Starts With A Bang

Ask Ethan: Can Failed Stars Eventually Succeed? (Synopsis)

The closest brown dwarf system to Earth, Luhman 16, contains enough total mass to form a red dwarf star if everything within it were combined. The question of whether this will ever happen in our Universe is an interesting one. Image credit: Janella Williams, Penn State University.

“[Brown dwarfs] appear to live a more exciting life than we presumed. They are too big to be planets and two small to be stars, but it does appear that if you watch one it has very active events… there is action going on.” -Lars Bildsten

For every star that’s out there in the Universe, for every object that ignited hydrogen fusion in its core, there are many other objects out there that never got massive enough to do so. The largest failures, those that gathered between 13 and 80 Jupiter masses’ worth of material, are known as brown dwarfs. They achieve deuterium fusion in their core, but never cross that critical threshold to become true stars.

These are the two brown dwarfs that make up Luhman 16, and they may eventually merge together to create a star. Image credit: NASA/JPL/Gemini Observatory/AURA/NSF.

Many brown dwarfs, just like many stars, though, come in binary systems. If you were to add up all the mass in some of these systems, it would, in fact, be enough to create a star out of. The closest brown dwarf binary to us, Luhman 16, has exactly the right conditions that it could create a star if a merger ever took place.

Luigi Bedin’s multi-year study observing the motions of the failed stars in Luhman 16 has shown us how their positions and motions have changed over time, with the cycloid nature resulting from Earth’s motion during the year. Image credit: Hubble / ESA, L. Bedin / INAF.

What are our prospects for this pair of failed stars, or any failed star, eventually succeeding after all? Find out on this week’s Ask Ethan!