APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

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APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by APOD Robot » Thu Mar 21, 2013 4:06 am

Image NGC 2736: The Pencil Nebula

Explanation: Moving left to right near the center of this beautifully detailed color composite, the thin, bright, braided filaments are actually long ripples in a sheet of glowing gas seen almost edge on. The interstellar shock wave plows through space at over 500,000 kilometers per hour. Cataloged as NGC 2736, its elongated appearance suggests its popular name, the Pencil Nebula. The Pencil Nebula is about 5 light-years long and 800 light-years away, but represents only a small part of the Vela supernova remnant. The Vela remnant itself is around 100 light-years in diameter, the expanding debris cloud of a star that was seen to explode about 11,000 years ago. Initially, the shock wave was moving at millions of kilometers per hour but has slowed considerably, sweeping up surrounding interstellar material. In the narrowband, wide field image, red and blue-green colors track the characteristic glow of ionized hydrogen and oxygen atoms.

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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by Beyond » Thu Mar 21, 2013 4:27 am

The Pencil Nebula ... Write on :!: That's where a star tried to erase itself. :mrgreen:
To find the Truth, you must go Beyond.

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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by ta152h0 » Thu Mar 21, 2013 4:48 am

5 light years is about how far the sun is to Proxima Centauri. That is a big place there
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by fausto.lubatti » Thu Mar 21, 2013 9:13 am

Wonderful picture: the colors are so delicate! :D

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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by orin stepanek » Thu Mar 21, 2013 11:37 am

8-) :D :thumb_up: :thumb_up: :clap: :clap: :yes: :yes:
Smileys say it all!
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by GTChappy » Thu Mar 21, 2013 2:38 pm

The Pencil Nebula...What would happen if our solar system just happened to be in the way of this thing? Shock wave? Instantaneous vaporization of the entire planet? Perhaps it would bring a solution to global warming?

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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by Chris Peterson » Thu Mar 21, 2013 3:03 pm

GTChappy wrote:The Pencil Nebula...What would happen if our solar system just happened to be in the way of this thing? Shock wave? Instantaneous vaporization of the entire planet? Perhaps it would bring a solution to global warming?
Absolutely nothing would happen. This structure is so tenuous that in a lab it would be called a hard vacuum. We wouldn't even be aware of its presence except through the use of sensitive instruments. And what little material is actually present wouldn't make it into the inner solar system at all, since the solar wind would blow it away.
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by Ann » Thu Mar 21, 2013 3:17 pm

It's a beautiful picture, and I'm impressed that narrowband photography can produce such delicate color images.

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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by Chris Peterson » Thu Mar 21, 2013 3:38 pm

Ann wrote:It's a beautiful picture, and I'm impressed that narrowband photography can produce such delicate color images.
Why? The display gamut of typical narrowband images is identical to that of broadband RGB. Perhaps you are referring to the fact that the gamut of this image is reduced because only two color channels are used? Some additional information on the processing would be interesting; the presence of white stars suggests that a green channel was synthesized, which also would expand the gamut.
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by Parrot Head Joe » Thu Mar 21, 2013 4:47 pm


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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by samueltownsend » Thu Mar 21, 2013 7:28 pm

Just a question: what forces cause this reported shock wave in interstellar space to slow down from millions of kph to .5million kph?

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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by Boomer12k » Thu Mar 21, 2013 8:01 pm

To me, it looks like a supersonic jet!!! ZOOOOMMM!!!


Nice picture!

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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by Boomer12k » Thu Mar 21, 2013 8:10 pm

samueltownsend wrote:Just a question: what forces cause this reported shock wave in interstellar space to slow down from millions of kph to .5million kph?
It is explained in the caption...."sweeping up surrounding interstellar material."

It is running into the fine interstellar medium and the collision evidently slows it down. It is thus accruing more MASS, or running into slight masses as it moves...which dissipates the energy. I assume. Think of it like an airplane crashing on a runway, and running into the soft, breakable concrete to slow down. As the plane's wheels crunch more breakable concrete, the energy is dissipated. Transferred to the concrete and the ground. Thus slowing the plane with friction.

I hope that is essentially correct.
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by neufer » Thu Mar 21, 2013 8:55 pm

Boomer12k wrote:
samueltownsend wrote:Just a question: what forces cause this reported shock wave in interstellar space to slow down from millions of kph to .5million kph?
It is explained in the caption...."sweeping up surrounding interstellar material."

It is running into the fine interstellar medium and the collision evidently slows it down. It is thus accruing more MASS, or running into slight masses as it moves...which dissipates the energy. I assume. Think of it like an airplane crashing on a runway, and running into the soft, breakable concrete to slow down. As the plane's wheels crunch more breakable concrete, the energy is dissipated. Transferred to the concrete and the ground. Thus slowing the plane with friction.

I hope that is essentially correct.
Friction implies a loss of momentum.

However, momentum could be conserved if the nebula mass grows inversely with the velocity.
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by ajg_oz » Thu Mar 21, 2013 9:42 pm

By my rough calculations the Vela remnant will sweep past the solar system in 25-30 thousand years (very rough cals).
What will happen to the sun during this event?
Perhaps nothing - the gases will be too thin by then.
Small change in it's output - only measureable by its spectral change.
Something much larger??
Has it already sweep passed other stars and did they change?

