Author: Robby Berman / Source: Big Think
- Scientists track gamma rays across the universe’s extragalactic background to calculate all of the starlight ever produced.
- For 10.8 billion years, star production has been decelerating.
- The research team measured nine years worth of data from the universe’s 739 known blazars.
The good news is that scientists believe they’ve figured out how much starlight the universe has ever produced since the Big Bang. Exciting. The bad news? Well, apparently star production peaked a long, long time ago, and ever since, the universe has been in the process of dying. Only seven new stars are born a year these days. You can keep buying green bananas, though; there’s time: We still have many billions of years before the stars that already exist go dark and cold.
Counting starlight
In Science, the Fermi-LAT Collaboration published, on November 30, a new inventory and history of the universe’s light. So, how much light has the universe produced? 4 × 10⁸⁴ photons. To spell that out, that’s 4,000,000,000,000,000,000,000,000,000,000,000,000
000,000,000,000,000,000,000,000,000,000,000,000,000,
000,000,000 photons.
The lead study author of the study, astrophysicist Marco Ajello, said his team was able to measure the entire amount of starlight ever emitted using the Fermi telescope.
“This has never been done before,” he told Clemson University’s the Newsstand. “Most of this light is emitted by stars that live in galaxies. Every single star that has existed has contributed to this emission, and we can use it to learn all the details about star formation and evolution and galaxy evolution.
”The Fermi team has been measuring nine years worth of data from the universe’s 739 known blazars.
This map of the entire sky shows the location of 739 blazars used in the Fermi Gamma-ray Space Telescope’s measurement. Brighter areas have stronger gamma rays. Image source: NASA/DOE/Fermi…
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