Most power gravitational wave sources

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Discussion Overview

The discussion revolves around the potential sources of gravitational waves (GWs) that might be detected first by gravitational wave detectors. Participants explore various astronomical phenomena, including neutron star mergers, black hole mergers, and pulsars, while expressing uncertainty about which source is most likely to be detected initially.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants suggest that the first detection could come from double pulsars or other high mass objects.
  • Others propose that neutron star-neutron star mergers, neutron star-black hole mergers, or black hole-black hole mergers are likely candidates for the first detection.
  • One participant emphasizes the importance of a nearby supernova as a potential detectable source within the local group of galaxies.
  • A request for a single most probable source leads to a discussion on the known existence of neutron star binaries and the uncertainty surrounding black hole binaries.
  • Some participants argue that a single pulsar may not emit strong gravitational waves due to its symmetric nature, while others contend that pulsars can have ellipticity, which may contribute to GW emissions.
  • A technical argument is presented regarding the conditions under which gravitational radiation is emitted, specifically addressing the role of the quadrupole moment tensor and the impact of surface irregularities on neutron stars.
  • References to external articles are made regarding the potential for 'mountains' on neutron stars to contribute to gravitational wave emissions.

Areas of Agreement / Disagreement

Participants express a range of views on the most likely sources of gravitational waves, with no consensus reached on a single source. There is ongoing debate about the conditions under which pulsars can emit gravitational waves and the significance of various astrophysical phenomena.

Contextual Notes

Discussions include assumptions about the existence and characteristics of neutron stars and black holes, as well as the limitations in current understanding of gravitational wave emissions from pulsars and other celestial bodies.

mersecske
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In reality what do you expect to be the first detection with GW detectors?
Closest pulsars?
 
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Probably double pulsars or other very high mass objects of the sort. Thats my guess. I can't really say for sure though, i don't know enough on the subject.
 
I think the first detection is expected to be either neutron star-neutron star mergers, neutron star-black hole mergers, or black hole-black hole mergers. A nearby supernova could also be detectable, perhaps within the local group of galaxies.
 
I need only one! Not a list. Which one has the biggest probability? In your opinion, if you are a master on this field.
 
Well, we know neutron star binaries exist, so we can make estimates of the rate at which they merge. We suspect black hole binaries exist, but we don't have good statistics on how many of them they are, so these estimates are more educated guesses. If we knew all of the answers, there would be no need to build the gravitational wave detectors! But, having said that, my guess is the first detection will be a neutron star binary merging to form a black hole. But we'll have to wait and see. We should have unambiguous GW detections once Advanced LIGO comes on line, which is expected to be ~2015.
 
And a single pulsar is not enough strong? And we know its position.
 
No, a symmetric rotating body does not emit gravitational waves. A binary star emits GW as the two stars orbit about each other, but the intensity is extremely weak.
 
No one can see the future on this one. =)
We'll just have to wait and see.
 
Pulsars can have elipticity!
 
  • #10
mersecske said:
Pulsars can have elipticity!

Those are still symmetric. =)
 
  • #11
not spherically, therefore GW is emitted
 
  • #12
mersecske said:
not spherically, therefore GW is emitted

This is not true. The intensity of gravitational radiation is proportional to [tex]\frac{d^3r^{ij}}{dt^3}\frac{d^3r_{ij}}{dt^3}[/tex] where [tex]r_{ij}[/tex] is the quadrupole moment tensor of the mass distribution. A rapidly rotating body like a pulsar is flattened into an oblate spheroid, but the quadrupole moment tensor is constant in time, so no gravitational radiation is emitted. If the pulsar has a "bump" on the surface, then some gravitational radiation would be emitted, but since the surface gravity of a neutron star is very large, the "bump" would be very small, and hence the gravitational radiation emitted would be miniscule.
 
Last edited:
  • #13
'Mountains' on neutron stars are supposed to contribute to gravity waves-

'Mountains' on stars could trigger gravitational waves
http://www.newscientist.com/article/dn13566

Mountains on neutron stars could boost gravitational wave detection
http://physicsworld.com/cws/article/news/39179

The following link might also be of interest that shows various binary systems (mainly smaller objects falling into a massive BH) and the resulting gravity waves-

Extreme Mass Ratio Inspiral Movies
http://www.tapir.caltech.edu/~sdrasco/animations/index.html
 

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