If you are a fan of really big numbers that do not really talk about the world, Clemson University astrophysicist Marco Ajello is great for you: 4 x 10 ^ 84.
This is the total number of photons that have successfully escaped from the stars and the dust that surrounds them in space during the history of the universe. You expect this value to be huge, of course, and that it is in all incomprehensible ranges. (For comparison, the recent estimate of how many atoms there is in the universe is only a few orders of magnitude smaller.)
However, to be able to calculate this number is a beneficial benefit for new research conducted by Ajel and his team. This research supports previous theories on star formation speeds in the history of the universe, using information that is captured in all those light worlds – formally known as the extragalactic background of light. [Gamma-Ray Universe: Photos by NASA’s Fermi Space Telescope]
The extragalactic background is, by definition, part of the near infrared, optical and ultraviolet radiation that produce stars that can get into space rather than collide with the dust that surrounds these stars. "Basically, it's the starlight that ended everywhere," said Ajello Space.com. "All the light emanating from the stars that are able to escape into the universe is basically a background."
But the extragalactic background of light is difficult to measure because it spreads so thin across the universe and overcomes bright light sources closer to Earth. So Ajello and his co-authors tried to solve this light beam by using blazars – a type of galaxy that hides a supermassive black hole in the core that shoots a huge stream of high-energy material more or less in our direction. Their data on those blazers and gamma-ray photons that they emit come from NASA's Fermi Gamma-ray space telescope.
The study is based on the unpleasant feature of blazars: Some of the most powerful light that produces bangs, to much less energy of light particles, like photons that we humans can see. This collision turns a pair of discontinuous photons into an electron and a positron, virtually disappearing the high-energy photon that the blazar has released. "In a sense, yes, it's a disadvantage if you focus only on studying blazars," said Manasvita Joshi, an astrophysicist at Boston University. "But for someone you can use it to your advantage."
The interaction between blazer photons and extragalactic photon photon lights begins at a certain level of energy. That is, scientists can extrapolate from light produced at lower energy levels to what should be produced at these higher levels of energy. Then they can calculate the difference that disappeared during collisions. And from there it's an easy guy on the other side of this collision to measure the extragalactic background.
By studying a lot of blazers – 739 to be accurate – at different distances from the Earth, the team could accurately identify changes in the extragalactic background. "By measuring how starlight is developing all over the universe, you can actually transform it into a corresponding measurement of the star formation," Ajello said. "We are following exactly how this has changed during the history of the universe." [Messier’s List: Hubble Telescope’s Stunning Views of Deep-Sky Objects]
"Now the new thing is used to determine the history of cosmic stars," Joshi said. This is a question that scientists have long been trying to solve, but so far they had to do it indirectly and rely on some initial assumptions that are never ideal. "Problem [with previous estimates] it's because your initial weight function is … it's really an estimate, it's an initial guess and it can pose uncertainty, "Joshi said.
So the fact that this different approach – by overcoming these initial assumptions – draws some conclusions about the formation of stars over time, calms astrophysics, Joshi said. It helps not only to verify these conclusions but also to indicate that scientists have been on the right path with initial assumptions that have led to old ways of estimating star formation over time.
So, when was the most popular time for the birth of stars? About 10 billion years ago. And the evidence is in their light.
The research is described in a paper published November 29 in Science.