The galaxies were discovered during a survey campaign called UDF12
. Using Hubble's Wide Field Camera 3, an area of space known as the Ultra Deep Field (UDF) was studied. The results of the survey show a decline in the number of galaxies the further back in time they looked. It supported their theory that the galaxies evolved over a continuous time frame, and were not formed all at once during the Big Bang.
The oldest of the galaxies is believed to have formed 13.7 billion years ago, some 380 million years after the Big Bang. The remaining galaxies are thought to have formed between 400-600 million years after the Big Bang. The primitive galaxies are a snapshot of what astronomers call "the cosmic dawn” of the universe.
The team who conducted the survey are excited to finally get a glipse of these previously unseen galaxies. Astronomers were not able to see them sooner because, due to their great distance, their light is just now reaching earth. They are also pleased to have evidence that their theory that the universe has expanded over time, and was not created by one cosmic event, was correct. California Institute of Technology Professor Richard Ellis, leader of the survey, told the BBC
"If you compare the number of galaxies that we see to the abundance of objects once the Universe had expanded a little bit, we describe a very smooth decline in the number of objects as we go back into cosmic history. Of course, the most distant object is interesting, but it's the census - the seven objects - that gives us the first indication of the population of objects in the heart of this… era."
According to ScienceBlog
, the main goal of UDF12 is to determine how quickly the number of galaxies increased during the early years of the universe. This latest discovery is a key piece of evidence for astronomers. They are also hoping to answer the question of what happened during a period of “reionization” when the universe reheated. Many of the galaxies that have been discovered up until now, were considered "modern galaxies". These primitive galaxies are of extreme interest to the UDF12 team. Avi Loeb, chair of the astronomy department at Harvard University, told Boston.com
“We don’t know the details exactly during that time. So one way of unraveling what really happened is to look at galaxies, like we are doing in this particular context.”