Free Astronomy Magazine July-August 2019

50 JULY-AUGUST 2019 SPACE CHRONICLES the nearby universe. This ambitious en- deavor, called the Hubble Legacy Field, also combines ob- servations taken by several Hubble deep- field surveys, includ- ing the eXtreme Deep Field (XDF), the deepest view of the universe. The wavelength range stretches from ultraviolet to near-in- frared light, captur- ing the key features of galaxy assembly over time. “Now that we have gone wider than in previous surveys, we are harvesting many more distant galaxies in the largest such dataset ever pro- duced by Hubble,” said Garth Illingworth of the University of California, Santa Cruz, leader of the team that assembled the image. “This one im- age contains the full history of the growth by NASA/ESA Hubble assembles wide view of the distant Universe A stronomers have put together the largest and most comprehensive “history book” of galaxies into one single image, using 16 years’ worth of ob- servations from NASA’s Hubble Space Tele- scope. The deep-sky mosaic, created from nearly 7,500 individual expo- sures, provides a wide portrait of the distant Universe, containing 265,000 galaxies that stretch back through 13.3 billion years of time to just 500 million years after the big bang. The faintest and farthest galaxies are just one ten-billionth the brightness of what the human eye can see. The universe’s evolu- tionary history is also chronicled in this one sweeping view. The portrait shows how galaxies change over time, building them- selves up to become the giant galaxies seen in T his image shows the sizes and locations within the Hubble Legacy Field of the two areas that Hubble first studied in this region, the Great Observatories Origins Deep Survey (GOODS) and the Hubble Ultra Deep Field (HUDF), along with the deepest image ever taken by Hubble, the eXtreme Deep Field (XDF). [NASA, ESA, G. Illingworth and D. Magee (University of California, Santa Cruz), K. Whitaker (Univer- sity of Connecticut), R. Bouwens (Leiden University), P. Oesch (Univer- sity of Geneva), and the Hubble Legacy Field team]