Gravitational lenses have exciting cosmological implications. Their bending of radio waves offers one of the very few ways of measuring the mass of a galaxy. Moreover, with a large sample of lenses we can test the predictions of cosmological models and hence study the geometry of the universe. By measuring the brightness variations in different parts of the image, it should be possible to estimate the distance to the galaxy and hence the rate of expansion and size of the universe. VLBI techniques come into their own for high-resolution studies of individual lensed systems which are important if the mass of the lensing galaxies is to be found.
Photographs show extensive filamentary streamers extending away from the centre.
However, the large amounts of obscuring dust in M82 make observing any of these supernovae with optical telescopes very unlikely. The starburst hypothesis for M82 cannot, therefore, be confirmed by optical observations. Fortunately, radio waves pass through the dust largely unaffected and so radio telescope can probe the inner regions of M82. This discovery is the clinching evidence that a population of massive stars has exploded in the centre of M82. One area in which interferometry has let to great advances is in the study of cosmic jets.