Astronomers using the Hubble Space Telescope have captured the most comprehensive picture ever assembled of the evolving universe - and one of the most colourful.
The study, called the Ultraviolet Coverage of the Hubble Ultra Deep Field (UVUDF) project, provides the missing link in star formation, researchers said.
Scientists combined the full range of colours available to Hubble, stretching all the way from ultraviolet to near-infrared light.
The resulting image - made from 841 orbits of telescope viewing time - contains approximately 10,000 galaxies, extending back in time to within a few hundred million years of the big bang.
Studying the ultraviolet images of galaxies in this intermediate time period enables astronomers to understand how galaxies like our Milky Way grew in size from small collections of very hot stars.
Because Earth's atmosphere filters most ultraviolet light, this work can only be accomplished with a space-based telescope.
"It's the deepest panchromatic image of the sky ever made. It reaches the faintness of one firefly as seen from the distance of the Moon," said Rogier Windhorst, professor at the School of Earth and Space Exploration in Arizona State University's College of Liberal Arts and Sciences.
Prior to this survey, astronomers had knowledge of star formation in nearby galaxies from missions such as NASA's GALEX observatory.
They also studied star birth in the most distant galaxies, which appear to us in their most primitive stages, thanks to the vast light travel time involved.
But for the period in between – a range extending from about 5 billion to 10 billion light-years away – they just didn't have enough data. This is the time when most of the stars in the universe were born.
Ultraviolet light comes from the hottest, most massive and youngest stars. By observing at these wavelengths, researchers get a direct look at which galaxies are forming stars and, just as importantly, where within those galaxies the stars are forming.