Why Are Supernovae and Kilonovae Essential for Advanced Life?

Question(s) of the week: How does the uranium and thorium from supernovae produce Earth’s magnetic field and plate tectonics? Can you give us more reasons why we need supernovae?

My answer: A supernova eruption event occurs either when (1) a giant star having completed its normative nuclear burning suffers catastrophic gravitational collapse, or (2) when a white dwarf star (a burnt out star) accretes sufficient matter from a companion star to generate a catastrophic gravitational collapse. This collapse produces a pressure and temperature so extremely high in the star’s core that iron and elements lighter than iron are forced to capture neutrons, thereby manufacturing elements heavier than iron.

Nearly all the elements heavier than iron are manufactured by supernovae. The remainder are manufactured by kilonovae, which result from the merger of two neutron stars.¹ Without supernovae and kilonovae there would be no elements heavier than iron anywhere or any time in the universe. The following life-essential elements are found in the bodies of every human being: cobalt, copper, zinc, arsenic, selenium, molybdenum, and iodine. Without these heavier-than-iron elements neither human beings, the functional equivalent of humans, nor nearly all large animals could possibly exist. Therefore, advanced life is impossible without supernovae and kilonovae.

I must warn readers, however, about overdosing on supplements rich in these heavier-than-iron elements. They are all “vital poisons.” Too little in your bodies will kill you. Too much in your bodies also will kill you.

Without supernovae and kilonovae there would be no thorium or uranium. Both of these elements are radioactive where the main isotopes of each have decay half-lives equal to 14.05 and 4.46 billion years, respectively. The radioactive decay of these elements generates heat and, because of the long half-lives, the heat release can be sustained for billions of years. Since Earth is super-endowed with uranium and thorium, the heat release from these elements is considerable.

The heat release from the radioactive decay of uranium and thorium is sufficient to produce and sustain a liquid core in Earth’s interior. This liquid core of predominantly ferrous elements (iron, cobalt, nickel) sustains a strong magnetic field. This strong magnetic field generates a magnetic field around Earth that protects Earth’s surface life from deadly cosmic and solar radiation. It also prevents solar radiation particles from sputtering away Earth’s atmosphere into interplanetary space.

The heat released from the decay of uranium and thorium causes the crustal plates of Earth to move relative to one another. This plate tectonics transformed Earth from a water world where water covered the entire surface of Earth to a planet possessing both surface oceans and surface continents. The combination of surface oceans and continents effectively recycles life-critical nutrients. Without long-lasting plate tectonics, life could exist on Earth for only a brief time period. Thus, for many reasons our lives and our civilization critically depend on a large number of supernova and kilonova events occurring in our galaxy. However, the number must be fine-tuned. The radiation emitted by supernovae and kilonovae is deadly. Too high of a frequency of supernova and kilonova events in our galaxy would expose Earth to an intensity of radiation from these events that would rule out the existence of advanced life. Too low of a frequency would mean that Earth would lack the uranium and thorium and other heavier-than-iron elements that advanced life needs.