Universe's oldest galaxy discovered


This photo may not look like much, but the implications are very important: Scientists using the W.M. Keck Observatory in Hawaii have discovered and imaged the Universe's oldest galaxy thus far.

Given the highly unromantic name EGS8p7, the galaxy formed just less than 600,000 million years after the Big Bang, which occurred a little less than 14 billion years ago.

More important than the photo is how they discovered EGS8p7. Using Keck Observatory's powerful infrared spectrograph, called MOSFIRE, the team dated the galaxy by detecting a signature of hot hydrogen gas heated by strong ultraviolet emission from newly born stars. Although this is a frequently detected signature in galaxies close to Earth, the detection of what's called Lyman-alpha emission at such a great distance is unexpected, as it is easily absorbed by the numerous hydrogen atoms thought to dominate the space between galaxies at the dawn of the Universe. The result gives new insight into "cosmic reionization," the process by which dark clouds of hydrogen were split into their constituent protons and electrons by the first generation of galaxies. Put simply, this gives us important insight into how the very first stars in the Universe formed after the Big Bang.

Because the discovery of such an early source with powerful Lyman-alpha emission is somewhat unexpected, it provides new insight into the manner by which galaxies contributed to the process of reionization.

"In some respects, the period of cosmic reionization is the final missing piece in our overall understanding of the evolution of the Universe," said California Institute of Technology (Caltech) astronomer Adi Zitrin, lead author of the discovery paper. "In addition to pushing back the frontier to a time when the Universe was only 600 million years old, what is exciting about the present discovery is that the study of sources such as EGSY8p7 will offer new insight into how this process occurred."

Every few years, it seems that another group of astronomers pushes the envelope farther and farther back. It'll be interesting to see how much farther back they go in the years ahead!

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