Omega Centauri: the tiny red stars (blue is hot red is cold) are just the sort of faint stars that can be imaged in a nearby cluster like this one but cannot be seen in distant galaxies. Image: NASA/ESA/Anderson/van der Marel.
Some of the oldest galaxies in the Universe have three times more stellar mass, and so many more stars, than all current models of galaxy evolution predict.
The finding comes from the Atlas3D international team, led by an Oxford University scientist, who found a way to remove the 'halo' of dark matter that has clouded previous calculations.The team's analysis means that all current models, which assumed for decades that the light we observe from a galaxy can be used to infer its stellar mass, will have to be revised.
It also suggests that researchers have a new riddle to ponder: exactly how galaxies forming so early in the life of the Universe got to be massive so fast.
A report of the research is published in this week's Nature.
'The light we see from galaxies is just the tip of the iceberg, but what we really need to measure are galaxy masses that all models directly predict,' said Michele Cappellari of Oxford University's Department of Physics, who led the work. 'Galaxies can contain huge numbers of small stars, planets or black holes that have lots of mass but give out very little or no light at all.
'Up until now models assumed that stellar light could be used to infer the stellar masses and any remaining discrepancy with the observed total mass could be hidden behind a "halo" of dark matter. Our analysis shows that they can't hide any longer: galaxies are diverse and some have many more stars and are even stranger than we'd assumed.'
"The research is exciting because it reveals how much more there is to discover about how galaxies, and the early Universe itself, evolved."
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