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View Full Version : Pulsars - give 'em a brake...



Charlie in Dayton
2003-Jul-02, 11:18 PM
They've found the speed limit for pulsars. (http://channels.netscape.com/ns/news/story.jsp?floc=FF-APO-1501&idq=/ff/story/0001%2F20030702%2F173388427.htm&sc=1501)

Kaptain K
2003-Jul-03, 10:39 AM
There is a lot of sloppy science in that article. Not bad, just sloppy. :o

Charlie in Dayton
2003-Jul-03, 03:27 PM
Solely because I wish to learn, and not repeat less-than-accurate procedures, details on that sloppy science, please?

tracer
2003-Jul-03, 10:33 PM
Well, there's this:

The collapse starts the pulsar spinning at about 30 turns a second.

If there is a nearby star, the pulsar, with its superior density, will begin pulling material from its stellar companion.
After a star collapses into a pulsar (neutron star), it won't be any more massive than it was before the collapse. Only if the pulsar's companion star expands (e.g. if it turns into a red giant) will the pulsar be able to pull material off of it.

Incidentally, star systems where the two stars are close enough together and big enough around for one star to draw material off of the other gravitationally are known collectively as "mass-exchange binary" systems. Similar systems can exist with white dwarfs and black holes.

sol_g2v
2003-Jul-04, 12:37 AM
If there is a nearby star, the pulsar, with its superior density, will begin pulling material from its stellar companion.

I don't see what's wrong with this statement. It is true that a pulsar or neutron star will pull stellar mattar from a companion if it is sufficiently close. This is also true for other stars besides pulsars.

tracer
2003-Jul-04, 12:46 AM
Yes -- if its companion is sufficiently close. The article implied that when the progenitor star collapsed into a pulsar, it would suddenly start pulling material off of its companion even if it wasn't pulling material off its companion before, due solely to the pulsar's higher density. Which is blatantly false.

Beaver
2003-Jul-04, 02:10 AM
Would it not even be less likely siphon of its companion cosidering the loss off mass when it blows of its shell?

Or because of the lower mass the stars move in closer into a tighter orbit, but before settling down they oscillate in and out giving the polsar the chance to start the sucking procedure, and once its starts they more closer and closer until they companion is cannibalized?

P.S. No offense to cannibals if this is not how its done :D

Manchurian Taikonaut
2005-Apr-22, 10:48 AM
Hots spots on neutron stars, the Phase variation in the X-ray emissions from three pulsars has been examined by XMM-Newton


animation above shows the phase variation of the X-ray emissions detected from PSR 1055-52, a middle aged neutron star (~500 000 thousand years old), located at about 2000 light-years away from us

http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=37005