Jeremiah Ostriker, an astrophysicist who helped set off a revolution in humankind’s view of the universe, revealing it to be as vaster, darker realm than the one we can see, ruled by invisible forms of matter and energy we still don’t understand, died on April 13 at his home on the Upper West Side of Manhattan. He was 87.

For more than four decades, mostly at Princeton University, Dr. Ostriker’s work altered our understanding of how galaxies form and evolve as he explored the nature of pulsars, the role of black holes in the evolution of the cosmos, and what the universe is made of. He won the National Medal of Science in 2000.

According to Dr. Martin Rees, a cosmologist at the University of Cambridge and the Astronomer Royal, Dr. Ostriker would come up with pioneering ideas on novel themes. “He inspired younger colleagues and collaborators, not just at Princeton but around the world.”