The European Southern Observatory’s Very Large Telescope captured the deepest ground-based U-band image of the universe ever obtained. It contains more than 27 million pixels and is the result of 55 hours of observations with the VIsible Multi Object Spectrograph (VIMOS).
This patchwork image, with its myriad of brightly colored galaxies, shows the Chandra Deep Field South (CDF-S) — arguably the most observed and best studied region in the entire sky. The CDF-S is one of the two regions selected as part of the Great Observatories Origins Deep Survey (GOODS), an effort of the worldwide astronomical community that unites the deepest observations from ground- and space-based facilities at all wavelengths from X-ray to radio. Its primary purpose is to provide astronomers with the most sensitive census of the distant universe to assist in their study of the formation and evolution of galaxies.
ESO’s new image combines data obtained with the VIMOS instrument in the U- and R-bands, as well as data obtained in the B-band with the Wide-Field Imager (WFI) attached to the 2.2-meter MPG/ESO telescope at La Silla in Chile.
The U-band image — the result of 40 hours of staring at the same region of the sky and just made ready by the GOODS team — is the deepest image ever taken from the ground in this wavelength domain. At these depths, the sky is almost completely covered by galaxies, each one, like the Milky Way, home to hundreds of billions of stars.
The study detected galaxies that are a billion times fainter than the unaided eye can see and over a range of colors that the eye can’t observe. This deep image has been essential to the discovery of a large number of new galaxies that are so far away that they are seen as they were when the universe was only 2 billion years old.
In this sea of galaxies, only a few stars belonging to the Milky Way are seen. One of them is so close, that it moves very fast on the sky. This “high proper motion star” is visible to the left of the second brightest star in the image. It appears as a funny elongated rainbow because the star moved during the data-gathering process.