- Twinkling in the sky is a diamond star of 10 billion
trillion trillion carats, astronomers have discovered.
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- The cosmic diamond is a chunk of crystallised carbon,
1,500 km across, some 50 light-years from the Earth in the constellation
Centaurus.
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- It's the compressed heart of an old star that was once
bright like our Sun but has since faded and shrunk.
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- Astronomers have decided to call the star "Lucy,"
after the Beatles song, "Lucy in the Sky with Diamonds."
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- Lucy in the sky
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- "You would need a jeweller's loupe the size of the
Sun to grade this diamond!" says astronomer Travis Metcalfe of the
Harvard-Smithsonian Center for Astrophysics, who led the team of researchers
that discovered it.
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- The diamond star completely outclasses the largest diamond
on Earth, the 530-carat Star of Africa which resides in the Crown Jewels
of England. The Star of Africa was cut from the largest diamond ever found
on Earth, a measly 3,100-carat gem.
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- The huge cosmic diamond - technically known as BPM 37093
- is actually a crystallised white dwarf. A white dwarf is the hot core
of a star, left over after the star uses up its nuclear fuel and dies.
It is made mostly of carbon.
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- For more than four decades, astronomers have thought
that the interiors of white dwarfs crystallised, but obtaining direct evidence
became possible only recently.
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- The white dwarf is not only radiant but also rings like
a gigantic gong, undergoing constant pulsations.
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- "By measuring those pulsations, we were able to
study the hidden interior of the white dwarf, just like seismograph measurements
of earthquakes allow geologists to study the interior of the Earth.
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- We figured out that the carbon interior of this white
dwarf has solidified to form the galaxy's largest diamond," says Metcalfe.
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- Astronomers expect our Sun will become a white dwarf
when it dies 5 billion years from now. Some two billion years after that,
the Sun's ember core will crystallise as well, leaving a giant diamond
in the centre of our Solar System.
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- "Our Sun will become a diamond that truly is forever,"
says Metcalfe.
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- © BBC MMIV
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- http://news.bbc.co.uk/2/hi/science/nature/3492919.stm
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