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APOD: MyCn18: An Hourglass Nebula (2002 Jun 15)
Posted: Fri Sep 03, 2010 5:56 pm
by bystander
Re: NASA IOTD: A Chameleon Sky
Posted: Fri Sep 03, 2010 6:38 pm
by owlice
The Venn diagram of the skies?
My Sin 18
Posted: Fri Sep 03, 2010 6:46 pm
by neufer
Mayall & Cannon's MyCn 18
http://en.wikipedia.org/wiki/Hourglass_Nebula wrote:
<<The Engraved Hourglass Nebula (also known as MyCn 18) is a young planetary nebula situated in the southern constellation MusCa about 8,000 light-years away from Earth. It was discovered by Margaret W. Mayall & Annie Jump Cannon during their work on an extended Henry Draper Catalogue (built between 1918 & 1924). At the time, it was designated simply as a small faint planetary nebula. Much improved telescopes and imaging techniques allowed the hourglass shape of the nebula to be discovered by Raghvendra Sahai & John Trauger of the Jet Propulsion Laboratory on January 18, 1996. It is conjectured that MyCn 18's hourglass shape is produced by the expansion of a fast stellar wind within a slowly expanding cloud which is denser near its equator than its poles.>>
Re: NASA IOTD: A Chameleon Sky
Posted: Fri Sep 03, 2010 6:54 pm
by RJN
Re: NASA IOTD: A Chameleon Sky
Posted: Fri Sep 03, 2010 7:01 pm
by mexhunter
Re: NASA IOTD: A Chameleon Sky
Posted: Fri Sep 03, 2010 7:16 pm
by bystander
Thanks. I did a
TinEye search, which usually shows APOD matches, but it didn't find this one.
Re: NASA IOTD: A Chameleon Sky
Posted: Fri Sep 03, 2010 9:05 pm
by RJN
Sometimes, if the image and text looks familiar, I type a few discerning words from the text into the APOD search engine to see what pops up. This one did. They don't have to, but I wish they would cite APOD as a source of the text. - RJN
Re: NASA IOTD: A Chameleon Sky
Posted: Fri Sep 03, 2010 9:10 pm
by bystander
RJN wrote:Sometimes, if the image and text looks familiar, I type a few discerning words from the text into the APOD search engine to see what pops up. This one did. They don't have to, but I wish they would cite APOD as a source of the text. - RJN
Yeah, you would think that NASA would, in any case.
(Title changed and moved to The Bridge)
Re: NASA IOTD: A Chameleon Sky
Posted: Fri Sep 03, 2010 10:37 pm
by orin stepanek
mexhunter wrote:
but I prefer in red:
César
I like the red also
Re: NASA IOTD: A Chameleon Sky
Posted: Sat Sep 04, 2010 1:24 am
by Beyond
owlice wrote:The Venn diagram of the skies?
I see it more as "The eye between both ends."
Re: APOD: MyCn18: An Hourglass Nebula (2002 Jun 15)
Posted: Sat Sep 04, 2010 8:24 pm
by otto oblande
This APOD reminds me of a vesica piscis,
http://en.wikipedia.org/wiki/Vesica_piscis"The Vesica piscis is a shape which is the intersection of two circles with the same radius, intersecting in such a way that the center of each circle lies on the circumference of the other. The name literally means the "bladder of a fish" in Latin. The shape is also called mandorla ("almond" in Italian).
The term is also used more generally for any symmetric lens."
with a Mycena Interrupta in the almond
http://en.wikipedia.org/wiki/Mycena"Mycena is a large genus of small saprotrophic mushrooms which are rarely more than a few centimeters in width. They are characterized by a white spore print, a small conical or bell-shaped cap, and a thin fragile stem. Most are grey or brown, but a few species have brighter colors. Most have a translucent and striate cap, which rarely has an incurved margin. ...
Thirty-three species are known to be bioluminescent, creating a glow known as foxfire. These species are divided among 16 lineages, leading to evolutionary uncertainty in whether the luminescence developed once and was lost among many species, or evolved in parallel by several species. The evolutionary purpose of the glowing is uncertain."
Re: APOD: MyCn18: An Hourglass Nebula (2002 Jun 15)
Posted: Sat Sep 04, 2010 8:39 pm
by neufer
otto oblande wrote:
This APOD reminds me of a vesica piscis,
with a
MyCena Interrupta in the almond
http://en.wikipedia.org/wiki/Mycena wrote:
MyCena is a large genus of small saprotrophic mushrooms which are rarely more than a few centimeters in width. They are characterized by a white spore print, a small conical or bell-shaped cap, and a thin fragile stem. Most are grey or brown, but a few species have brighter colors. Most have a translucent and striate cap, which rarely has an incurved margin. ...
Thirty-three species are known to be bioluminescent, creating a glow known as foxfire. These species are divided among 16 lineages, leading to evolutionary uncertainty in whether the luminescence developed once and was lost among many species, or evolved in parallel by several species.
The evolutionary purpose of the glowing is uncertain."
http://apod.nasa.gov/apod/ap960209.html wrote:
<<What's happening in the eye-like center of this planetary nebula? The geometry revealed in this Hubble Space Telescope view of the central part of an "etched hourglass nebula" known as
MyCn18 presents a puzzle. First, the axis of this central region does not line up well with the outer hourglass structure. Next, the hot star (the white spot to the left of center) which ejected this gaseous nebula as it evolved towards its white dwarf phase, is not exactly at the center of the "eye". These unexpected results leave astronomers looking for the missing pieces of the ejection process that created this unusual and beautiful structure.>>
Foxfire
Posted: Sat Sep 04, 2010 10:03 pm
by neufer
http://en.wikipedia.org/wiki/Foxfire_%28bioluminescence%29 wrote:
<<Foxfire is the term for the bioluminescence created in the right conditions by a few species of fungi that decay wood. The luminescence is often attributed to members of the genus Armillaria, the Honey mushroom, though others are reported, and as many as 71 individual species have been identified. On the suggestion of Benjamin Franklin it was used for light in the Turtle, an early submarine. In the novel Adventures of Huckleberry Finn by Mark Twain, the characters of Huckleberry Finn and Tom Sawyer use foxfire as a source of light in order to dig a tunnel.>>
http://www.bio.net/bionet/mm/mycology/1998-December/007011.html wrote:
<<"The greenish light, known as "foxfire," is given out not only by the mushrooms themselves but also by the mycelium, the fungal filaments that often permeate the wood of diseased trees. The surface layers of the mycelium of such impregnated wood, which is called "touchwood," can be seen to glow fairly brightly for one or two weeks. This property has inspired fear and wonder since time immemorial. Imagine finding a tree branch shining bright (with apologies to William Blake) in the forests of the night! Legends describing such eerie encounters can be found in ancient Greek, Roman, and Indian texts.
The whole subject of bioluminescence is wanting for an explanation. Luminescent animals may conceivably use the light to find mates or food, but this can hardly be the reason mushrooms glow in the dark. People from many parts of the world have found uses for these natural lanterns. The Swedish historian Olaus Magnus wrote in 1652 that people in the far north of Scandinavia would place pieces of rotten oak bark at intervals when venturing into the forest. They could then find their way back by following the light. Similarly, during World War I soldiers in the trenches placed touchwood on their helmets to keep from bumping into others in the dark.>>