First high-resolution low-frequency radio image of a quasar

Physics Today : The Low-Frequency Array (LOFAR) is a network of eight radio observatories—five in the Netherlands, three in Germany—that operate in one of the most challenging spectral regions for astronomy: wavelengths of 1–10 meters. Yesterday the LOFAR collaboration announced it had achieved a significant milestone: its first high-resolution image of a quasar. Observing in the 1-m to 10-m waveband is difficult because of high background and weak signals. It’s worthwhile because at the high redshifts of galaxy formation an important tracer of neutral hydrogen, the 21-cm emission line, is redshifted into the waveband.