Imagine yourself in a boat of a magnificent ocean, the water stretches to the far horizon, with the weakest notes of land just behind it. In the morning, just before dawn, there was a dense fog on the coast. As your cool touches your early watch, you catch a light from the corner of your eye that flicker through the mist.
And – yes – there! Another lighthouse, closer, his light a little stronger. As you scan the horizon, more headlights signal the dangers of the distant shoreline.
You know this coast by returning to the same port year after year. You know that the headlamps are the same brightness made by the same production and maintained in good working order over the years.
So, take time when you play a small game. Consult with your diagrams, know the distance to each lighthouse and where the light comes to reach your sharp salt. But their light, bright and bright on a clear night, is darkened and overshadowed by the constant fog. You know how bright they are you must to be and you can compare this brightness to what you see by looking at the layers and layers of fog to see how much fog embraces the shoreline.
It's not like having something better to do.
This is exactly the procedure astronomers have recently used to measure the total amount of starlight in the universe – minus, of course, the mist and the headlamps and the salty sailors.
Our cosmic lights are the active galaxies, the most powerful engines in the universe, where matter that flows through giant black holes is compressed and heated, lit by a flames of radiation before it is swallowed up by the horizon of the event. In their death, these shattering, chaotic stacks of gases emit more energy than millions of galaxies and are able to pump their light into the universe.
When they are ignited in the young cosmos, they appear to us as lights, brilliant but distant.
Between these headlights and our telescopes is everything matter in the universe. Most of the universe is empty, but the filling of these cavities is the accumulated light of all generations of stars who lived and died from distant epochs, illuminating the cosmos in a dark and thin mist of photons.
Radiation coming from remote, active galaxies is extremely high – no surprise given the strong nature of their origins. And as this high-energy light passes through the universe, she meets this thin mist. Chance interaction through accidental interaction, arbitrary collision in any collision, high energy radiation loses energy and distracts.
By exploring the light of more than 700 active galaxies, the team of astronomers could estimate the entire starlight produced throughout the universe and in space time from the time of the first stars just 500 million years after the Big Bang to the present day. Graphic Count? 4 × 10 ^ 84 photons, which is … a lot.
This estimate is in agreement with other calculations of the so-called extragalactic background light, but is buried in the last observation, while others are a disturbing discovery: our universe dies.
By comparing the light from different active galaxies located at different distances from us, astronomers could not only calculate the total amount of stellar light ever produced, but also trace the tides and streams of this starlight through billions of years of space history.
And the terrible news is that the lights go out one by one. The best, as we can say, in various observations and assessments is that our universe reached its peak in the star 9 billion years ago, when space was only a quarter of its present age.
The exact cause still misses us. Of course, our expanding universe has something to do with it – galaxies move away from each other on average, resulting in fewer mergers and less supplies of fresh material flowing into galaxies where they can burn that gas in new stars. But why was the tip at this point, so long ago? Why does the star collapse so fast? Or, perhaps, why did the stars continue to exist for so long despite the collapse of the once great empire?
Difficult questions without easy answers. So far, at least we're in the mist.
Read more: "Gamma Determination of the History of the Star Formation of the Universe"