APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

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Expand view Topic review: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by Ann » Thu Feb 02, 2012 8:34 am

I haven't commented on this one. I have been lazy, and a little bit sick.

Well, this APOD is a very nice portrait of the dust that is first made by a red giant and then spread out into space by the "series of gentle explosions" that creates the planetary nebula.

Ordinary red giants, the ones that come from intermediate-mass stars like the Sun - I refuse to call the Sun a low-mass star when it is more massive than 95% of the stars in the galaxy! - well, these ordinary red giants are responsible for a whole lot of the creation of heavy elements in the universe. Each and every one of the ordinary red giants create heavy elements, for example iron, when they are near the end of their lives. Each red giant creates a moderately small amount of heavy elements, not at all comparable to the fantastic heavy element production of a supernova. But because supernovae are rare, but ordinary red giants are common, it could well be that the total heavy element production by red giants is comparable to the element production by supernovae.

http://en.wikipedia.org/wiki/Stellar_evolution wrote about red giant stars on the brink of becoming planetary nebulae:
Stars in this phase of life are called Late type stars, OH-IR stars or Mira-type stars, depending on their exact characteristics. The expelled gas is relatively rich in heavy elements created within the star and may be particularly oxygen or carbon enriched, depending on the type of the star.
So stars like the progenitor of the Helix Nebula are important creators of heavy elements in the universe, the kind of elements that you need in order to build planets and people.

Out Sun will do the universe this kind of service, too, when it dies. So when the Sun lived, it sustained a living planet, and when it dies, it will give the universe elements to build more planets like the Earth.

Ann

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by Beyond » Thu Feb 02, 2012 3:33 am

neufer wrote:
Chris Peterson wrote:
Let's just say that the formation of a planetary nebula is a very low-energy event compared with a supernova.

"Excitement" is in in the eye of the beholder.

I 'see' that Art still likes to keep his eye on things. :yes: , he does. :thumb_up:

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by clintonbob » Thu Feb 02, 2012 3:04 am

clintonbob wrote:If a planetary nebula is spherical, how come we see it as cylindrical? Why doesn't the expanding gas coming directly towards us prevent us from seeing anything but a sphere of gas?
Thanks

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by neufer » Wed Feb 01, 2012 2:11 am

clintonbob wrote:If a planetary nebula is spherical, how come we see it as cylindrical? Why doesn't the expanding gas coming directly towards us prevent us from seeing anything but a sphere of gas?
http://en.wikipedia.org/wiki/Planetary_nebula#Morphology wrote:
<<Only about 20% of planetary nebulae are spherically symmetric . A wide variety of shapes exist with some very complex forms seen. Planetary nebulae are classified by different authors into: stellar, disk, ring, irregular, helical, bipolar, quadrupolar, and other types, although the majority of them belong to just three types: spherical, elliptical and bipolar. The nebulae of the last type show the strongest concentration to the galactic plane and their progenitors are therefore relatively young massive stars. On the other hand spherical nebulae are likely produced by the old stars similar to the Sun.

The huge variety of the shapes is partially the projection effect—the same nebula when viewed under different angles will look differently. Nevertheless the reason for the huge variety of physical shapes is not fully understood, but may be caused the 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. It has been determined that the more massive stars produces more irregularly shaped nebulae. 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.>>

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by clintonbob » Wed Feb 01, 2012 1:50 am

If a planetary nebula is spherical, how come we see it as cylindrical? Why doesn't the expanding gas coming directly towards us prevent us from seeing anything but a sphere of gas?

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by ellesmith » Wed Feb 01, 2012 12:41 am

It looks EXACTLY like the EYE in Lord of the Rings ....and now all of us are "Ones who have seen the Eye."....rename it? Thanks APOD!

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by neufer » Tue Jan 31, 2012 10:56 pm

Chris Peterson wrote:
Let's just say that the formation of a planetary nebula is a very low-energy event compared with a supernova.

"Excitement" is in in the eye of the beholder.

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by Boomer12k » Tue Jan 31, 2012 10:24 pm

JamieWalker wrote:Yeah, I KNOW what the real name of this nebula is... But most people I know, refer to it as "The Eye of God" And I just wanted to get that on record for posterity.

I actually call it that too. It does not look to me like I am looking down a coil...

:---[===] *

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by JamieWalker » Tue Jan 31, 2012 8:38 pm

Yeah, I KNOW what the real name of this nebula is... But most people I know, refer to it as "The Eye of God" And I just wanted to get that on record for posterity.

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by Wolf Kotenberg » Tue Jan 31, 2012 7:11 pm

I am definitaly " fluoresced ". Now for an ice cold one

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by Chris Peterson » Tue Jan 31, 2012 6:54 pm

Beyond wrote:Gee, Chris, you're making what would seem to an exciting happening, rather dull and mundane. Or is that only when it's not a super-nova? If it's a super-nova, THEN it gets exciting :?: :?:
Let's just say that the formation of a planetary nebula is a very low-energy event compared with a supernova. "Excitement" is in in the eye of the beholder.

