What’s on : Lectures

Stellar Alchemy and the Origin of Cosmic Elements

10 Mar 2020
Start time
7:30 PM
Tempest Anderson Hall
Professor Jordi José, UPC Barcelona

Event Information

Stellar Alchemy and the Origin of Cosmic Elements
Jordi José, Dept. Physics, UPC Barcelona

Where do the nitrogen (N) in our DNA, the calcium (Ca) in our bones, the iron (Fe) in our blood, or the oxygen (O) we breathe come from? As the late planetary scientist Carl Sagan used to say, we are made of starstuff. Most of the ordinary (visible) matter in the Universe, from a terrestrial pebble to a human, a giant star, or a galaxy, is made of protons and neutrons arranged in different configurations called elements. There are 82 elements that have stable isotopes, all the way from hydrogen (H) to lead (Pb), except for technetium (Tc) and promethium (Pm). Several dozen elements have only unstable isotopes, naturally abundant or artificially synthesized in nuclear physics labs.

During eons, the Cosmos was a chemically hostile environment, almost devoid of elements, except for the very light ones [(hydrogen (H), helium (He), and some marginal amounts of lithium (Li)], created during the first hundreds seconds after the Big Bang. For about 200 million years, during the so-called Dark Ages, the Universe just expanded and cooled down. But the emergence of the first stars, formed by effect of gravity, changed the picture completely: such nuclear furnaces have been responsible for turning the handful of light elements synthesized right after the Big Bang into a suite of heavier elements. Indeed, most elements up to Fe are synthesized by nuclear fusion in “normal” stars of different masses, while elements heavier than Fe are produced in a number of astrophysical sites, including the late stages of the evolution of low- and intermediate-mass stars, core-collapse supernovae, and neutron star mergers.

This talk summarizes a breathtaking 13.8 billion-year cosmic journey, from the Big Bang to the role played by stellar explosions in shaping the chemical abundance pattern that we see today in the Universe.

Crab Nebula image: courtesy NASA and STSci

Dr Alison Laird’s lecture will follow at a later date and she will introduce ProfessorJosé

Astrophysics mini theme