Stars: An Introduction

Astronomy

Chemistry/Physics/Mathematics

• Determine what a star is.
• Understand how stars shine.
• Realize the importance of stars.

Q: What makes stars different from planets? Discuss the differences.
A: Stars are massive bodies in space that are self-luminous. This means that they can generate their own light. Stars are composed primarily of hydrogen, which undergoes a fusion process and becomes helium. This fusion of elements provides the energy for the self-luminosity. Planets are large objects in space that are composed of heavier elements such as carbon, iron, and oxygen. Planets do not provide light and none of the material on the planet undergoes fusion.

Q: According to this article, our Sun is a "garden variety star." How is our Sun different from other stars?
A: It means that our Sun is rather average when compared to other stars. Some stars are bigger, more massive, and brighter. Others are smaller, less massive, and less bright. Some are much older than our Sun, and others are much younger.

Q: What happens to a star when it converts all the hydrogen at its center into helium?
A: In stars with masses comparable to and greater than that of our Sun, the helium in the core ignites and fuses into heavier elements, like carbon and oxygen, releasing energy in the process. Very massive stars continue this process, fusing the carbon into even heavier elements, such as iron and nickel. The most massive stars eventually end their lives with an explosion called a supernova. This explosion ejects the heavy elements into space.

The Sun is composed mainly of hydrogen and helium. Heavier elements, like carbon, oxygen, nitrogen, iron, and gold, make up only about 2% of the Sun's mass.

The Sun's luminosity is referred to as one solar luminosity. This is comparable to the luminosity of 4 trillion trillion one-hundred-watt light bulbs.

Stars produce energy through a process known as fusion. Fusion occurs when lighter elements, such as hydrogen, combine into heavier elements, such as helium, with a release of energy.

Stars do not shine forever. Stars are of a finite size, which means that eventually they will run out of fuel, much like a car runs out of gas.

Kelvin: SI unit of temperature; zero degrees Celsius equals 273 degrees Kelvin.

luminosity: brightness of a star, equal to the total energy radiated per second from the body.

fusion: nuclear process in which two light nuclei combine, at extremely high temperatures, to form a heavier nucleus and release vast amounts of energy.

supernova: explosion of a massive star.