The Sun Had Sisters 155
[TheBORG] writes to mention a Space.com article about the Sun's departed solar siblings. Our own medium-sized yellow star was far from alone when it was formed, with hundreds of fellow solar bodies and a supernova to keep it company. From the article: "The evidence for the solar sisters was found in daughters--such as decayed particles from radioactive isotopes of iron--trapped in meteorites, which can be studied as fossil remnants of the early solar system. These daughter species allowed Looney and his colleagues to discern that a supernova with the mass of about 20 suns exploded relatively near the early Sun when it formed 4.6 billion years ago; and where there are supernovas or any massive star, you also see hundreds to thousands of sun-like stars, he said. The cluster of thousands of stars dispersed billions of years ago due to a lack of gravitational pull, Looney said, leaving the sisters 'lost in space' and our Sun looking like an only child ever since, he said."
Like the Pointer Sisters.... (Score:2, Funny)
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Not just another Looney Theory... (Score:4, Funny)
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yeah but (Score:2)
Pah! (Score:1, Funny)
Re:Pah! (Score:4, Funny)
Really? How do we know that?
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Really? How do we know that?
Ya gotta have faith, man!
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Oh yeah, believable... (Score:2)
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Just wait till he starts on his next theory.. (Score:4, Funny)
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Sisters? (Score:5, Funny)
Comment removed (Score:5, Funny)
Huh? (Score:1)
Apparently conservation of mass laws were different back then.
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Re:Huh? (Score:5, Insightful)
I'm surprised that the Universe is as developed as it is, being this young.
Regards,
--
*Art
Re:Huh? (Score:5, Interesting)
I'm pretty sure that's not true. Remember: the larger the star, the shorter its life. Really large stars have lifetimes of just a few tens of millions of years, while red dwarfs can live trillions, according to current theory. While a 20 solar mass star isn't that big, I imagine it still didn't last long.
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Er, that sounds a lot like the Anthropomorphic Principal [wikipedia.org] could explain that.
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Weirdest typo I've seen all year.
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Re:Huh? (Score:5, Informative)
As the same star evolves, it depletes hydrogen (proton) soon at the core. But because the star is still massive, it enables to burn helium, then carbon, oxygen, nitrogen, and eventually it starts burning more heavier elements via nuclear processing (til iron -- Fe -- which cannot be burned to generate nuclear energy).
This heavier element synthesis is accelerated by high temperature and pressure (basically) at the core of a star. For a very massive star (Mass ~ 100 sun) it lives only about a few million years before it begins to show the sign of aging (heavier metallic elements in its atmosphere). And when these stars die, their explosions would disperse these heavier elements throughout its neighboring space (also upon explosion, an ample flux of neutrons would bombard other atoms and eventually the atoms trap the neutrons to form heavier elements than Fe; Strontium, uranium, plutonium and gold are good examples of such process).
In a small star like the Sun, the synthesis process takes place very slowly (in the time scale of a few billion years). So it's only natural that astrophysicits think today that there must have been a lot of very massive stars formed in the early days of the Universe to explain its metallicity level seen today.
Re:Huh? (Score:5, Informative)
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At any rate, it's best not to take notice, as the world seems to be on max pedophile alert.
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conservation of mass is not the issue. The sun-like stars were not made from the mass of the exploded star. The explosion caused a shock wave in the interstaller gas. The shock wave is a density variation that trigged gravatational colapse at hundrds of points in the cloud. Some of those points became stars.
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Apparently you had trouble comprehending TFA, assuming you read it in the first place.
End of the univers already happened? (Score:1)
So it's slightly possible that George Lucas wasn't lying and the whole galactic-terran-empire "long-long ago" thing really happened?
In all seriousness though (well, half seriousness), suppose this would mean that Earth IS that bunch of humans huddled around a burning-trash-can of a black-hole?
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I think it the exact opposite; the Sol system is the stellar equivalent of the Riviera. Too bad we keep littering up the place.
Down another rung of importance. (Score:5, Funny)
Put's watching my diet in perpective, that's for certain.
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Puny electrons!
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Have you considered shopping around for a new sense of humour?
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Curses! And I just got this thing after buying a new macbook because of the bash terminal & bsd backend. Wow, I was so focused on what appeared to be a troll-like response that I missed that.
Thanks for the heads up
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lack of gravitational pull?? (Score:3, Interesting)
Re:lack of gravitational pull?? (Score:5, Funny)
So the claim is that hundreds, maybe thousands, of sun-like stars were in close proximity to each other, but they didn't generate enough gravity to stay in the same neighborhood? How does that make any kind of sense?
