4 x 10p84 particles of light

Astronomers have measured all the starlight ever emitted Astronomers used distant blazars to tally up all the stray photons roaming through space.  It amounts to 4 x 1084 particles of light, or photons. That’s roughly equivalent to all the photons the sun would emit if it burned for 100 billion trillion years — long beyond the 5 billion years it has left. The universe itself is only 13.7 billion years old. Measuring all those stray photons and figuring out when they were emitted can help astronomers write a timeline of star formation across the last 11 billion years, since the first stars were born, astrophysicist Marco Ajello of Clemson University in South Carolina and colleagues report in the Nov. 30 Science.

Read More