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View Full Version : Discussion: How Millisecond Pulsars Spin So Fast



Fraser
2005-Jul-20, 04:46 PM
SUMMARY: Observations with the Chandra X-Ray Observatory have given astronomers some clues about what causes millisecond pulsars - extremely dense stars which can spin many times a second. Several of these pulsars were discovered in a stellar cluster called 47 Tucanae, where the stars are less than .1 light years apart. Astronomers think these pulsars started as regular neutron stars, but tightly joined with stellar companions they picked up in the cluster. Eventually they get so close they start drawing material off the companion, which causes them to speed up.

View full article (http://www.universetoday.com/am/publish/origin_of_millisecond_pulsars_47tucw.html)

What do you think about this story? Post your comments below.

Moseley
2005-Jul-22, 10:58 AM
It seems to me that the conditions within such a dense stellar object may be considerably more extreme than those observed here on earth and activities which we observe in our temperature and pressure range may not occur when these are raised significantly.
I understand that the pulse we see is a result of matter falling to the surface of the neutron star but why is it that the matter only falls to one point on the surface? Is it not continually occreting and lighting up?
As an aside, would frame-dragging, which Gravity Probe B and others have been investigating, be more extensive around a denser object or are such effects mass-related only?
Sorry for the usual vagueness.

Shahbaz Nihal
2005-Jul-23, 04:29 AM
Well your point is right. But if any of neutron in neutron star undergoes decay, the emitted p[article wopuld surely fall back due to immense gravity.

Nereid
2005-Jul-27, 02:57 PM
A very cool story!

It will be interesting to see how many pulsars - millisecond or otherwise - X-ray binaries, etc will eventually be found in all ~150 globular clusters associated with our Milky Way, plus the various dwarf spherical satellite galaxies, and (if possible) to compare them all with pulsars and X-ray binaries in GCs associated with other LG galaxies, esp M33 and M31.
It seems to me that the conditions within such a dense stellar object may be considerably more extreme than those observed here on earth and activities which we observe in our temperature and pressure range may not occur when these are raised significantly.
Right you are! Creating 'neutron star' conditions in labs on Earth is impossible (with current technology) - and creating a neutron star in our immediate neighbourhood is definitely not a good idea!!
I understand that the pulse we see is a result of matter falling to the surface of the neutron star but why is it that the matter only falls to one point on the surface? Is it not continually occreting and lighting up?
Excellent question. From this site (http://www.cfa.ustc.edu.cn/course/CHAISSON/AT422/HTML/AT42202.htm): "Two “hot spots” on the surface of a neutron star, or in the magnetosphere just above the surface, continuously emit radiation in a narrow “searchlight” pattern. These spots are most likely localized regions near the neutron star’s magnetic poles, where charged particles, accelerated to extremely high energies by the star’s rotating magnetic field, emit radiation along the star’s magnetic axis. The hot spots radiate more or less steadily and the resulting beams sweep through space, like a revolving lighthouse beacon, as the neutron star rotates. Indeed, this pulsar model is often known as the lighthouse model."
As an aside, would frame-dragging, which Gravity Probe B and others have been investigating, be more extensive around a denser object or are such effects mass-related only?
Yes ... now if only we could send GPB to orbit a few km above a cold neutron star ...
Sorry for the usual vagueness.

Moseley
2005-Jul-28, 11:10 AM
Thank you Nereid, as usual you are not the slightest bit vague, answering all my queries.