Welcome to brain Stuff, a production of I Heart Radio, Hey brain Stuff Lauren Vogelbon. Here, imagine the number four. Now imagine that it's at the head of a number with eighty four zeros behind it. And that is the number of photons emitted by all of the stars in the observable universe, going back to when the now thirteen point seven billion year old universe had been around for
just a billion years or so. And that's according to a team of researchers headed by one Marco A. YAlO, an astrophysicist in the College of Science at Clemson University. It's based on an analysis of data from NASA's ten year old Fermie Gamma Rays space telescope, which enabled the researchers to compile a history of star formation over most of the universe's lifetime. The scientists detailed their findings in
a paper published in eighteen in the journal Science. Measuring starlight for most of the universe's history required considerable ingenuity for the article. This episode is based on hows To Forks obtained prepared remarks from a yellow via email. He explained that the total amount of light emitted by stars is comprised of two types. Quote. One is stellar light that survives absorption by dust. This is what we measured. The rest is stellar light absorbed by dust and re
emitted in the infrared. We are not sensitive to that. It turns out half of the energy emitted by stars across the history of the universe is reprocessed by stars. At longer infrared wavelengths, the sky is filled with photons
emitted long ago by distant stars. This is called the extra galactic background light, or e b L. And nevertheless, except for the Moon and stars from our own galaxy, the sky appears dark to our eyes according to a yellow that's because most of the starlight that reaches Earth from the rest of the vast universe is extremely faint, the equivalent of a sixty watt lightbulb viewed in complete
darkness from about two point five million miles away. To get around that problem, A. YAlO and his team perused ten years of data from the FAMI telescope and looked at the e b LS interaction with gamma rays emitted by distant blazers. Blazers being black holes that can send powerful streams of radiation out into the universe. The researchers calculated the extent to which the gamma rays from those blazers had been absorbed or altered by collisions with the
e b l's photons. A. Yelo describes tracking the e b L as the astrophysicists equivalent of quote following the rainbow and discovering a pot of gold. The e b L is the rainbow, and its knowledge can finally disclose a lot of useful information. The researchers technique enabled them to see the history of star formation in the universe, which they found had peaked about three billion years after the Big Bang and has slowed dramatically since then. Slowed
but never completely stopped. The Milky Way, for example, creates about seven new stars each year. A note that the researchers count does not include the amount of starlight emitted in the first billion years of the universe's existence. Yelo said, this is an epoch we can't really probe yet. That's one reason he and other scientists are looking forward to the launch of the James Webb Space Telescope, which NASA says will be sufficiently sensitive to detect the first stars.
It's currently set to launch on December. Today's episode is based on the article how much starlight has been omitted since the beginning of time on house to works dot com, written by Patrick da Tiger Brainstuff is production of I Heart Radio in partnership with house to works dot com, and it's produced by Tyler Klang. For four more podcasts from my heart Radio, visit the heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows. H