Around halfway through the film, the ship encounters a 'spear', a long cylindrical object moving on a parallel trajectory to the Aniara, at a marginally higher speed. The captain and senior crew seem convinced that it's a probe sent from Earth and likely containing fuel rods.
the probe proves to be made of an impenetrable element not on the current periodic table. We see attempts to cut it with drills, blowtorches and lasers and scanned it with with geiger counters, x-rays and electron microscopy to try to find out what's in it. At the very end of the film we see that they've even tried explosives to get into it, all to no avail
So what is the 'Spear', who sent it and why?