Astronomers have created the largest and comprehensive "history book" of galaxies in one image, using 16 years of observations by NASA's Hubble Space Telescope.
The deep mosaic, created from nearly 7,500 individual exposures, provides a broad portrait of the distant universe, which contains 265,000 galaxies that stretch back through 13.3 billion years to only 500 million years after the big bang. The smallest and smallest galaxies are just ten billion brilliance of what the human eye can see. The evolutionary history of the universe is also recorded in this same overwhelming view. The portrait shows how galaxies change over time, building themselves to be huge galaxies seen in the nearby universe.
This ambitious effort, called Hubble Legacy Field, also combines observations taken by several Hubble deep field surveys, including the Deep eXtreme field (XDF), the deepest view of the universe. The wavelength range extends from ultraviolet light to infra-red light, capturing the key features of galaxy assembly over time.
"Now that we have gone wider than in previous surveys, we harvested many more galaxies in the largest dataset ever produced by Hubble," said Garth Illingworth from the University of California, Santa Cruz, the team leader who assembled the image. The same image includes a full history of galaxy growth in the universe, from their time as babies when they became adults.
No image will exceed this until future space telescopes are launched. "We have put this mosaic together as a tool to use by us and by other astronomers," Illingworth added. "The expectation is that this survey will lead to an even more coherent, detailed and greater understanding of the evolution of the universe in the years to come."
The image produces a huge catalog of distant galaxies. "Such wonderful resolution measurements of the many galaxies in this catalog enable a wide exchange of allgactic study," says Katherine Whitaker, leading catalog researcher from the University of Connecticut, at Storrs. "Often these types of surveys have led to unforeseen findings that have had the most impact on our understanding of the evolution of galaxy."
Galaxies are the “space markers”, as described by astronomer Edwin Hubble once a century ago. Galaxies allow astronomers to track the expansion of the universe, offer clues to the basic physics of the cosmos, show when the chemical elements began, and enable the conditions that led to the appearance of our ultimate solar system t .
This broader view contains about 30 times as many galaxies as in the previous deep fields. The new portrait, a mosaic of multiple snapshots, covers almost the width of the full Moon. The XDF, which penetrated deeper into the space than this wider view, lies in this region, but covers less than one tenth of the full diameter of the t Moon. The Legacy Field also reveals a zoo of unusual objects. Many of them are remnants of "train wrecks", time in the early universe when small, young galaxies collided and merged with other galaxies.
Matching all the observations was a huge task. The image includes the combined work of 31 Hubble programs by different teams of astronomers. Hubble has spent more time on this small area than on any other region of the air, totaling more than 250 days, representing almost three quarters of the year.
"Our aim was to collect the 16 years of exposures to an image of heritage," explains Dan Magee, University of California, Santa Cruz, the data processing leader and team. "In the past, most of these exposures were not designed in a consistent way that can be used by any researcher. Astronomers can choose the data in the Inheritance Field they want and work with him immediately, rather than having to make a great deal of data reduction before conducting scientific analysis.
The image, along with the individual exposures that are part of the new scene, is available to the global astronomical community through the Mikulski Archive for Space Telescopes (MAST). MAST, an online database of astronomical data from other Hubble and NASA missions, is based at the Space Telescope Science Institute in Baltimore, Maryland.
The Hubble Space Telescope has come a long way in taking deeper "core samples" of the distant universe. After Hubble's launch in 1990, astronomers discussed whether it was worth spending a piece of telescope time to go on a "fishing expedition" to take a very long exposures of air that appeared empty. Hubble's Deep Field image in 1995 held several thousand galaxies unseen in one point. The bold effort was a landmark demonstration and a definitive concept test that set the stage for future deep field images. In 2002, Advanced Camera for Hubble Surveys even went deeper to reveal 10,000 galaxies in one snapshot. Astronomers used Hubble's Wide Field Camera 3 (WFC3) exposures, which were installed in 2009, to collect the eXtreme Deep Field snapshot in 2012. Unlike previous Hubble cameras, WFC3 the telescope covers wider wavelength range, from ultraviolet to infra-red.
This new image mosaic is the first in a series of Hubble Legacy Field images. The team is working on a second set of images, totaling more than 5,200 Hubble exposures, in another part of the sky. In the future, astronomers are hoping to expand the multi-width range in legacy images to include wavelength infrared data and high energy X-ray observations from two other NASA Large Observatories, Spitzer Space Telescope and X-ray Observatory. Chandra.
The vast number of galaxies in the Legacy Field's image is also the main targets for future telescopes. "This will set the platform for NASA's Infrared Airport Telescope Survey (WFIRST)," Illingworth said. "The Legacy Field is a pathfinder for WFIRST, which will hold an image 100 times larger than a typical Hubble picture. In just three weeks of observations by WFIRST, astronomers will be able to assemble a field that 's much deeper and more than twice more than the Hubble Field Legacy. "
An astronomer helps create an image & history book; the universe
Mikulski Archive for Space Telescopes (MAST): archive.stsci.edu/
HubbleSite Legacy Field image downloads: hubblesite.org/image/4492/news
Hubble astronomers assemble a broad view of the evolving universe (2019, May 16)
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