P 7 20 Questions

1. P 7 20 Questions Traffic Light Quiz

2. Rules • Everyone should reveal their answer at the same time • Count down: 3, 2, 1, show!

3. 1. The parallax angle of a star is.. • twice the angle moved against the background of distant stars in 6 months • half the angle moved against the background of distant stars in 6 months • the angle moved against the background of distant stars in 6 months

4. 2. A smaller parallax angle means.. • The star is further away • The star is closer • The star is not as bright

5. 3. What is a parsec? • The distance to a star with a parallax angle of one degree of arc • The distance to a star with a parallax angle of one minute of arc • The distance to a star with a parallax angle of one second of arc

6. 4. What is a light year? • The distance travelled by light in a year • The time it takes light to travel one parsec • The time it takes light to travel around the Sun

7. 5. What is the typical distance between adjacent stars? • A few million km • A few parsecs • A few thousand parsecs

8. 6. The intrinsic brightness (luminosity) of a star depends on… • its distance from us and its colour • its size and its mass • its temperature and its size

9. 7. What is a Cepheid variable? • A star with brightness that changes periodically • A galaxy that contains a wide variety of stars • A star that is changing from a red giant to a white dwarf

10. 8. What does the period of a Cepheid variable depend on? • How far the star is away • How old the star is • How bright the star is

11. 9. What is a galaxy? • A cluster of hundreds of stars • A cluster of billions of stars • A group of millions of planets

12. 10. What did most astronomers believe at the start of the 20th century? • Our galaxy is the only one in the Universe • Our Sun is the only star in our galaxy • Our planet is the only one in the solar system

13. 11. What was the “Curtis-Shapley debate” all about • Whether nebulae were in our galaxy or separate galaxies themselves • Whether Cepheid variables were any use for determining stellar distances • Whether our Universe was expanding or not

14. 12. What is a “megaparsec” • A hundred parsecs • A thousand parsecs • A million parsecs

15. 13. What is the typical distance between galaxies? • A few parsecs • A few thousand parsecs • A few megaparsecs

16. 14. The further a galaxy is away.. • the faster it moves away from us • the slower it moves away from us • the slower it moves towards us

17. 15. What was the explanation for Hubble’s observations • The Universe is much bigger than we thought • The Universe started from a big bang • The Universe is expanding

18. 16. All the stars you can see with the naked eye are.. • in our solar system • in our galaxy • in our cluster of galaxies

19. 17. Which of these is furthest away from us? • Pluto • Alpha Centauri (a star) • Andromeda (a galaxy)

20. 18.A galaxy is 3 x 1021km away. If the Hubble constant is 2 x 10-18s-1, what is the speed of recession? • 1500km/s • 6000km/s • 0.66km/s Speed = Hubble constant x distance

21. 19. What is the correct relationship between galaxy distance and recession speed? • recession speed = Hubble constant x distance • Hubble constant = recession speed x distance • distance = Hubble constant x recession speed

22. 20. Why are Cepheid variables useful? • They allow us to estimate the mass of distant stars • They allow us to estimate the distance to stars and galaxies • They allow us to estimate the temperature of distant stars