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Caltech Astronomers Spot the Farthest and Oldest Galaxy Yet

Posted September 8, 2015

Researchers at Caltech had recently spotted a new galaxy – called EGS8p7 – which they believe to be the oldest and farthest ever found. The galaxy is 13.2 billion years old and is in possession of certain qualities that challenge the timeline of our Universe‘s evolution.

EGSY8p7 is the oldest and farthest galaxy ever discovered. Image courtesy of NASA/JPL/Hubble.

EGSY8p7 is the oldest and farthest galaxy ever discovered. Image courtesy of NASA/JPL/Hubble.

To determine EGS8p7’s redshift – the movement toward longer wavelengths of the spectral lines emitted by a celestial object that is caused by the object moving away from the Earth – the research team worked with the Multi-Object Spectrometer for Infrared Exploration (MOSFIRE) at the W. M. Keck Observatory in Hawaii, and found that the galaxy emits a certain type of radiation, which, in theory, should have been absorbed by clouds of neutral hydrogen that dominated the early Universe.

“If you look at the galaxies in the early Universe, there is a lot of neutral hydrogen that is not transparent to this emission,” said one of the researchers Adi Zitrin, a NASA Hubble Postdoctoral Scholar in Astronomy. “We expect that most of the radiation from this galaxy would be absorbed by the hydrogen in the intervening space. Yet still we see Lyman-alpha from this galaxy.”

One possible explanation for this is that hydrogen reionization by the first stars, thought to have started taking place when the Universe was half-billion to a billion years old, did not happen all once, but rather spread in patches that were not coherent in all directions.

The new-found galaxy, which is unusually luminous, could be powered by a number of extraordinarily hot stars, and have special properties that enabled it to create a large bubble of ionized hydrogen much earlier than it became possible for more typical galaxies that existed at the time.

“We are currently calculating more thoroughly the exact chances of finding this galaxy and seeing this emission from it, and to understand whether we need to revise the timeline of the reionization, which is one of the major key questions to answer in our understanding of the evolution of the universe”.

Zitrin and his colleague Richard Ellis – a former Caltech researcher, now a Professor of Astrophysics at University College, London – described the galaxy in the latest issue of the Astrophysical Journal Letters.


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