May 05, 2011
Thousands of publications bear witness to the rich harvest which the researchers have gathered so far with the radio telescope. What do you think were the highlights?
Kramer: “That’s a difficult question to answer, of course, because every scientist is going to have a slightly different “ranking”. Maybe the best-known result – because it can be found in almost every book on radio astronomy – is the map of the radio sky from the famous 408-megahertz survey by a team working with Glyn Haslam. Other colleagues would surely mention many other areas of astrophysics where outstanding achievements have been made. New molecules and spectral lines have been discovered in interstellar space, for example, and important molecules, such as ammonium and water, were detected for the first time outside the Milky Way. At the same time the telescope has also shown that there are enormous, ordered magnetic field structures in other galaxies. And it discovered the most distant water in the universe, at a distance of eleven billion light years! For me personally it was a fantastic result that we at Effelsberg detected the relativistic effect of geodetic precession outside the solar system and in strong gravitational fields.
The telescope is now 40 years old. Can it keep up with the current technical standards?
Of course! It’s not only still the largest telescope in Europe and only a few metres smaller than the Green Bank telescope in the USA, the 100-metre antenna is really better than ever: the design of the telescope is every engineer’s dream and, thanks to good maintenance and regular updates, it is still in top condition, even today. At the moment we are working on updating the receiving systems, because the huge progress in digital electronics in recent years has provided us with outstanding technical possibilities of which we could only dream before. We can therefore now significantly improve the telescope's characteristics – even after 40 years.
Have the observation tasks of the radio telescope shifted?
Not really. Even today astronomers from all over the world come to carry out experiments of all kinds. These include observations at high and low radio frequencies, the spectroscopy of interstellar molecules, measurements of the polarization of galaxies, and the networking of Effelsberg with other telescopes to generate “sharper” images. But the fact of the matter is that some of the observations required can now be done by two telescopes of the 100-metre class: by ours in Effelsberg and by the Green Bank telescope in the USA. Both have different strengths, but we now have the chance to use valuable time for large, very ambitious projects. So for the first time in the history of Effelsberg we are now conducting a sensitive search of the whole sky for cosmic clocks, the so-called pulsars. This is very exciting, because you never know what you will find.
There are radio telescopes all over the world; your institute is an important partner of the Atacama Pathfinder Experiment (Apex) in Chile, for example. Max Planck researchers are also working with the radio antennas on the Plateau de Bure in the French Alps. What role does the 100-metre telescope in Effelsberg play in this respect?
In contrast to the visual part of the electromagnetic spectrum, radio frequencies cover a much larger region, relatively speaking, which is reflected in the incredible breadth of the science. At high radio frequencies, as are measured with Apex or on the Plateau de Bure, the focus is on investigating thermal sources, where we usually deal with low-energy processes. Although with Effelsberg we measure photons with even lower energy, these have often been generated by the most energized processes we know. In order to understand the universe overall, we must therefore cover all of these frequencies so that the different radio telescopes optimally complement each other. A good example here is again the pulsars which we cannot see with Apex or on the Plateau der Bure. For this we really need telescopes like Effelsberg.