From the February 2015 issue

Web Extra: The impact of Hubble’s deep fields

No one could have expected that the space telescope’s long exposures would allow scientists to see galaxies 95 percent of the way back to the Big Bang.
By | Published: February 23, 2015
Hubble Ultra Deep Field
The Hubble Ultra Deep Field allows astronomers to see galaxies as they were 13 billion years ago, just 600 million to 800 million years after the Big Bang.
NASA/ESA/G. Illingworth and R. Bouwens (UCSC)/The HUDF09 Team
In 1995, the Hubble Space Telescope was back in business and capturing amazing data on various objects in the universe. Astronomers were backed up requesting time on the new instrument for their research, things at Hubble’s science hub, the Space Telescope Science Institute, were running smoothly. So it came as a bit of a surprise when then STScI Director Robert Williams and colleagues took up more than 200 hours of telescope time in late December that year to captured 342 exposures of a seemingly nondescript part of the sky in Ursa Major. But the resulting image would turn astronomy on its head. Such deep exposures revealed thousands of galaxies in a relatively small apparent space.

“Studies prior to the launch had indicated that we would see some galaxies, but it was really unclear how many we would see and how far away they would be,” Williams told Contributing Editor Liz Kruesi. “We weren’t sure exactly what the result would be but felt it was really important to demonstrate what the distant universe would appear [like] with Hubble. It is important for the advance of science to undertake risky ventures.”

Since that original Hubble Deep Field, astronomers have taken several more long exposures to reveal the distant universe, including Hubble Ultra Deep Fields (HUDF) in 2004 and 2009. Astronomy covered these stunning images in detail, which you can read from the stories below.

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