Tiny galaxies are bursting with star births a lot faster than scientists have expected, predicting that the number of stars would double in just ten million years if this rate of star births continues.

In comparison, our Milky Way has taken a thousand times longer to double in stellar population.

The newly discovered dwarf galaxies, uncovered by the NASA/ESA Hubble Space Telescope, are around a hundred times smaller than the Milky Way with extremely high star formation rates.

Astronomers believe that this rapid star birth represents an important phase in the formation of dwarf galaxies.

"The galaxies have been there all along, but up until recently astronomers have been able only to survey tiny patches of sky at the sensitivities necessary to detect them," says author, Arjen van der Wel of the Max Planck Institute for Astronomy in Heidelberg, Germany.

The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), the three-year survey to analyze the most distant galaxies in the Universe, is the first demographic of dwarf galaxies at such an early epoch on the Universe's history, but astronomers said that they weren’t specifically looking for these tiny galaxies and that the Hubble images were able to capture the formation of star births because the radiation from young, hot stars has caused the oxygen in the gas surrounding them to light up like a fluorescent sign.

"We weren't looking specifically for these galaxies, but they stood out because of their unusual colors," said van der Wel.

"In addition to the images, Hubble has captured spectra from a handful of these galaxies that show us the detailed physics of what's happening within them and confirm their extreme star-forming nature," says co-author Amber Straughn at NASA's Goddard Space Flight Center in Greenbelt, USA.

The authors said that the observations of ancient galaxies are somewhat at odds with recent studies of the dwarf galaxies that are currently orbiting the Milky Way.

"Those studies suggest that star formation was a relatively slow process, stretching out over billions of years," explains Harry Ferguson of the Space Telescope Science Institute (STScI) in Baltimore, USA, co-leader of the CANDELS survey.

"The CANDELS finding that there were galaxies of roughly the same size forming stars at very rapid rates at early times is forcing us to re-examine what we thought we knew about dwarf galaxy evolution."

Researchers plan to continue their observation and gather more information on star births to determine the history of star formation.

"As our observations continues we should find many more of these young galaxies and gather more details on their star-forming histories," said team member Anton Koekemoer, of STScI, who is producing the Hubble imaging for the survey.

CANDELS uncovered the 69 dwarf galaxies in near infrared images that were taken with Hubble's Wide Field Camera 3 and Advanced Camera for Surveys, concentrating on two regions in the sky, the Great Observatories Origin Deep Survey South and the UKIDSS Ultra Deep Survey, part of the UKIRT Infrared Deep Sky Survey, said the authors.

Although the observation suggest that newly discovered galaxies were very common nine billion years ago the mystery on why the newly found dwarf galaxies were making batches of stars at such a high rate remains, while computer simulations show that star formation in small galaxies may be composed of many tales.

The authors explained that gas cools and collapses to form stars, the stars then reheat the gas through, for example, supernova explosions which blow the gas away, and after some time the gas cools and collapses again producing a new burst of star formation and continuing the cycle.

"While these theoretical predictions may provide hints to explain the star formation in these newly discovered galaxies, the observed 'bursts' are much more intense than those reproduced by the simulations," says van der Wel.

An infrared observatory scheduled to be launched later this decade called the NASA/ESA/CSA James Webb Space Telescope will be able to probe these faint galaxies at an even earlier era to see the glow of the first generation of stars, providing detailed information of the galaxies' chemical composition, wrote the authors.

"With Webb, we'll probably see even more of these galaxies, perhaps even pristine galaxies that are experiencing their first episode of star formation," Ferguson says. "Being able to probe down to dwarf galaxies in the early Universe will help us understand the formation of the first stars and galaxies."