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A Terrestrial-Mass Planet on the Run?

20 Nov 2020, 17:00 UTC
A Terrestrial-Mass Planet on the Run?
(200 words excerpt, click title or image to see full post)

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.
Severing Attachments
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 ...

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