Oldest and Farthest Galaxy Discovered by Caltech Scientists

A team of researchers at Caltech has put years of efforts studying the universe and looking for its oldest objects and has stumbled up on the most farthest and perhaps the oldest galaxy ever found – called EGS8p7.  The article about the discovery was published in Astrophysical Journal Letters with Adi Zitrin and Richard Ellis. Richard Ellis is Caltech’s recent retiree and Adi Zitrin is a NASA postdoctoral scholar. The galaxy EGS8p7 is estimated to be 13.2 billion years old and the universe itself is 13.8 billion years old. The galaxy was selected as a candidate for investigation based up on data recorded by the Hubble and Spitzer Space telescope. The MOSFIRE (multi –object spectrometer for infrared exploration) was used by the researchers for determining the galaxy’s redshift at Hawaii’s W.M. Keck Observatory. MOSFIRE is capable of detecting chemical signatures of distant galaxies as well as stars at infrared wavelengths. 

This involves analyzing the color shift of the light that happens because of the Doppler Effect. The Doppler Effect is responsible for dropping of a truck siren’s pitch as it passes away. However, in the case of planetary objects instead of sound, the light stretches and shifts to the side of red wavelengths. When observing the very early objects, the Redshift is of little use and is often used for measuring the distance to galaxies. After the Big Bang took place, universe was but a cluster of charged particles. The early universe wasn’t capable of transmitting light since the free electrons scattered the photons. The universe cooled down after the 380,000 years allowing combining of free protons and electrons and thus capable of transmitting light.

It is almost certain that the EGS8p7 is very old but it has some light signatures that are putting the researchers in to confusion that such an old galaxy doesn’t emit such bright light. The reason might be that there was a lot of neutral hydrogen in the early universe. Neutral hydrogen absorbs the emitted light of stars and the light wasn’t able to pass for a billion years. Another theory put forward to account for the galaxy’s bright light is that in its core there are extremely hot stars. So the earliest galaxies were formed reionizing the neutral gas just when the universe was half a billion years old. Today the universe remains ionized. Before reionization, radiation of new galaxies called Lyman-alpha line would have been absorbed by the neutral hydrogen. This is the usual indicator of star formation.

Zitrin says, “If you look at the 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.”

Ellis says, “The surprising aspect about the present discovery is that we have detected this Lyman-alpha line in an apparently faint galaxy at a redshift of 8.68, corresponding to a time when the universe should be full of absorbing hydrogen clouds.” Before this discovery, the farthest redshift detected was of 7.73.