Made of stars: how the universe forged the elements in your body
Michelle Thaller explains why we are made of stars, Anna Frebel traces heavy elements to the first stars and neutron star mergers, and Harry Cliff asks why matter survived at all. Their accounts connect everyday atoms to events billions of years old, one of the clearest ways to grasp our place in the cosmos.
In how many stages were the atoms in a human body assembled? Show answer
At least three: particles surviving the early matter and antimatter contest, light elements from the Big Bang, and heavier elements made later by stars and neutron star collisions.
What three particles make up every atom, according to Harry Cliff? Show answer
Electrons, up quarks and down quarks. He describes each as a ripple in a quantum field that fills all of space.
Why does Cliff call us leftovers? Show answer
The Big Bang should have made equal matter and antimatter, which would annihilate. Only one in a billion particles survived, and those make up everything.
Which elements did the Big Bang leave behind? Show answer
Only hydrogen, helium and a trace of lithium, according to Anna Frebel.
What did the first stars contribute? Show answer
They were around 100 times the Sun's mass and exploded within a few million years, seeding the universe with its first carbon, oxygen, magnesium and iron.
Up to which element do stars fuse lighter elements into heavier ones? Show answer
Up to iron. Heavier elements need a different route.
What is the r-process? Show answer
Rapid neutron capture. A seed nucleus such as iron is bombarded with neutrons faster than it can decay, then decays into stable heavy elements up to thorium and uranium, in about two seconds.
What confirmed neutron star mergers as a site of the r-process? Show answer
In 2017, detectors caught gravitational waves from two merging neutron stars, and telescopes saw a fading glow that matched freshly made heavy elements decaying.
Why does Frebel call carbon possibly the most important element? Show answer
Carbon and oxygen let gas clouds cool and fragment into small, long-lived stars like the Sun, which make planets and life possible.
What did the Bennu asteroid sample contain? Show answer
All the nucleobases of both DNA and RNA, plus others life on Earth does not use, and signs the asteroid was once soaked in water.
How do astronomers know what stars are made of? Show answer
Spectroscopy. Starlight is split into colors, and every element leaves its own fingerprint in that rainbow.
What qualifier should go with the phrase that we are made of stars? Show answer
Hydrogen and helium date from the Big Bang, and the heaviest elements come mostly from neutron capture, not ordinary fusion.