IAO 1998, Теория, 16–18 години — Задача 2
III International Astronomy Olympiad
Условие
There are Cepheid variables in all galaxies and in our own Galaxy as well. Why was the "period–luminosity" relation first established for the Cepheids in the Magellanic Clouds?
Решение
Because all Cepheids in the Magellanic Clouds located almost at the same distance from the Earth, their brightness is proportional to their luminosity. Therefore astronomers have found period-brightness relation for Cepheids in the Magellanic Clouds, which gave them a hint to their period-luminosity relation. Any other galaxy gives the same opportunity as the Magellanic Clouds, but all of them are far from us, and we couldn't investigate Cepheids beyond the Magellanic Clouds until recently.
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