Allow me to introduce my good friend, Kinetic Energy.
supernova remnant? (Score:2)
Unless the argument here is that the Sun itself was blown away from the site of the supernova...
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Aye, but where's the supernova remnant itself? The rapidly-rotating neutron star with the nasty high-energy pulsar radiation? It was at the center of the explosion, so it had an initial kinetic energy of nearly zero.
A massive, rapidly rotating object has a kinetic energy of nearly zero? What professor did you hear this from, he/she needs a beatdown.
A few things that commonly confuse people: 1) Kinetic energy is NOT conserved. TOTAL ENERGY is. 2) Momentum and kinetic energy are NOT THE SAME THING. 3) A
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I mean translational kinetic energy, fergawdsake. Good grief, must we wallow in Dictionopolis definitioneering when there's interesting astrophysics to ponder?
There is a huge translational kinetic energy involved -- the translation of each individual particle in the neutron star as it rotates. The body viewed as a whole has no translational energy. The sum of the translational energies of all the particles is equal to the rotational K.E. of the body. This energy can't just disappear when the body breaks
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It's becoming more common now to see pulsars and neutron stars with really high peculiar velocities away from the site of the explosion. Inhomogeneous conditions during the collapse and explosion can propel the remnant away from the center of
cool! (Score:2)
thanks! (Score:2)
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Yup.
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So here we are, orphaned, adrift and alone. An object lesson for all to observe ...
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You'll have to be careful that using good numerics before you conclude too much from that program. If you use simple forward Euler differencing
du/dt = ( u(t+dt)-u(t) )/dt + O(dt)
for even a simple two-body system using the inverse-square law, the orbiting object will spiral outward due to accumulated discretization error. It's a good lesson in why you should use something higher-order, such a
Runge-Kutta!! (Score:4, Funny)
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That's a nice way to intuit it, and it's preceisely what's happening for first-order methods.
In mathy terms, the second-order terms in du/dt are important, the problem is "stiff", and so you have to use a higher-order method to do better. You're right that a first-order method will screw this up regardless of the discretization size, and in fact, it's not unique to astrophysical problems. ;-) -- Paul
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Because approximations done over short periods involving large margins of error are easy for our brains to do?
If you could only catch a ball by placing the center of gravity of your hand at an exact point (or a millimiter-sized area) through which the center of gravity of the ball would pass, then nobody would be able to catch. The fact is that we have an intuitive (
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You're both wrong, of course. The order of discretization has nothinig to do with
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You're both wrong, of course. The order of discretization has nothinig to do with this, the naive choice of coordinates does.
This "naive" method is PRECISELY what we are discussing. Look at my comment. [slashdot.org] Notice my usage of the word "naive." Notice that you are not following the topic.
This thread is not about the impossibility of an energy-conserving first order method. It is SPECIFICALLY about the naive cartesian Euler method, which is what I presumed the OP implemented.
But hey, you get to show off yo
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This thread is not about the impossibility of an energy-conserving first order method. It is SPECIFICALLY about the naive cartesian Euler method, which is what I presumed the OP implemented.
Sorry if you feel like I'm stepping on your toes here, but the thread is specifically NOT about cartesian anything. The GP was referring to Euler discretization of time and pronounced that this somehow poses a problem. Which is doesn't, if you pick proper coordinates.
The second paragraph in the comment you link to i
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The second paragraph in the comment you link to is false as it is written there. That's all there is to it. A newtonian model can be completely exact even if the time-steps are finite. As long as you choose proper circular coordinates.
What I should have said, instead of "the simplest method possible," was "the most immediately obvious method." To me, using cartesian coordinates is the most immediately obvious. Anyway, I'm interested in first order simulations in polar coordinates -- how well does this t
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I've had an idea for a while for an analog computer which computes orbits.
First step, acquire a star. Second step, acquire a planet and place it in orbit around the star. Record what happens. See, it's an analog computer that calculates orbits!
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Write a program using standard Newtonian physics that takes as its input a cluster of 'stars' of various masses. Start the program. After a while there is nothing left because all og the stars havesling shoted themselfs off to never never land.
There are two reasons this happens. First, even in a BOUND gravitational system (potential energy plus kinetic energy is a negative quantity), individual bodies can still be ejected as long as the total energy remains the same. However, in the real universe there
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PS: I should have mentioned an example when I wrote this post [slashdot.org]. See problem 2 in this homework solution [uci.edu] from a numerical analysis class [uci.edu]. -- Paul
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Well, that's just because you were modelling pre-existant 'stars', rather than modelling how 'planets' came to be. Planets only rotate in the same direction and in the same plane because the dust cloud they formed from was rotating in that direction, and formed a dust disk due to gravity before planets formed. Other gravitationally bound objects like comets can have any kind of strange orbit, like what you saw in yo
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I would speculate that it does make sense if you actually do the math, as astrophysicists are wont to do.
