There are still a great many things about our Universe that leave scientists stumped. We aren’t even close to understanding the processes the Universe went through before we got here, but two days ago we made an important step in that direction. Finally, by employing several sources, green pea galaxies help scientists confirm decade long theory.
Finally, astronomers were able to confirm a theory they’ve had ever since they first discovered that it happened about the early re-ionization of the Universe.
You see, in the several hundred thousand years following the Big Bang, the Universe was so extremely dense and hot that matter wasn’t in a neutral state – instead it was ionized.
With time, about 380,000 years later, to be more exact, the Universe’s expansion had slowed down enough to allow it to cool down; this led to matter becoming neutral and to the first of the Universe’s constructs to take relative shape – gaseous clouds of helium and hydrogen.
With the appearance of gravity, these clouds got pushed together so hard that they created the first solid forms in the Universe, the first stars and galaxies.
However, and here comes the decade long dilemma, roughly one billion years after the Big Bang, when the Universe was still quite young, it reheated again and cause its most common element, hydrogen, to become ionized once more, in what the scientists call cosmic re-ionization.
Ever since they discovered that the process took place, scientists have believed that galaxies were responsible for the Universe’s re-ionization, but they lacked any way to prove it. And this is where modern technology comes in.
By using a huge database that encompasses over one million galaxies, the Sloan Digital Sky Survey, researchers managed to isolate around 5,000 galaxies that would help in what they needed – green pea galaxies, which are small, round, and compact galaxies, appearing green to light sensors, and which are hosts to huge stellar explosions and winds powerful enough to spew out ionizing photons.
Eventually limiting their observations to 5, and then to a single green pea galaxy 3 billion light years from Earth, the researchers used the Hubble telescope’s ultraviolet radiation detecting feature, to observe that it ejects ionizing photons at an intensity never before seen, at somewhere around 8%.
This finally confirmed the scientific world’s theory that the Universe’s re-ionization was caused by the ionizing photons present in the ultraviolet radiation emitted from galaxies.
Image source: Wikimedia