Question

What was the first basis on which stars were classified (choose all that apply)?

a) Brightness.
b) Color.
c) Size.
d) Distance from Earth.

Answer 1

Stars were originally classified based on their apparent brightness and color, due to historical observational methods established by ancient astronomers like Hipparchus, which are tied to star magnitudes and temperatures respectively.

Step-by-step explanation:

The first basis on which stars were classified historically included brightness and color. The ancient astronomer Hipparchus divided stars into apparent magnitudes based on their apparent brightness, calling the brightest stars 'stars of the first magnitude' and continuing the classification to fainter stars. The apparent brightness of a star depends on its luminosity (total energy emitted per second) and its distance from Earth. Colors of stars, which range from red to blue-white, are determined by their temperatures, with red being cooler and blue-white being hotter. Both brightness and color were early methods to classify stars, used long before the distance to stars could reliably be measured.