IAO 2023, Теория — Задача 1 (αγ). Крабовидная туманность / Crab nebula
XXVII International Astronomy Olympiad — Theoretical round / Задачи теоретического тура · 8 т.
Только для перевода. / For translation only.
Напоминание. Большинство задач составлены таким образом, что при написании решений от участника требуется минимальное использование какого-либо языка. Таким образом, допускается минимум текстов в решениях задач (ни на родном языке, ни на одном из официальных языков IAO). Уделяйте больше внимания формулам, рисункам и графикам. Разрешается употреблять несколько ключевых слов на английском языке (например, “Yes”, “No”, “Assume”, “Answer”, “Average”, “Minimum”, “Maximum”, “Impossible situation” и т.д.), а также термины, содержащиеся в прилагаемых таблицах, и названия объектов.
Reminding. Most of the problems are compiled in such a way that when writing solutions, minimal use of any language is required from the participant. So minimum texts is allowed in solutions of the problems (neither in the native language, nor in one of the official languages of the IAO). Pay more attention to formulas, drawings and graphs. It is permitted to write a few keywords in English (for example, “Yes”, “No”, “Assume”, “Answer”, “Average”, “Minimum”, “Maximum”, “Impossible situation”, etc.), as well as terms contained in the accompanying tables and names of objects.
Source notes / Примечания к источнику
The scan repeats the Russian second statement page. Russian and English versions are retained as sections of the same seven tasks. The note after 6.6 prints 8.3/8.5/8.6; the English scan has a handwritten correction. The solution’s final magnitude for task 2 prints +5 rather than −5, the eclipse expression prints L₁−L₂, and the redshift relation prints a(tₑ)/a(tₒ); these source expressions are preserved. The criteria for 6.5/6.6 have unrelated white-dwarf text crossed out without replacement. Reference data are also present within the question PDF and are not extra tasks.
Условие
Русский
Каков сейчас реальный физический диаметр (в км и астрономических единицах) Крабовидной туманности? Крабовидная туманность – остатки сверхновой, вспышку которой на Земле зафиксировали 4 июля 1054 года. Она расположена в созвездии Тельца и в настоящее время её видимый угловой размер составляет около 5′.
English
What is the actual physical diameter (in km and astronomical units) of the Crab Nebula right now? The crab nebula is the remnants of a supernova, the outbreak of which was recorded on Earth on July 4, 1054. It is located in the constellation of Taurus and currently its apparent angular size is about 5′.
Справочные данные / Reference data

Решение
The distance to an object having a parallax of 0.0005″ (this value can be found in the table of stars and objects) is equal to:
The apparent angular size of 5′ at this distance corresponds to the physical size
which is
However, this is the size of the nebula at the time when the light from it began to come to us, that is, 6500 years ago. Thus, the total age of the Crab Nebula is currently 969 + 6500 ≈ 7500 years. And if in 969 years it expanded to au or km, then, assuming a linear expansion, in 7500 years it expanded by
Or, calculating differently, in astronomical units it will be
Answer: km, au Accuracy with more than 1 significant digit is inappropriate.
Basic criteria
| Criterion | pts |
|---|---|
| The distance through a parallax | 1 |
| Apparent (as we see) the physical size | 1 |
| Rate of expansion, formulae, calculations | 3 |
| Final answer km, au | 1 |
| Correct number significant digits in answer | 2 |
| Total | 8 |
Handwritten annotations
The source margins mark the parallax step “1 p.”, apparent size “1 p.”, expansion “3 p.”, final conversion “1 p.”, and significant digits “2 p.”.
Theoretical round. Sketches for solutions. For jury job ONLY
These solutions are written for jury members, so they contain a lot of explanations in the form of text. Students are instructed to minimize text, mostly use formulas, calculations, drawings and graphs, writing extra tests is not encouraged in the solutions. It is permitted to write a few keywords in English (for example, “Yes”, “No”, “Assume”, “Answer”, “Average”, “Minimum”, “Maximum”, “Impossible situation”, etc.), as well as terms contained in the accompanying tables and names of objects.
The given sketches are not full; the team leaders have to give more detailed explanations to students. But the correct solutions in the students’ papers (enough for 8 pts) may be shorter.
Jury members should evaluate the student’s solutions in essence, and not by looking on formal existence the mentioned sentences or formulae. The formal presence of the mentioned positions in the text is not necessary to give the respective points. Points should be done if the following steps de facto using these positions.
Theoretical round. Basic criteria. For work of Jury
Note. Jury members should evaluate the student’s solutions in essence, and not by looking on formal existence the mentioned sentences or formulae. The formal presence of the mentioned positions in the text is not necessary to give the respective points. Points should be done if the following steps de facto use these positions. (For example, except the final conclusion, all the points in solution of problem 2 may be in only one common formula.)
Note. Jury members should elaborate more detailed criteria, and also create criteria for other correct ways of the student’s solutions.
Note. Everywhere “formula” means “correct formula”, “calculation” means “correct calculation”, “picture” means “correct picture”, etc., and in all cases: based on correct facts and intermediate formulae or calculations.
Note. Everywhere final calculation means also using correct number of significant digits. Extra significant digits, especially in estimational problems, will lead to subtraction of the points.
Note. Solutions with absurd or almost absurd answers should be rated lower (maybe ignoring the scoring schemes below, and maybe down to zero).
Everywhere – excessive number of significant digits in the answer – minus 1–2 points.
Теми и трудност
Трудност: неоценена.
Светлина и астрономически измервания · Определяне на разстояния · Ъглов размер
Предпоставки: Разширена олимпиадна подготовка
Оригинал в Архива: theo.pdf · официални решения: theosol.pdf · допълнителни данни: data.pdf