Astronomers have spotted the remains of galaxies that have been eaten by another.
The
discovery, the first ever seen in such fine detail, showed that gas in a
distant spiral galaxy was not its own - but had actually been taken
from its neighbours.And the research could help scientists better understand how such ‘cannibal galaxies’ evolve and interact with others.
Astrophysicist
Dr Ángel R. López-Sánchez, from the Australian Astronomical Observatory
(AAO) and Macquarie University, made the discovery with his colleagues.
The
galaxy they studied was a so-called barred spiral galaxy known as NGC
1512, located about 38 million light-years from Earth in the
constellation Horologium.
It is currently in the process of
devouring a nearby smaller dwarf galaxy, but evidence suggests that it
has 'eaten' others in the past. Using
the 12.8ft (3.9m) Anglo-Australian Telescope (AAT), near Coonabarabran,
New South Wales, they measured the ‘chemical enrichment’ in the gas of
the galaxy. Chemical
enrichment occurs when stars churn the hydrogen and helium from the Big
Bang into heavier elements through nuclear reactions at their cores.
These
new elements are released back into space when the stars die, enriching
the surrounding gas with chemicals like oxygen, which the team
measured. ‘We
were expecting to find fresh gas or gas enriched at the same level as
that of the galaxy being consumed, but were surprised to find the gases
were actually the remnants of galaxies swallowed earlier,’ Dr
López-Sánchez said.
'The
diffuse gas in the outer regions of NGC 1512 is not the pristine gas
created in the Big Bang but is gas that has already been processed by
previous generations of stars.'
In
particular, the team found large amounts of cold hydrogen gas in the
outer regions of NGC 1512 that was responsible for star formation.
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