Starship Asterisk*

JohnD wrote:

• Hamlet: Or like a whale.
  
  Polonius: Very like a whale.

http://www.greywhale.com/blue.htm wrote:
<<The heart of an adult blue whale is about the size of VW Beetle. The carotid artery is about 12" to 18" in diameter, compared to 1/4" for humans. The heart (pulse) rate at rest is 5 to 10 beats per minute.>>

alter-ego wrote:Just thought this might help

edkal wrote:Does anyone else see the figure in the bottom half with flowing robes moving to the right with arms outstretched?

Chris Peterson wrote:

Amir wrote:yes my sentence was wrong. what i meant was that the 7times/sec pulses may not be necessarily because of the rotation around the axis of rotation; they may be the result of another motion like Precession.
could it be?

In principle, I suppose a very newly created pulsar might precess, and if its emission were polar, that could create periodicity. But I think the nature of the forces involved would snub precession very quickly. In any case, I don't think any actual pulsars have been associated with precession.

As far as we can tell from surveys of radio pulsars, precession in isolated neutron stars is a
rare phenomenon. Precession, once excited, would eventually damp through internal friction.
The rareness of precession could mean that it is rarely excited in isolated neutron stars.

Amir wrote:yes my sentence was wrong. what i meant was that the 7times/sec pulses may not be necessarily because of the rotation around the axis of rotation; they may be the result of another motion like Precession.
could it be?

tesla wrote:7revolutions per second on a 20klm diameter object gives a surface speed of 220klm/sec or almost 800,000klms /hour. Like I said, you have to have mythical material to keep it from flying apart.

It is not established beyond reasonable doubt, it is only a current theory, based on known facts at present. A theory is not scientific fact

Chris Peterson wrote:

tesla wrote:If the Chandra image spans 100 light years, then the so called pulsar is more than 20klms in diameter. Spinning 7 times a second? Please! Even if it is, at that rotation speed it would fly apart, simple mechanical theory.

Please describe this "simple mechanical theory" you are referring to. You are apparently making some sort of assumption about the material strength of a neutron star that is different from the assumptions of the entire scientific community. Here's a hint about how to approach this question: consider the gravitational force experienced by a particle on the surface, and compare it to the centrifugal force due to rotation.

At seven rotations per second, this pulsar is very much at the slow end of things (in fact, I don't know of a slower rotator than this one). The fastest pulsar rotates 100 times faster. That this class of pulsars is caused by rotating neutron stars is established beyond reasonable doubt.

Chris Peterson wrote:All pulsars are rapidly rotating objects, including the one at the center of the Crab nebula. Rotation only powers one class of pulsar, but all pulsars derive their periodicity from rotation.

zbvhs wrote:The text says the pulsar is in the bright central region. Which bright central region? The blue high-energy one at the bottom or the yellow low-energy one at the top?

Amir wrote:but yes, they do not necessarily spin. see this Image Tour about Crab nebula by Hubble Site which also mentions the neutron star inside of it.

tesla wrote:If the Chandra image spans 100 light years, then the so called pulsar is more than 20klms in diameter. Spinning 7 times a second? Please! Even if it is, at that rotation speed it would fly apart, simple mechanical theory.

tesla wrote:...That does not necessarily mean spin!

Glokthathrzyk wrote:On distance: Are you saying that the blast from the supernova reached out 15,300 light years to create the pulsar, or that something somehow propelled faster than light to become the pulsar????? An enquiring mind(?) wants to know :P :)

Glokthathrzyk wrote:On distance: Are you saying that the blast from the supernova reached out 15,300 light years to create the pulsar, or that something somehow propelled faster than light to become the pulsar????? An enquiring mind(?) wants to know

Chris Peterson wrote:

Guest wrote:"As far as pulsars go, PSR B1509-58 appears young. Light from the supernova explosion that gave birth to it would have first reached Earth some 1,700 years ago. ...PSR B1509-58 is about 17,000 light-years away in the southern constellation Circinus." So how far away it is 1,700 light years or 17,000 light years?

It is 17,000 light years away. The supernova was visible here on the Earth 1,700 years ago; we are seeing this pulsar 1,700 years after its creation (which might actually be considered to have happened 18,700 years ago).