On average, only one comet per year can be seen soaring across the sky with the naked eye. If you're very lucky, you might have seen one for yourself, and this picture will look very familiar. But as much as it looks like a comet, this object baffled astronomers when it turned out to be a simple asteroid!
Credit:
NASA, ESA, D. Jewitt (University of California, Los Angeles), J. Agarwal (Max Planck Institute for Solar System Research), H. Weaver (Johns Hopkins University Applied Physics Laboratory), M. Mutchler (STScI), and S. Larson (University of Arizona)