Mercury and Magnetism

4 Jul 2021

At https://phys.org/news/2021-07-mercury-big-iron-core-magnetism.html ... the prevailing theory that Mercury has a big iron core relative to its crust is under attack. The consensus theory is that much of Mercury's rocky mantle has  been blown away due to collisions in the early solar system. They are always early of course - to keep them at arms length. It left a big, dense, metal core, and this was thought to explain its magnetism. It was bound to happen once the properties of the SDun became better known but new research is now said to reveal that collisions are probably not to blame. It is all down to the Sun's magnetism - and Mercury is the planet nearest to the Sun.

At https://phys.org/news/2021-06-black-holes-swallow-neutron-stars.html .. after listening to a BBC presenter labouring over the text, reading out from a cue no doubt, the fact that a black hole had swallowed a neutron star, I noticed this on PhysOrg. No doubt the source of the BBC news story. It seems it all happened a long time ago - 900 million light years away. Two black holes in two separate galaxies, are assumed to have merged, and in the process, a black hole gobbled up a neutron star. The nocturnal meal triggered a gravitational wave that eventually reached our solar system in January 2020. It seems the theory has now become fact, and gravitational waves are a new consensus, marking black hole mergers. What has actually been seen - or detected. A blast of light from a faraway galaxy. Modelling is an integral part of the research. Gravitational waves have allowed scientists to detect collisions of pairs of black holes and pairs of neutron stars. The mixed collision of a neutron star with a black hole is said to be the elusive missing piece of the picture of object mergers. The research is published in the Astrophysical Research Letters of June 29th [2021]. What was observed, we are told, were two gravitational wave events - and follow up observation has failed to see another burst of energy, since January 2020. See https://dx.doi.org/10.3847/2041-8213/ac082e [https://www.iopscience.iop.org/article/10.3847/2041-8213/ac082e] ... the research supports the consensus view. It resulted in a gushing BBC news story that probably went over the heads of most people - or at least the fact that computer simulation, modelling, and assumptions are inherent in the claim. It is of course accepted by most people that gravitational waves really are a signal of some kind of important cosmological event. After all, we've seen the pictures. However, consensus theories do not necessarily have a long shelf life. Bigger and more powerful telescopes, and telescope arrays, will either support the consensus view, or undermine it.