Within the vast expanse of the Milky Way, U.S. astronomers estimate that some 17 billion Earth-sized planets exist and likely located in the so-called habitable zones, where water in liquid form is found.

If recent findings that were presented Monday before the American Astronomical Society were to be believed, the existence of life forms inside the realms of our very own galaxy is highly possible.

According to Dr Francois Fressin of the Harvard-Smithsonian Centre for Astrophysics, new analysis of the data collected and transmitted by the Kepler spacecraft, launched in 2009 by U.S. space agency NASA, suggested that billion of planets are right inside Milky Way's territory and great of many of them are close proximity to Earth's size.

This projection was based on the estimated 150,000 stars that Kepler has covered so far, 17 per cent of them "host a planet up to 1.25 times the size of the Earth," Dr Fressin told BBC.

The new analysis, he added, presents an exciting prospect for humanity, indicating too that within the Solar System, planets that resemble Earth in size, form and hopefully features are actually aplenty in numbers.

"If you look up on a starry night, each star you're looking at, almost each one of them, has a planetary system," Dr Fressin was reported by The Associated Press (AP) as saying during his Monday presentation in California.

This piece of good news delivered by Kepler is accompanied by another encouraging development - that scientists are now looking at a total of 2740 potential planet candidates, also within the Milky Way confines.

Kepler has recently discovered 461 new candidate planets and some of which were deemed as Earth-sized, according to Christopher Burke of the SETI Institute.

Four of these newly-detected planets, Dr Burke added, are observed having "less than twice the size of Earth."

"(They) are potentially in the habitable zone, the location around a star where it could potentially have liquid water to sustain life," the mission's chief scientist told BBC.

For a planet to be listed as liveable, it has to be in "the so-called Goldilocks zone where it's not too hot or too cold for water to be in liquid form on the surface," AP said on its report.

And Kepler, according to NASA, is well on its way to map as many Earth-like planets as possible in the years to come, with the space agency adding that the spacecraft was chiefly designed to look for not only one but numerous Earths.