Comet-like objects crossing the Milky Way could carry bacteria across thousands of light years and spread life around the galaxy, scientists believe.

Experts say the discovery last year of the asteroid 'Oumuamua - the first interstellar object ever seen in the solar system - has raised hopes of discovering life that has been transported across space.

In a new study researchers said the entire Milky Way could be exchanging life 'across vast distances' and that microbes might be able to withstand the long journeys.

The paper's authors said bacteria could potentially survive for millions of years and even some more complex organisms had managed to stay alive in the vacuum of space.

Scroll down for video

Experts say the discovery last year of the asteroid 'Oumuamua (pictured in an artist's impression) - the first interstellar object ever seen in the solar system - has raised hopes of discovering life that has been transported across space

Our solar system might expect to capture one 'Oumuamua-like object every 100 years, scientists said, according to Science Mag.

The asteroid 'Oumuamua flew past Earth at 97,200mph last year and has shone new light on the interstellar objects zipping across the galaxy.

Many more of them would pass through the solar system but not all of them are likely to be captured by its gravitational fields, the scientists said.

The latest paper, published at Harvard University, is titled Galactic Panspermia - a reference to the idea that life is spread across the universe by comets and asteroids.

It said that if interstellar objects were moving at the speed of 'Oumuamua - 16 miles per second - there would be 10 million of them captured in the Milky Way over a period of a million years.

Binary star systems such as Alpha Centauri - the nearest star system to our Sun - would have a better chance than Earth's solar system of capturing the possibly life-carrying asteroids, the scientists said.

The authors said: 'If panspermia operates on galactic scales, it may be that there are little or no habitable exoplanets without life.

The cigar-shaped asteroid 'Oumuamua (artist's impression) was spotted by the Haleakala observatory in Hawaii on October 19 last year. In only another four years, it will pass Neptune's orbit on its way back into interstellar space

'Consequently, if a survey of exoplanetary atmospheres across the Milky Way found that nearly all habitable planets had biosignatures, this would be strong evidence for galactic panspermia.

'Considering the vast number of objects which are expected to be captured finding signs of extraterrestrial technology will be difficult, although a worthwhile search.'

Researchers would also need to distinguish between bacteria randomly flung across the galaxy and microbes deliberately dispatched by an advanced civilisation, they said.

The cigar-shaped asteroid 'Oumuamua was spotted by the Haleakala observatory in Hawaii on October 19 last year.

In only another four years, it will pass Neptune's orbit on its way back into interstellar space.