mollwollfumble said:
Tau.Neutrino said:
Space-warping star system proves Einstein’s general theory of relativity right. Again
Just over a century ago, Einstein predicted that the gravity of massive objects could warp spacetime.
In the past five years we’ve seen Einstein’s theory of general relativity play out in the detection of gravitational waves, the imaging of a black hole, and the orbit of stars around the supermassive black hole at the centre of our galaxy.
more…
> PSR J1141-654 a fast-spinning white dwarf star is circled by a neutron star (pulsar).
> The orbit shrinks by about 7 millimetres a day. But as time went on, it became clear that the stars weren’t acting as predicted by Einstein’s theory.
> I had assumed that we’d done something wrong, there was a brief period of time that I thought I disproved Einstein’s theory, in the end they twigged that the fast-spinning white dwarf star drags space and time with it. Lense-Thirring effect or frame-dragging. We did not think that this would be measurable for this system.
Nice work, I wouldn’t have thought that frame dragging would be measurable around a white dwarf either.
> https://science.sciencemag.org/content/367/6477/577
Dang, sci-hub links are out of order. Anyone tried https://citationsy.com/blog/download-research-papers-scientific-articles-free-scihub/ ?
sci-hub is back.
The science article is … well …extremely unuseful. What I wanted to see was a comparison of calculation with and without the Lense-Thirring (LT) effect due to white dwarf rotation, to see what the magnitude of it is. Not a whisper of that in the article.
All there is is a best estimate of the binary’s masses, orbital diameter and inclination, a limit on spin, and that’s about it. I see hardly any clue as to even what observed parameters were used to derive these properties.
The final sentence “SR J1141–6545 therefore exhibits another manifestation of Einstein’s general theory of relativity: LT frame dragging” pops out of nowhere, there is no “therefore” about it.
Let’s see if I can dig deep into the text to get something out of it.
“Both QPM and LT effects induced by the WD spin (and only these effects) provide non-negligible contributions to xSO.
Here “non-negotiable” is hardly a precise measure, or a way of distinguishing between LT and QPM.
The term QPM isn’t clearly defined either, it could be taken to mean “Newtonian contributions from a mass-quadrupole moment”
Then there’s xSO itself, which means what? “The largest is a change in orbital inclination i that is due to the precession of the orbital plane caused by the spin of the WD” is xSO, but a lot is still not clear.
“contributes <21% of xobs” refers to an effect other than xSO”.
So LT contributes a “non-negligible” part to perhaps of the order of 100% minus 21% of 
which has presumably something to do with pulsar slowdown or speedup, it’s not clear which.
Which is hardly a precise statement. How did it get past the peer reviewers?