Planetary nebula
hideA planetary nebula is an emission nebula consisting of a glowing shell of gas and plasma formed by certain types of stars when they die. The name originated in the 18th century because of their similarity in appearance to giant planets when viewed through small optical telescopes, and is unrelated to the planets of the solar system. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.
At the end of the star's life, during the red giant phase, the outer layers of the star are expelled via pulsations and strong stellar winds. Without these opaque layers, the remaining core of the star shines brightly and is very hot. The ultraviolet radiation emitted by this core ionises the ejected outer layers of the star which radiate as a planetary nebula.
Planetary nebulae are important objects in astronomy because they play a crucial role in the chemical evolution of the galaxy, returning material to the interstellar medium which has been enriched in heavy elements and other products of nucleosynthesis (such as carbon, nitrogen, oxygen and calcium). In other galaxies, planetary nebulae may be the only objects observable enough to yield useful information about chemical abundances.
In recent years, Hubble Space Telescope images have revealed many planetary nebulae to have extremely complex and varied morphologies. About a fifth are roughly spherical, but the majority are not spherically symmetric. The mechanisms which produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may all play a role.
For more information about Planetary nebula, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with planetary nebula
A New Method of Estimating Stellar Distances
Dec 21, 2009 |
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(PhysOrg.com) -- The star Chi Cygni is located about 550 light-years away, in the direction of the constellation of Cygnus the Swan. It is a notable star because, unlike the sun which still burns hydrogen ...
Newly discovered star one of hottest in Galaxy (w/ Video)
Dec 02, 2009 |
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(PhysOrg.com) -- Astronomers at The University of Manchester's Jodrell Bank Centre for Astrophysics have discovered one of the hottest stars in the Galaxy with a surface temperature of around 200,000 degrees ...
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Born in beauty: Proplyds in the Orion Nebula (w/ Video)
Dec 14, 2009 |
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(PhysOrg.com) -- A collection of 30 never-before-released images of embryonic planetary systems in the Orion Nebula are the highlight of the longest single Hubble Space Telescope project ever dedicated to ...
Blushing dusty nebula
Dec 01, 2009 |
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On Earth, we tend to find dust nothing more than a nuisance that blankets our furniture and causes us to sneeze. Cosmic dust can also be a hindrance to astronomers because cameras using visible light cannot ...
Hubble's Festive View of a Grand Star-Forming Region (w/ Video)
Dec 15, 2009 |
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(PhysOrg.com) -- Just in time for the holidays: a Hubble Space Telescope picture postcard of hundreds of brilliant blue stars wreathed by warm, glowing clouds. The festive portrait is the most detailed view of the largest ...
Astronomers discover 'tilted planets'
Dec 22, 2009 |
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(PhysOrg.com) -- University of Exeter, UK, research has added to a growing evidence that several giant planets have orbits so tilted that their orbits can be perpendicular or even backwards relative to their ...
Keck Telescopes Take Deeper Look at Planetary Nurseries
Dec 23, 2009 |
4.7 / 5 (7) |
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(PhysOrg.com) -- Astronomers using the W. M. Keck Observatory have peered far into a young planetary system, giving an unprecedented view of dust and gas that might eventually form planets similar to Jupiter, ...
Stellar family portrait takes imaging technique to new extremes
Dec 03, 2009 |
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Noted for harbouring Eta Carinae -- one of the wildest and most massive stars in our galaxy -- the impressive Carina Nebula also houses a handful of massive clusters of young stars. The youngest of these stellar ...
Close-up photos of dying star show our sun's fate (w/ Video)
Dec 15, 2009 |
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(PhysOrg.com) -- About 550 light-years from Earth, a star like our Sun is writhing in its death throes. Chi Cygni has swollen in size to become a red giant star so large that it would swallow every planet ...
Scientist uncovers relics of ancient cosmos
Space & Earth / Space Exploration
Dec 14, 2009 |
4.5 / 5 (19) |
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(PhysOrg.com) -- A University of Manchester scientist, working as part of an international team, has uncovered an unexpectedly rich trove of relicts from the ancient cosmos.
Life on Mars theory boosted by new methane study
Space & Earth / Space Exploration
Dec 08, 2009 |
4.9 / 5 (31) |
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Scientists have ruled out the possibility that methane is delivered to Mars by meteorites, raising fresh hopes that the gas might be generated by life on the red planet, in research published tomorrow in Earth an ...
Icy moons of Saturn and Jupiter may have conditions needed for life
Dec 15, 2009 |
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(PhysOrg.com) -- Scientists once thought that life could originate only within a solar system's "habitable zone," where a planet would be neither too hot nor too cold for liquid water to exist on its surface. ...
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