Sorry, but it's awfully typical: Slashdot reports
Dearly Departed (Score:4, Interesting)
How does that work? These stars are the gravitational pull, local "depressions" in the spacetime fabric that bend space around them towards themselves. Which is gravitational pull. Which must be overcome by some other force, either other gravitational pull from some other, larger/closer mass(es), or momentum from a kinetic event like a collision. Maybe the exploding supernova knocked them out of the area. Maybe, if it was big enough, its departing mass would have not only knocked the stars away, but pulled them away, overcoming their mutual gravitational attraction through greater departing, but still attractive, mass.
But something did. That's the biggest missing factor in this whole proposed scenario, in Robin Lloyd's Space.com story about it at least, that it needs to hold it together. Theories fall apart because of a lack of gravity, star clusters not so much.
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The article doesn't say exactly, but there's some easy inferences. We were part of a star cluster. There was a large star in the cluster, providing a large amount of gravitational attraction. That star then went nova, shedding a large portion of its mass. Ta-da, there is no longer enou
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Yeah, or it was something else. There are about a billion things that could have prevented the star cluster from being stable. I was merely presenting the simplest and most obvious one, just as an example. Your post implied that it seemed implausible that a star cluster could fly apart, and that without this crucial piece of information you refused to believe the conclusion that there was in fact such a cluster -- "Theo
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Answer: Virtually nothing. Why nothing? Because the mass is the same, and it's got the same center of mass. It's therefore equivalent. If a star goes nova, it still has the same center of mass and weighs the same (minus a small fraction of mass being converted into energy during the nova process).
Just giving you some more stuff to ponder.
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A supernova is a star exploding, as in ejecting all or the majority of its mass outward in all directions.
The math that allows you to treat an object as though it were a point of the same mass at the object's center of mass does not work when you are inside the object (i.e. the expanding sphere of the exploding star's shockwave has passed you). I
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I'm not seeing your point. The mass of the exploded star is moving outward at 3% of the speed of light, so in an astronomically insignificant time frame that mass will be outside of the star cluster and thus not contributing to holding it together any more.
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How does that work?
There was a supernova that was pulling them together. It blew up.
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Others have speculated that the remaining stars' existing orbits around the now diffuse/moved gravitational center of the now-supernova flung them tangentially as the center of mass moved.
"It blew up" is a description referring m
Was One Named Nemesis? (Score:5, Interesting)
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And in an alternate universe... (Score:3, Funny)
The sun's sisters? (Score:5, Funny)
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But they all lost marketshare. (Score:2)
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So was this the equivalent (Score:2, Funny)
Can't be (Score:2, Funny)
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Uhm... What? The bible doesn't go back that far. In fact, neither does human life.
Duh, that was a joke, a sarcasm, you insensitive clod.
The actual paper, if you want to read it (Score:5, Interesting)
An expected scenario (Score:2)
Stars start forming when giant molecular clouds are compressed, typically by the mass density wave of a spiral arm. This creates a star-forming region, where many thousands of stars will be formed in close proximity. Because the gas is able to efficiently shed kinetic energy (transforming it into heat), the stars have low velocities relative to each other, so are gravitationally bound in an "open cluste
so no chance of a date then? (Score:2)
How do you tell the gender of a star? (Score:2)
A couple of more serious questions:
Surely if a supernova was that close it would be the event that started the formation of the sun, rather than happening after its formation.
What's the effect of the outgassing (explosion) on the proper motion of the created stars? What percentage escape the gravitational field of the embedded neutron star?
Isn't this obvious (Score:2)
Sun Sis Saga (Score:2)
MjM
Re:"If our favorite planet, Earth... (Score:4, Funny)
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These stars are siblings because they arose from the same process at around the same time as our sun... e.g., thay have the same parent. Locus has nothing to do with it.
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What tickles me is the idea that had they been able to get a bit more gravity the sisters could have stayed together. How happy they would have been!
Then again maybe each of them had precisely the right amount of gravity, but they were hurrying along far too quickly. Hence they could not live happily ever after. Take this lesson to heart, dear reader.
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Maybe the moon was larger, yet somehow decayed into what it is today.
WTF??? Are you suggesting that a star could have "decayed" into something like the moon?? Are you even being serious? (if you are not well it sounds just like you are)