Notes from Jefferson Lab Science Series: 'The Origins of the Elements', Dr. Edward Murphy, November 13, 2012
The Origin of the Elements - YouTube

Immediately after the Big Bang, the Universe was a dark plasma of unformed subatomic particles. The Universe expanded in seconds, cooled, and began forming Hydrogen and Helium atoms (along with trace amounts of Lithium).

Cosmic Microwave Background

Gravity caused the newly formed gases to clump together and formed the earliest stars. While medium sized stars like the Sun exisit for ten to twelve billions of years, with the abundance of fuel (hydrogen), the first generations of stars were likey massive, but short-lived -- lasting (only) several millions of years, and created the heavier elements that make up you. Your atoms likely resided in at least three generations of stars before coming together in the middle of our solar system.

The first time your atoms found themselves in a star, they were likely near the surface of the star and not in the core. That star exploded and blew those atoms out into space. Your atoms joined others to create a star-forming nebula, and the second time your atoms found themselves in a star, it was likely again in the outer layer of the star. The third time your atoms found themselves in a star it might well have been in the core (along with Gold and other heavier elements). When that star exploded, your atoms found themselves not in a star, but in the planetary-forming regions surrounding the Sun. The fourth time your atoms found themselves in a star-forming region, they found themselves in the matter that formed the surface, and only the surface of the Earth.

Scientists use Absorption and Emission Line Spectrum to identify and analyze elements.

Absorption Line Spectrum

Emission Line Spectrum

Every element on the Periodic Table has its own unique spectra. Hydrogen has four, very specific, absorption/emission lines.

The Periodic Table seconds after the 'Big Bang':

The Periodic Table minutes after the 'Big Bang'

1 Hydrogen - 75%, 2 Helium - 24% +, and a trace amount of 3 Lithium. After a period of rapid expansion, the plasma of the universe cooled and formed gases. Gravity began 'clumping' the newly formed gases together and formed stars.

Medium sized stars like the Sun spend most of their 10-12 billion year life cycles fusing Hydrogen into Helium.

Solar/Stellar Reactions

Hydrogen protons combine to form 'heavy' hydrogen (2H). Those atoms fuse with a Hydrogen to form 3 Helium. 3 Helium atoms combine to form two Hydrogen and one 4 Helium atom - Helium with two protons and two neutrons. The net result is four Hydrogen atoms combine to form one Helium atom. Six hundred million tons of Hydrogen is converted to Helium EVERY SECOND in the core of the Sun.

A star like the Sun contracts for billions of years until its Hydrogen fuel source is depleted. The outer layer of the star collapses until temperatures become hot enough to fuse Helium into Carbon (6C). This occurs for approximately 100 million-years. The pressure of Helium fussion provides an outward thrust that expands the star to many times its original size, forming a Red Giant.

Hydrogen, Helium, Lithium, Berylluim, Boron, Carbon, Nitrogen and Oxygen

Eventually the Red Giant will eject its nebula and fade away as a White Dwarf star. When it ceases to produce energy altogether it darkens to become a Black Dwarf star. While stars the size of the Sun do produce elements heavier than Helium, those elements remain bound in the dead core of the star.

The heavier elements of the Periodic Table (some of the elements that make up you) were, and are, created only in the core of short lived, massive stars.¹

Hydrogen, Helium, Carbon, Neon, Oxygen, Silcon and Iron core

Hydrogen, Helium, Lithium, Berylluim, Boron, Carbon, Nitrogen and Oxygen -- Fluorine, Neon,
Sodium, Magnesium, Aluminum, Silicon, Phosphorus, Sulfur, Chlorine, Argon,
Potassium, Calcium, Scandium, Titanium, Vanadium, Chromium, Manganese and Iron.

Elements heavier than Iron are created only in the last two seconds of a massive star's life cycle¹ when, rather than simply colapsing into White Dwarf stars, they explode in Supernova.

Uranium (atomic number 92, atomic weight 238.0289) is the heaviest known naturally-occurring element in the universe.

Abundances of the Elements in the Universe

The ten most abundant (by weight) elements in the Universe are: Hydrogen, Helium, Oxygen, Carbon, Nitrogen (N), Neon, Magnesium, Silicon, Iron and Sulfur (S)

The Chemical Composition of You

The mass of your body is mostly made up of water (H2O), combining two Hydrogen atoms for each Oxygen
-- by mass, two Hydrogen = 2, while one Oxygen = 16 (with eight protons AND eight neutrons).

notes/updates since the 2012 Jefferson Lab Science Series talk

1) The alchemy of merging neutron stars -- November 7, 2019 - origin of large quantities of elements heavier than iron

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