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NASA Fits 265,000 Galaxies Into Single Hubble Image

BY 05.06.2019

NASA astronomers assembled 16 years’ worth of Hubble Space Telescope observations in one stunning image.

The deep-sky mosaic, created from nearly 7,500 individual exposures, provides a comprehensive portrait of the distant universe.

Stretching through 13.3 billion years of time—to 500 million years after the Big Bang—the illustration contains 265,000 galaxies, the faintest and farthest of which are just one ten-billionth the brightness of what the human eye can see.

This cropped image mosaic presents a wide portrait of the distant universe and contains roughly 200,000 galaxies (via NASA/ESA/University of California, Santa Cruz/University of Connecticut/Leiden University/University of Geneva/Hubble Legacy Field team)

NASA astronomers assembled 16 years’ worth of Hubble Space Telescope observations in one stunning image.

The deep-sky mosaic, created from nearly 7,500 individual exposures, provides a comprehensive portrait of the distant universe.

Stretching through 13.3 billion years of time—to 500 million years after the Big Bang—the illustration contains 265,000 galaxies, the faintest and farthest of which are just one ten-billionth the brightness of what the human eye can see.

To the untrained eye, this speckled image might not look like much.

But the Hubble Legacy Field is a truly ambitious endeavor, combining observations from several Hubble deep-field surveys to show how galaxies change over time, building themselves up to become giant star systems.

“Now that we have gone wider than in previous surveys, we are harvesting many more distant galaxies in the largest such dataset ever produced by Hubble,” team leader Garth Illingworth, of the University of California, Santa Cruz (UCSC), said in a statement. “This one image contains the full history of the growth of galaxies in the universe, from their time as ‘infants’ to when they grew into fully fledged ‘adults.’”

No image will surpass this one until future space telescopes are launched, according to NASA.

“Our goal was to assemble all 16 years of exposures into a legacy image,” data processing lead Dan Magee of UCSC explained. “Previously, most of these exposures had not been put together in a consistent way that can be used by any researcher.

“Astronomers can select data in the Legacy Field they want and work with it immediately,” he continued. “As opposed to having to perform a huge amount of data reduction before conducting scientific analysis.”

After its launch into low Earth orbit in 1990, astronomers debated whether it was worth sending the Hubble Space Telescope on a “fishing expedition” to take a very long exposure of a small, seemingly blank piece of sky.

Spoiler alert: It was.

The resulting Hubble Deep Field image in 1995 captures several thousand unseen galaxies in one go; in 2002, Hubble’s Advanced Camera for Surveys went even deeper to uncover 10,000 galaxies in a single snapshot.

The Hubble Legacy Field is one of the widest views ever taken of the universe with Hubble (via NASA/ESA/University of California, Santa Cruz/Goddard Space Flight Center/Arizona State University)

Astronomers used exposures taken by Hubble’s Wide Field Camera 3, installed in 2009, to assemble the eXtreme Deep Field (XDF) snapshot in 2012—the deepest view of the universe.

This new image, comprising the collective work of 31 Hubble programs by different teams, is the first in a series of Hubble Legacy Field photographs.

It contains about 30 times as many galaxies as in previous deep fields, and uncovers a zoo of unusual objects, many of which are remnants of galactic “train wrecks”—a time in the early universe, NASA explained, when small, young galaxies collided and merged.

“Such exquisite high-resolution measurements of the numerous galaxies in this catalog enable a wide swath of extragalactic study,” according to catalog lead researcher Katherine Whitaker, of the University of Connecticut. “Often, these kinds of surveys have yielded unanticipated discoveries which have had the greatest impact in our understanding of galaxy evolution.”

The team is working on a second set of images, totaling more than 5,200 exposures in another area of the sky.