Steiner is director, Instituto de Estudos Avançados, University of São Paulo, Brazil. He obtained his PhD in astronomy from IAG/USP, São Paulo, and did postdoctoral work in high energy physics at the Harvard-Smithsonian Center for Astrophysics. He proposed the theory of "Liners", in which such common objects as mini-quasars are explained, proposed the existence of a new class of stars called 'The V Sagittae Stars' and explained their extraordinary luminosity as due to hydrostatic nuclear reactions on the surface of accreting white dwarfs. He is a member of the Brazilian Academy of Sciences; Brazilian Astronomical Society; Brazilian Society for Advancement of Science; International Astronomical Union; and American Astronomical Society. He was awarded the Knight of the National Order of Scientific Merit (1998) and Knight of the Rio Branco Order, President of Brazil (2001).