The Most Distant Galaxy Has Been Discovered
There have been great strides recently in determining the origins of stars in the Universe. Combined data from the Spitzer and Hubble Space Telescopes has revealed the furthest known galaxy to date and was believed to have formed about 13.2 billion years ago when the Universe was still quite young. The research was led by Nicola Laporte from Instituto de Astrofísica de Canarias in Spain and has been accepted for publication by Astronomy and Astrophysics Letters.
The galaxy, dubbed Abell2744 Y1, was spotted by scientists working on NASA’s Frontier Fields program. This program combines the data from Hubble and Spitzer to peer back to the earliest galaxies in the Universe. Frontier Fields is currently examining six galaxy clusters, chosen for a variety of factors including luminosity and lensing ability. Gravitational lensing occurs when distant light is magnified by galaxies and galaxy clusters. Though it is highly distorted, the astronomers can correct the signal and produce a good image. Once Hubble detects the faint visible light a candidate galaxy, Spitzer is used to verify the findings by analyzing the infrared light.
Abbell2744, which was seen when the Universe was a mere 650 million years old, is about thirty times smaller than the Milky Way though it likely had 10 times more stars. This is believed to be typical of the earliest galaxies, as the earliest stars lived fast and died young.
The galaxy’s distance is denoted by its redshift, which occurs when the wavelengths from the radiation are stretched due to the accelerating expansion of the Universe. As the source of light gets further away from the observer, the radiation appears to have a longer wavelength and appears more “red” on the electromagnetic spectrum. Thus, redshift is used to describe distance. Abell 2744 has a redshift of 8, which is the largest ever recorded. Though there are other candidate galaxies with a redshift of 11, they have not yet been confirmed. Prior to this discovery, the most distant known galaxy had a redshift of 7.51.
The Frontier Fields program is pushing the Hubble to look further into the past than it has ever done before, in hopes of learning more about the early Universe and to discover if the galaxies discovered by Hubble’s Ultra Deep Field (which existed 400,000-800,000 years after the Big Bang) are standard for that time around the Universe. The announcement of Abell2744 is the first from this program. It is hoped that many discoveries of this nature will follow as the program progresses.
Any persistent ambiguity about the earliest galaxies may be resolved after the James Webb Space Telescope is launched in 2018. Its primary mirror will have about seven times more area than the Hubble’s primary mirror and will also collect infrared data. The telescope will orbit at a distance of 1.5 million km (930,000 miles) away from Earth, far beyond the moon, in order to cancel out interference.