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 20 th 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 10 21 km away. If the Hubble constant is 2 x 10 -18 s -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