Yes your read
right, universe fossils. Most of you might have heard about the fact that the
star upon which you just made a wish is dead. The reason why this fact is so
true, is because even though a star died thousands of years ago, its light keeps
traveling in space. Thanks to this phenomenon, we get to know more about the
past. That’s why these remnants have been described as universe or space
fossils.
Now what NASA
scientists scientist Marco Ajello a postdoctoral researcher at the Kavli
Institute for Particle Astrophysics and Cosmology at Stanford University in
California and the Space Sciences Laboratory at the University of California at
Berkeley.and his investigation team have done, is measure the amount of space
fossils. This means they have measured the exact amount of starlight that has
ever existed since the universes origins.
This fossil
starlight named by scientists as extragalactic background light (EBL) acts as a
cosmic fog.
But how do
they do it? Well Scientists used Fermi’s Large area telescope or LAT, to
analyze the gamma rays from a 150 blazars, that means galaxies powered by
blackholes, and found out energies of around 3 billion electron volts, that
means at least 1 billion times the energy of visible light
Blazars are
galaxies powered by supermassive blackholes which are fed from matter. When matter is swallowed by this supermassive
blackhole, it collides with other particles causing gamma rays and many other
rays from the light spectrum (i.e. x-rays ) to be ejected violently in opposite
directions, just like this image below.
this is an artist's concept of a quasar, also part of the family of blazars
With these large amount of energy ejected as light (gamma rays) scientists can measure the amount of space fossils and know more about our origins.
When scientist compare the gamma rays emitted from 150 different blazars and that that has been received they of course find some difference. The reason is because when gamma rays collide against these "space fossils" or EBL, starlight "cosmic fog", transform into something else.
image captured by the Fermi's Large Area Telescope. Green dots are blazars, orange line milky way. Image from NASA.
Yes, when gamma rays hit the EBL, they become electrons and its antimatter part called positrons. We no longer have gamma rays but, two different particles. Since not all the gamma rays hit againts cosmic fog, we still receive certain amount of them.
Comparing these results and measurements scientists have been able to measure not only the amount of cosmic fossils or cosmic fog, but also space's density.
What scientists have concluded is that the distance between two different stars is around 4,150 light-years. For you to have a better idea of how much a light-year is you need to know first the distance between the Earth and the Sun.
The distance between the Earth and the Sun is 150 million km. This distance is commonly known as an Astronomical Unit or AU. Now returning to the light-year, one light year equals 63,000 Astronomical Units. Can you imagine that?
For you to be able to travel only 1 light-year you would need to travel the distance between the sun and the Earth 63,000 times! now imagine 4,150 light years!
More investigations like this one could lead us to more precise data about our origins and the universe first stars that lit their light for the first time.
