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| Dust Rings around CW Leonia, Image credit ESA/PACS/MESS & ESO/VLT |
A team of
astrophysicists, led by Professor Leen Dacin at K U Leuven, have made an
amazing discovery. The research, published in Astronomy & Astrophysics,
shows dozens of cold dust arcs around a giant star known as CW Leo. Leo, a
late-stage red giant star, gives us an insight into how our own Sun may look in
4.5 billion years time.
Stunning new
images showing dust shells emitted at intervals of 500 to 1,700 years have been
obtained from the Herschel Space Observatory, launched by ESA in 2009.
Professor Decin explained: “Herschel is made to observe cool material, like
that found far away from the central star. So, it was not really an accidental
discovery.” The researchers deliberately employed PACS, one of two cameras
onboard the Herschel Space Observatory, as it was specifically designed to look
at the far-infrared light associated with extremely cold objects. This was
crucial to the identification of the shells, as their temperatures can reach as
low as -248oC, leaving them beyond the scope of many observatories.
The
laborious process of refining the PACS images proved fruitfull when the team
identified the long suspected, non-concentric shells of dust as far as 1arcmin
from the stars centre. “Until recently it seemed the surroundings of giant
stars were homogenous, but more and more we see that this isn't the case”,
Professor Decin enthused: “The new Herschel images confirm that in a stunning
way."
It
is assumed that further dust rings existed but may have already collided with
and dispersed into the interstellar medium; a mixture of ions, cosmic rays and
other matter surrounding the star. Dr Tanya Lim, a collaborator on the paper from
the Rutherford Lab in Oxford, revealed: “It is the interactions between the
dust and interstellar medium which are interesting because these
interactions change the chemistry of the ISM.”
However,
where these shells occur also says something about the history of mass loss for
these carbon rich stars. CW Leo is a direct analogy for our own Sun, and
research like this could be invaluable for determining how it will react in
it’s later stages.