Neutron star (pulsars)

socrbob
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Topic 226231

If pulsars only emit beams, and we have to be inline with those beams to detect them. How many more pulsars are there that are emitting beams that are out of line with us?

Mike Hewson
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There are far more unseen

There are far more unseen pulsars than those that are detected for at least the very reason that you quote - the geometry of the pulsar system with respect to us. I think the figure is of the order of a billion for the Milky way alone, whereas we have only discovered a few thousand. 

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

mikey
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Mike Hewson wrote: There are

Mike Hewson wrote:

There are far more unseen pulsars than those that are detected for at least the very reason that you quote - the geometry of the pulsar system with respect to us. I think the figure is of the order of a billion for the Milky way alone, whereas we have only discovered a few thousand. 

Cheers, Mike.

If as the previous poster said we can't detect everything from the Earth itself is there a satellite going up to help with that at some point?

Mike Hewson
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Popping up a satellite won't

Popping up a satellite won't improve our chances of changing the perspective from Earth of any given pulsar system. You'd have to translate by some light years to catch any of the beams of the ones we're missing currently. There are just enormously more ways of missing a beam direction than catching one. Space is really really big, etc.

For those pulsars whose beams that do shine this way as it is, then a satellite might improve the detection of that relatively small group by removing the interference of the Earth's atmosphere.

FWIW it is a good thing that we don't have any pulsars close by to observe, as they really hose the nearby space with alot of radiative power and it would quite unhealthy to be around. Imagine a really really big microwave cooker ..... all the numbers to do with pulsars ( neutron stars ) are staggering on a human scale.

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

mikey
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Mike Hewson wrote:Popping

Mike Hewson wrote:

Popping up a satellite won't improve our chances of changing the perspective from Earth of any given pulsar system. You'd have to translate by some light years to catch any of the beams of the ones we're missing currently. There are just enormously more ways of missing a beam direction than catching one. Space is really really big, etc.

For those pulsars whose beams that do shine this way as it is, then a satellite might improve the detection of that relatively small group by removing the interference of the Earth's atmosphere.

FWIW it is a good thing that we don't have any pulsars close by to observe, as they really hose the nearby space with alot of radiative power and it would quite unhealthy to be around. Imagine a really really big microwave cooker ..... all the numbers to do with pulsars ( neutron stars ) are staggering on a human scale.

Cheers, Mike. 

Thanks Mike

Gary Charpentier
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A few light years is still

A few light years is still right next to us.  Even at the way across the galaxy is nothing compared to the CL J1001+0220 galaxy cluster at 11,100,000,000 light years.  We will only see those that happen to align in our direction.

cecht
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Are the gravitational waves

Are the gravitational waves from binary pulsars directional or in any way related to the beams?

Ideas are not fixed, nor should they be; we live in model-dependent reality.

GWGeorge007
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Gary Charpentier wrote:A

Gary Charpentier wrote:

A few light years is still right next to us... 

You are so right!

Just a thought for a moment...

Currently we can see through the lens of the Hubble Telescope a total of 13.7 Billion light years into the past.  If we turned it around and looked the opposite direction, it would also be 13.7 Billion light years that we could see, making it a total of 27.4 Billion0 light years from edge (?) to edge.  (I hope I got that right)

To put the distance of the "observable universe" in perspective, lets assume that one light year = one inch.

With that being said, the "observable universe" would be a total of ~432,450 miles across.

And that is not all of the universe.  It is expanding, and continues to expand at an increasing rate.  By the time it took the light from the edge of the universe to reach us (13.7 Billion years), that light source has moved further away from us.  How far?  Some scientists believe it to be 90+ Billion light years across from edge to edge.

That is HUGE!!

By Gary's comment (above), a few light years are just a few inches compared to 432K miles!
 

[EDIT]

Sorry, I had to edit my post to include "Billion" several times.

George

Mike Hewson
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cecht wrote:Are the

cecht wrote:

Are the gravitational waves from binary pulsars directional or in any way related to the beams?

They are effectively omni-directional. The frequencies of the two may be related however, since both are linked to the rotation of the neutron star. If we ever detect the gravitational waves from such spinning stars, most will not have a detectable electromagnetic pulsar signal - we should be so lucky to define both for a single object.

As for millions, billions, trillions and what not ..... that's where the word 'astronomical' helps. :-)

Cheers, Mike.

( edit ) It's worthwhile adding that pulsars are extremely stable in their rotation rate/frequency - comparable in regularity to atomic clocks - so in general, it is only relative motions b/w source and observer that cause variation. This is factored into our parameter search space here at E@H. The notable exception is 'glitches' - an extremely short period of timing change - and thought to be likely due to star 'quakes'. In addition these celestial clocks are used in pulsar timing arrays, the idea being that they can or do vary consistently from our point of view if there are any GWs passing by of sufficient magnitude and duration

 

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

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