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4

WD+NS collision cannot leave nothing behind. Gravitational mass defect of NS is ~10% of its rest mass -- thus whatever energy released in the collision cannot disrupt the NS. The energy released is basically the nuclear energy of the WD material burning into heavier elements as it gets heated in the process of collision. That amounts to at most ~0.2% of the ...

6

You can't estimate Hubble's constant using the method you propose, for two reasons. (1) Redshift and luminosity distance are only linearly related by the Hubble parameter at small redshifts. (2) You need an independent estimate of the redshift (e.g. from a spectrum of a host galaxy or something - see here for example or Abbott et al. 2017) to get the Hubble ...

2

The comoving radial distance goes into Hubble's law, A redshift of 0.71 and a Luminosity distance of 4450 Mpc corresponds to a comoving distance of about 2590 Mpc (according to Ned Smiths cosmology calculator, and assuming a flat cosmology). Which should give you something closer to H₀=0.7

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Are there any wavelengths in between the ranges of these different detectors that we wouldn't be able to detect? Yes! There is the millihertz band, which will be detectable by the space-based observatory LISA, and the decihertz band that approximately covers the range from the millihertz band to the range that is observable by ground-based detectors such as ...

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Yes, there is a huge range of frequencies between those to which aLIGO is sensitive ($30$ -$3000$ Hz) and the pulsar timing arrays ($10^{-10}$ - $10^{-7}$ Hz). The ESA spacecraft LISA, a proposed mission which received approval in 2017 and which may launch in 2037+, is meant to fill this gap. The plot below represents (roughly speaking) the minimum ...

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I'm going to break this up into two parts. Supernovae The effect a supernova will have on a planet is, as one would expect, dependent on a lot of factors. Like how close a planet is to the supernova if it's far away then how long will it take for the remnant to pass by it, etc. But a couple of guiding principles boil down to the following: Once the mass ...

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