Infrared Helix

orin stepanek · Post by **orin stepanek** » Thu Jan 12, 2006 1:14 pm

http://antwrp.gsfc.nasa.gov/apod/ap060112.html

A dying star? It looks like the star is already dead. Am I missing something? Is this how some of the heavier elements are created? Or does this process have to go through further evolution?
Orin

Empeda2 · Post by **Empeda2** » Thu Jan 12, 2006 2:06 pm

Current stellar theory suggests that the type of star that would produce a planetary nebula (if, for simplicity's sake, we assume the star form from almost pure Hydrogen), would probably only created elements up to Carbon, Oxygen and Nitrogen through fusion processes.

What that image is showing is the star 'shedding' it's outer envelope, this would contain mainly hydrogen and helium, leaving the 'core' as a white dwarf, composed mainly of Carbon, Oxygen and Nitrogen. This will slowly cool to become a black dwarf (not a black hole!) and there is no fusion processes to maintain it's temperate.

To get larger elements in this way, you need a larger star, that has enough mass to fuse C, N and O to heavier elements - up to 56Fe (the most stable isotope).

This is a highly simplistic description but shows the basis for current stellar theory. Stars such as our sun for example, would not have formed from pure hydrogen, and would already have some heavy elements in it at formation.

JohnD · Post by **JohnD** » Thu Jan 12, 2006 2:23 pm

Why is this star know as the Helix?
Does it appear as a spiral in a smaller view with less resolution?

And is it a disc of material that we see, hence 'planetary' or a globe?

Thnaks,
John

Empeda2 · Post by **Empeda2** » Thu Jan 12, 2006 4:50 pm

It's more like a bubble - they called planetary nebulae due to historical reasons - they looked a bit like planetary systems.

The look like a ring/disc because they aren't very opaque, but at the edges you're obviously looking through more material than you are from the 'side' facing us.

As to why it's called the Helix? I dunno....

orin stepanek · Post by **orin stepanek** » Thu Jan 12, 2006 4:52 pm

The Sun is expected to go through its own Planetary Nebula phase ... in another 5 billion years.

I assumed the Helix was already a secondary or third generation star as our sun is expected to go out in the same manner as the APOD suggests.
Orin

Empeda2 · Post by **Empeda2** » Thu Jan 12, 2006 4:53 pm

Why it's called the helix - to do with how it appears in photographs apparently.....

http://www.seds.org/messier/xtra/ngc/n7293.html

Empeda2 · Post by **Empeda2** » Thu Jan 12, 2006 4:54 pm

orin stepanek wrote:The Sun is expected to go through its own Planetary Nebula phase ... in another 5 billion years.

I assumed the Helix was already a secondary or third generation star as our sun is expected to go out in the same manner as the APOD suggests.
Orin

But - what are those cometary knots? Too big to be oort cloud comets - each one's twice the size of our solar system!

orin stepanek · Post by **orin stepanek** » Thu Jan 12, 2006 5:02 pm

Are you saying the Helix came from a primary star because of the cometary knots? And are there maybe 4th or 5th generation stars out there? Probably a dumb question, but if the sun goes out in a few billion years than I'm sure the debris will get recycled eventually??
Orin

orin stepanek · Post by **orin stepanek** » Fri Jan 13, 2006 1:08 am

http://map.gsfc.nasa.gov/m_uni/uni_101stars.html

I guess I didn't think of the sun as a primary star. If so' then why are there so much heavy elements around? I was under the impression that the heavy materials would have to be around 2nd or 3rd generation stars.

Orin

S. Bilderback · Post by **S. Bilderback** » Fri Jan 13, 2006 1:57 am

As far as I know the Sun was formed from second and/or third generation recycled Big Bang remnants. Is there something in that article that states differently?

orin stepanek · Post by **orin stepanek** » Fri Jan 13, 2006 2:09 am

It was the main sequence stars like our sun burning out the hydrogen and fusion to helium that sounds to me like a primary star. Wouldn't a secondary or third generation star have heavier elements in its core???
Orin

Empeda2 · Post by **Empeda2** » Fri Jan 13, 2006 12:24 pm

orin stepanek wrote:Are you saying the Helix came from a primary star because of the cometary knots? And are there maybe 4th or 5th generation stars out there? Probably a dumb question, but if the sun goes out in a few billion years than I'm sure the debris will get recycled eventually??
Orin

No! Not at all - I'm jsut curious as to what people think the cometary knots are?