The mysterious interstellar object 3I/ATLAS is just weeks away from reaching its closest point to Earth: it's expected to pass within just 170 million miles of our home planet on December 19, giving astronomers an unprecedented opportunity to take a closer look as it whizzes past. As Harvard astronomer Avi Loeb points out in a new blog post, they'll be building on intriguing existing observations from ground telescopes - including a paper published in the journal Astronomy & Astrophysics in October by a team of researchers in Europe and Africa that found signs that it's radiating a "heartbeat" pulse of light that repeats every 16.16 hours.