The life and death of stars.

Nothing brightens the cosmos like a supernova. The demise of a star releases enormous quantities energy and material that's like pollen for a new generation of stars, planets and life itself.

Ultimately, humankind's fascination with the stars in the heavens is an ageless quest to learn more about ourselves and our own origins. Where did we come from, what are we made of? These and other gut level questions are the sparks that ignite our most profound curiosity.

The ancient Greeks speculated matter was an arrangement of invisibly small building blocks and coined the name 'atom' to represent the indivisible pieces. Al though they lacked the technology and scientific discipline, Greek atomists ,like Democritus of Abdera, came close to our modern day understanding of nature around the year 400BC. Over the past century, we've discovered twelve basic building blocks of which three- protons, neutrons and electrons- are required to combine and make everything in the Universe, including ourselves.

Science has revealed that everything in the Universe is composed of the same basic ingredients and over time, they can be recycled to make something different. For example, every atom in our bodies was once part of something else. Over time, rocks can become living things and living things, following their demise, can become fossilized rocks. What's true for us is also true for the stars.

99 percent of the Universe is hydrogen and helium. These were created in the first seconds following the Big Bang. But, our world contains 94 naturally occurring elements. Where did they come from?

In addition to the three fundamental particles of nature, there exists four essential forces that operate throughout the Universe. Two of the these, the strong and weak nuclear force, occur within the atom and have an extremely limited range. The third, called electromagnetism, is responsible for electricity, magnetism and light. It also acts on the atomic level to hold matter together by giving a positive charge to protons and a negative charge to electrons. The fourth has an almost infinite range, It shapes and controls the Universe on the grandest scale and is both the creator and destroyer of planets and the stars themselves. It's known as gravity.

Chemistry is actually a science of numbers that enables us to understand how the four essential forces interact with the three fundamental particles.

For instance, the nucleus of an atom is made of protons and neutrons. If an atom has one proton, its called hydrogen. If it has two protons, its helium; Lithium has three protons; beryllium has four; and so on up to 92 protons, which is called uranium. The chemistry of an atom depends on its number of protons and is called the atomic number. Elements are usually arranged in their order of complexity on the periodic table.

The number of protons and neutrons in the nucleus are held together by the strong nuclear force which acts like short hooks to hold the nucleus together. The number of positively charged protons in an atom equals the number of negatively charged electrons flying in a cloud surrounding the nucleus. Thus, an atom is electrically neutral. Since things with negative charges repel other things with negative charges, electrons keep atoms from spontaneously combining and allow us to set a coffee cup on a table without it falling through.

Interestingly, there is no difference between three nuclei of helium (with two protons) and the nucleus of carbon (with six protons) if the hooks of the strong nuclear force have been engaged. Adding nuclei of one atom to another creates new elements. However, engaging the hooks of the strong nuclear force require the nuclei to be brought very close together. This can only happen under very high temperatures, in the tens of millions of degrees, where the atoms are moving too fast for the repulsive electromagnetic force of the electrons to keep them apart.

Fortunately, conditions like this are common throughout the Cosmos. Where?     More »