Characteristics of Stars

1. Characteristics of Stars

2. Characteristics of Stars The Sun is an average star: it’s not hot or cool it’s not large or small. We can compare stars by colour, temperature, size, brightness and spectrum.P.458

3. The Sun is larger than 95% of the stars. Dwarf Star Sun Giant Star Super Giant Star

4. Colour and Temperature Colour: Stars range in colour from red, orange, yellow, white, to blue. Red ----------- Yellow (Sun) ----------- > Blue Temperature: Stars range in temperature from 2000oC--50 000oC. 2 000oC ---------5 000oC (Sun)--------- > 50 000oC

5. Colour and Temperature Colour and temperature are linked. The 2000oC stars are red in colour. The 50 000oC stars are blue in colour.

6. Colour and Temperature Page 458

7. Brightness Brightness is related to the distance from the earth and the age of the star.

8. Task Read page 458 – 460 and makes notes in your notebook. Answer questions on page 460, 1 – 6 inclusive.

9. Questions - P. 460 • How is the colour of a star related to its temperature? The colour of a star depends on its temperature, from red and orange (cool stars) to yellow and white (hotter stars) to blue (very hot stars). 2. Explain why a cooler star could actually appear brighter than a hotter star. A cool star, such as a red giant, could be either closer to us or much larger than a hotter star, such as a white dwarf (or, it could be closer and larger).

10. Questions - P. 460 3. What system of magnitude, which astronomers use, measure the brightness of a star? Explain why. The apparent magnitude would be more useful than the absolute magnitude because we want to compare how bright the stars appear to the observer. 4. One night, you observe two stars that have the same apparent magnitude. Could these two stars be giving off different amounts of light? Explain. Very likely the stars would be giving off different amounts of light because, even though they have the same apparent brightness, their distances from us are probably different.

11. Questions - P. 460 5. What effect would pollution in the atmosphere have on a star’s apparent magnitude and absolute magnitude? Pollution would reduce the amount of light we see and, thus, the apparent magnitude. Pollution would have no effect on the actual amount of light given off by a star, so it would not affect the absulute magnitude. 6. What instrument does an astronomer use to determine the spectrum of a star? Why is this instrument better than using only a telescope? An astronomer uses a spectroscope to determine the spectrum of a star. A telescope does not cause the light to spread out the way a spectroscope does..