There are no aliens on an interstellar rock flying around the solar system. This interstellar rock, called Oumuamua, is a very unusual cigar shape and caused a lot of speculation. Scientists from Harvard University thought it might be an artificial spaceship, because it accelerated as it was leaving the solar system.
A new paper in Nature Astronomy has analysed Oumuamua and provided reasons for why it is such a weird shape and passed through our solar system. Scientists now think that it is the start of a new planet being formed!
This story is related to the Cosmology section in the Physics A Level course.