Images of tiny galaxies bursting with starbirth in early universe
Using its infrared vision to peer nine billion years back in time, the NASA/ESA Hubble Space Telescope has uncovered 69 tiny, young galaxies that are brimming with star formation.
The galaxies are churning out stars at such a rate that the number of stars in them would double in just ten million years. For comparison, our home galaxy, the Milky Way, has taken a thousand times longer to double its stellar population.
These newly discovered dwarf galaxies are around a hundred times smaller than the Milky Way. Their star formation rates are extremely high, even for the young universe, when most galaxies were forming stars at higher rates than they are today.
They have turned up in the Hubble images because the radiation from young, hot stars has caused the oxygen in the gas surrounding them to light up like a fluorescent sign.
Astronomers believe this rapid starbirth represents an important phase in the formation of dwarf galaxies, the most common galaxy type in the cosmos.
Arjen van der Wel of the Max Planck Institute for Astronomy in Heidelberg, Germany, is lead author of a paper that will appear in a forthcoming issue of the Astrophysical Journal. He said:
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. We weren’t looking specifically for these galaxies, but they stood out because of their unusual colors.
The observations suggest that the newly discovered galaxies were very common nine billion years ago. But it is a mystery why the newly found dwarf galaxies were making batches of stars at such a high rate. Computer simulations show that star formation in small galaxies may be episodic. Gas cools and collapses to form stars. The stars then reheat the gas through, for example, supernova explosions, which blow the gas away. After some time, the gas cools and collapses again, producing a new burst of star formation, continuing the cycle. van der Wel said:
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.
The observations were part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), a three-year survey to analyze the most distant galaxies in the Universe. CANDELS is the first census of dwarf galaxies at such an early epoch on the universe’s history.
Bottom line: Using its infrared vision to peer nine billion years back in time, the NASA/ESA Hubble Space Telescope has uncovered 69 tiny, young galaxies that are brimming with star formation.The galaxies are churning out stars at such a rate that the number of stars in them would double in just ten million years.