Gigantic Galaxy 8.5 Billion Light Years Away
Astronomers have discovered a giant gathering of galaxies located 8.5 billion light-years away, in a very remote part of the universe, thanks to NASA’s Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE). It is believed to be one of the five most massive in existence. Galaxy clusters are gravitationally bound groups of thousands of galaxies, which themselves each contain hundreds of billions of stars. The clusters grow bigger and bigger over time as they acquire new members.
In the coming year, the team plans to sift through more than 1,700 additional galaxy cluster candidates with Spitzer, looking for biggest of the bunch. Because light takes time to reach us, we can see very distant objects as they were in the past. For example, we are seeing the new found galaxy cluster – called Massive Overdense Object (MOO) J1142+1527 – as it existed 8.5 billion years ago, long before Earth formed. As light from remote galaxies makes its way to us, it becomes stretched to longer, infrared wavelengths by the expansion of space. That’s where WISE and Spitzer help out. In the infrared images produced by Spitzer, these distant galaxies stand out as red dots, while closer galaxies look white.
Astronomers first combed through the WISE catalog to find candidates for clusters of distant galaxies. WISE catalogued hundreds of millions of objects in images taken over the entire sky from 2010 to 2011. They then used Spitzer to narrow in on 200 of the most interesting objects, in a project named the ‘Massive and Distant Clusters of WISE Survey,’ or MaDCoWS. Spitzer doesn’t observe the whole sky like WISE, but can see more detail. From these observations, MOO J1142+1527 jumped out as one of the most extreme.
Using data from the Combined Array for Research in Millimeter-wave Astronomy (CARMA) telescopes near Owens Valley in California, the scientists were then able to determine that the cluster’s mass is a quadrillion times that of our sun – making it the most massive known cluster that far back in space and time. MOO J1142+1527 may be one of only a handful of clusters of this heft in the early universe, according to the scientists’ estimates. The red galaxies at the center of the image make up the heart of the galaxy cluster. This colour image is constructed from multi-wavelength observations: Infrared observations from NASA’s Spitzer Space Telescope are shown in red; near-infrared and visible light captured by the Gemini Observatory atop Mauna Kea in Hawaii is green and blue; and radio light from the Combined Array for Research in Millimeter-wave Astronomy (CARMA), near Owens Valley in California, is purple.