APOD: MyCn18: An Hourglass Nebula (2002 Jun 15)

[bystander]

MyCn18: An Hourglass Nebula
Astronomy Picture of the Day | 15 June 2002

[b][i]Credit: NASA/HST/WFPC2 R Sahai and J Trauger (JPL)[/i][/b]

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The sands of time are running out for the central star of this hourglass-shaped planetary nebula. With its nuclear fuel exhausted, this brief, spectacular, closing phase of a Sun-like star's life occurs as its outer layers are ejected - its core becoming a cooling, fading white dwarf. In 1995, astronomers used the Hubble Space Telescope (HST) to make a series of images of planetary nebulae, including the one above. Here, delicate rings of colorful glowing gas (nitrogen-red, hydrogen-green, and oxygen-blue) outline the tenuous walls of the "hourglass". The unprecedented sharpness of the HST images has revealed surprising details of the nebula ejection process and may help resolve the outstanding mystery of the variety of complex shapes and symmetries of planetary nebulae.

A Chameleon Sky
NASA Image of the Day | 03 Sep 2010

[owlice]

The Venn diagram of the skies?

[neufer]

Mayall & Cannon's MyCn 18

<<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.>>

[RJN]

http://antwrp.gsfc.nasa.gov/apod/ap020615.html

[mexhunter]

Already we have seen in APOD:
http://apod.nasa.gov/apod/ap960209.html

and

http://apod.nasa.gov/apod/ap020615.html

but I prefer in red:


http://wallpapercavern.com/walls/hourgl ... normal.jpg
Grettings
César

[bystander]

http://antwrp.gsfc.nasa.gov/apod/ap020615.html

Thanks. I did a TinEye search, which usually shows APOD matches, but it didn't find this one.

[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

[bystander]

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)

[orin stepanek]

but I prefer in red:

César

I like the red also

[Beyond]

The Venn diagram of the skies?

I see it more as "The eye between both ends."

[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."

Click to view full size image

with a Mycena Interrupta in the almond

Click to view full size image

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."

[neufer]

[size=150][b][color=#FF0000]My[/color][color=#0000FF]C[/color]e[color=#0000FF]n[/color]a[/b][/size] Interrupta

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This APOD reminds me of a vesica piscis,
with a MyCena Interrupta in the almond

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."

APOD, February 9, 1996: [size=150][b][color=#FF0000]My[/color][color=#0000FF]Cn[/color][color=#BF00BF]18[/color][/b][/size]

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<<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.>>

[neufer]

<<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.>>

Panellus stipticus, Mt. Vernon, Wisconsin.

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<<"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.>>