Low-mass white dwarf

Mass is conserved, and stars evolve according to a Main Sequence. The low-mass white dwarf should come from a low-mass red dwarf. Problem: those red dwarfs from the formation of galaxies are... still here. So why do we see any white dwarf which should be older than THE WHOLE UNIVERSE.

I have to give not only a hat-tip but credit this time to Mark Tapscott, who might otherwise be inclined to say "our models are wrong" and then some Calvinist entryism. Here he's bringing evidence against interest.

Outside interference, was the answer. Kareem El-Badry finds the culprit: they were in binaries. He found 21 not-yet-dead stars that are elongated as their mass is being pulled toward their companions. For eight of these their companions aren't actually consuming the mass (anymore?); the other thirteen are still transferring hydrogen across the void. The opposite of the polluted dwarf, then. UPDATE 2/4/22: Kind of like those big merge-stars out in the halo. UPDATE 2/15: There's a lot of that, going around. UPDATE 3/2: When a gravity-well isn't black.

The smaller star, by losing the outer layer of hydrogen, stays on the Main Sequence; the core didn't lose mass. The helium / hydrogen balance is further skewed, but it also loses heat for its core. As for the larger star, I am likewise unsure; its added hydrogen may buy it some more time, but as it gets more massive the core would burn hydrogen that much faster. It seems, though, that death does come for the smaller star; it dies a K that was born A. (Also I suspect some born-G types like our own Sun might lie among the 21.)