FromQuarkstoQuasars

Feast Your Eyes on One of the Most Distant (Known) Galaxies in the Universe

Jaime TrosperNovember 23rd 2013
Image Credit: NASA/ESA/STScI/JHU (Source)
Image Credit: NASA/ESA/STScI/JHU (Source)

In the above image, the pixelated photo on the lower right may not look like much, but it may very well be the most distant galaxies ever photographed by Spitzer and Hubble. This galaxy is so distant that light first shone from it when the universe was a mere 500 MILLION years old. It may provide some valuable answers to astronomers about the transitional period between the dark and colorless early universe to a modern cosmic expanse filled with the light of trillions of stars — with brilliant nebulae looming through stellar nurseries and an untold number of planets that circle alien suns.

 Image Credit: NASA, ESA, K. Sharon (Tel Aviv University) and E. Ofek (Caltech)
Image Credit: NASA, ESA, K. Sharon (Tel Aviv University) and E. Ofek (Caltech)

A common method of determining cosmic distances relies on measuring the red-shift of objects in the universe. Objects that are traveling away from our line of sight (due to the accelerated expansion of the universe) will be shifted towards a longer wavelength, which happens to be red. Objects that are traveling towards us (like the Andromeda galaxy) will shift towards a shorter wavelength, thus appearing blue. This galaxy has a red-shift of 9.6. Unfortunately, this means that actually seeing the thing is extremely difficult, as even the most sensitive space telescopes have their limits (which happen to fall a little short, in this case). So instead, we rely on a method called gravitational lensing.

In this method, we use the light from background objects, which is amplified due to to the warping of spacetime (this warping is caused by all objects that have mass). Since there are massive galaxy clusters lying on the outskirts of our galaxy and the one we’re recently observed, the warping of spacetime magnifies the light, bringing the galaxy into focus some 15 times more than it would appear had the cluster of galaxies not provided gravitational lensing as a tool for detection.

And this observation is truly a triumph of technology — the light from this particular primordial galaxy has traveled 13.2 billion light-years before it was ultimately captured by Hubble’s infrared filters. To put that into perspective, the universe was only 3.6 percent of its current age when the light set forth on its path to the Milky Way.

Figure 1: Artists conception of the evolution of the structure of the universe, starting with the epoch of recombination and ending with the formation of the first stars and galaxies. (Credit & Caption)
Figure 1: Artists conception of the evolution of the structure of the universe, starting with the epoch of recombination and ending with the formation of the first stars and galaxies. (Credit & Caption)

Astronomers have estimated that we’re looking at the galaxy as it appeared when it was a mere 200 million year old. Since its total mass is only 1% that of the Milky Way, this gives credence to the theories put forth by some researchers, which suggests that the first galaxies in a young universe started out very tiny before they progressively merged together, forming the large galaxies that we see surrounding us today. It’s also thought that this transition (from tiny galaxies to the larger ones that we see now) played a role in the “epoch of reionization,” which began around 400,000 years after the big bang. During this time, neutral hydrogen gas was formed, cooling particles as entropy increased.

It was at this point that the first stars arose in the tiny galaxies formed in that period. The energy released from them is believed to be the catalyst for the neutral hydrogen to lose an electron through a process called ionization — a state the gas has remained in even billions of years later.

When Hubble’s successor, the James Webb telescope, is launched in 2018  this galaxy is sure to be looked at much closer. As Leonidas Moustakas, a research scientist at NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif said: “In essence, during the epoch of reionization, the lights came on in the universe.” And soon, we will have an opportunity to get a between view of them.

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