Astronomers have discovered and mapped an enormous structure in the early universe with a mass the equivalent to one million billion times that of the Sun. The proto-supercluster, which has been dramatically named Hyperion after the Titan of Greek mythology, is estimated to have formed only 2.3 billion years after the creation of the cosmos in the Big Bang.
Superclusters in our local universe are mindbogglingly massive. They are made up of thousands of galaxies, and stretch for hundreds of millions of light-years in diameter.
The newly-revealed Hyperion proto-supercluster represents an earlier stage in the evolution of these celestial heavyweights. The discovery was made by an international team of astronomers using a combination of new observations and an analysis of archive data.
Data used in the study was collected by the Visible Multi-Object Spectrograph (VIMOS) instrument mounted on the European Southern Observatory's Very Large Telescope (VLT), located at the Paranal Observatory in Chile.
VIMOS is designed to break down the light emitted by distant galaxies into spectra. Think of an object's spectrum as its light fingerprint.
A forensic detective could analyse a fingerprint and tell you a surprising amount of information about the person that left it. The same is true of a spectra. By observing such a cosmic fingerprint, astronomers can work out some of the key characteristics of a heavenly object, including what it is made of, and its motion.
Unlike some other spectrographs, VIMOS is not designed to take the spectra from just a single source.
Initially, VIMOS observes a large swathe of sky, containing hundreds of enormous galaxies. From this preliminary image, astronomers can identify galaxies of interest, such as those belonging to Hyperion, and tag them for further study.
A laser-cutter then takes the data, and drills small slits in a metal sheet that correspond with the locations of the target galaxies. The metal plate is then integrated with VIMOS, which can now focus on collecting data on the desired galaxies while blocking out the light from surrounding sources, which would otherwise confuse the spectra from the marked targets.
The data revealed Hyperion to be the largest structure ever discovered in the early universe. The supercluster is estimated to have formed roughly 2.3 billion years after the Big Bang, and yet has a mass similar to that of superclusters in the local universe. This surprised astronomers, as structures the size of Hyperion are normally thought to form significantly later.
The team identified and mapped the positions of 10,000 galaxies that form the structure. In the process, the researchers identified at least seven high-density regions linked together by looser filaments of galaxies.
The structure is different from superclusters located closer to the Milky Way. These tend to feature a more concentrated distribution of mass, rather than the uniform distribution of dense blobs and connecting filaments observed in Hyperion. The difference is probably a result of Hyperion's relative youth.
"Understanding Hyperion and how it compares to similar recent structures can give insights into how the Universe developed in the past and will evolve into the future, and allows us the opportunity to challenge some models of supercluster formation," comments Olga Cucciati of the Istituto Nazionale di Astrofisica, Bologna, and first author of the discovery paper. "Unearthing this cosmic titan helps uncover the history of these large-scale structures."
The study has been published in the journal Astronomy & Astrophysics.
An animation of the Hyperion proto-supercluster created using VIMOS data can be seen in the video below.
Source: European Southern Observatory
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