Where Did All The Lithium Go? 

The instant of the Big Bang gave birth to hydrogen, helium and a small amount of lithium. Hydrogen and helium are the main elements that fuse to give stars their heat, energy and intrinsic brightness. 

When discussing matters of cosmology I may have neglected lithium slightly. Lithium is one of the oldest elements in the known universe but it doesn’t play an active role in keeping stars fuelled nor does it appear abundantly in comets and asteroids like iron does. 

Lithium is a soft alkali metal which can cut very easily. It is very reactive, flammable and when used in labs in its pure form it is stored in mineral oil. When cut open the moisture of the air can cause it to corrode very quickly. It is soluble as an ion and found quite abundantly in seawater. 

Lithium is somewhat of a wonder material with many different uses for us on Earth. It is used in watch batteries, historically as propellant for torpedoes and as a medication tablet to treat illnesses like Bipolar Disorder and Schizophrenia. I have become very familiar with it as a medication through my day job.

Cosmologists and physicists predicted that lithium must be abundant in the older stars in the cosmos. When studied with modern telescopes with state of the art sensors to detect stellar composition, the amount of lithium in older stars was very surprisingly low. This begs the question, where did all the lithium go?

Surely it is easy to hypothesise that lithium would be reasonably abundant given it was the first of three elements born from the Big Bang and the very early Universe expanded in every direction faster than the speed of light before cooling and becoming the universe we see now. 

After observing the very old stars, many millions of years old and more, the lithium levels just weren’t there! In physics this is called “The Lithium Discrepancy” and quite a discrepancy it was at the time. 

The reason for the lesser lithium in old stars is that the lithium eventually mixes Into the interior of the star and destroyed. Interestingly, newer stars have a much higher level of lithium because it is produced in younger stars. As a rule of thumb, lithium is more abundant in much cooler stars as the temperature within isn’t high enough to destroy it.

Lithium has been observed in one particular bright orange star, Centaurus X-4. If a star like this is orbiting a high mass object like a neutron star or black hole the lithium will be pulled to the surface so it is easier to observe. 

Also, in 2013 a supernova was found to be ejecting lithium! This was the first time lithium had been observed in a supernova explosion and hasn’t been seen since, or at least verified. 

Although the Nova Centauri didnt send a huge amount of lithium out to the galaxy, most likely less than a billionth of the mass of the Sun, there have been hundreds of  billions of stellar explosions in the history of our own galaxy, the Milky Way. It certainly goes a long way to explain the observed and unexpected amounts of lithium in our galaxy.

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