astrophysics question

CMDR DERPY SMOOG

CMDR DERPY SMOOG
so i found a neutron star orbiting very close to its parent star. so close it only had an orbital period of a few hours. as i was looking at this it occurred to me that an object with enough mass would pull material from nearby stars just like a black hole would. this thought led me to wishing the game could show accretion discs. and then i got to wondering: is it possible for a small but dense stellar object, like a white dwarf or something, to pull enough material from another body to extend its own life or even revive it self to a degree? the idea of parasite stars living way longer then they should by eating other stellar objects is kind of fascinating. and really scary.

just looked up a video on accretions discs and had the realization: everything in our galaxy orbits sag a right? that means out entire galaxy is just sag a's accretion disc. XD
 
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Orvidius

Orvidius
Yep, small bodies such as white dwarfs do indeed steal mass from their companions. It gets a bit complicated, but there are a variety of scenarios that can come from this.

For instance, Type 1a Supernovae involve a white dwarf stealing mass, until it reaches a critical threshold and explodes. Sadly, they do not regain outer layers and "come back to life", but rather create this form of supernova. On the plus side, these are very useful in astronomy as a "standard candle" since the explosion occurs with a very predictable brightness.

In other cases, two main sequence stars can result in the initially lower mass star eventually being the one to have a supernova and leave behind a neutron star, as an example.

In the case of a neutron star with a closely orbiting star, the neutron star will steal mass and gain angular momentum, making it spin faster over time. This is how we get "millisecond pulsars", which in the game appear as those insanely fast spinning neutron stars.

What happens depends a great deal on the initial size and mass of the two objects and how closely they are orbiting.
 

ChipStar65

ChipStar65
Orvidius said:
Yep, small bodies such as white dwarfs do indeed steal mass from their companions. It gets a bit complicated, but there are a variety of scenarios that can come from this.

For instance, Type 1a Supernovae involve a white dwarf stealing mass, until it reaches a critical threshold and explodes. Sadly, they do not regain outer layers and "come back to life", but rather create this form of supernova. On the plus side, these are very useful in astronomy as a "standard candle" since the explosion occurs with a very predictable brightness.

In other cases, two main sequence stars can result in the initially lower mass star eventually being the one to have a supernova and leave behind a neutron star, as an example.

In the case of a neutron star with a closely orbiting star, the neutron star will steal mass and gain angular momentum, making it spin faster over time. This is how we get "millisecond pulsars", which in the game appear as those insanely fast spinning neutron stars.

What happens depends a great deal on the initial size and mass of the two objects and how closely they are orbiting.
Click to expand...
I love it when Commanders talk nerdy. :D

I was rather disappointed at first by ED's lack of such spectacular physical effects as mass sharing between close binaries, gravitational distortion due to close orbits of planets, and other such details. But in truth if the Universe was portrayed as it actually is, it would not be as populated as in the game, because it is a stupendously more hazardous environment than that we play in. Even including such minor effects as realistic stellar winds and stellar events like coronal mass ejections would mean about 75% of settled planets and stations would die off very quickly. So, I just play.
 
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GrandAdmiralThrawn

GrandAdmiralThrawn
I assume a neutron star stealing a lot of mass from its partner wouldn't revive, but rather just cross the Tolman–Oppenheimer–Volkoff* limit and collapse into a black hole?

*I had to look that up on Wikipedia, because I always forget the names of the mass limits for white dwarfs and neutron stars...
 

ChipStar65

ChipStar65
GrandAdmiralThrawn said:
I assume a neutron star stealing a lot of mass from its partner wouldn't revive, but rather just cross the Tolman–Oppenheimer–Volkoff* limit and collapse into a black hole?

*I had to look that up on Wikipedia, because I always forget the names of the mass limits for white dwarfs and neutron stars...
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An interesting question to ponder, or to look up!
www.quora.com

What happens when a neutron star devours another star?

