Astronomers have assembled a new portrait of the deepest-ever view of the Universe by combining 10 years of NASA’s Hubble Space Telescope observations.
This image, called the Hubble eXtreme Deep Field (XDF), shows a small patch of sky in the constellation of Fornax. XDF contains several of the most distant objects ever identified, among these are: Supernova Primo, at a redshift of 1.55, the most distant type Ia supernova ever observed; UDFj-39546284, at a redshift of 10.3, is a candidate for the most distant galaxy yet discovered; UDFy-38135539, at a redshift of 8.6, is the most distant galaxy to have had its distance independently corroborated with spectroscopy; UDFy-33435698, at a redshift of 8.6 (NASA / ESA / G. Illingworth / D. Magee / P. Oesch / University of California / R. Bouwens / Leiden University / HUDF09 team)
The new full-color image, called the eXtreme Deep Field (XDF), is more sensitive than the original Hubble Ultra Deep Field, an image of a small area of space in the constellation of Fornax created in 2003-2004.
About 5500 galaxies are contained within this small field of view. The faintest galaxies are one ten-billionth the brightness that the unaided human eye can see.
Magnificent spiral galaxies similar in shape to the Milky Way and its neighbor the Andromeda galaxy appear in this image, as do large, fuzzy red galaxies in which the formation of new stars has ceased. These red galaxies are the remnants of dramatic collisions between galaxies and are in their declining years as the stars within them age.
Peppered across the field are tiny, faint, and yet more distant galaxies that are like the seedlings from which today’s magnificent galaxies grew. The history of galaxies – from soon after the first galaxies were born to the great galaxies of today, like the Milky Way – is laid out in this one remarkable image.
“The XDF is the deepest image of the sky ever obtained and reveals the faintest and most distant galaxies ever seen. XDF allows us to explore further back in time than ever before,” said Dr Garth Illingworth of the University of California at Santa Cruz, principal investigator of the Hubble Ultra Deep Field 2009 programme.
The Universe is 13.7 billion years old, and the XDF reveals galaxies that span back 13.2 billion years in time. Most of the galaxies in the XDF are seen when they were young, small, and growing, often violently as they collided and merged together. The early Universe was a time of dramatic birth for galaxies containing brilliant blue stars far brighter than our Sun.
The light from those past events is just arriving at Earth now, and so the XDF is a time tunnel into the distant past when the Universe was just a fraction of its current age. The youngest galaxy found in the XDF existed just 450 million years after the Universe’s birth in the Big Bang.