Radio Astronomy as a way to explore the universe

Since the earliest of times, space has inspired our imagination. Cinema and television deeply influence the picture that we have of what goes beyond our daily lives on Earth. Many of us are familiar with terms like galaxies, extragalactic systems, comets, and asteroids.

Radio Astronomy as a leading field of expertise

Since its very beginnings around 1932, radio astronomy has developed into one of the most important methods of exploring the universe. This statement is proven by the fact that almost all of the observational astronomers who have won the Nobel prize were radio astronomers; in 1974 (Sir Martin Ryle & Antony Hewish), 1978 (Arno A. Penzias & Robert W. Wilson), and most recently in 1993 (Russell A. Hulse & Joseph H. Taylor Jr.).

What does radio astronomy do?

By observing at radio wavelenghts radio astronomy can explore the depths of space. Observations made with the largest optical instruments can be complemented in this way. In contrast to optical procedures, radio astronomical observations are not hindered by 'clouds of dust' in the cosmos. For instance, it was only possible to determine the exact structure of the Milky Way with radio astronomic measurements. Generally speaking, the optical astronomy can see the “thermal universe” whereas radio astronomy is open to the “magnetic universe”. Furthermore, previously unknown astronomical objects like quasars and pulsars have been discovered.

What does the Institute explore?

The Institute's fields of study encompass many questions from the general field of astronomy. Early stages in the development of the universe can be examined by means of gravitational lenses. Observations and theoretical analyses concerning stellar evolution are also on the agenda, as well as the exploration of magnetic fields in spiral galaxies like the Andromeda nebula. Last but not least, comets and asteroids are investigated.

The 100-metre radio telescope

The 100-metre radio telescope in Effelsberg is used by members of the Institute, as well as a large number of guest scientists from all over the world. The aerial photograph on the left shows the radio telescope with its mirror surface (the outer part of which was renewed in 1998). The control centre on the mountainside can be seen on the lower left. It hosts the control room, the measuring and computing rooms, electronic laboratories and workshops as well as to guest rooms for the scientists on site.

How does the parabolic reflector work?

The telescope consists of a parabolic main mirror with a diameter of 100 meters and a secondary mirror with a 6.5 metre diameter. The parabolic reflector concentrates radiation from space on a common focal point, the so-called primary focus. The focal point is located 30 metres above the mirror's surface. A secondary mirror near the focal point diverts the radiation towards a second focal point- the secondary focus- in the middle of the primary mirror. Both focal points are home to measuring cabins with low-noise detecting systems, and they can be used interchangeably.

The receivers used at the primary focus point detect frequencies between 800 MHz and 86 GHz. Switching between different receivers is done manually until the upgrade to be made in 2006. A focal length of 385 metres at the secondary focus point makes it possible for several receivers between 2.7 and 43 GHz to be used at the same time, and these receivers are ready for operation at any time. Even at larger distances from the optical axis geometrical errors are kept relatively small.