Born-again star foreshadows fate of Solar
System
Astronomers have found evidence for a dying
Sun-like star coming briefly back to life after casting its gassy shells out
into space, mimicking the possible fate our own Solar System faces in a few
billion years.
This new picture of the planetary nebula Abell
30, located 5500 light-years from Earth, is a composite of visible images from
the NASA/ESA Hubble Space Telescope and X-ray data from ESA’s XMM-Newton and
NASA’s Chandra space telescopes.
‘Planetary nebula’ is the name given to the
often-concentric shells of stellar material cast into space by dying stars. To
astronomers of the 18th century, these objects looked like the colourful ‘blob’
of a planet through their telescopes, and the name stuck.
Astronomers now know that as a star with less
than eight times the mass of the Sun swells into a red giant towards the end of
its life, its outer layers are expelled via pulsations
and winds. Ultraviolet radiation shining out from the stripped-down hot stellar
core then lights up the ejected shells, resulting in intricate artworks that
can be seen by modern telescopes.
The star at the heart of Abell 30 experienced
its first brush with death 12 500 years ago – as seen from Earth – when its
outer shell was stripped off by a slow and dense stellar wind.
Optical telescopes see the remnant of this
evolutionary stage as a large, near-spherical shell of glowing material
expanding out into space. Then, about 850 years ago, the star suddenly came
back to life, coughing out knots of helium and carbon-rich material in a violent
event.
The star’s outer envelope briefly expanded
during this born-again episode, but then very rapidly contracted again witin 20
years. This had the knock-on effect of accelerating the wind from the star to
its present speed of 4000 kilometres per second – over 14 million kilometres
per hour.
As this fast stellar wind catches up and
interacts with the slower wind and clumps of previously ejected material,
complex structures are formed, including the delicate comet-like tails seen
near the central star in this image. The stellar wind bombarding dense clumps
of material provides a chilling look at the possible fate of Earth and its
fellow planets in our own Solar System in a few billion years’ time.
When our Sun emits its final gasps of life at
the heart of a planetary nebula, its strong stellar wind and harsh radiation
will blast and evaporate any planets that may have survived the red giant phase
of stellar evolution.
If any distant civilisation is watching with
high-power telescopes at the time, they might see the glowing embers of the
planets light up in X-rays as they are engulfed in the stellar wind.
For further information visit: http://www.esa.int/esaCP/SEM0UBGPI9H_index_0.html
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