L J Ravi THE Nobel Prize in physics this year has been shared by Roger Penrose, the mathematical physicist, for his work on the theoretical basis of black holes, and Reinhard Genzel, and Andrea Ghez, two astronomers, who led independent teams, for verifying the existence of such a black hole at the centre of our Milky Way galaxy. Penrose showed that the consequence of Einstein’s general theory of relativity is the formation of black holes, not simply of collapsing stars, but also in certain dense regions of space. Such black holes capture everything: nothing can come out, not even light. Genzel and Ghez and their teams independently showed by tracking the trajectory of a star that a super heavy object – around four million solar masses – exists at the centre of the Milky Way galaxy. Ghez is the fourth woman to win a Nobel prize in physics, the first one being Marie Curie in 1903. There are two connections to India on black holes. The first is through physics. It was S Chandrasekhar, an Indian physicist, who had shown in 1930 that if a star was larger than 1.4 times the solar mass, it would not stop collapsing. Chandrasekhar was C V Raman’s nephew, India’s first Nobel laureate in physics. He moved to the US in 1936 and assumed American citizenship in 1953. Below this mass – known now as the Chandrasekhar limit – the star would become a white dwarf. If the mass of the star was higher, he did not know what would happen. We now know that it would blow-up in a supernova; or blow-up and then collapse, with their atoms squeezed into the nucleus-sized spaces forming a neutron star; or not stop collapsing creating a black hole. Chandrasekhar received the Nobel Prize for physics in 1983.
