The Universe has (almost) no more secrets. Today comes the widest, most profound and complete image ever obtained of the cosmos, created by the scientists of NASA, ESA and various research institutions thanks to the observations of the Hubble space telescope during 16 years. We are before the most detailed and vast portrait of the entire known universe, which includes 265 thousand extremely distant galaxies. The results of this ambitious project, called Hubble Legacy Field, were released by NASA, which unveils the image (shown below) and explains it in a video animation.
The Universe in an image
The researchers obtained the image by combining the observation data of 16 years of Hubble's work, or putting together a mosaic of instant shots extracted at various times during this period. In this picture of the universe they have included very distant galaxies: the most distant and weak ones have a brightness that is ten billionths of times lower than that which the human eye can perceive. To achieve this result, various surveys were used, including those of the Hubble eXtreme Deep Field (Xdf). Xdf is an image of a small part of space in the center of the ultra-deep field of Hubble (Hubble Ultra Deep Field) in the constellation of Fornace, the deepest view ever obtained of space. Currently, the authors explain, no image can beat this and exceed its performance until a new generation of even more advanced telescopes is developed.
The galaxies, the markers of Space
At one time scientists were able to capture hundreds of thousands of galaxies. "A single image contains the complete history of galaxy growth," explains Garth Illingworth of the University of California at Santa Cruz, who coordinated the team in the making of the image, "since they were just born when they are adults" . The classification of all these galaxies provides a real catalog, a sort of book of the universe. This type of study in the past has opened the door to unexpected discoveries to understand how the universe has evolved, as pointed out by Katherine Whitaker of the University of Connecticut to Storrs, who coordinated the team that dealt with cataloging galaxies. The galaxies are in fact the markers of Space, according to a definition given a century ago by the astronomer Edwin Hubble (from which the telescope takes its name). Studying their characteristics, including evolution, allows us to understand the essential mechanisms with which the cosmos works. And among these also to discover the presence of black holes (like the one just photographed, at the center of the Messier 87 galaxy), of dark matter and of other objects unknown in the universe.
To the future
In the future, scientists hope to expand the observations. The idea is to insert data based on infrared observations at longer wavelengths and high-energy X-rays, including images of NASA's Spitzer space telescope, which looks in the infrared, and Chandra X-ray Observatory, also of NASA, for the study of the sky in X-rays. Everything will come together in the Wide Field Infrared Survey Telescope (Wfirst), adds Illingworth: "in just three weeks of observations by the Wfirst, astronomers will be able to assemble a field much deeper and more than twice that obtained from the Hubble Legacy Field ". But that is not all. Thanks also to the launch - planned for 2021 - of the James Webb space telescope for infrared astronomy, it will be possible to study even more in detail the evolution of galaxies, including how newborns have become adults. The goal, the researchers explain, is to identify the first and oldest galaxies in the universe.
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