Answer: A neutron star is relatively massive and extremely dense, which is why they have a tendency to attract matter from their companion stars—remember that most stars are part of binary systems or systems with even more stars, so there is a distinct possibility of this happening. Accretion Th...
www.quora.com www.quora.com
 

GrandAdmiralThrawn

GrandAdmiralThrawn
But this doesn't fully answer the question I think.. While it describes some of the processes, what if the neutron star just keeps consuming matter? According to the [Solstice blog], a german (or maybe originally Italian?) astrophysicist going by the name of Luciano Rezzolla said this:

[...] “Surprisingly, we now know that even the fastest rotation can at most increase the maximum mass of 20% at most,” remarks Rezzolla.[...]
Click to expand...

So even if it starts to spin crazy fast, its mass limit won't increase that much. So by sucking in even more matter from an accretion disk or a companion star, it should collapse? No?

If no, then why not?
 

ChipStar65

ChipStar65
Orvidius said:
If it absorbed enough mass, then yes, it would collapse into a black hole.
Click to expand...
But neutron stars do not (cannot?) "absorb mass." Remember, neutrons stars are just that -- neutrons and (almost*) only neutrons, packed by gravitational collapse into a sphere so compact a teaspoon-sized portion would weight millions (billions?) of tons. Gravity has even overcome the strong nuclear forces that tends to make neutrons resist such compaction in normal matter. There is just no space between the neutrons for any other matter to exist.

The conditions at the neutron star's surface are such that any normal matter getting too close, say from an accretion disc, will be first ionized, then superheated to a plasma, and eventually ejected in a much-transformed state via a polar jet formed by the neutron star's intense magnetic field -- hence pulsars. In the case of magnetars, the situation is even more extreme, with the accretions contributing to what amounts to star quakes that generate what we know as gamma ray bursters. All this produces prodigious amounts of intense radiation, but I doubt there is an equivalent to a Type 1A supernova (such as happens with white dwarf stars under similar situations) because the matter just has no chance to undergo any sort of nuclear interactions like fusion, it would be ripped to subatomic shreds and then either converted to broad-spectrum EM radiation or shot out in the polar jet before that could happen.

As I understand it, mass accretion by neutron stars can revive their rotation, spinning them up so that the intense friction in the disc would start heating the accreted matter until the above scenario is set in motion.

*some poor forsaken electrons may hang about looking for a proton to bond with, but they'd be very lonely.
 

Sapyx

Sapyx
CMDR DERPY SMOOG said:
...everything in our galaxy orbits sag a right? that means out entire galaxy is just sag a's accretion disc.
Click to expand...
Sorry, but no. While Sag A* is really, really massive, with millions of solar masses, it is easily outweighed by the billions of solar masses that comprise the rest of the Galactic Core. While the stars within a few hundred light-years of Sag A* are all strongly affected by Sag A*'s existence, either orbiting it directly or having their courses altered by it, the rest of the galaxy barely even knows it's there, from a gravitational point of view.

There isn't even a force keeping Sag A* directly in the centre - that's just where it happens to be right now (though our best guess is that it isn't quite in the exact centre, but is a few hundred LYs off to one side). So theoretically, an advanced civilization could (figuratively) strap some gigantic engines onto Sag A* and fly it out of the galaxy, and the rest of the galaxy wouldn't even notice that Sag A* wasn't there any more, it would keep orbiting merrily around itself, just as it currently does.
 

CMDR DERPY SMOOG

CMDR DERPY SMOOG
everything i know is a LIE! lol joking aside i kind of suspected as much. i recently found out that earth doesn't actually orbit the sun directly but a point in space very close to it that is the center of mass for our solar system. blew my mind a little but it makes sense.
 

LordFerret

LordFerret
You've seen the graphic which depicts how the planets truly orbit the sun?
O633QU.gif


Now realize that every star in the galaxy is moving in a similar manner, each in its own direction (proper motion), within its local fluff aka local bubble (interstellar gas cloud), and the whole shabang of such clouds in the various arms of the galaxy moves around Sag A* (for all intent of purpose), interacting with each other (some shrinking, some expanding)... and the galaxy itself, also moving, within the local group (of galaxies), also moving, within a particular supercluster... which in our case would be the Virgo Supercluster (which might yet be a part of an even larger supercluster.....

and on and on and on and on. :cool:;)
 
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Trotsky2112

T
I agree with the above suggestions. FDev should put in cooler stuff like CMEs and Accretion discs and stuff. But if 75% of stations in a system would die when that happened...