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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by neufer » Thu Mar 21, 2013 10:09 pm

ajg_oz wrote:
By my rough calculations the Vela remnant will sweep past the solar system in 25-30 thousand years (very rough cals).
Since it took approximately 11,000-12,300 years to reach it's current apparent size of ~8º
then one might assume that It must take at least ~125,000 years before it appears large enough to have reached us.
ajg_oz wrote:
What will happen to the sun during this event?
Perhaps nothing - the gases will be too thin by then.
Small change in it's output - only measurable by its spectral change.
Something much larger??
  • It will just be more Local Fluff to contend with (PILLOW FIGHT :!: ) :
http://en.wikipedia.org/wiki/Local_Fluff wrote: <<The Local Interstellar Cloud (or Local Fluff or LIC) is the interstellar cloud roughly 30 light years or 9.2 parsecs across through which the Earth's Solar System is currently moving. The Solar System is thought to have entered the Local Interstellar Cloud at some time between 44,000 and 150,000 years ago and is expected to remain within it for another 10,000 to 20,000 years. The cloud has a temperature of about 6,000 K, about the same temperature as the surface of the Sun. However, its specific heat capacity is very low as it is not very dense, with 0.3 atoms per cubic centimeter; less dense than the average for the interstellar medium in the Milky Way (0.5 atoms/cm3), though six times denser than the gas in the Local Bubble (0.05 atoms/cm3) which surrounds the local cloud. In comparison, Earth's atmosphere at the edge of space has 12 billion atoms per cubic centimeter, dropping to 52 million at 150 km.

The cloud is flowing outwards from the Scorpius-Centaurus Association, a stellar association that is a star-forming region.

The Local Interstellar Cloud's potential effects on Earth are prevented by the solar wind and the Sun's magnetic field. This interaction with the heliosphere is under study by the Interstellar Boundary Explorer (IBEX), a NASA satellite mapping the boundary between the Solar System and interstellar space.>>
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by Chris Peterson » Fri Mar 22, 2013 12:20 am

ajg_oz wrote:By my rough calculations the Vela remnant will sweep past the solar system in 25-30 thousand years (very rough cals).
It's not moving in the right direction to pass through the Solar System. And if it were, it would take much longer than 30,000 years, and would have become subsonic and largely dissipated.
What will happen to the sun during this event?
Even if our Solar System were in the middle of one of those shock waves right now, nothing would be happening to us, and we wouldn't even be able to see it without instruments.
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by Chris Peterson » Fri Mar 22, 2013 12:29 am

samueltownsend wrote:Just a question: what forces cause this reported shock wave in interstellar space to slow down from millions of kph to .5million kph?
Consider what a shock wave actually is. We're seeing the front created by particles moving faster than the speed of sound in their medium. The particles were ejected from the supernova at over 10,000 km/s, into the interstellar medium, with a speed of sound around 100 km/s. So the ejected particles are traveling Mach 100 or more. The shock front is created by those particles colliding with particles of the interstellar medium. They lose some kinetic energy by transfer to the ISM particles, and they lose more by ejecting electrons, ionizing themselves and the ISM, with that energy converted to EM radiation in the optical and radio wavelengths. A lot of kinetic energy is lost, resulting in rapid slowing of the particles, and of the associated shock wave.
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by Chris Peterson » Fri Mar 22, 2013 12:31 am

neufer wrote:Friction implies a loss of momentum.
However, momentum could be conserved if the nebula mass grows inversely with the velocity.
No, friction implies a transfer of momentum. Momentum is always conserved (unless you choose to limit the system to just the particles originally ejected, which would make no sense at all).
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by neufer » Fri Mar 22, 2013 2:48 am

Chris Peterson wrote:
neufer wrote:
Friction implies a loss of momentum.
However, momentum could be conserved if the nebula mass grows inversely with the velocity.
No, friction implies a transfer of momentum. Momentum is always conserved (unless you choose to limit the system to just the particles originally ejected, which would make no sense at all).
Semantics.

Use of the term "friction" in this situation makes no sense at all (unless, possibly, one chooses to limit the system to just the particles originally ejected).

In most cases where the use of the term "friction" does make sense it effectively implies a loss of momentum.
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by ta152h0 » Fri Mar 22, 2013 3:32 am

Well, I am going to go grab me a bag of popcorn and watch the developments.
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by samueltownsend » Fri Mar 22, 2013 8:43 am

Yesterday I posed the question "what forces cause this reported shock wave in interstellar space to slow down from millions of kph to .5million kph?"
OK, let's say an explosion of particles occurs, and the density of all those particles decreases as a function of the radial distance traveled. In a relatively short time the ratio between the particle diameter and the distance between particles becomes "astronomical", which is also the case with interstellar space. The odds of collision of particles becomes so low that the great majority of particles travel without encounter, therefore no loss of momentum. So what am I missing here?

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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by DavidLeodis » Fri Mar 22, 2013 1:06 pm

I assume that the short bright red filaments are ionized Hydrogen and the longer more numerous blue filaments are ionized Oxygen, but I wonder if the pale diffuse red all over the image is also due to ionized Hydrogen :?:. I would appreciate any help on this query.

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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by neufer » Fri Mar 22, 2013 1:33 pm

DavidLeodis wrote:
I assume that the short bright red filaments are ionized Hydrogen and the longer more numerous blue filaments are ionized Oxygen, but I wonder if the pale diffuse red all over the image is also due to ionized Hydrogen :?:. I would appreciate any help on this query.
That is correct.
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Re: APOD: NGC 2736: The Pencil Nebula (2013 Mar 21)

Post by DavidLeodis » Fri Mar 22, 2013 2:00 pm

Thanks neufer for your help, which is appreciated. :)