The Hubble Ultra Deep Field is located in the constellation Fornax. Hubble aimed at this small, relatively dark patch of southern sky because it contains few bright foreground stars and little obscuring dust from the Milky Way, making extremely faint and distant galaxies easier to detect.
The original HUDF exposures were collected from September 2003 through January 2004, and the first image was released on March 9, 2004. Hubble accumulated roughly 11 days of exposure time, revealing about 10,000 galaxies in a field only a few arcminutes across. Many appear as they existed when the universe was less than a billion years old.
Fornax is a southern constellation whose name means “furnace.” The field lies southwest of Orion and overlaps the region known as the Chandra Deep Field South, allowing astronomers to combine Hubble’s optical and infrared observations with deep X-ray data. Common mix-ups include confusing Fornax with Orion, which is nearby in the sky, or with the Fornax Cluster, a separate concentration of galaxies within the same constellation.