Astronomy Scioly Cornell C, Exams of Astronomy

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2024 Science Olympiad at Cornell

Astronomy C

Answer Key + Score Distributions

Score Distributions (out of 8 total possible points) (out of 125 total possible points) (out of 58 total possible points) (out of 191 total possible points)

Section 1 (each 2 pts by default)

For #1-#9, circle ‘T’ (True) or ‘F’ (False)

1. T F (+1)
2. T F (+1)
3. T F (+1)
4. T F (+1)
5. T F (+1)
6. T F (+1)
7. T F (+1)
8. T F (+1)
9. T F (+1)
10. __ B ____
11. __ C ____
12. __ C ____
13. __ B ____
14. __ A ____ (+3)
15. __ A ____
16. __ D ____ (+3)
17. __ B ____
18. __ A ____
19. __ B ____
20. __ B ____
21. __ B ____
    22. Spectroscopic parallax
    23. Pebble/Core Accretion/Streaming Instability and Gravitational/Disk Instability
    24. Pebble/Core Accretion/Streaming Instability (also accept migration)
    25. Oligarchic Growth (+3)
    26. Bondi Sphere (+3)
    27. HII Regions

Section 2 (each 2 pts by default)

1. __ C ____

2. __ B ____

3. __ D ____

4. __ A ____

5. Orion Nebula (+1)
6. __ C ____
7. __ D ____
8. __ C ____
9. __ C ____
10. __ B ____
11. __ A ____
12. Red
13. Gravitational contraction/Kelvin-Helmholtz mechanism
14. __ B ____

15. i) Star (+1) ii) Planet (+1) iii) (Primary) transit (+1) Note: “eclipse” is not specific enough
16. __ A ____ (+1)
17. It contains SiO 2 /quartz
18. Possible answers (non-comprehensive list): -Test models with other chemicals in them (e.g. other aerosol species) -Collect or analyze more (transit or other) data -Compare to results from a different modeling or data reduction scheme -Look for other possible signals of SiO 2 (e.g. at a different part of the spectrum) -Perform modeling to evaluate whether it’s likely for SiO 2 to appear in such an atmosphere in the first place
19. __ A ____
20. __ D ____
21. __ A ____
22. __ B ____
23. __ D ____
24. __ B ____
    25. __ A ____ [Question omitted from grading]
    26. Unusually low surface temperature [led to conclusion that the atmosphere of the planet must be volatile, leading further spectroscopic search which found absorption patterns signifying presence of CO and CO2]
    27. Unusually high metallicity or anything regarding high levels of heavier elements
    28. Core Accretion/Pebble Accretion/Streaming Instability
    29. __ C ____
    30. __ B ____
    31. __ A ____
    32. Flare star (specifically, UV Ceti) or T Tauri variable (partial credit for “intrinsic variable”)
    33. Atmospheric Escape (anything along the lines of atmospheric gas being released from planet)

16. (3 points) Radial velocity can be inferred from Doppler shift (via spectral lines and due to relativistic principles) (+1) , so the Doppler shift of the host star is measured to determine the presence of an exoplanet companion, whose presence causes the host star to rotate around the star-planet barycenter (+1; explanation need not be specific for this point, but it should be clear that the Doppler shift of the star is measured). The Doppler shift has a greater absolute magnitude (+1) for the planet (at least whenever the motion is not strictly transverse).
17. (4 points) Theta Cornelliana B: Periapsis = 0.056 AU, Apoapsis = 0.344 AU, C: Periapsis = 19. AU, Apoapsis = 20.6 AU (+1 for each)
18. (4 points) Theta Cornelliana B (+1). Ratio of brightness = ratio of albedo / (ratio of distances from host star)^2 = (0.42/0.15) * (19.4/0.056)^2 = 336035 (accept 335500 to 336500) (+3).
19. (5 points) At the periapsis (+2) (consider Kepler’s second law); v^2 = 1.67 * 10^10 (you must convert distances to m), then the energy is 2.19 * 10^38 J (accept 2.00-2.40 * 10^38 J) (+3)
20. (5 points) Theta Cornelliana B (+1) , as it has greater eccentricity and much lesser semi-major axis (+1 for mentioning either of these two points. Do not award +2 even if both points are mentioned) , which makes precession effects much more apparent. Potential causes include the geodetic effect or Lense-Thirring precession (or just general effects of general relativity – “spacetime curvature” or “general relativity” are also sufficient to earn this point), the asphericity (oblateness) of the host star (creating a mass quadrupole moment), and the presence of an unseen exoplanet companion (c is almost certainly too weak to produce a noticeable effect) perturbing the orbit of Theta Cornelliana B (+2 for mentioning any one of these effects, +3 for mentioning 2 (or more) of these effects). Image Sources ● XKCD: https://xkcd.com/2202/ ● 1A: https://www.astro4edu.org/resources/diagram/2149RS77wy92/ and https://www.astro4edu.org/resources/diagram/lH42QC364e69/ ● 2A: https://esahubble.org/images/heic0601a/ ● 2B: https://esawebb.org/images/WASP17b/ ● 2C: https://www.esa.int/ESA_Multimedia/Images/2024/05/Super-Earth_exoplanet_55_Cancri_e_seco ndary_eclipse_light_curve ● 2D: https://esahubble.org/images/heic1521a/ ● 3A: https://commons.wikimedia.org/wiki/File:PMS_evolution_tracks.svg, original unmodified source is Steven W. Stahler and Francesco Palla, "The Formation of Stars"; doi:10.1002/