Astronomers find a galaxy very far, far away

By Paul Harper

The discovery of the faint, small galaxy opens a window onto the deepest, remotest epochs of cosmic history. Photo / NASA/ESA/STScI/JHU
The discovery of the faint, small galaxy opens a window onto the deepest, remotest epochs of cosmic history. Photo / NASA/ESA/STScI/JHU

Astronomers have found what they believe may be the most distant galaxy ever seen.

NASA said light from the galaxy travelled about 13.2 billion light-years before it was captured by NASA's Spitzer and Hubble space telescopes and first shone when our 13.7-billion-year-old universe was only 500 million years old.

Astronomers said the galaxy existed when the universe began to transition from the so-called cosmic dark ages. During this period, the universe went from a dark, starless expanse to a cosmos full of galaxies.

The discovery of the faint, small galaxy opens a window into the deepest, remotest epochs of cosmic history.

"This galaxy is the most distant object we have ever observed with high confidence," said Wei Zheng, a principal research scientist in the department of physics and astronomy at Johns Hopkins University in Baltimore and lead author of a new paper appearing in Nature.

"Future work involving this galaxy, as well as others like it that we hope to find, will allow us to study the universe's earliest objects and how the dark ages ended."

Based on the Hubble and Spitzer observations, astronomers believe the distant galaxy was less than 200 million years old when it was viewed. It also is small and compact, containing only about 1 per cent of the Milky Way's mass.

According to leading cosmological theories, the first galaxies indeed should have started out tiny. The galaxies then progressively merged, eventually accumulating into the sizable galaxies of the more modern universe.

NASA said these first galaxies likely played the dominant role in the epoch of reionisation, the event that signalled the demise of the universe's dark ages. This epoch began about 400,000 years after the Big Bang when neutral hydrogen gas formed from cooling particles.

The first luminous stars and their host galaxies emerged a few hundred million years later. The energy released by these earliest galaxies is thought to have caused the neutral hydrogen strewn throughout the universe to ionize, or lose an electron, a state that the gas has remained in since that time.

"In essence, during the epoch of reionisation, the lights came on in the universe," said paper co-author Leonidas Moustakas, a research scientist at NASA's Jet Propulsion Laboratory.

Astronomers relied on "gravitational lensing" to catch sight of the galaxy. In gravitational lensing, a phenomenon predicted by Albert Einstein a century ago, the gravity of foreground objects warps and magnifies the light from background objects, making it easier to view the distant galaxy.

Astronomers plan to study the rise of the first stars and galaxies and the epoch of reionisation with the successor to both Hubble and Spitzer, NASA's James Webb Telescope, which is scheduled for launch in 2018. The newly described distant galaxy likely will be a prime target.

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