WASHINGTON — NASA's planet-hunting telescope has discovered two planets that seem like ideal places for some sort of life to flourish. They are just the right size and in just the right place near their star.

The distant duo are the best candidates for habitable planets that astronomers have found so far, said William Borucki, the chief scientist for NASA's Kepler telescope.

The discoveries, published online Thursday in the journal Science, mark a milestone in the search for planets where life could exist.

The new discoveries, called Kepler-62-e and Kepler-62-f, are just right. And they are fraternal twins. They circle the same star, an orange dwarf, and are next to each other — closer together than Earth and Mars.

The planets are slightly wider than Earth, but not too big. Kepler-62-e is like a Hawaiian world and Kepler-62-f is a bit nippy, more Alaskan, Borucki said.

The planets circle a star that is 7 billion years old — about 2.5 billion years older than our sun.

"If there's life at all on those planets, it must be very advanced," said Borucki.