13 Billion BC -Enigma of Ancient Galaxies at the Very Edge of the Observable Universe

6a00d8341bf7f753ef0120a7003fe5970b.jpg A tiny faint dot in a Hubble picture (bottom of page) has been confirmed as the most distant galaxy ever detected in the Universe. So distant it took 13 billion years for its light to reach Earth, or even more dramatically, we are seeing the galaxy as it was just 600 million years after the Big Bang. The image left, discovered at the Hawaiian Mauna Kea Observatory, is a galaxy 12.8 billion light-years from Earth, as large as the Milky Way galaxy that harbors a supermassive black hole that contains at least a billion times as much matter as does our Sun.

"If you look at the object in the Hubble image, it really isn't much," said Dr Matt Lehnert of the Observatoire de Paris, France, and lead author on the paper published in Nature. "We really don't know much about it, but it looks like it is quite small – much, much smaller than our own Milky Way Galaxy. It's probably got only a tenth to a hundredth of the stars in the Milky Way. And that's part of the difficulty in observing it – if it's not big, it's not bright," he told BBC News.

So, apart from its status as a record-breaker, the newly discovered Hubble galaxy, classified as UDFy-38135539, is of keen interest because it is embedded directly in this time period – the "epoch of re-ionisation", as it is called, or Universe 2.0.

The galaxy was one of several interesting candidates identified in the Hubble Ultra Deep Field (UDF) image of the Fornax Constellation acquired with the telescope's new Wide Field Camera 3 last year. As a source of light, it barely registers on the Hubble picture which was made from an exposure lasting 48 hours. ESO astronomers knew from the UDF data that the galaxy must be very far away, but it took some fine tuning using the Yepun Very Large Telescope unit on Mount Paranal in Chile's Atacama Desert to determine the precise distance. Using this measure, known as redshift, the astronomers could confirm that UDFy-38135539 was more than 13 billion light-years distant (a redshift of 8.55).

At this early time, theory indicates, the Universe would not have been fully transparent. Much of it would have been filled with a hydrogen "fog" that absorbed the fierce ultraviolet light coming off the young galaxies. Only as these galaxies ionised this neutral gas filling the space between them did their light sweep out across the cosmos.

One of the more puzzling aspects of the discovery is that the glow from UDFy-38135539 would not have been strong enough on its own to burrow a path through the opaque hydrogen fog. This means there must be fainter, less massive galaxies – unseen in the Hubble UDF.

Astronomers have other candidates of similar distance in the UDF they hope to confirm soon. However, the real breakthrough in observing the epoch of re-ionisation is probably going to have to wait until more powerful telescopes and techniques are established.

This next-generation astronomy will include Hubble's successor (the James Webb Space Telescope) and the Extremely Large Telescope (ELT) to be built near the VLT in Chile. The ELT will catch the faintest starlight with a mirror some 42m across. That is five times the diameter of Yepun's primary mirror.

In 2009, scientists located a giant almost 13-billion year old galaxy. Detecting this huge galaxy  was a challenge because of the massive quantities of light coming from the black hole, and if you think you spotted two problems in that sentence, read on.

The galaxy, which is 12.8 billion light-years from Earth, is as large as the Milky Way galaxy and harbors a supermassive black hole that contains at least a billion times as much matter as does our Sun.

"It is surprising that such a giant galaxy existed when the universe was only one-sixteenth of its present age, and that it hosted a black hole one billion times more massive than the sun. The galaxy and black hole must have formed very rapidly in the early universe," said University of Hawaii astronomer Dr. Tomotsugu Goto who discovered the object.

"How can a galaxy be giant when it's the same size as our own?" is because of lightspeed – the galaxy is almost thirteen billion light-years away, which means it's almost thirteen billion years ago, which is almost as much "ago" as there is.  When the universe was only about a billion years old even a Milky Way sized galaxy was pretty big, and the supermassive black hole in the center was impressively huge.

Which brings us to the second issue: light coming from a black hole.  Everyone knows that nothing can escape from a black hole, not even light, but that's only after matter passes the "event horizon" – the ultimate one-way sign in spacetime.  But as matter falls in towards this cut-off point it's heated up by friction, radiating energy away as light, and this emission from infalling matter makes up over half of all the light detected from the distant galaxy.  This is why we didn't see it before – a little thing like a few hundred billion stars was outshone by the superheated material around the black hole.

Detection was made possible by newly upgraded CCD (Charge-Coupled Device) Cameras fitted to the Suprime-Cam in the Hawaiian Mauna Kea observatory.  The improvement was engineered by Professor Satoshi Miyazaki and colleagues of the National Observatory of Japan.

The new early-stage black hole-galaxy system will be an important clue in the evolution of such supermassive black holes.  While asking how they get so big might sound simple (they just keep eating stuff, including each other), their ability such spectacular size in so short a time isn't explained by any current creation theories.  And by "spectacular size" me mean about a giga-Sun of mass.  

Yet another reminder of the amazing: our amazing ability to detect such incredibility, and the amazing universe where such awe-inspiring objects can be lost down the back of the cosmological sofa until we look really hard.

_49590154_hubble_field2_464 (1)

Casey Kazan  with Luke McKinney via BBC News

Image: is a false-color image of the QSO, the most distant black hole currently known. In addition to the bright central black hole (white), the image shows the surrounding host galaxy (red). 

Tomotsugu Goto, University of Hawaii at ManoaGiant Galaxy Detected


"The Galaxy" in Your Inbox, Free, Daily