New view of Hubble Telescope on the evolving universe

Astronomers have assembled the largest and most comprehensive "history book" of galaxies into one image, based on 16 years of observations by NASA's Hubble Space Telescope.

The deep sky mosaic, created from nearly 7,500 individual exhibitions, provides a broad portrait of the distant universe, containing 265,000 galaxies that span over 13.3 billion years, up to 500 million years only after the big bang. The weakest and farthest galaxies are only one-ten billionth of the brightness of what the human eye can see. The evolutionary history of the universe is also recounted in this overview. The portrait shows how galaxies evolve over time, building to become the giant galaxies seen in the near universe.

This ambitious undertaking, called Hubble Legacy Field, also combines the observations of several deep field investigations of Hubble, including the extreme Deep Field (XDF), the deepest vision of the universe. The range of wavelengths extends from ultraviolet to near infrared light, capturing the key features of galaxy assembly over time.

"Now that we are wider than in previous surveys, we are exploiting far more distant galaxies in the largest dataset ever produced by Hubble," said Garth Illingworth of the University of California at Santa Cruz, responsible of the team that assembled the image. . "This picture contains the whole story of the growth of galaxies in the universe, from childhood to growth in" adults "in their own right."

The video begins with a view of the thousands of galaxies in the Hubble ultra-deep field and zooms out to reveal the largest field inherited from Hubble, containing 265,000 galaxies. Credits: NASA, ESA, G. Illingworth (University of California, Santa Cruz) and G. Bacon (STScI)

No image will surpass it before launching future space telescopes. "We have designed this mosaic as a tool for us and other astronomers to use," said Illingworth. "This survey is expected to lead to an even more coherent, in-depth and in-depth understanding of the evolution of the universe in the years to come."

The image gives an extensive catalog of distant galaxies. "Such exquisite high-resolution measurements of the many galaxies in this catalog allow for many extragalactic studies," said lead catalog researcher Katherine Whitaker of the University of Connecticut in Storrs. "Often, this type of investigation has resulted in unexpected discoveries that have had the greatest impact on our understanding of the evolution of the galaxy."

Galaxies are the "markers of space", as astronomer Edwin Hubble described a century ago. The galaxies allow astronomers to follow the expansion of the universe, to give clues to the underlying physics of the cosmos, to show the origin of the chemical elements and to create the conditions that led to the appearance of our solar system and our life.

This larger view contains about 30 times more galaxies than in previous deep fields. The new portrait, a mosaic of snapshots, covers almost the entire width of the full moon. The XDF, which has penetrated more deeply into space than this wider view, is located in this region, but it covers less than one tenth of the diameter of the full moon. The Legacy Field also discovers a zoo of unusual objects. Many of them are the remains of the galactic "train wreck", a time of early universe when small and young galaxies collided and merged with others. galaxies.

Assembling all the observations was a huge task. The picture includes the collective work of 31 Hubble programs by different teams of astronomers. Hubble spent more time on this tiny area than on any other area of ​​the sky, totaling more than 250 days, representing nearly three quarters of the year.

"Our goal was to bring the 16 years of exposure into one legacy image," said Dan Magee of the University of California, Santa Cruz, who is responsible for the team's data processing. "Previously, most of these exposures had not been collected consistently and could not be used by any researcher. Astronomers can select the desired data in the Legacy field and use it immediately, instead of having to drastically reduce their working time before performing a scientific analysis. "

The image, as well as the individual exhibits that make up the new view, are available to the world astronomical community through the Mikulski Archive for Space Telescopes (MAST). MAST, an online database of Hubble astronomical data and other NASA missions, is located at the Space Telescope Science Institute in Baltimore, Maryland.

The Hubble Space Telescope has come a long way in taking deeper and deeper "core samples" of the distant universe. After the launch of Hubble in 1990, astronomers debated whether it was worthwhile spending part of the telescope's time participating in a "fishing expedition" in order to take a very long exposure of one small piece of seemingly pristine sky. The Hubble Deep Field image obtained in 1995 captured several thousand unseen galaxies at one point. This bold effort was a historical demonstration and a compelling proof of concept that paved the way for future deep-field imagery. In 2002, Hubble's Advanced Camera for Surveys went one step further to discover 10,000 galaxies in one snapshot. Astronomers used the exposures taken by Hubble's Wide Field Camera 3 (WFC3), installed in 2009, to assemble the eXtreme Deep Field snapshot in 2012. Unlike previous Hubble cameras, the telescope WFC3 spans a range of lengths. wider wave range, from ultraviolet to near infrared.

This new mosaic of images is the first in a series of images Hubble Legacy Field. The team is working on a second series of images, totaling more than 5,200 Hubble shows, in another area of ​​the sky. In the future, astronomers hope to expand the multi-wavelength range of existing images to include longer infrared data and high-energy X-ray observations from two other large observatories of the world. NASA, the Spitzer Space Telescope and the Chandra X-ray Observatory.

The large number of galaxies in the Legacy Field image is also a prime target for future telescopes. "This will really pave the way for NASA's future wide-field infrared surveyor telescope (WFIRST)," said Illingworth. "Legacy Field is a tracking tool for WFIRST, which will capture an image 100 times larger than a typical Hubble photo. In just three weeks of observations by WFIRST, astronomers will be able to assemble a much deeper field and twice as large as the Hubble Field Legacy Field. "

In addition, NASA's next James Webb Space Telescope will allow astronomers to further their research on historical heritage and reveal the real growth of new galaxies. Webb's infrared coverage will go beyond the limits of Hubble and Spitzer to help astronomers identify the first galaxies in the universe.

The Hubble Space Telescope is an international cooperation project between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in the Maryland Greenbelt manages the telescope. The Institute of Space Telescope Sciences (STScI) in Baltimore, Maryland, conducts Hubble's scientific activities. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.