Most of the planets obey the rules. They are orbiting a star. You are predictable. Steady. The kind of planets you bring home to your parents. However, some planets are free thinkers, and a team led by astronomers at the University of Warsaw has found a particularly wild planet that has found its own way in our Milky Way.
The exoplanet (a planet outside our solar system) does not appear to be bound by a regular orbit around a star, making it an exceptionally rare find.
The researchers announced in a statement last week the discovery of "the smallest Earth-sized free-floating planet found," and published an article in The Astrophysical Journal Letters. We've seen Evidence for rogue planetsbut not so dainty.
Due to the size, properties and path of the exoplanet, it could not be detected with our usual tricks for planet recognition. Instead, the researchers used the power of Gravitational microlens, a technique inspired by Albert Einstein's general theory of relativity. Astronomers can use the gravity of space objects like stars as massive magnifying glasses to see far and deep into space.
A NASA video explains the concept of rogue planets.
Warsaw University's OGLE survey examines space in search of microlens events among hundreds of millions of stars. In this case, the rogue planet passed a star and caused a brief deflection and focus that triggered a noticeable brightening of the star, as seen by a telescope on Earth.
"Microlens events attributed to free-floating planets have a timescale of barely a few hours," said the university. "By measuring the duration of a microlens event (and the shape of its light curve), we can estimate the mass of the lens object." The team discovered the Earth-sized rogue planet through a microlens event (officially called OGLE-2016-BLG-1928) that lasted just 42 minutes.
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The planet would have formed like any other, but was later thrown out of its solar system through interactions with other planets or space objects. Rogue planets like this one could give us insight into the early days of our own system.
Astronomers would like to find out how common small rogue planets could be. This can only be the tip of a cosmic iceberg. We should learn a lot more once NASA's Nancy Grace Roman Space Telescope will be put into operation in the mid-2020s. Until then, we can celebrate the discovery of a free spirit of space travel that reminds us (just a little) of Earth.
