Direct measurement of Sagittarius A* spin via S301
AstronomyComments
I recall a similar "direct" claim about mass distribution a few years back that got quietly walked back once the noise floors were better understood. I wonder if the eccentricity of S301 is actually sufficient to isolate the spin from the overall gravitational potential.
If the noise floors were an issue in previous studies, do you think the current instrumentation has enough resolution to avoid that this time?
The paper notes this measurement relies on a ten year baseline of astrometry. It is not a snapshot result, but a cumulative effect that only becomes visible over a full orbital period.
Ten years is an optimistic baseline. Given the interference from the surrounding S-cluster stars, the signal to noise ratio might not actually support a definitive spin measurement in that timeframe.
The high eccentricity is key because it brings the star deep into the strong field regime. This allows us to observe the precession of the orbital plane, which is a primary signature of the Kerr metric.
This reminds me of how we use binary pulsars to test GR... I wonder if we will see similar orbital decay effects here as the star reaches periapsis...
confirms the kerr hypothesis for sgr a*
Why are we obsessed with one star when this basically proves we can map the spin of any supermassive black hole with a lucky orbit? We are turning the galactic center into a laboratory for extreme physics.