ASTRONOMY  

SCIENCE  OLYMPIAD  BOYCEVILLE  INVITATIONAL  

3  DECEMBER  2016                    School  Name                    Team  #                                    Participant  1                    Participant  2                    Score                    

Welcome  to  the  2016  Boyceville  invitational    This  test  has  52  questions,  each  worth  1  point    Please  use  the  answer  sheet  provided  for  your  answers  

1. A star is 80 parsec away and has an apparent magnitude of 4.52. What is its absolute magnitude? 2. The observable B-V color index of a star is related to what physical stellar property? 3. Star A is at a distance of 30.0 pc. Star B is at a distance of 75.4 pc. They have the same intrinsic brightness. How many magnitudes fainter than star A does star B appear in the night sky? 4. An object is approximately 560 pc from the Earth and visible with the naked eye in the night sky. What kind of object is this most likely? a) An early-type (O) star b) A white dwarf c) A planetary nebula d) A galaxy 5. You observe a binary star system and find one star orbits the other star every 5 years at a distance of 10 AU. What is the total mass of the two stars in solar masses? 6, 7, 8. Name three forms a stellar remnant can take. 9, 10. What is the Chandrasekhar limit and what is its value?

11. The HR diagram below is for what kind of object?

In this HR diagram what are the names of the labeled features? 12. A= 13. B= 14. C= 15. D= 16. E= 17. F= 18. Which label indicates the stars on this HR diagram that are currently the most massive? 19. What kind of nuclear fusion is happening in the stars near D? a) core-hydrogen b) hydrogen-shell c) core helium + hydrogen shell d) helium-shell + hydrogen-shell e) none

20. In the spectra to the right, the hydrogen H-alpha line near 656 A shows strong dips for A, F and G stars, but not for O stars. Why is this? a) hydrogen is more common in A, F and G stars b) the hydrogen is less highly ionized in A, F and G stars c) O stars are so hot that they have hydrogen emission lines that fill in the absorption d) O stars have already burned all their hydrogen 21. The large number of closely-spaced lines seen in the spectra of B, A, F stars near 390 nm is due to a) black-body effects b) hydrogen c) helium d) calcium 22. The spectrum of the M5V star does not show clean absorption lines because a) such stars are too faint to take good spectra of b) they have no hydrogen in their atmosphere and lines of other elements overlap c) their atmospheres contain molecules that have many closely-spaced lines d) they rotate fast so that the Doppler effect smears out the lines 23. What type of spectrum does the gas in a planetary nebula produce? a) absorption-line b) emission -line c) continuous 24. A planetary nebula is visible because a) The gases in it are really hot and thus emit radiation b) The atoms and ions in it are excited by UV radiation from the star c) The dust in the nebula is heated by UV radiation from the star d) The gases in it reflect the light of the central star

Match the following images in the image set to one of the objects in the following list: Henize 2-428; HM Cnc; Mira; NGC1846; NGC2392; SN G1.9+0.3; Sirius SNR0509-67.5; SS Cyg; Stringray Nebula; Tycho's SNR 25. Image A= 26. Image C= 27. Image E= 28. Image G= 29. Image J= 30. Image L= 31. Image N= 32. Image P= 33. Which five images in the image set show supernova remnants? 34. What wavelength was image B taken in? 35. What do the colors in image A represent? 36. Which image in the image set shows Henize 2-428? 37. Henize 2-428 is special because a) It is a asymmetrical planetary nebula b) It contains a white dwarf to which an evolved AGB star is transferring mass c) It contains two massive white dwarfs d) It is a planetary nebula in a globular cluster 38. What is the object in image J? 39. Which lightcurve is associated with the object from question 38? 40. What causes the trail of light in image J? a) Hot material shed by the star b) Material irradiated by UV radiation from the star c) Material heated by the interaction of the stellar wind and the ISM d) Light emitted by the star reflected off dust in the ISM

41. Which image shows Tycho's SNR? 42. In which wavelength regime was this image (question 41) taken? a) X-ray b) ultraviolet c) optical d) infrared e) radio 43. The spectra to the right include that of Tycho's SNR. What physical effect allows us to take a spectrum of an object that exploded 444 years ago? 44. What do these spectra reveal? a) Tycho's SNR was created by a SN type Ia explosion b) The gases in the SNR are moving really fast c) The SN produced Silicon and Iron d) Tycho's SN was not unusual 45. To determine whether a supernova is type Ia or type II we use a) the shape of the lightcurve b) the presence/absence of hydrogen in its spectrum c) whether it had a massive star or white dwarf as progenitor d) the maximum absolute magnitude of the explosion 46. A 2 solar mass star will evolve from the main-sequence, through the red giant, yellow giant and AGB phase to become a white dwarf, which is the exposed core of the star; what elements is such a white dwarf mostly made of? 47. The spectrum to the right is that of a typical DA white dwarf. From this spectrum what would you conclude is the most common element in the white dwarf?

48. Which image shows an artist's impression of a double degenerate system? 49. Which image shows the lightcurve of the object from question 48? 50. This system has an orbital period of 321.5 seconds, and from the spectrum an orbital velocity of 400 km/s is deduced. What physical effect allows deducing the orbital velocity? 51. What is the separation of the two objects In question 50, in km? 52. The two degenerates from question 50 are losing orbital energy and spiraling toward each other due to which physical process?

A B C

D E F

G H

J

K L M

N O P

Q R

S T

ANSWER SHEET 1. 19. 37. 2. 20. 38. 3. 21. 39. 4. 22. 40. 5. 23. 41. 6. 24. 42. 7. 25. 43. 8. 26. 44. 9. 27. 45. 10. 28. 46. 11. 29. 47. 12. 30. 48. 13. 31. 49. 14. 32. 50. 15. 33. 51. 16. 34. 52. 17. 35. 18. 36.

KEY 1. M=0 19. c (core He+H shell) 37. c (two massive WD) 2. Temperature 20. b (H less ionized) 38. Mira 3. 2 magnitudes 21. b (hydrogen) 39. Q 4. a (early type) 22. b (emission line) 40. c (wind/ISM interaction 5. 40 solar masses 23. c (molecules) 41. F or L 6. white dwarf 24. b (excited) 42. infrared 7. neutron star 25. Stringray Neb 43. light echo 8. black hole 26. NGC2392 44. ia (it is SN Ia) 9. max.poss. WD mass 27. SNR0509-67.5 45. b (H present/absent) 10. 1.44 Msun 28. HM Cnc 46. carbon+oxygen 11. globular cluster 29. Mira 47. hydrogen 12. main sequence 30. Tycho's SNR 48. G 13. MS turnoff 31. SS Cyg 49. T 14. Red giant branch 32. NGC1846 50. Doppler effect 15. Horizontal branch 33. B,E,F,K,L 51. 20,000 km 16. Blue stragglers 34. X-rays 52. gravitational radiation 17. White dwarfs 35. different ions 18. E (blue stragglers) 37. D 1. m-M = 5 log D - 5 = 5 log(80) - 5 = 4.52; M = m - 4.52 = 4.52 - 4.52 = 0 3. 75.4 / 30 is a factor 2.512; brightness decreases as the square of the distance ratio, so star B is a factor 2.512*2.512 fainter, or 2 magnitudes. 5. Kepler's 3rd law: a3/P2=M, if a in AU, P in yr, M in Msun, => M = 103 / 52 = 40 Msun 51. v = 2π a / P, so a = vP / 2π = 400 km/s * 321.5 s / 2π = 2.046x104 km