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PARIS: European astrophysicists said on Wednesday they could settle a mystery about how galaxies crank up in size, developing from proto-structures in the early Universe to the billion-star behemoths of today.
Analysis of ancient light, known as redshift, indicates that the first galaxies were formed nearly 13 billion years ago, about a billion years after the Big Bang that created the Universe.
They then dramatically fattened up to become the giant systems we see today, and the question is why.
Until now, many experts believed that galaxies increased in size by colliding with others, in the same way that a company can grow by merging with a competitor. But a rival theory argues that this is not the only way.
A gentler, incremental approach also works, under which a youthful galaxy sucks in cool interstellar gas as the raw material for making new stars, according to this argument.
A team of astronomers, reporting in the British journal Nature, put the idea to the test using a light-analysing spectrograph on Europe's Very Large Telescope (VLT) in Chile's Atacama desert.
The group chose three very distant galaxies, smoothly rotating discs, similar to the Milky Way, in order to ensure that any buildup was not the result of a collision with other galaxies.
What they were looking for was a chemical signature of so-called heavy elements, or elements that are formed from the primordial gases of hydrogen and helium.
In all three cases, the sky-gazers found a patch close to the galactic centre that was a breeding ground for stars and had markedly fewer heavy elements.
The results are the first direct evidence that the accretion of pristine gas really happened and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe, said team leader Giovanni Cresci of the Arcetri Astrophysical Observatory, Italy.
The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day, the European Southern Observatory (ESO) said in a press release.
Theories of galaxy formation and evolution may have to be rewritten. -AFP
DAWN.COM | Sci-Tech | Cool gas answers riddle of galaxy growth
Analysis of ancient light, known as redshift, indicates that the first galaxies were formed nearly 13 billion years ago, about a billion years after the Big Bang that created the Universe.
They then dramatically fattened up to become the giant systems we see today, and the question is why.
Until now, many experts believed that galaxies increased in size by colliding with others, in the same way that a company can grow by merging with a competitor. But a rival theory argues that this is not the only way.
A gentler, incremental approach also works, under which a youthful galaxy sucks in cool interstellar gas as the raw material for making new stars, according to this argument.
A team of astronomers, reporting in the British journal Nature, put the idea to the test using a light-analysing spectrograph on Europe's Very Large Telescope (VLT) in Chile's Atacama desert.
The group chose three very distant galaxies, smoothly rotating discs, similar to the Milky Way, in order to ensure that any buildup was not the result of a collision with other galaxies.
What they were looking for was a chemical signature of so-called heavy elements, or elements that are formed from the primordial gases of hydrogen and helium.
In all three cases, the sky-gazers found a patch close to the galactic centre that was a breeding ground for stars and had markedly fewer heavy elements.
The results are the first direct evidence that the accretion of pristine gas really happened and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe, said team leader Giovanni Cresci of the Arcetri Astrophysical Observatory, Italy.
The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day, the European Southern Observatory (ESO) said in a press release.
Theories of galaxy formation and evolution may have to be rewritten. -AFP
DAWN.COM | Sci-Tech | Cool gas answers riddle of galaxy growth
