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Scientists have suggested that planets which float freely without a parent star, also known as orphan planets, are in fact extremely common in our galaxy. It is believed that these isolated worlds were somehow ejected from developing systems and now free-float around the galaxy.

The theory is based on findings of a New Zealand–Japan joint survey in 2006-2007 which scanned the center of the Milky Way discovering up to 10 orphan planets around the size of Jupiter. On the basis of these discoveries the scientific team estimate that there may be twice as many orphan planets than stars in our galaxy.

David Bennet, a NASA co-author of the study said “our survey is like a population census, we sampled a portion of the galaxy, and based on these data, can estimate overall numbers in the galaxy”. If the estimates are correct it would mean there are hundreds of billions of orphan planets in the Milky Way alone.

Lone planets smaller than the Jupiter were not able to be detected by the survey but scientists taking part in the study suggest that planets with an Earth like mass would be far more likely to be ejected from a system and are therefore far more common.

The study cannot dismiss the possibility that these planets are orbiting around very distant stars but previous research indicates that such occurrences are very rare.

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