Download The Stars, the Elements and You

The Stars, the Elements and You
You have learned that the Sun makes elements in the process of nuclear fusion. And maybe by now you
also know that there are 92 naturally occurring elements (92 different atoms) found here on Earth and
throughout the Solar System (and throughout the Universe as well!) including ones you’ve heard of like
hydrogen, carbon, oxygen, calcium, iron and ones you might not have heard of like lithium, boron, or
vanadium. Atoms are very basic. You probably know they have three particle parts: protons and
neutrons that make up the nucleus (center of the atom) and electrons whirling around the nucleus at
near light-speeds. Atoms have two most important numbers associated with each atom (there are
other important numbers as well!). These are the atomic number (always a whole number) and the
atomic mass (usually a whole number and a decimal fraction). If you look at a periodic table of the
elements, the atomic number is usually found in the top of the box for any atom, and the atomic mass is
usually found at the bottom of the box. The atomic number is the number of protons and identifies the
atom based on it’s properties. The atomic mass is the number of protons and neutrons and is just what
it suggests it is: the mass of the atom. The reason that the atomic mass is not a whole number is that
most atoms have versions of themselves called isotopes which have more or less neutrons, but always
the same number of protons (very important point!). Isotopes are critical in providing evidence for all
kinds of things we know about Earth, life on Earth, the Solar System and everything in the Universe! You
of course, are made of chemicals built from the elements. In your body are elements from hydrogen
(atomic number 1) up to elements with atomic masses larger than iron (atomic number 26). Did the
elements in your body come from the Sun? No. The elements that make up the Sun and everything in
the Solar System including you came from a huge gas and dust cloud (called a nebulae) that was the
result of the massive explosions (supernovae) of many giant stars. Our Sun can only make elements up
to iron which has an atomic number of 26. A clue that we are made (and everything on Earth around
us..) from the giant star explosions is that we have all 92 elements on Earth and in the Solar System. Just
as elements are formed in our Sun by fusing (putting together) the nuclei of atoms to make more
massive atoms, so it is in supernovae. These explosions are so powerful that a single supernova can
outshine an entire galaxy (hundreds of billions of stars) for a brief moment! And in that brief moment as
the elements up to iron that were made in the massive stars earlier are hurtling outward through space
at incredible speeds, the nuclei of those atoms slam together at random with such force that even
heavier atoms are synthesized (made)! This is the only way that we know that elements heavier than
Iron can be synthesized, except for some interesting human science “tricks” that we learned in the 20th
Century. Specifically we can synthesize some elements in the lab by making nuclei stick together when
we accelerate and smash them together (tiny amounts, safe and controlled), and as a byproduct of
nuclear reactions including the kinds that occur in nuclear power plants (amounts large enough to
accumulate over time and be used or stored where they won’t do harm, potentially dangerous but
usually controlled) and in the explosions of nuclear weapons (small amounts, but very dangerous and
uncontrolled). But we will probably never be able to created the massive power that occurs inside the
core of a star about to go supernova. We will thus likely never be able to do what stars do: make all the
elements up to uranium (element 92). At least not in abundance. By the way, you might be wondering
where these ancient stars got their elements. Some must have formed from even earlier supernovae,
but the most ancient of all stars (now long gone) were built from hydrogen and helium (atomic number
2) which came from the Big Bang (the very beginning of the Universe itself)! So you are made of material
that came from other stars that are now long gone (billions of years ago!) and you rely upon the energy
of the Sun which synthesizes new atoms every second of every day in the Sun! And to state it again,
nope, sorry, our Sun is not massive enough to end it’s “life” (stars are not alive, but they are sometimes
spoken of that way as a metaphor…) in a huge supernova explosion. Rats!
Answer the following questions based on what you just read.
1. How many naturally occurring elements are there? Where are they found? Name six elements.
2. What are the three particle parts of an atom. Which parts are found in the nucleus? Define atomic
number. Define atomic mass. What is an isotope? Why are they important as scientific evidence?
3. Where did the elements in your body come from? Where did the hydrogen and helium come from
(this answer is found at the end of the reading!) What is a supernova? What do you think supernovae
means? What kind of star produces supernova?
4. What are some human “tricks” we have learned in the 20th Century to synthesize atoms? Which way
is the least dangerous? Which is the most dangerous?
5. Will we ever be able to make elements the way they are made in stars? Why or why not?
6. Our Solar System formed 4.6 billion years ago, so how old must the stars that went supernova be at
the very least? What is the Big Bang? Will our Sun go supernova? Why or why not?
7. Sometimes you read or hear the phrase that humans are made of “star stuff”. Explain what that
means.