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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."
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.
Dard Vader not amused
Comment removed based on user account deletion
Fast, for a star, but it's 1/300th of c. So it'll be at least 300,000 years to get 1000 ly out, getting to the edge of the galaxy. By then we'll either be extinct or know all about the dark matter.
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?
Wow. I knew we had a central black hole, but I didn't realise it distorted space that much. What value is the pi where you live?
Real Daleks don't climb stairs - they level the building.
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?