“Space is big. Really big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist, but that’s just peanuts to space.” — Douglas Adams, The Hitchhiker’s Guide to the Galaxy
Hubble astronomers have assembled the largest, most complete image of the universe ever recorded, by stitching together data gathered by multiple telescopes over years of observations.
Back in 1995, astronomers created the first attempt at imaging the deep universe by having Hubble “stare” at an empty patch of sky for one million seconds. The resulting image, the Hubble Deep Field, became one of the most popular space photographs ever taken. It’s the feature image for this article. But the HDF was an extremely small photo. It focused on approximately one 24-millionth of the sky. Later surveys, including the Great Observatories Origins Deep Survey, Hubble Ultra-Deep Field, and eXtreme Deep Field, built on this initial imaging with additional telescopes, or examined a different area of the sky in greater detail (the original HDF imagined an area of space within Ursa Major, while the UDF and XDF both focused on an area of space in the constellation Fornax). New cameras added to the Hubble after 1995 were also used in some of these surveys.
Astronomers have created this latest image, dubbed the Hubble Legacy Field, by combining data used in previous sky surveys. Here’s HubbleSite.org:
Now, astronomers are releasing a new deep-field image by weaving together exposures from several of these previous galaxy “fishing expeditions.” Their efforts have produced the largest, most comprehensive “history book” of galaxies in the universe. The snapshot, a combination of nearly 7,500 separate Hubble exposures, represents 16 years’ worth of observations. The ambitious endeavor is called the Hubble Legacy Field. The new view contains about 30 times as many galaxies as in the HUDF. The wavelength range stretches from ultraviolet to near-infrared light, capturing all the features of galaxy assembly over time.
The image mosaic presents a wide portrait of the distant universe and contains roughly 265,000 galaxies. They stretch back through 13.3 billion years of time to just 500 million years after the universe’s birth in the big bang.
And here, without further ado, is the aforementioned Hubble Legacy Field:
The same view in zoom-out, via video:
This image contains a history of galactic formation, from the infancy of the earliest galaxies, composed entirely of metal-poor stars, to more recent galaxies and star systems (larger galaxies are generally closer to us, and therefore “nearer” both in physical distance and time).
“Such exquisite high-resolution measurements of the numerous galaxies in this catalog enable a wide swath of extragalactic study,” said catalog lead researcher Katherine Whitaker of the University of Connecticut, in Storrs. “Often, these kinds of surveys have yielded unanticipated discoveries which have had the greatest impact on our understanding of galaxy evolution.” Previously, the single images that make up the Hubble Legacy Field had not been assembled in a consistent way that made them easy for researchers to use.
This is expected to be the largest, highest-resolution available image of distant galaxies until next-generation telescopes like the James Webb are online and available. The same team that built this image is now working to construct other mosaics like it, with the hope of widening their work to include data captured in non-visible spectrums like long-wavelength infrared and high-energy X-ray observations.
Feature image by Wikipedia
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