Associated Press that the planet is a “pretty prime candidate” for harboring life.

This is only the ninth of 116 star systems to be explored. There are many more — astronomers estimate the universe contains about 1 septillion stars, a portion of which hold their own system of planets. The Milky Way alone is believed to have 100 billion to 200 billion stars.

So billions, perhaps trillions, of planets could be out in space, waiting to be discovered. Many of them are likely to circle in a habitable range, Vogt said.

Comfy conditions

Until now, only planets with tighter, faster and hotter orbits have been found.

The new planet is different. (Rather than use its scientific name, Vogt calls it Zarmina, in honor of his Kabul-born wife. “It’s a beautiful planet … and I’m a lucky guy,” he said.)

It is virtually our next-door neighbor, in cosmic terms. It circles a dim red star called Gliese 581 that’s only 20 light-years away. But don’t cash in your frequent flier miles yet — at the current speed of space travel, it would take tens of thousands of years to get there.

Wind gusts don’t seem to exceed 40 mph.

It doesn’t spin. Fixated on its star, one side is always torrid and the other is frigid. However, in between the hot and cold zones is a temperate region that is downright comfy — and perhaps hospitable enough for organic chemistry to take place, building the amino acids that are the foundation of life.

“Not spinning — that’s actually a huge advantage” for potential life, Vogt said. “You could evolve on the hot side, like a desert lizard. Or you could evolve on the cold side, like a polar bear. Between the two, you could move around, wearing shirt sleeves.”

‘Chances for life … are 100 percent’

Although it’s unknown whether water exists on the planet, it is at the right distance from its star to potentially harbor it.

However, because there’s the potential for water, and because all sorts of extreme life can exist where there is water, Vogt believes “that chances for life on this planet are 100 percent.”

In its dusky light, it would always feel like twilight or dawn. The sky is likely white, not blue.

It is probably a rocky place, just a bit bigger than Earth. With three times our mass, any visitor would feel a bit heavier — but it would be possible to walk upright and not float away, Vogt said.

It has just enough gravity to hold onto its atmosphere, although the composition is still unknown.

Its 37-day orbit is ideal, Vogt said. It’s not so close to its star that it gets sucked in, any life exploding into a puff of plasma. Nor is it so far away that it drifts into space, where atoms quit vibrating.

To learn more, Vogt said it might be possible to send a robotic probe using an experimental nuclear propulsion system.

We could get there in 220 years, he said, “if we started now.”