In the school texts of astronomy, we find that the angle of parallax is the smallest angle of the right-angled triangle formed by the Earth's orbit radius and the lines that go from its ends to a nearby star, from which one wants to measure distance. The didactic problem addressed by this text is as follows: despite the recurrent information about the ”shifting” of the near star relative to the background stars, as the Earth moves around the Sun, there is no clear indication of how this angle is measured in the sources consulted. Two approaches are suggested to address this problem: the first is an essentially geometric activity, to be developed by the students in the classroom environment. The second concerns a field photographic activity, in which the distance to terrestrial objects is determined by parallax. In the final considerations, the authors argue that this is a didactic problem, and that it must therefore be dealt with in this context.
Keywords:
astronomy teaching; trigonometric parallax; distance to stars
