Experts say an earth-like planet that they have discovered has the crucial conditions needed for life to exist.

It sits directly in the middle of what is referred to as the habitable or Goldilocks zone.

It is unlike any of the nearly 500 other planets astronomers have found outside Earth's solar system.

The planet is said to be neither too far from its star nor too close, and it could contain liquid water.

"People have been getting closer and closer over the last couple of years, they have been finding planets that are on the hot edge of the habitable zone and on the cold edge of the habitable zone, but finally we have one right in the middle," said co-discoverer R. Paul Butler of the Carnegie Institution of Washington on Wednesday.

But there remain many unanswered questions about this strange planet.

It is about three times the mass of Earth, slightly larger in width and much closer to its star, 14 million miles away versus 93 million.

It is so close to its version of the sun that it orbits every 37 days.

And it does not rotate much, so one side is almost always bright, the other dark.

Temperatures can be as hot as 160 degrees or as frigid as minus 25 degrees below zero, but in between, in the land of constant sunrise, it would be "shirt-sleeve weather," according to co-discoverer Steven Vogt of the University of California at Santa Cruz.