Describe the magnitude scale and compare the ancient method to the current methodology used today

Question

What will be an ideal response?

Answer 1

Astronomers describe the brightness of stars using the magnitude scale, a system that first appeared in the writings of the astronomer Claudius Ptolemy about the year 140 . Those early astronomers divided the stars into six classes. The brightest stars were called first-magnitude stars and the next brightest set, second-magnitude stars. The scale continued downward to sixth-magnitude stars, the faintest visible to the human eye. Thus, the larger the magnitude number, the fainter the star. This might make sense if you think of the brightest stars as first-class stars and the faintest visible stars as sixth-class stars. Ancient astronomers could only estimate magnitudes by eye, but modern astronomers can use scientific instruments to measure the brightness of stars to high precision; so they have carefully redefined the magnitude scale. These numbers are known as apparent visual magnitudes (mV) because they describe how the stars look to human eyes observing from Earth.

Student should give some comparative values of star magnitudes. (see Figure 2-6)