Universe Today
It's an amazing thing, staring into deep space with the help of a high-powered telescope. In addition to being able to through the vast reaches of space, one is also able to effectively see through time.
Using the Subaru Telescope's Suprime-Cam, a team of astronomers has done just that. In short, they looked back 13 billion years and discovered 7 early galaxies that appeared quite suddenly within 700 million years of the Big Bang. In so doing, they discovered clues to one of astronomy's most burning questions: when and how early galaxies formed in our universe.
The team, led by graduate student Akira Konno and Dr. Masami Ouchi (Associate Professor at the University of Tokyo's ICRR) was looking for a specific kind of galaxy called a Lyman-alpha emitter (LAE), to understand the role such galaxies may have played in an event called "cosmic reionization".
The current cosmological model states that the universe was born in the Big Bang some 13.8 billion years ago. In its earliest epochs, it was filled with a hot "soup" of charged protons and electrons. As the newborn universe expanded, its temperature decreased uniformly.
When the universe was 400,000 years old, conditions were cool enough to allow the protons and electrons to bond and form neutral hydrogen atoms. That event is called "recombination" and resulted in a universe filled with a "fog" of these neutral atoms.
Eventually the first stars and galaxies began to form, and their ultraviolet light ionized the hydrogen atoms, and "divided" the neutral hydrogen into protons and electrons again. As this occurred, the "fog" of neutral hydrogen cleared.
Astronomers call this event "cosmic reionization" and think that it ended about 12.8 billion years ago - a billion years after the Big Bang. The timing of this event – when it started and how long it lasted – is one of the big questions in astronomy.
To investigate this cosmic reionization, the Subaru team searched for early LAE galaxies at a distance of 13.1 billion light years. Although Hubble Space Telescope has found more distant LAE galaxies, the discovery of seven such galaxies at 13.1 billion light-years represents a distance milestone for Subaru Telescope.