USAAAO 2020, I кръг — Задача 22
USAAAO National Astronomy Olympiad First Round 02/10/2020-02/16/2020 · 10 февруари 2020 г. · 1 т.
Указания
This exam contains 8 pages and 30 questions. Each question is worth 1 point, so there are 30 points total. Students MUST take the exam between 02/10/2020-02/16/2020. Proctors must scan students’ responses by 11:59 pm PST on 02/16/2020.
PHYSICAL AND ASTRONOMICAL CONSTANTS
| c | Speed of light in vacuo | |
| e | Elementary charge | |
| Neutron rest mass | ||
| Proton rest mass | ||
| Electron rest mass | ||
| h | Planck’s constant | |
| Hubble’s constant | 70 (km/s)/Mpc | |
| k | Boltzmann’s constant | |
| b | Wien’s constant | |
| G | Gravitational constant | |
| Stefan-Boltzmann constant | ||
| First Radiation Constant | ||
| Second Radiation Constant | ||
| Avogadro constant | ||
| R | Gas constant | |
| Bohr radius | ||
| Bohr magneton | ||
| Solar mass | ||
| Solar radius | ||
| Solar luminosity | ||
| Solar temperature | 5770 K | |
| Earth mass | ||
| Mean Earth radius | ||
| Earth moment of Inertia | ||
| R☾ | Mean Moon radius | |
| M♃ | Mean Jupiter mass | |
| R♃ | Mean Jupiter radius | |
| a♃ | Mean orbital radius of Jupiter | 5.2 AU |
| a☾ | Mean semimajor axis Moon orbit | |
| 1 light year | ||
| 1 AU | Astronomical Unit | |
| 1 pc | Parsec | |
| 1 year | ||
| 1 erg |
ENERGY CONVERSION : 1 joule (J) = electronvolts (eV)
Условие
From the shortest distances to the longest, what is the correct order of distance determination techniques?
A. Parallax, type Ia supernovae, cepheids
B. Parallax, cepheids, type Ia supernovae
C. Type Ia supernovae, cepheids, parallax
D. Cepheids, parallax, type Ia supernovae
E. Cepheids, type Ia supernovae, parallax
Отговори
- Parallax, cepheids, type Ia supernovae
Решение
B: Parallax, cepheids, type Ia supernovae
Because parallax involves resolving physical displacements in the sky, it is limited by the physical resolution of telescopes, so it is best suited for short-enough distances where the transverse displacement is detectable (the closer, the more so). Using Cepheids involves being able to measure the magnitudes of the Cepheids over a period of time and being able to detect the magnitude of the changes in order to determine said period. However, because the absolute magnitude of a Cepheid must be determined by the period, it cannot be used once the oscillations in apparent magnitude become so small that the period cannot be determined. At that point, the Type Ia supernovae become useful because their absolute magnitudes are fixed (given that they occur at a fixed white dwarf mass), so as long as one can see it and determine the apparent magnitude, one has all the info needed to determine distance.
Оригинал в Архива: 2020_usaaao_first_round.pdf · официални решения: usaaao_first_round_answer_key_2020.pdf