LOS ANGELES – Astronomer Leonard Searle, a former director of the Carnegie Observatories whose observations provided crucial information in determining the conditions of the Big Bang that created the universe and helped explain how heavy elements are produced in stars, has died. He was 79.

Searle died July 2 at his home in Pasadena, Calif., according to the Carnegie Institution for Science in Washington, D.C.

Searle also played a crucial role in the construction of the twin 255-inch Magellan telescopes at Carnegie’s Las Campanas Observatory in Chile, which opened in 2000 and are considered the best natural imaging telescopes in the world.

He was “a thoughtful man who chose his problems carefully,” said Robert Preston, a director emeritus of the Carnegie Observatories. “The things that he accomplished were of lasting value; they’re still used today.”

The Big Bang was a singularity that started the formation of the universe and researchers have been curious about the precise conditions that existed during the explosion. That event produced massive numbers of elementary particles that, as the gas expanded and cooled, condensed to form hydrogen, helium and trace amounts of lithium and beryllium.

The other elements were subsequently created in the nuclear furnaces of stars. To calculate the temperature and pressure that existed in the Big Bang, it is crucial to know the ratio of helium to hydrogen that existed immediately afterward, and that was a problem Searle and Wallace Sargent attacked.