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Donald Lynden-Bells many contributions to astrophysics encompass general relativity, galactic dynamics, telescope design and observational astronomy. In the 1960s, his papers on stellar dynamics led to fundamental insights into the equilibria of elliptical galaxies, the growth of spiral patterns in disc galaxies and the stability of differentially rotating, self-gravitating flows. Donald introduced the ideas of `violent relaxation and `the gravothermal catastrophe in pioneering work on the thermodynamics of galaxies and negative heat capacities. He shared the inaugural Kavli Prize in Astrophysics in 2008 for his contributions to our understanding of quasars. His prediction that dead quasars or supermassive black holes may reside in the nuclei of nearby galaxies has been confirmed by multiple pieces of independent evidence. His work on accretion discs led to new insights into their workings, as well as the realisation that the infrared excess in T Tauri stars was caused by protostellar discs around these young stars. He introduced the influential idea of monolithic collapse of a gas cloud as a formation mechanism for the Milky Way Galaxy. As this gave way to modern ideas of merging and accretion as drivers of galaxy formation, Donald was the first to realise the importance of tidal streams as measures of the past history and present day gravity field of the Galaxy. Though primarily a theorist, Donald participated in one of the first observational programs to measure the large-scale streaming of nearby galaxies. This led to the discovery of the `Great Attractor. The depth and versatility of his contributions mark Donald out as one of the most influential and pre-eminent astronomers of his day.
Stephen Hawkings contributions to the understanding of gravity, black holes and cosmology were truly immense. They began with the singularity theorems in the 1960s followed by his discovery that black holes have an entropy and consequently a finite t
Stirling Colgate was a remarkably imaginative physicist, an independent thinker with a wide breadth of interests and contagious enthusiasm, a born leader with enduring drive to attack fundamental problems in science. Among his many achievements, he f
Julian Besag was an outstanding statistical scientist, distinguished for his pioneering work on the statistical theory and analysis of spatial processes, especially conditional lattice systems. His work has been seminal in statistical developments ov
I review the history and development of Modified Newtonian Dynamics (MOND) beginning with the phenomenological basis as it existed in the early 1980s. I consider Milgroms papers of 1983 introducing the idea and its consequences for galaxies and galax
Allan Sandage was an observational astronomer who was happiest at a telescope. On Hubbles sudden death Allan Sandage inherited the programmes using the worlds largest optical telescope at Palomar to determine the distances and number counts of galaxi