The Parker Solar spacecraft, which reaches a speed of 532,000 km/h, is the fastest human-made object, but it is still very slow compared to other celestial objects in the universe.
According to human knowledge, the fastest thing in the universe is photons of light, followed by subatomic particles when they are inside particle accelerators or high-energy astronomical events. However, they are too small to observe. Instead, the search for the fastest and large enough object to be seen with the naked eye is perhaps more interesting, as reported by IFL Science on April 20th.
The universe is expanding. This means that everything is moving away from each other. The further an object is, the faster it is moving away. Therefore, for humans, the fastest-moving object in the universe can also be the object farthest away. However, this record is constantly being broken, especially as new tools such as the James Webb Space Telescope appear. Since starting operation last year, the James Webb telescope has discovered some “new candidates” for the title of farthest galaxy and will undoubtedly continue to find more such candidates.
However, for any inhabitant (if any) living in those galaxies, they are not moving fast at all. They will only see some very distant galaxies moving, their own galaxy seeming stationary, and nearby galaxies also moving very slowly. To simplify, the search for the fastest and large enough object to be seen with the naked eye will be limited to the fastest-moving objects compared to nearby objects.
The fastest human-made product, the Parker Solar spacecraft, reaches a speed of 532,000 km/h relative to the Sun and is expected to fly even faster, by more than 30%, if there are no hiccups. However, this speed is still extremely slow compared to the speed at which some planets orbit their star. For example, SWIFT J1756.9-2508b, a likely exoplanet, orbits a pulsar in less than an hour. This means that its average speed is about 766 km per second, equal to about 0.2% of the speed of light.
Black holes rotating around each other can reach much faster speeds, but scientists often only detect them from gravitational waves after they merge. An exception is the two black holes in the PKS 2131-021 galaxy. Currently, they still take two years to orbit each other, but this process is accelerating.
In terms of linear motion, some stars are ejected from galaxies when they get too close to a supernova or are part of a “stellar ejecta”.