Maybe a heat shield like on Darth Vader's Mustafar base?
 

GrandAdmiralThrawn

GrandAdmiralThrawn
ChipStar65 said:
But neutron stars do not (cannot?) "absorb mass." [...]
Click to expand...
Is that really the case? Some people like e.g. Professor [Cole Miller] from the Institute of Astronomy at the University of Maryland [appear to think] that they can (see answer to question #3), and that guy's main field of research is high-energy processes related to neutron stars and black holes.

There are also articles which describe a "neutronization" of protons and electrons in the star's crust, like [here].

I am just a layman of course, so I'm not quite sure what to believe or rather what to accept as the most likely scenario.
 

Orvidius

Orvidius
Yeah, there's still a lot of debate about just how neutron stars might "eat" material. I haven't kept up with it, so I can't really say where that stands. Right now I think the main known mechanism of neutron star gravitational collapse into a black hole is via collision (such as two neutron stars colliding). A lot of the material gets ejected in such collisions, with a considerable amount of mass converted to energy in the form of gravitational waves, but as long as the remaining mass is sufficient, it will result in a black hole.
 

ChipStar65

ChipStar65
GrandAdmiralThrawn said:
Is that really the case? Some people like e.g. Professor [Cole Miller] from the Institute of Astronomy at the University of Maryland [appear to think] that they can (see answer to question #3), and that guy's main field of research is high-energy processes related to neutron stars and black holes.

There are also articles which describe a "neutronization" of protons and electrons in the star's crust, like [here].

I am just a layman of course, so I'm not quite sure what to believe or rather what to accept as the most likely scenario.
Click to expand...
Cole's answer seems to assume the ability to accumulate mass in a relatively normal manner, without processes that would convert to energy or eject such matter as might begin to accumulate. He "thinks" it could, but there is no observational confirmation of this, whereas pulsars and magnetars, both indications of interactions between neutron stars and normal matter, are observable. But note I also made my comment condiitonal -- "(cannot?)" -- because we have not made enough observations to completely rule out the possibility. You mention "neutronization," which I also briefly alluded to with the lonely electrons, and I suppose if certain conditions allowed such a process to proceed unchecked for long enough, it could lead to reaching a precipitative mass limit, but so far as I know this is just conjecture.

The mechanisms of gravitational collapse and black hole formation in Type II supernovae are not known with certain clarity, though they have become generally apparent from accumulating observations and theoretical considerations. The principal aspect that would be missing from a neutron star's accretion scenario is the existence of the gravitationally unsupportable iron stellar core that is what collapses to generate both the Type II supernova explosion and the neutron star or black hole remnant. Iron cannot undergo any sort of fusion reaction, which is why the core is unsustainable. At the tipping point, it collapses within milliseconds, and the sub-atomic "rebound" from this event causes the visible supernova effects, which can be relatively easily studied. But the collapse of the core into a degenerate state of matter is not readily observable except in its residual effects -- theory has to account for why neutron stars and black holes exist after the collapse, but such theories depend upon specific initial conditions, e.g., the presence of an unstable iron core. I've not encountered any similar theories concerning neutron star mass accumulation, though I admit to only an interested layman's awareness of such. It seems to me that the kind of supernova generated by a hypothetical neutron star collapse would not observationally match either Type Ia or Type II supernovae, because the initial conditions are substantially different. Have "exotic" supernovae been observed? I think that would be fairly well known if so.

The recently observed collision between two neutron stars (or what is theorized to be such given the observational data) may shed some light on this whole arena, because that is one of the scenarios where neutron stars collapsing into a black hole is considered quite feasible if the stars merge and the resulting object has sufficient mass.

www.npr.org

Astronomers Strike Gravitational Gold In Colliding Neutron Stars

In an astonishing discovery, astronomers used gravitational waves to locate two neutron stars smashing together. The collision created 200 Earth masses of pure gold, along with other elements.
www.npr.org www.npr.org

But note the statement that the observations of this event did not quite match theorists' predictions -- exactly the reason to wait for observational data before saying anything other than "perhaps."
 
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malenfant

M
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