by APOD Robot » Thu Aug 26, 2010 4:03 am
M27: Not a Comet
Explanation: While hunting for comets in the skies above 18th century France,
astronomer Charles Messier diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his
now famous not-a-comet list. In fact, 21st century astronomers would identify it as a
planetary nebula, but it's not a planet either, even though it may
appear round and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a
gaseous emission nebula created as a
sun-like star runs out of nuclear fuel in its core. The nebula forms as the star's outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star's intense but invisible
ultraviolet light. Known by the popular name of the
Dumbbell Nebula, the beautifully symmetric interstellar gas cloud is over 2.5 light-years across and about 1,200 light-years away in the
constellation Vulpecula. This
impressive color composite highlights details within the well-studied central region and fainter, seldom imaged features in the nebula's
outer halo. It includes narrowband images recorded using filters sensitive to emission from oxygen atoms, shown in blue-green hues, and hydrogen atoms in red.
[/b]
[url=http://apod.nasa.gov/apod/ap100826.html][img]http://apod.nasa.gov/apod/calendar/S_100826.jpg[/img] [size=150]M27: Not a Comet[/size][/url]
[b] Explanation: [/b] While hunting for comets in the skies above 18th century France, [url=http://www.seds.org/messier/xtra/history/biograph.html]astronomer Charles Messier[/url] diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his [url=http://www.seds.org/messier/xtra/history/m-cat.html]now famous not-a-comet list[/url]. In fact, 21st century astronomers would identify it as a [url=http://www.seds.org/messier/planetar.html]planetary nebula[/url], but it's not a planet either, even though it may [url=http://apod.nasa.gov/apod/ap030614.html]appear round[/url] and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a [url=http://www.astro.washington.edu/balick/WFPC2/]gaseous emission nebula[/url] created as a [url=http://apod.nasa.gov/apod/ap100221.html]sun-like star runs out[/url] of nuclear fuel in its core. The nebula forms as the star's outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star's intense but invisible [url=http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html]ultraviolet light[/url]. Known by the popular name of the [url=http://www.seds.org/messier/m/m027.html]Dumbbell Nebula[/url], the beautifully symmetric interstellar gas cloud is over 2.5 light-years across and about 1,200 light-years away in the [url=http://hawastsoc.org/deepsky/vul/index.html]constellation Vulpecula[/url]. This [url=http://www.telescopes.cc/m27.htm]impressive color composite[/url] highlights details within the well-studied central region and fainter, seldom imaged features in the nebula's [url=http://apod.nasa.gov/apod/ap100509.html]outer halo[/url]. It includes narrowband images recorded using filters sensitive to emission from oxygen atoms, shown in blue-green hues, and hydrogen atoms in red.
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