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1

I'll try to be careful to distinguish between orbital rotation and spin. The requirement for a non-spinning finish is that the sum of the orbital and angular momentums of the material that remains is zero. Even in clasical physics this is clearly impossible with equal masses and in the absence of loss of mass due to supernovae (which would further impede ...


2

I'm sure that an exactly spinless final black hole is theoretically possible, but it would be a very, very precise fine-tuning, akin to balancing a pencil on it's point. Also, your configuration is unlikely to produce a spinless black hole, because when the plunge phase of the merger happens, the stars will suddenly fall from the innermost stable orbit, and ...


2

I think if there is a binary system of stars then the size of neutron stars can be estimated. This method i would call direction estimation because even for most direct observations various theories are always involved. When the neutron star passes over the burning star its intensity is dimmed. How much it is dimmed depends on the size ratio of visible and ...


5

10km is about right, 5km is definitely wrong and there are theoretical arguments and also observational evidence that this is the case. The Schwarzschild radius, inside which an object would be a black hole, is $3(M/M_{\odot})$ km. As neutron stars have a typical mass of $1.5M_{\odot}$ then a 5km radius would have them hovering just above disappearing ...


5

Yes, there are lots of optical observations of isolated (non-pulsar) neutron stars. Such observations have been done for many, many years. An early example would be Kulkarni & van Kerkwijk (1998) who detected optical radiation from the counterpart to RX0720.4-3125. http://arxiv.org/abs/astro-ph/9803024 The authors discuss various mechanisms that ...


3

Most of the books which I looked at give approximately 10 km as the radius of a neutron star. Just yesterday I looked at a book by Dave Goldberg titled The Universe In the Rearview Mirror (2013) which says that they're "only about 5 km in radius" [p.225]. Is this true, [i.e., is there some recent evidence for this], or did he make a mistake here? These are ...


3

There have been a few detected in the visible range by Hubble Space telescope and Keck observatory. The magnitude is less than 25 for the Hubble image(PSR0656+14). Neutron stars are very hot, 600,000 or more Kelvin and very small (Hubble star was 28 kilometers in diameter) so their visible luminosity is very low. The emission is redshifted due to General ...


1

5 km in radius seems like a mistake. a 3 solar mass object has a schwarzschild radius of about 9.0 km. (Hence the 10 km estimate for the size of a Neutron star). A little smaller than that and it becomes a black hole. Also, as I understand it, Neutron stars, like white dwarfs, grow smaller as they add mass. Less massive Neutron stars in the 1.4-1.5 ...



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