How The Universe's Oldest Known Galaxy Defied Odds To Shine 13.2 Billion Years Ago

One of universe's most distant and oldest galaxies has defied odds to reveal itself to researchers on Earth who are now wondering if some of scientific community's understanding of such cosmic objects has to be revised.

According to Haaretz, scientists at California Institute of Technology first spotted the galaxy EGS8p7 earlier this year using the Hubble and Spitzer Space telescopes. They then analyzed the emissions from the galaxy using the multi-object spectrometer for infrared exploration (MOSFIRE) at Hawaii's W.M. Keck observatory only to find that it is 13.2 billion years old. The universe is 13.8 billion years old.

Why is EGS8p7 an against-the-odds find?

The current understanding of the universe's evolution is that light transmission by newly formed galaxies immediately after the Big Bang was not possible as charged particles in a hot primordial soup scattered photos (light particles). However, when the universe cooled down and charged particles united to form neutral hydrogen, light transmission was made possible albeit for a little while.

Not long after (in cosmic terms) hydrogen pervaded the young universe, stars in galaxies started functioning. The all-pervading hydrogen absorbed much of the radiation from the stars and was re-ionized, leading to creation of charged particles for another time after Big Bang. The universe is said to be in this ionized state today.

EGS8p7 dates to a time when interstellar hydrogen was ionized and continued to absorb all radiation. Up until now, the accepted notion was hydrogen prevented any young galaxy from transmitting its light. A galaxy located 13.2 billion years away in space and time should thus not be visible.

"If you look at galaxies in the early universe, there is a lot of neutral hydrogen that is not transparent to this emission. 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," said Adi Zitrin, one of authors who described the finding of EGS8p7 published in Astrophysical Journal Letters.

The study's authors are now considering whether the ionization of hydrogen was a uniform event. They suspect it was patchy, allowing galaxies like EGS8p7 to transmit. Also, the galaxy itself could be populated by unusually hot objects.

"The galaxy we have observed, EGS8p7, which is unusually luminous, may be powered by a population of unusually hot stars, and it may have special properties that enabled it to create a large bubble of ionized hydrogen much earlier than is possible for more typical galaxies at these times," says Sirio Belli, a Caltech graduate student who worked on the project.