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This extraordinary bubble, glowing like
the ghost of a star in the haunting darkness of space, may appear
supernatural and mysterious, but it is a familiar astronomical object: a
planetary nebula, the remnants of a dying star. This is the best view
of the little-known object ESO 378-1 yet obtained and was captured by
ESO's Very Large Telescope in northern Chile.
Nicknamed the Southern Owl Nebula,
this shimmering orb is a planetary nebula with a diameter of almost
four light-years. Its informal name relates to its visual cousin in the
northern hemisphere, the Owl Nebula. ESO 378-1 , which is also catalogued as PN K 1-22 and PN G283.6+25.3, is located in the constellation of Hydra (The Female Water Snake).
Like all planetary nebulae,
ESO 378-1 is a relatively short-lived phenomenon, lasting only a few
tens of thousands of years, compared to a typical stellar lifetime of
several billion years .
Planetary nebulae are created by the ejected and expanding gas of
dying stars. Although they are brilliant and intriguing objects in the
initial stages of formation, these bubbles fade away as their
constituent gas moves away and the central stars grow dimmer.
For a planetary nebula to form, the aging star must have a mass less
than about eight times that of the Sun.
Stars that are heavier than this
limit will end their lives in dramatic fashion as supernova explosions.
As these less massive stars grow old they start to lose their outer layers of gas to stellar winds.
After most of these outer layers have dissipated, the remaining hot
stellar core starts to emit ultraviolet radiation which then ionises the
surrounding gas. This ionisation causes the expanding shell of ghostly
gas to begin to glow in bright colours.
After the planetary nebula has faded away, the leftover stellar
remnant will burn for another billion years before consuming all its
remaining fuel. It will then become a tiny — but hot and very dense —
white dwarf that will slowly cool over billions of years. The Sun will
produce a planetary nebula several billion years in the future and will
afterwards also spend its twilight years as a white dwarf.
Planetary nebulae play a crucial role in the chemical enrichment and
evolution of the Universe. Elements such as carbon and nitrogen, as well
as some other heavier elements, are created in these stars and returned
to the interstellar medium. Out of this material new stars, planets and
eventually life can form. Hence astronomer Carl Sagan's famous phrase: "We are made of star stuff."
This picture comes from the ESO Cosmic Gems
programme, an outreach initiative to produce images of interesting,
intriguing or visually attractive objects using ESO telescopes for the
purposes of education and public outreach. The programme makes use of
telescope time that cannot be used for science observations. All data
collected may also be suitable for scientific purposes, and are made
available to astronomers through ESO's science archive.
 The ESO in the name of this object refers to a catalogue of
objects compiled in the 1970s and 80s from careful inspection of new
photographs taken with the ESO 1-metre Schmidt telescope at La Silla.
 The lifetime of a planetary nebula
as a fraction of a star's life is about the same as the life of a soap
bubble compared to the age of the child who blows it.
ESO is the foremost intergovernmental astronomy organisation in Europe
and the world's most productive ground-based astronomical observatory by
far. It is supported by 16 countries: Austria, Belgium, Brazil, the
Czech Republic, Denmark, France, Finland, Germany, Italy, the
Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United
Kingdom, along with the host state of Chile. ESO carries out an
ambitious programme focused on the design, construction and operation of
powerful ground-based observing facilities enabling astronomers to make
important scientific discoveries. ESO also plays a leading role in
promoting and organising cooperation in astronomical research. ESO
operates three unique world-class observing sites in Chile: La Silla,
Paranal and Chajnantor. At Paranal, ESO operates the Very Large
Telescope, the world's most advanced visible-light astronomical
observatory and two survey telescopes. VISTA works in the infrared and
is the world's largest survey telescope and the VLT Survey Telescope is
the largest telescope designed to exclusively survey the skies in
visible light. ESO is a major partner in ALMA, the largest astronomical
project in existence. And on Cerro Armazones, close to Paranal, ESO is
building the 39-metre European Extremely Large Telescope, the E-ELT,
which will become "the world’s biggest eye on the sky".