This star field is one of the many that can be found with even a small telescope. Nuclear fusion is the mechanism that makes these stars shine and radiate through the galaxy.

Last week in Starwatch, in the first part of a trilogy of the birth, life and death of a star, I described how stars are born.

Balls of hydrogen gas gravitationally coalesce out of loose clouds of hydrogen referred to as nebulae. Gravity is what makes this all happen, and gravitational force is proportional to mass.

Stars come out of the celestial womb when these balls of gas become massive enough to fire up their nuclear fusion furnaces inside.

When that happens, incredible amounts of light and radiation are produced, and a proto star becomes a star and lives out its celestial life. However, some balls of hydrogen gas never become massive enough to fire up nuclear fusion.

A good example of that is Jupiter, the largest planet in our solar system. Even though it’s 300 times more massive than Earth and so big that it could fit more than 1,200 of our Earths inside it, Jupiter doesn’t have enough mass and gravitational pressure to kick start nuclear fusion in its core.

Nuclear fusion is the mechanism that makes a star shine and radiate all kinds of energy. Gravitational compression builds the heat up tremendously.

Our sun is an average sized star in our Milky Way Galaxy with a mass in kilograms of two with 30 zeros after it, with one kilogram equaling just more than 2.2 pounds. That kind of mass generates a colossal amount of gravitational pressure in the core of the sun, to the tune of more than 500 billion pounds per square inch!

With that kind of pressure, the temperature at the core of the sun exceeds 27 million degrees. More massive stars have even more gravitational pressure and even higher temperatures.

Because of gravitational pressure, hydrogen atoms are packed together in the core of stars a zillion times more than any canned sardines.

At the same time, because of the insanely high temperatures, the hyper crammed hydrogen atoms are flying around at incredible speeds. You don’t need to be a rocket scientist to figure out what happens. These hydrogen atoms slam into each other with incredible violence. There are millions of these collisions every millisecond! By their very nature, hydrogen atoms tend to be electrically repulsive to each other. They don’t even like to be close!

Instead, the force of these collisions totally overwhelms their atomic independence so not only do they bash into each other, they actually fuse together. This is the process of nuclear fusion. It’s like shooting two pool balls so hard at each other that they become one big pool ball! In the core of stars, hydrogen atoms are fusing together to form heavier helium atoms.

It takes four hydrogen atoms fusing together to form one heavier helium atom, and in the process, colossal amounts of energy are produced.

That’s the tricky and extremely complicated part of nuclear fusion. It all has to do with Albert Einstein’s famous assertion that energy and mass can be interchanged if you have the right conditions, and those conditions are met in the violent cores of stars.

The collective radiation from all of these hydrogen atom collisions, in the form of light, heat, gamma rays and X-rays slowly makes its way to the outer layer of a star. From there, the radiation travels in all directions from the star at the speed of light, more than 186,000 miles per second.

Essentially, hydrogen is the fuel of a star, helium is the ash and energy is a byproduct.

In just one second, our sun converts almost 700 million tons of hydrogen to helium and energy. In spite of that incredible rate of consumption, our sun won’t run out of hydrogen for about another five billion years!

Because our sun is an average star in terms of its size and mass, the supply of hydrogen atoms in its core will hold out a lot longer than more massive stars. The really big stellar guys can run through their supply of hydrogen in just a few billion years, while the sun has an active lifetime of well more than 10 billion years.

Eventually though, all stars in our Butler heavens, including our beloved sun, will run out of hydrogen atoms in their collective cores and the death process kicks in.

Stellar death will be the subject of next week’s Starwatch and believe me, stars don’t die quietly. Some really go out with a bang!

Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and is author of the book, “Pennsylvania Starwatch,” available at bookstores and at his website www.lynchandthestars.com.