A Rare Post from The Dark Energy Survey: “CSI: Early Universe”

Dark Energy Icon

Det. B. Nord [FNAL]

For this installment of Cosmic Scene Investigation, we travel to one of the earliest collisions of large-scale structures in the known universe.

csi
From DES. Credits in text.

el gordo
Another view. El Gordo consists of two separate galaxy subclusters colliding at several million
kilometres per hour.
Credit: ESO/SOAR/NASA

A splatter of red (denoting galaxies) lies at the center of this image, and extends toward the lower left. These are the remnants of a cosmic collision. Aeons ago, one group plunged through another at millions of miles per hour, leaving in its wake a wreckage. The galaxy cluster ‘El Gordo‘ is all that remains of this raucous event, which took place less than a billion years after the universe started.

From the deserts of Chile, the Atacama Cosmology Telescope was the first to detect this prodigious system. NASA’s Chandra X-ray Observatory, the [ESO] Very Large Telescope, and NASA’s Spitzer Telescope have also collected forensic evidence across the energy spectrum, from the infrared to the X-ray. All put together, we see a system similar to the infamous Bullet Cluster: a pair of clumps converted to a churning, violent amalgam of hot gas, dust and light.

An extremophile in the truest sense, El Gordo is the earliest-occurring cluster of its caliber. Its hot gas is burning at 360 million degrees Fahrenheit (200 million degrees Celsius), and it weighs in at a million billion times the mass of Earth’s sun. Compare this to the Virgo cluster of galaxies, the celestial city that holds our Milky Way and its neighbors. El Gordo’s mass is about the same, but it is over a hundred times hotter.

Dark energy is the name given to that substance, that energy, that is making spacetime spread out faster and faster. In the early universe, the small chunks that make up El Gordo were able to overcome dark energy (if it even existed then) and move toward each other to produce this cosmic crash scene. How many more like it are out there? The case remains open.

See the full article here.

The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and will mount it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Starting in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.


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