Most of the conversations at the Strobel dinner table revolve around teaching and physical science, which is exciting for two empty STEM teachers.
A few days before the high school students arrived on campus, my wife wondered what she was going to do with her science students, since they weren’t getting their textbooks and Chromebooks until the fifth day of the semester.
She decided to do a paper-and-pencil exercise on the periodic table of elements. I suggested an astronomical connection with the “cosmic connection to the elements”.
The periodic table is a graphical representation of the different types of atoms in the universe, such as hydrogen, helium, carbon, oxygen, iron, uranium, etc. Each type of atom called an “element” has a unique chemical property.
There are 92 natural elements in the universe and more than twenty elements that we have synthesized in our high energy laboratories.
Every atom has two basic parts: a central massive nucleus made up of protons and neutrons and a cloud of low-mass electrons swirling around the nucleus. Much of chemistry depends on the arrangement of outer electrons, so the periodic table arranges the elements into groupings of similar outer electron configurations and increases the total number of electrons from left to right and top to bottom.
Since the number of positively charged protons corresponds to the number of negatively charged electrons in a neutral atom, the increasing number of protons in the elements of the periodic table goes hand in hand with the increasing number of electrons. Neutrons are there and help hold the nucleus together, so most chemistry ignores neutrons.
The cosmic connection comes when we talk about the origin of atoms. Chemists will often say that different materials are created from different types of chemical reactions, such as when carbon dioxide and water react with the energy of sunlight to create sugars plus oxygen in the process. which we call photosynthesis or when burning coal or oil creates carbon dioxide. .
Snobbish astronomers and nuclear physicists scoff at this “creation” and say that chemical reactions “just mix atoms”. The number of different types of atoms – the elements – in a chemical reaction remains the same, but the way the different elements connect or bond to each other changes in a chemical reaction. However, where do the individual atoms themselves come from?
Many scientific researches have led us to discover that all the atoms of the Earth, planets, moons, etc. came from cosmic processes, most having to do with the stars. Most of the hydrogen, which has a proton in the nucleus, was created in the first microsecond after the universe began to expand (the Big Bang) when the universe was extremely hot and dense. Most of the helium in the universe was created in the first few minutes after the start of the expansion when some of the hydrogen was shattered in a process called nuclear fusion, similar to what is happening now in the heart of stars like the sun.
With hydrogen fusion, four hydrogen nuclei – four protons – are crushed to form a helium nucleus, which has two protons and two neutrons. It turns out that the helium nucleus has a total mass less than the combined mass of the original four protons. The mass that was lost in nuclear fusion was converted into energy — light! That’s what makes the stars shine. Stars are now slowly increasing the amount of helium in the universe.
Nuclear fusion requires extremely high temperatures and densities. As stars age, they run out of hydrogen to fuse into the core, and the core fills with helium. The core compresses and heats up enough for the helium to fuse together to form heavier elements such as lithium, carbon, oxygen, silicon, and iron. The more massive a star, the more types of elements it can produce because creating nuclei with more protons requires ever higher temperatures and densities.
Explosive stellar events called supernovae can make many even heavier elements such as nickel, copper, zinc, etc. from a super-fast nuclear fusion process that only takes a few minutes. Supernovae occur when very massive stars die and their cores suddenly collapse or when already dead low-mass stars called white dwarfs in a binary system suck up too much gas from their nearby companion star. It turns out that the cores of dead high-mass stars called neutron stars also briefly have nuclear fusion when they collide with other neutron stars. Most of the gold and uranium in the universe comes from it.
Our theory of the creation of all the different elements from nuclear fusion correctly predicts the observed abundances of all naturally occurring heavy elements found throughout the universe. We now understand why certain elements like carbon, oxygen, silicon and iron are common and the heavier elements like gold, mercury and uranium are so rare.
In order to create a planet like Earth (and life on such a planet), enough heavy elements must be created in previous generations of stars, then concentrated in the interstellar clouds to collect in large chunks around the stars. forming stars. There is necessarily a “lag” between the beginning of the universe and the beginning of life.
Upcoming Dark Sky Festival
Put the Dark Sky Festival in Sequoia and Kings National Parks on your calendar for September 24.
There will be presentations as well as a star party. The Kern Astronomical Society will have many telescopes that people can use under really dark skies.
Contributing columnist Nick Strobel is director of the William M. Thomas Planetarium at Bakersfield College and author of the award-winning website AstronomyNotes.com.