What happened to all that lithium? The question has preoccupied astronomers for decades. While cosmologists have successfully predicted the abundance of other light elements from the Big Bang, lithium has always come up short. Now perhaps a team of astronomers has found the reason: Lithium-rich asteroids are hitting white dwarfs.
As amazing as it sounds, we can use core theory to understand the conditions of the universe when it was only a dozen minutes old. In this inferno, the lightest elements – hydrogen, helium and lithium – began. Astronomers have been able to compare the predicted abundances of these elements to what they see in the entire universe, and everything matches … except lithium.
It's called the "Cosmological Lithium Problem" because it is exactly what it is. We know that this story of the Big Bang is largely correct. So where did all the lithium go?
Wherever it is, it's not in stars or interstellar gas clouds – we looked there.
And now, a new survey by a team of astronomers from the University of North Carolina Chapel Hill, the University of Montreal, and the Los Alamos National Laboratory believes they have the answer: white dwarfs.
Using the Southern Astrophysical Research Telescope, astronomers observed two very ancient systems of the white dwarfs, whose planets had formed over 9 billion years ago. These planets have long since disappeared and destroyed when their parent stars became white dwarfs.
But then parts of these planets crashed against the white dwarfs, where astronomers found signs of much more lithium than normal.
It is possible that the missing lithium in the universe is bound in planets and asteroids and can only be made visible to astronomers when these objects collide with their parent stars. Only more observations will show and maybe we will finally find all that lithium.