Scientists have long believed that there may be billions to trillions of rogue planets drifting through our galaxy, unattached to any host star. A recent study has now identified one such candidate — potentially the first terrestrial-mass world we’ve spotted on the run.
Artist’s impression of a free-floating, Earth-like planet. [Christine Pulliam (CfA)]We’ve discovered more than 4,000 exoplanets in the last three decades, spanning a dramatic range of masses, sizes, temperatures, compositions, orbital properties, and more. The vast majority of them, however, share one feature: they all orbit a star.
While this may seem like normal behavior — after all, we’re rather attached to our own star, here on Earth — planetary formation models predict that there should be a large population of free-floating planets in our galaxy. According to the models, these typically sub-Earth-mass planets get kicked out from their parent systems through interactions with other bodies (usually bullying gas giants).
How can we observationally confirm this picture? Without the beacon of a host star’s light, free-floating planets are challenging to detect — but they’re discoverable via a method called gravitational microlensing.
Gravitational microlensing is a powerful tool for detecting exoplanets. This illustration shows the bending of ...