IAO 2004, Всички кръгове — Задача 3. α3. Occultation
IX International Astronomy Olympiad · 1 октомври 2004 г.
Внимание: Бележка към темата
Old photocopy scan. Two short passages of the official solutions are lost where the photocopied pages join (problem 4 between pages 4 and 5, the Sunrise solution between pages 13 and 14). The sky maps of the observational round are not in the archive file.
Условие
Venus makes a central occultation of a star at the time of maximum elongation. Please find the duration of the occultation. The orbits of Venus and Earth may be considered as circular ones.
Отговори
- 9.8 min
Решение
At the time of Venus's maximum elongation the angular velocity of its sky motion is equal to the angular velocity of the Sun motion by the ecliptic:
The distance between Venus and Earth at the time of maximum elongation can be calculated using Pythagoras' theorem since the angle (Sun – Venus – Earth) is equal to 90°.
Here and are the radii of Venus and the Earth orbits, respectively. Let's denote Venus radius by , then its angular diameter from this distance will be equal to
The duration of the central occultation will be
Note: numerical values for the orbit radii of Earth and Venus, radius of Venus should be taken from the Solar System data.
Group α, theoretical round
Data from the “Table of planetary data” may be used for the solving of every problem.
And the White Bear and Penguin are waiting for you on the practical round.
Group β, theoretical round
Data from the “Table of planetary data” may be used for the solving of every problem.
And the White Bear and Penguin are waiting for you in the practical round.
Parameters of orbits. Physical characteristics of some planets, Moon and Sun
Элементы орбит. Физические характеристики некоторых планет, Луны и Солнца
| Body, planet | Average distance to central body, in astr. units | Average distance to central body, in mln. km | Sidereal (or analogous) period, in trop. years | Sidereal (or analogous) period, in days | Eccentricity e | Equat. diameter, km | Mass, kg | Av. density, g/cm | Grav. acceler. at surf., m/s | Max. magn. from Earth **) | Albedo |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Солнце Sun | 1392000 | 1989000 | 1,409 | ||||||||
| Меркурий Mercury | 0,387 | 57,9 | 0,241 | 87,97 | 0,206 | 4 879 | 0,3302 | 5,43 | 3,70 | 0,06 | |
| Венера Venus | 0,723 | 108,2 | 0,615 | 224,70 | 0,007 | 12 104 | 4,8690 | 5,24 | 8,87 | 0,78 | |
| Земля Earth | 1,000 | 149,6 | 1,000 | 365,26 | 0,017 | 12 756 | 5,9742 | 5,515 | 9,81 | 0,36 | |
| Луна Moon | 0,00257 | 0,38440 | 0,0748 | 27,3217 | 0,055 | 3 475 | 0,0735 | 3,34 | 1,62 | 0,07 |
**) Для внешних планет и Луны – в среднем противостоянии.
**) For outer planets and Moon – in mean opposition.
Оригинал в Архива: iao2004.pdf