![]() VLT observations show this cloud to be glowing because it is bathed in the intense radiation coming from the quasar, and not from stars inside the cloud. The astronomers did however detect an interesting smaller cloud of gas about 2500 light-years wide near the quasar, which they call 'the blob'. "With the powerful combination of Hubble and the VLT we are confident that we would have been able to detect a normal host galaxy," said Pierre Magain of the Université de Liège, Belgium. We must therefore conclude that, contrary to our expectations, this bright quasar is not surrounded by a massive galaxy. 20 to 170 times smaller than typical host galaxies (which normally have radii ranging from about 6000 to 50 000 light-years). This means that if any host galaxy exists, it must either be at least six times fainter than typical host galaxies, or have a radius smaller than about 300 light-years, i.e. The star served as a reference pinpoint light source that was used to disentangle the quasar light from any possible light from an underlying galaxy.ĭespite the innovative techniques used, no host galaxy was seen around HE0450-2958. Combining Hubble’s ultra-sharp images and spectroscopy from ESO’s VLT, they observed their sample of 20 quasars at the same time as a reference star. To overcome this problem, the astronomers devised a new and highly efficient strategy. However, observing the host galaxy of a quasar is challenging work because the quasar completely outshines the host and masks the galaxy’s underlying structure. The past decade of observations, largely with the Hubble telescope, has shown that quasars are normally associated with massive host galaxies. The best fed of these objects shine as 'quasars' (standing for 'quasi-stellar object' because they had initially been thought of as stars). These black holes sometimes dramatically manifest themselves by devouring matter that they gravitationally swallow from their surroundings. ![]() With masses that are hundreds of millions times bigger than the Sun, super-massive black holes are commonly found in the centres of the most massive galaxies, including our own Milky Way. ![]() The astronomers suggest that this may indicate a rare case of a collision between a seemingly normal spiral galaxy and an 'exotic' object harbouring a very massive black hole. But when they studied the bright quasar HE0450-2958, located some 5000 million light-years away, they could not find evidence for a host galaxy. For 19 of them, they found, as expected, that these super-massive black holes are surrounded by a host galaxy. The team conducted a detailed study of 20 relatively nearby quasars. Quasar HE0450-2958, after advanced image processing
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