Until recent decades, the only things that changed visibly within a human lifetime outside our solar system were supernovae, and the apparent positions of nearby stars (and that only barely measurably).
Modern equipment has uncovered many objects of several kinds that change visibly in human time-scales. Here are a few examples.
Still, the only things that change outside our galaxy in human lifetimes are supernovae (well, and cepheid variable stars…).
I started this list in the mid-2000s. For some years I was trying to keep up with new examples, but nowadays, I’m afraid, new discoveries are coming too fast for me to keep up with.
Eta Carinae is the largest star known in our galaxy, being some 120 to 220 times as massive as our Sun, with a companion star that is 30 to 80 times as massive as our Sun orbiting it every 5½ years. Beyond that, it is hard to make direct observations, because the stars are obscured by material that has recently been ejected from the system. It formed only a few millions of years ago, and hasn’t long to live, as stars go.
The bell-shaped object is the remains of an outburst of the star that occured in 1827. It still changes visibly within months.
Unfortunately not a video, but a “difference of two images taken 17 months apart”
In 1987, the first relatively-nearby supernova of recent times appeared. It was not in our galaxy, but in its satellite, the Large Magellanic Cloud. After the flash of the explosion, that lasted several days, some strange patterns appeared in the environs of the star.
These bead-like effects are interpreted as supernova debris crashing into surrounding gases, probably thrown off by preceding outbursts from the star.
The crab nebula is associated with a supernova that was observed in 1054 AD. Its remains are still expanding at about 5% the speed of light.
Original at APOD 2023 March 20, this is a sequece of photographs made with the same equipment over a span of 14 years.
This is light from a flash made by the star, reflected off dust and gas in the vicinity of the star, moving as successive observations are made. So, this isn’t material moving, it is light moving through material.
The star pulses every 40 days or so, waves of light from those pulses pass through surrounding dust and are echoed back to us.
See: Light echoes whisper the distance to a star
Our local big black hole, weighing in at around 3 million solar masses, can’t be seen at visible wavelengths of light, but has a very big effect on surrounding stars.
These are big stars, behaving like comets orbiting the black hole. But some are in very fast orbits, with periods of 11 years or so, although their orbital radii are several times that of our solar system.
Main site at Max-Planck-Institut für extraterrestrische Physik, with further animations
By the Chandra X-ray observatory: it looks like an artist’s rendition of a hypothetical accretion disk and jet, but it is an actual observation.
There is an apparent shock wave, apparently in a disk-like structure, punctured by a jet. The disk is far too large to be an accretion disk. I don’t know what it is.
The jet is clearly moving. In the accretion disk, the motion is that of shock waves moving through the disk.
Scorpius X-1 was the first discovered extraterrestrial X-ray source. It is relatively nearby (9000 light years distant), and is thought to consist of a medium-sized star and a neutron star orbiting one another every 19 hours. The neutron star would strip material off its companion, which would accrete to its surface, periodically producing an accretion disk and jet.
The jet consists of two beams, one pointed toward us, one away. Here we see a clump in the lobe pointed at us, moving very rapidly—at nearly the speed of light.
From our vantage point, the size of the source and the lobes is very small. These pictures were made using numerous radio telescopes; only such equipment could resolve these small details.
Accretion disks and gas jets are a common of occurrence in several rather different situations. Besides the big jets associated with distant black holes (where the disk is too small to be seen) and some neutron stars, they are often found about young stars nearby.
A video of the central region: