View Full Version : Question about Second Generation Stars

2009-Feb-16, 10:58 PM
(Re-posted from when I originally posted this in the wrong area)

I was thinking about something today and I was wondering if you nice people may have an answer for me.

Let's say, hypothetically, you have a first generation star with planets and moons and astroids, the whole bit around it and it goes super-nova, blows up boils all its planets away to their constituent molecules, you know the drill. Now, I'd assume that, since a sun exploding does not require any sort of outside force, the center of mass of that solar system should remain constant, thanks to our buddy Issac Newton. So let's say that we take our cleared out area of space and over time the atoms in it somehow congeal into new stars and new planets. First off, I don't know enough about the life of stars and second generation stars to know how likely it is that a star forms as opposed to a pulsar or anything else of that nature, but let's say, for arguments sake, that a star forms in the center of that solar system.

Now, based on what I know, I believe that the star should form in the same position as the last star, it being the most massive object in that solar system, I feel like it should form at least near the center of mass of the solar system. And I also know that this is fully explainable with Kepler and Newton. What I'm wondering is if there's a different way of looking at this through Einstein.

What little I know about the general theory of relativity is that gravity is describable as the warping of space-time, fixing that whole "does light need mass to be bent by gravity" question, since we know that light simply travels on geodesics and it's natural path when traveling across curved space-time is a curved path. Now then, since my preamble was horribly long, I'll make my question short. Is it possible to imagine that perhaps some of those warps in space-time remain after the supernova? That objects congeal in similar areas of space due to the shape of space-time itself as opposed to just the attraction of gravity? Or is that just sort of a ridiculous thought?

I know that took a while and I rambled on a bit. Thank anyone who actually took the time to read the whole thing. Anyone who's got any sort of direction on an answer, that'd be much appreciated.

2009-Feb-16, 11:04 PM
I'm not entirely sure what you're asking here. Are you asking if it's possible to form a new star "on top of" the remnants of an exploded supernova? The answer to that seems to be that it isn't - if a massive star explodes, it'll leave behind either a neutron star or a black hole, and you won't be able to form a star around either of those.

The presence of "pulsar planets" indicates that it's possible for planets to form around pulsars from material that is (somehow) left behind after the explosion, but they won't form in the same orbits as any previous planets. It's not like there are 'echoes' or 'dimples' left in space time that would allow worlds to preferentially form there.

Is that what you're asking?

2009-Feb-16, 11:06 PM
Yeah. That was pretty much it. Thanks, EDG. Well done on actually being able to parse my convoluted post and figure out what I was asking.

2009-Feb-16, 11:51 PM
It would seem highly unlikely that a planet could form around the remnant star following a supernova. Nevertheless, the first exoplanet discovered is a planet around a pulsar. I don't think a sound explanation is known for this peculiar and unexpected discovery.

Jeff Root
2009-Feb-17, 12:09 AM
A first-generation star would not have planets. Formation of planets
requires dust, and there was no dust in the molecular clouds that the
first generation of stars formed from.

Or are you using the term "first generation" to mean the generation
after the parent generation? I think that's how the terms work in

The molecular clouds which form stars generally have thousands of
times the mass of a single star. Many stars form in a cloud, but once
the stars begin to give off stellar winds, the rest of the gas and dust
is blown away. So most of the cloud is blown away.

Stars begin to form deep inside a molecular cloud, where it is dark,
and thus cold and getting colder. When part of the cloud is cold
enough, that part of the cloud collapses under its own gravity.

This all means it is practically impossible to predict where enough
gas and dust will collect together and then get cold enough to form
a star, or how big the star will finally be.

-- Jeff, in Minneapolis

2009-Feb-17, 12:12 AM
I suppose the super nova is slightly off center so the center of mass will continue in a slightly different orbit around the galaxy. Nothing is stationary, unless we define something as stationary. Much of the matter conversion to energy of the super nova occurs near the boundary of the core and the outer layers of the original star, so the core gets compressed to a compact star. Most of the outer layers are expelled at much faster than escape velocity of the galaxy, perhaps 0.1 c, so it never returns and leaves the galaxy in ten billion years or less. The gravity of the pieces is essentially irrelevant to the solar system by the time it is ten light years from the center of gravity. Neil

2009-Feb-17, 03:03 AM
Or are you using the term "first generation" to mean the generation after the parent generation? I think that's how the terms work in biology.

I don't think he meant "first generation" to mean "the earliest stars with very low metal content". I think he just meant it to mean "the first star that's there that blows up", and the second generation would be "anything that forms from the debris of that". Just like pulsar planets are sometimes referred to as "second generation planets", because it's a second round of planet-forming around the central body.

2009-Feb-17, 10:02 AM
I understood stellar formation of the second or third generation would be detectable by the presence of heavy metals. Which we are told could only have formed in the cauldron of a super giant or more massive than our sun by some degree nova event. Do I have this right that the mass ejected as nebulous matter is where the birthing of a stellar mass happens. It needs to collide or mingle with other bodies of mass to do this. A shock wave, or nova event. The remnants of a previous solar system are dead cold dark and without such energy to achieve this. Any planetary matter far enough away to survive the death of its star is now just wandering away from what was the center of mass.?

2009-Feb-21, 09:01 PM
A planetary system only forms in a third generation star system, roughly as follows:

Generation 1: interstellar matter aggregates to a single star
Generation 2: when this star starts to convert the iron-nickel class of elements into energy the amount of energy that is released will explode it in a Type 1 supernova. The explosion products are a dust cloud that recondenses back into a red giant and an X-ray star that evolves back into a white dwarf. So generation 2 is a red giant/white dwarf pair.
Generation 3: The red giant will develop according to the main sequence until it dies of old age in a Type II supernova. Since the white dwarf does not age the supernova will blow the white dwarf into pieces. These pieces typically form a planetary system where the dust cloud reaggregates into a red gaint and follows the main sequence again. You are right that the two centers of gravity if the generation 2 binary system will be the focal points of the elliptic orbits of the planets.

I know this goes against common knowledge but mainstream cosmology has the stellar development sequence backwards.

2009-Feb-21, 09:11 PM
StevenO, if you wish discuss non-mainstream hypotheses/theories, you are required to do so by creating a thread in the Against the Mainstream forum. You may not discuss alternate theories in the Q&A forum.

Please familiarize yourself with the board rules which you can find here (http://www.bautforum.com/forum-rules-faqs-information/32864-rules-posting-board.html). In particular, please pay attention to Rule 13 which covers non-mainstream theories.