How Do Scientists Classify Stars?

Introduction

Stars have always been a source of great interest to people here on Earth. Even as far back as the Romans, they have tried to name and classify the stars. The earliest form of classification happened when the Greeks and Romans assigned their gods' names to the different patterns of stars in the sky. As the knowledge of stars grew, so did the classification process. Modern scientists use a complicated system to classify the stars in to several different groups given a letter name. The star classification process is a work in process, and will likely be ever-changing to fit new things that we discover about our universe.

Star Spectrums

Each star is classified by its spectrum. In the first days of star classification, it was difficult to classify stars this way, because there was not a set system that every scientist used. The light that we see on earth is the only thing we have to use to classify stars. Therefore, scientists came up with a way to classify stars based on the light spectrum that they give off to earth.

Classification by Letters

The letter system OBAFGKM is currently what scientists used to classify stars. These letters are based on a temperature scale, combined with different elements that are present around certain stars. O stars are the hottest, with M stars being the coldest. O stars contain helium, B stars helium and hydrogen, A stars have hydrogen and ionized metals, F stars have hydrogen, ionized calcium, and iron, G stars contain calcium and ionized metals, K stars have neutral metals and sodium, and M stars have a lot of sodium and titanium oxide.

Classification by Temperature

The temperature of a star is what scientists use to classify them. This is done by measuring the heat that comes from that star, and how it is absorbed by the elements around that star. Things called absorption lines help scientists see what elements are blocking certain waves of heat coming from a particular star. They then determine what letter the star gets based on these results.

Classification by Color

The color of the star has a lot to do with how they determine the temperature of that star. Scientists watch the stars to see what color they appear. The differences in temperature will make the stars appear different colors in the sky. They not only use the visible colors of the stars but also measure the invisible colors such as what are produced in infrared lights and other kinds of invisible light spectrum.

Elements and Star Classification

The different elements that are present around different stars alter the way that the light reflects back to earth. The letter classification system differentiates between the kinds of elements and light that they produce. All stars are currently classified according to this system. However, as scientists learn more about the stars, the classification system will likely change.