Only about 13 white dwarf-brown dwarf binaries exist within 100 parsecs of the Sun.

Astronomers rarely find pairs where a white dwarfwhite dwarfA dense remnant of a low-mass star that has exhausted its nuclear fuel., the burned-out core of a dead star, orbits together with a brown dwarfbrown dwarfA substellar object not massive enough to sustain hydrogen fusion, between planets and stars., an object too small to become a normal star. Researchers wanted to know why these pairs are so scarce near our Sun. To test this, they updated a computer simulation program that tracks how pairs of stars form and age over time, adding rules for how brown dwarfs evolve. Their model simulated the stellar neighborhood within 100 pc of the Sun. They found that these pairs truly are rare: they predict only 13+-5 systems, matching what telescopes actually see and making up just 0.1% of local white dwarfs. The model matches real star temperatures, masses, and orbits well, though the simulated brown dwarfs turned out hotter than real ones.

Why it matters

This work confirms why astronomers see so few of these rare pairs, helping refine models of how stars and substellar objects form and evolve. It guides future observations and improves our understanding of binary systems in the galaxy.

Questions answered