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by Beyond » Tue Jan 31, 2012 6:47 pm

Gee, Chris, you're making what would seem to an exciting happening, rather dull and mundane. Or is that only when it's not a super-nova? If it's a super-nova, THEN it gets exciting :?: :?:

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by Chris Peterson » Tue Jan 31, 2012 6:04 pm

OsmoA wrote:Just wondering: what happens to possible planets and their trajectories when the star explodes?
We see an image like this, and imagine a very violent event. But things are much less extreme in practice. At the end of its life, a star of low or intermediate mass sheds its outer layers in a series of fairly weak explosions. During the entire process, most of the star's mass is retained- a typical white dwarf masses perhaps 80% of its progenitor. So in reality, not all that much mass is lost, and the gas that is ejected is quite tenuous at typical planetary orbital radiuses. So nothing at all happens to planets from the expanding nebula- they certainly aren't blown outwards! However, the shift of some mass from the center of the system to a distributed cloud or shell around the system will have some effect. As the system evolves to one with a lower central mass, the planetary orbits must necessarily shift outwards somewhat, and the orbital periods increase. The shift in position, however, will neither be radical nor rapid.

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by Chris Peterson » Tue Jan 31, 2012 5:49 pm

leon.l7027@gmail.com wrote:Given the distance, 700 ly, and the estimate of when it took place (at the link to "inner edge"), 12,000 years ago, the supernova should have been seen, if not recorded in a cave or other long-lasting medium, about 13,000 years ago by Cro-magnon folk. Any archae-astronomers out there to help our queries?
This is a planetary nebula, not a supernova remnant. There was no supernova- the progenitor star was not massive enough for that.

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by zbvhs » Tue Jan 31, 2012 5:17 pm

These things are curiosities, indeed. I would expect that they would be generally spherical in shape rather than cylindrical or toroidal. We see bright stuff at the sides because we're looking on a line of sight tangential to the surface of the sphere. On a line of sight through the center, the material is too tenuous to be seen.

The star is a white dwarf, which means it first went through a red-giant stage and then simply collapsed without a lot of calamity like a supernova. The radiation we see is due to remnant heat; all nuclear reactions have ceased and the star is a slowly cooling cinder. Presumably, most close-in planets would have been consumed in the red-giant stage. Any outer gas giants would have had their atmospheres stripped away and only their rocky cores would remain.

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by leon.l7027@gmail.com » Tue Jan 31, 2012 1:51 pm

Given the distance, 700 ly, and the estimate of when it took place (at the link to "inner edge"), 12,000 years ago, the supernova should have been seen, if not recorded in a cave or other long-lasting medium, about 13,000 years ago by Cro-magnon folk. Any archae-astronomers out there to help our queries?

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by FloridaMike » Tue Jan 31, 2012 1:45 pm

The Eye of Sauron.

Re: APOD: The Helix Nebula (2012 Jan 31) those Globuals

by thongar » Tue Jan 31, 2012 1:45 pm

Gentle People:

If a Star is dying and in so doing is tearing itself apart., like all explosions Things are never cleanly obliturated. There are pieces. Those globuals are pieces of the star. Since the star is gas and gravity the Globuals are gas and gravity. This is a given and confirmed by the analysis. Now as to the origin?

In all the beautiful pictures and information on our own sun shown in APOD, with its mixed gases raging through its interior, haven't any of you astronomers noticed that if you have mixing and flows, you also have different densities AND different gravities. We see this on Earth, why is it not the same on/in the sun? These gravity pockets in the sun may be like rocks in the Earth, and actually Are. No matter how smal or how large, how slow or fast an explosion is, in an explosion, the light matter and the heavy matter move at different speeds (Newtonian Physics).

Globuals are pieces of the star, big pieces of dense Matter/Gravity that survived the final destruction of the star. They held together because gravity in the Globual was stronger that the force tearing the sun apart. But they are heavier than the gas and plasma, they are slower than the blat wave because of momentum, they are the slowest runners. The comet tail is the result of the still occuing radiation from that explosion moving faster than they are.

There is no mystery, all you need to do, is to look at it as an engineer. Somtimes comparitive observation beats math in explaination, I bet if you look at the helix with explosive dynamics in mind, the Math will catch up.

Captn Tommy

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by Guest » Tue Jan 31, 2012 12:40 pm

Will the Sun look like this one day? I realized at that point the concept of "day" will no longer be relevant (without our Sun!).

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by biddie67 » Tue Jan 31, 2012 12:37 pm

At the least, won't they be pushed out of their orbits? Incenderated? Broken apart if a solid planet? Blown away if a gaseous planet? All dependent upon the force of the blast and the distance of the planet from the exploding sun?

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by OsmoA » Tue Jan 31, 2012 6:45 am

Just wondering: what happens to possible planets and their trajectories when the star explodes?

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by Boomer12k » Tue Jan 31, 2012 6:44 am

Does anybody know the approximate AGE of the star when it exploded?
Also, what was the estimated mass? And WHEN Earth time did the explosion occur? Did anyone record it?

Nice Picture.

:---{===] *

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by bystander » Tue Jan 31, 2012 6:15 am

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by owlice » Tue Jan 31, 2012 5:56 am

Thanks, Chris; I'll let TPTB know.

Re: APOD: The Helix Nebula from the VISTA... (2012 Jan 31)

by Flase » Tue Jan 31, 2012 5:45 am

It's interesting to see the different shapes of these nebulae. You could learn something about the structure of the star that died. We can look at the disc of Betelgeuse, for example and see bright patches and hazard a guess about what shape the nebula will be when it blows.

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