Free Astronomy Magazine July-August 2019

52 JULY-AUGUST 2019 SPACE CHRONICLES other region of the sky, totaling more than 250 days, representing nearly three-quarters of a year. “Our goal was to as- semble all 16 years of ex- posures into a legacy image,” explained Dan Magee, of the University of California, Santa Cruz, the team’s data process- ing lead. “Previously, most of these exposures had not been put to- gether in a consistent way that can be used by any researcher. Astronomers can select the data in the Legacy Field they want and work with it immediately, as opposed to having to perform a huge amount of data reduction before conducting scientific analysis.” The image, along with the individual exposures that make up the new view, is available to the worldwide as- tronomical community through the Mikulski Archive for Space Telescopes (MAST). MAST, an online database of astronomical data from Hubble and other NASA mis- described them a century ago. Galaxies allow astron- omers to trace the expansion of the universe, offer clues to the underlying physics of the cosmos, show when the chemical elements originated, and enable the condi- tions that eventually led to the appearance of our solar system and life. This wider view contains about 30 times as many galaxies as in the previous deep fields. The new portrait, a mo- saic of multiple snapshots, covers almost the width of the full Moon. The XDF, which penetrated deeper into space than this wider view, lies in this region, but it covers less than one- tenth of the full Moon’s diameter. The Legacy Field also uncovers a zoo of un- usual objects. Many of them are the remnants of galactic “train wrecks,” a time in the early universe when small, young galax- ies collided and merged with other galaxies. Assembling all of the ob- servations was an im- mense task. The image comprises the collective work of 31 Hubble pro- grams by different teams of astronomers. Hubble has spent more time on this tiny area than on any T his graphic compares the dimensions of the Hubble Legacy Field on the sky with the angular size of the Moon. [Hubble Legacy Field Image: NASA, ESA, and G. Illingworth and D. Magee (University of California, Santa Cruz); Moon Image: NASA, GSFC, and Arizona State University] T his video ex- plores the de- tail of the Hubble Legacy Field. [NASA, ESA, G. Illingworth and D. Magee (University of California, Santa Cruz), K. Whitaker (University of Connecticut), R. Bouwens (Leiden University), P. Oesch (University of Geneva), and the Hubble Legacy Field team. Music: James Creasey]