You can't get much more mysterious than the interstellar asteroid 'Oumuamua, but is it mysterious enough to be an artificial probe designed by a spacefaring alien civilization? Researchers at the Breakthrough Listen initiative want to find out, and have begun observing the asteroid in an effort to determine if it's a naturally occurring object (unfortunately that's the far more likely scenario) or something else entirely.
When astronomers first discovered 'Oumuamua on October 19, the asteroid had already made its closest approach to the Sun, and was racing towards the outer reaches of the Solar System. Data collected on the asteroid allowed scientists to piece together its orbital trajectory to a high degree of accuracy.
The orbital data, in conjunction with the knowledge that 'Oumuamua was hurtling through the solar system at a top speed of around 196,000 mph (315,431 km/h) led scientists to conclude that the object was not gravitationally bound to our Sun, and was instead a transient visitor from interstellar space.