Stars cook up nearly all of the approximately 60 atomic elements in people’s bodies. But exactly how that works remains a mystery. Astrophysicists have developed cutting-edge computer simulations to grapple with an array of related puzzles:
• What were stars like when they first appeared in the universe over 13 billion years ago, starting the process of modern element production?
• What do we know about the nature of the death of massive stars — signaled by Type II supernovae — that fashion crucial elements such as calcium and oxygen?
• How might the burned-out stars called white dwarfs be brought to ruin by other stars in so-called Type Ia supernovae, inciting the fiery alchemy that yielded much of the iron in our blood and the potassium in our brains?
Scientists are still trying to figure out what triggers an individual Type Ia supernova and to determine the identity of the partner star to the exploding white dwarf. The Hubble Space Telescope’s recent discovery of the earliest known Type Ia supernova from more than 10 billion years ago, plus other results, favor a scenario in which two white dwarfs merge.
The results indicate that crucial elements in people formed later in the history of the universe than many had expected, says David Jones, the lead astronomer on the Hubble study. “It took (very roughly) about 750 million years longer to form the first 50 percent of the iron in the modern universe.”
Early Fireball Star
Out of the primordial hydrogen and heliumcreated in the Big Bang, clouds coalesced within 100 million years, eventually forming the first stars. This simulation shows light from an early star 100 million years after the Big Bang. When this fireball — millions of times brighter than the sun — dies in a titanic explosion called a supernova, it hurls out elements such asoxygen, carbon and magnesium.
About 500 million years after the Big Bang, one of the first galaxies in the universe formed, containing stars of about the same mass as the sun — which can live for 10 billion years — as well as lighter stars. The green and whitish regions depict elements such as carbon and oxygen.
This simulated image shows the first half-second of an explosion of a star 15 times more massive than the sun. Called a core collapse supernova explosion, one example of which is a Type II, these are a source of about a dozen major elements in people, including iron,calcium, phosphorus, potassium, sulfurand zinc. The sphere in the center is a newly born neutron star, the superdense corpse that remains of the former star. The scale from top to bottom is 1,000 kilometers, or 621 miles.
About one-and-a-half minutes into a Type Ia supernova explosion, elements created in the blast — iron (red), surrounded by silicon andsulfur (green) — are spat out with typical velocities of about 6,214 miles per second. Someoxygen (blue) is left after the explosion, but little carbon remains.
A star the size of the sun becomes a “red giant” toward the end of its 10-billion-year life span, a phase in which its outer atmosphere expands a great deal. The white region at the center is the dense, hot core where hydrogen and heliumare still burning in two concentric shells. Between those two shells, carbon is combining with helium to form oxygen.
Human Body Ingredients
The four ingredients below are essential parts of the body’s protein, carbohydrate and fat architecture. (Expressed as percentage of body weight).
Oxygen — 65.0%
Critical to the conversion of food into energy.
Carbon — 18.5%
The so-called backbone of the building blocks of the body and a key part of other important compounds, such as testosterone and estrogen.
Hydrogen — 9.5%
Helps transport nutrients, remove wastes and regulate body temperature. Also plays an important role in energy production.
Nitrogen — 3.3%
Found in amino acids, the building blocks of proteins; an essential part of the nucleic acids that constitute DNA.
Other Key Elements
Calcium — 1.5%
Lends rigidity and strength to bones and teeth; also important for the functioning of nerves and muscles, and for blood clotting.
Phosphorus — 1.0%
Needed for building and maintaining bones and teeth; also found in the molecule ATP (adenosine triphosphate), which provides energy that drives chemical reactions in cells.
Potassium — 0.4%
Important for electrical signaling in nerves and maintaining the balance of water in the body.
Sulfur — 0.3%
Found in cartilage, insulin (the hormone that enables the body to use sugar), breast milk, proteins that play a role in the immune system, and keratin, a substance in skin, hair and nails.
Chlorine — 0.2%
Needed by nerves to function properly; also helps produce gastric juices.
Sodium — 0.2%
Plays a critical role in nerves’ electrical signaling; also helps regulate the amount of water in the body.
Magnesium — 0.1%
Plays an important role in the structure of the skeleton and muscles; also found in molecules that help enzymes use ATP to supply energy for chemical reactions in cells.
Iodine (trace amount)
Part of an essential hormone produced by the thyroid gland; regulates metabolism.
Iron (trace amount)
Part of hemoglobin, which carries oxygen in red blood cells.