Arizona State Astronomers Discover Faint Galaxy 13 Billion Light Years Away

Posted on June 2, 2012

Astronomers at Arizona State University have found an exceptionally distant galaxy. The galaxy - located 13 billion light years from Earth - is ranked among the top 10 most distant objects currently known in space. Light from the recently detected galaxy left the object about 800 million years after the beginning of the universe.

A team of astronomers, led by James Rhoads, Sangeeta Malhotra, and Pascale Hibon of the School of Earth and Space Exploration at ASU, identified the remote galaxy after scanning a moon-sized patch of sky with the IMACS instrument on the Magellan Telescopes at the Carnegie Institution's Las Campanas Observatory in Chile. The galaxy has been designated LAEJ095950.99+021219.1. A false color image of the galaxy is pictured above. LAEJ095950.99+021219.1 appears as the green source near the center of the image

Rhoads says, "This galaxy is being observed at a young age. We are seeing it as it was in the very distant past, when the universe was a mere 800 million years old. This image is like a baby picture of this galaxy, taken when the universe was only 5 percent of its current age. Studying these very early galaxies is important because it helps us understand how galaxies form and grow."

The find was enabled by the combination of the Magellan telescopes' tremendous light gathering capability and image quality and by the unique ability of the IMACS instrument to obtain either images or spectra across a very wide field of view. This galaxy, like the others that Malhotra, Rhoads, and their team seek, is extremely faint and was detected by the light emitted by ionized hydrogen. A special filter fitted to the telescope camera was designed to catch light of narrow wavelength ranges, allowing the astronomers to conduct a very sensitive search in the infrared wavelength range.

Malhotra, an associate professor in the school, says, "We have been using this technique since 1998 and pushing it to ever-greater distances and sensitivities in our search for the first galaxies at the edge of the universe. Young galaxies must be observed at infrared wavelengths and this is not easy to do using ground-based telescopes, since the Earth's atmosphere itself glows and large detectors are hard to make."

To detect these very distant objects astronomers look for sources which have very high redshifts. Astronomers refer to an object's distance by a number called its redshift, which relates to how much its light has stretched to longer, redder wavelengths due to the expansion of the universe. Objects with larger redshifts are farther away and are seen further back in time. LAEJ095950.99+021219.1 has a redshift of 7. Only a handful of galaxies have confirmed redshifts greater than 7. None of them are as faint as LAEJ095950.99+021219.1.

The research paper was published here in the June 1 issue of The Astrophysical Journal Letters. The research was supported by the National Science Foundation (NSF).

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