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Dead Star Set to Escape the Milky Way
slackah wrote to mention a NewScientist.com article discussing a fast-moving stellar corpse on its way out of our galaxy. From the article: "The object, called B1508+55, is a rotating neutron star, or pulsar. It is the superdense core of a massive star that exploded as a supernova about 2.5 million years ago. The explosion seems to have ejected the pulsar with such force that it will eventually escape the Milky Way entirely, says team member Shami Chatterjee, an astronomer with NRAO and CfA."
I wonder how long we can track this object once it leaves the galaxy. Any perturbations of its path will tell us about the dark matter between galaxies and the gravitational pull such putative dark matter exerts.
It's too big to be a space station.
This kind of thing makes me wonder how static the current shape of our galaxy is. Do stars (dead or otherwise) leave all the time, and do they ever come in from somewhere else? Do ejected stars form the cores of new galaxies? I doubt we'll ever get a chance to see much of this in action anyway since the galaxy in general moves so slowly, but it's still neat.
:)
It also occurs to me that this isn't really news: depending on how far away the star is/was, there's a fair chance that it left our galaxy millions of years ago
when you find yourself envying a neutron star.
Ok, the article didn't say anything about when it will leave the milky way. It just said that B1508+55 was going to leave the milky way, and that it had been traveling for 2.5million years from its point of origin in Cygnus. That translates to a velocity of 1100km/s or being able to cross 1/3 of the night sky from the time of birth to the present.
There are two things that excite me about this. 1) B1508+55 is a massive radio emitting object which is boldly going into the intergalactic space where all that putative dark matter is supposed to be. If its path bends we might end up discovering a "dark galaxy". Of course someone with access to human astronomy records must be around to observe this when it happens.
2) Cygnus spits out a lot of these objects. Maybe if we get a very much faster one, we can have a more convenient probe.
Strange how one can be so impressed by something, he knows so little about...
The concept of escaping the galaxy is awsome, but it would be nice to know more about it...
So I did some research: Milky Way Galaxy is: ~100,000 light years in diameter; ~3,000 light years in thickness; ~250,000 light years in circumference.
Basically, its huge. The ratio of our solar system to the milky way galaxy is 1:65,000,000.
From this I believe that just about anything can escape the galaxy, it would just take an extremely long time. However, as I have stated, my knowledge on the subject is limited, so it is possible that the planets and stars are arranged in such a way, that the gravitational pull would always redirct any object to go back. (i.e.: meteors and asteroids pass Earth in patterns and intervals, without leaving the galaxy).
The subject is very interesting, and if someone could bring more light on it, it would be helpful...
Dard Vader not amused
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It's a trap!
Get your Unix fortune now!
Those neutron stars are the product of stellar cores collapsing into a neutron star (and then sheding the outer hull thats impacting on the core rebounce shockwave in a class II supernova).
Now if such a collapse isnt absolutly symetrical, there will be higher spherical hermonics in the neutron core oszillation, and thus the impact of the hull on the core will give it a random impuls vector (the first harmonic being the 2 hemispheres oszilating with 180degree phase difference).
The observation of those fast moving neutron stars helped the understanding of this processes, as there isnt much that can accelerate them after their creation to this speeds.
A common speed of a class2 supernova product is in the 100-1000 km/s range (about 2 orders of magnitures lower than the speed of the the ejected hull, thus the visible SNR still seemingly have the neutron star in the center), which is way enough for most to leave our galaxy (300 or so is needed)
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
The main point is: the core isnt EXPLODING, its COLLAPSING to a neutron star. The "explosion" is just a rebounce off the core (_slightly_ simplified :) ).
After the collapse, the kinetic energy of the quasi free falling neutron matter will overcompress the neutron star core, and then it will oscillate.
As the collapse istn something perfectly symetrical, there will be significant amplitude of the first harmonic of the oscillation. Thus (for example) the matter hitting the star on one hemisphere will have the core expanding in their direction with quite some speed, while the other side will see it receeding). As the impact isnt very long, there wont be time to average out. In the moment the hull impacts, the core will "push" itself away from that quasi-spherical shell thats hitting it.
(you have to remember: there is significant mass in that shell. Only a small part of the star actually ends of in the neutron star, so there IS enough mass in the hull for conservation of momentum)
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
When I bet the star itself yelled "freeeeedom!"
[self dealloc];
7700 years, anyway, according to the article.
But it's never a good idea to take these announcements at face value. It's far from clear the thing has anything to do with a supernova, or that it's a neutron star at all -- presuming any of them exist at all. What we do know is that its light (radio, x-rays, etc.) pulses at a rate too fast for them to understand unless it's a tiny thing spinning.
The reason they insist it has to be something spinning is that they have studied almost no plasma fluid dynamics, so they can't understand something blasting out radio, light, and x-rays that doesn't have a star in the middle of it. They don't understand fluid instabilities and current oscillations, so they're at a complete loss to understand the (quite common) sudden, often temporary changes in oscillation rate in pulsars.
What little they have studied, typically, is a trivial approximation to plasma fluid dynamics known as "magneto- hydro-dynamics" (MHD) which assumes space is superconducting and magnetic fields can't change distribution or strength. (They talk in all earnestness of magnetic fields "frozen" in place -- even in the sun!) Therefore, they can't understand how large flows of charged particles -- currents, which they insist on calling "jets" -- produce their own magnetic fields and flow along them, or how these flows' fields can interact in marvelously complex ways.
Everything you read about "dark matter", "supermassive black holes", and "neutron stars" amounts to a desperate attempt to find some way to make the extremely weak and purely attractional gravity account for the complicated things they see. The mathematics behind plasma fluid dynamics is too hard for them, and they just can't stand that. It makes their press releases funny to read, but it's sad, too. (Think of the lives wasted on planetary epicycles.)