Introduction

The European Space Agency (ESA) and the European Southern Observatory (ESO) have produced a series of astronomical exercises for use in high school. The prime object of the series is to present various small projects that will transmit some of the excitement and satisfaction of scientific discovery to students.

The first four exercises focus on measurements of distances in the Universe, one of the most basic problems in modern astrophysics. The students apply different methods to determine the distance of astronomical objects such as the supernova SN 1987A, the spiral galaxy Messier 100, the Cat's Eye Planetary Nebula and the globular cluster Messier 12. Among others, it is possible to make quite accurate estimates of the age of the Universe and its expansion velocity, without the use of computers or sophisticated software.

PLEASE NOTE: The interactive versions of the exercises work in Internet Explorer 4.0+, and the newer versions of Netscape and Mozilla (see About astroex.org for more details). Netscape 4.7x is not supported.