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Author Topic: Why Are Planetary Nebula NOT all the same shape ?  (Read 4384 times)

Offline neilep

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Dear Nebulizers,

Do ewe like my collection of planetary nebulae ?




Nice eh ?..being delivered next Tuesday.

Nebulae are my all time favourite emission type gassy things that are given off when some stars die.....which is nice !

Two questions if I may indulge ewe ?...Why are they called Planetary Nebulae ? and why are they not all the same shape ?...yes..there are lots of roundy ones, but even they are all different !

Having an ' exit hole' that resembles a nebular I sat on my neighbours head this morning at 3am in the hope that he could give me an answer but unless someone can translate "mmmmmpptthh.. hmmmppthhhhhhh....arghmpthhhhhh " accompanied by lots of arms and leg thwacking , I guess the answer will remain a mystery !

Can ewe help ?

Thanks


Hugs and shmishes


mwah mwah mwah mwah mwah



Neil
Nebula Need-To-Knower

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lyner

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Why Are Planetary Nebula NOT all the same shape ?
« Reply #1 on: 21/10/2008 12:24:08 »
'Nebula' is a latin word, meaning 'mist'
see http://en.wiktionary.org/wiki/nebula

Your pictures are very pretty but remember the colours are probably false - to make features stand out.
If you drop ink into a bowl of water, the patterns will be fairly random too. There will be features which depend on the height from which you drop the ink (total energy available) but they never look just the same; it's a random process.
Nebulae start off as huge gas and dust clouds with a range of sizes so you could expect quite a variety of shapes. Then there are the explosions which may be involved (they can be formed by supernovae) and the fact that we are seeing them at all different stages in their lifetime. . . .
 

Offline Evie

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Why Are Planetary Nebula NOT all the same shape ?
« Reply #2 on: 21/10/2008 14:45:23 »


"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."

"Only about 20% of planetary nebulae are spherically symmetric (for example, see Abell 39.) A wide variety of shapes exist with some very complex forms seen. The reason for the huge variety of shapes is not fully understood, but may be caused by gravitational interactions with companion stars if the central stars are double stars. Another possibility is that planets disrupt the flow of material away from the star as the nebula forms. In January 2005, astronomers announced the first detection of magnetic fields around the central stars of two planetary nebulae, and hypothesised that the fields might be partly or wholly responsible for their remarkable shapes."

http://en.wikipedia.org/wiki/Planetary_nebula
 

Offline DoctorBeaver

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Why Are Planetary Nebula NOT all the same shape ?
« Reply #3 on: 23/10/2008 08:30:07 »
Different shaped nebulae can form as a result of inhomogeneities in the original gas cloud, or because clouds merge that had different angular alignment.

I have also seen it speculated, although I can't find the reference at the moment, that heavier elements may play some part in it.
 

Offline neilep

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Why Are Planetary Nebula NOT all the same shape ?
« Reply #4 on: 27/10/2008 12:52:36 »
'Nebula' is a latin word, meaning 'mist'
see http://en.wiktionary.org/wiki/nebula

Your pictures are very pretty but remember the colours are probably false - to make features stand out.
If you drop ink into a bowl of water, the patterns will be fairly random too. There will be features which depend on the height from which you drop the ink (total energy available) but they never look just the same; it's a random process.
Nebulae start off as huge gas and dust clouds with a range of sizes so you could expect quite a variety of shapes. Then there are the explosions which may be involved (they can be formed by supernovae) and the fact that we are seeing them at all different stages in their lifetime. . . .

Thank You very much sophiecentaur.

This is very useful and very helpful information. It all seems a lot clearer now !
 

Offline neilep

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Why Are Planetary Nebula NOT all the same shape ?
« Reply #5 on: 27/10/2008 12:55:47 »


"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."

"Only about 20% of planetary nebulae are spherically symmetric (for example, see Abell 39.) A wide variety of shapes exist with some very complex forms seen. The reason for the huge variety of shapes is not fully understood, but may be caused by gravitational interactions with companion stars if the central stars are double stars. Another possibility is that planets disrupt the flow of material away from the star as the nebula forms. In January 2005, astronomers announced the first detection of magnetic fields around the central stars of two planetary nebulae, and hypothesised that the fields might be partly or wholly responsible for their remarkable shapes."

http://en.wikipedia.org/wiki/Planetary_nebula

Thank you also very much Evie. Wonderful informative information that makes me a happy sheep who knows about Planetary nebula. I'm even understanding it !!

 

Offline neilep

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Why Are Planetary Nebula NOT all the same shape ?
« Reply #6 on: 27/10/2008 12:59:44 »
Different shaped nebulae can form as a result of inhomogeneities in the original gas cloud, or because clouds merge that had different angular alignment.

I have also seen it speculated, although I can't find the reference at the moment, that heavier elements may play some part in it.

Thank You DOCTOR Beave..."inhomogeneities"...wow, I never realised the processing of milk extended to cosmological phenomena !

I appreciate your response and you can rest assured that I am a learn-ed sheepy now !
 

Offline engrByDayPianstByNight

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Why Are Planetary Nebula NOT all the same shape ?
« Reply #7 on: 27/10/2008 14:24:58 »
Dear Nebulizers,

Do ewe like my collection of planetary nebulae ?


Very impressive. How long have you beencollecting refrigerator magnets from all the nebulae you've visited, neilep> ;). I only collect coins, though...


Also, your pictures confirm that statistics given by Evie that "only about 20% of planetary nebulae are spherically symmetric."
 

lyner

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Why Are Planetary Nebula NOT all the same shape ?
« Reply #8 on: 27/10/2008 14:28:57 »
Quote
"inhomogeneities"...wow
And the milky way goes past yer eyes every night.
 

Offline Soul Surfer

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Why Are Planetary Nebula NOT all the same shape ?
« Reply #9 on: 27/10/2008 19:40:58 »
Nailep  not all of the pictures that were included in your question page are planetary nebulae  there are pictures of supernova remnants and star forming areas included.

To return to your question.  Planetary nebulae are one of the late phases of moderate sized stars like the sun when they get towards the end of their life.  They become what is known as asymptotic giants. the size and temperature of a star is a function of the amount of energy its core is producing and its mass which defines the gravitational field that is holding the star together for a star of a given mass as the core emits more energy (when for example the nuclear burning of hydrogen to helium a shell ie gets bigger and closer to the surface)  the surface of the star must radiate more energy ie it gets bigger but counterintuitively to get bigger it gets cooler which makes it radiate less strongly so it has to get a lot bigger.  That's why most stars become what is called red giants towards the end of their lives.  For the smaller stars like the sun this can go so far that the star effectively blows away a large proportion of its mass to become a vast object the size of a solar system or larger.  This is a planetary nebula.  Clearly such an object is very loosely bound gravitationally and can be disturbed by other objects either massive stars or gas clouds nearby.
« Last Edit: 27/10/2008 19:42:37 by Soul Surfer »
 

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Why Are Planetary Nebula NOT all the same shape ?
« Reply #9 on: 27/10/2008 19:40:58 »

 

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